[Iain Churches[_2_]]

Patrick posted some interesting facts about ground buss
connections, which I have extracted from another thread
and pasted here, because I think the subject is important
enough to warrant its own thread.

He wrote:

The 0V rail of the preamp should be a short buss wire about 100mm long
with ends connected to the RCA plug 0V bodies at inputs and outputs.
ALL parts with OV connections should be made to this buss,
and the CHASSIS or CASE connected via a 5 watt 27 ohm R, and the case
taken to the green/yellow wire to the wall socket so the case can't
become live to mains or the B+. There should be NO direct connection of
the OV buss to the case.
--


I ask:

In other words the mains supply case should be bonded to the case,
and the 0V (signal grounds) taken to the ground point via a 27 Ohm
5W resistor?

Why is this?

My experience with ground buss amps is limited. I have never been
able to make them quiet enough. I found that the exact position in
which a wire was placed on the buss was critical, and that a difference
was audible.It may be there is something lacking in my implementation
of the buss.

I prefer to use a star ground, as follows. Earth (ground) connection
from the supply - the only green yellow wire in the amplifier is taken
straight to the chassis bonding screw. The input and output RCA
signal connectors I used are the isolated type (Neutrik NF2D)

http://www.neutrik.com/uk/en/audio/2...-0_detail.aspx

I run a separate wire (black) from each of the RCA input and output
ground tags to the star ground. Signal wires on the input side have
their shields connected at the RCA socket end only.

On the psu, I run separate grounds (heavier wire) from each cap
separately to the star. They are not linked. The only exception to
this is the 1st (reservoir) electrolytic , which is connected directly
to the neg terminal of the FW bridge, and then to the star.

This is a topology I have seen used on amps that perform well,
and has been taught to me as a good solution.
It seems to work. My 50W power amp has only 80µV
of noise (-108dB) and no audible hum even with the ear
against the speaker (Tannoy Gold 15 inch)

Regards to all
Iain

[Patrick Turner]

Iain Churches wrote:

Patrick posted some interesting facts about ground buss
connections, which I have extracted from another thread
and pasted here, because I think the subject is important
enough to warrant its own thread.

He wrote:

The 0V rail of the preamp should be a short buss wire about 100mm long
with ends connected to the RCA plug 0V bodies at inputs and outputs.
ALL parts with OV connections should be made to this buss,
and the CHASSIS or CASE connected via a 5 watt 27 ohm R, and the case
taken to the green/yellow wire to the wall socket so the case can't
become live to mains or the B+. There should be NO direct connection of
the OV buss to the case.
--

I ask:

In other words the mains supply case should be bonded to the case,
and the 0V (signal grounds) taken to the ground point via a 27 Ohm
5W resistor?

Why is this?

Because chassis can have magnetically induced voltages in them,
they should never be used for the 0V rail.

And where you have preamp and power amp each with chassis used as the
0V, then
you can all too easily have a horrid earth loop with noise injected to
the signal
path. The use of the 27 ohms is a much higher resistance than the shield
of a coax cable
which is at 0V, so there won't be a significant signal across this
shield wire
between to components if the chassis are not strapped to the 0V buss.


My experience with ground buss amps is limited. I have never been
able to make them quiet enough. I found that the exact position in
which a wire was placed on the buss was critical, and that a difference
was audible.It may be there is something lacking in my implementation
of the buss.

It does take some getting right.

Especially in MC amps for unbalanced MC cart inputs, but I manage it all
easily enough
to keep doing it.


I prefer to use a star ground, as follows. Earth (ground) connection
from the supply - the only green yellow wire in the amplifier is taken
straight to the chassis bonding screw. The input and output RCA
signal connectors I used are the isolated type (Neutrik NF2D)

Nothing wrong with star grounding, ie all bits with a 0V terminal
go to ONE point, but in fact you don't have to and a length of thick
wire
is fine.
This buss should never be directly connected to the chassis.

Thge chassis ALWAYS MUST be EARTHED via the green/yellow wire.

The 0V should be connected indirectly to the chassis but via a lowish
resistance which is
maybe 100 times the resistance of the coax wire shielding between
components.



http://www.neutrik.com/uk/en/audio/2...-0_detail.aspx

I run a separate wire (black) from each of the RCA input and output
ground tags to the star ground. Signal wires on the input side have
their shields connected at the RCA socket end only.

On the psu, I run separate grounds (heavier wire) from each cap
separately to the star. They are not linked. The only exception to
this is the 1st (reservoir) electrolytic , which is connected directly
to the neg terminal of the FW bridge, and then to the star.

After awhile, you realize what 0V wires you really need, and
which ones are a must and which are just not a must.

This is a topology I have seen used on amps that perform well,
and has been taught to me as a good solution.
It seems to work. My 50W power amp has only 80µV
of noise (-108dB) and no audible hum even with the ear
against the speaker (Tannoy Gold 15 inch)

If the gain of a power amp is say 20x, or +26dB,
then if the noise is determined by the input tube
and measured with its grid taken to 0V,
and if the input tube has equivalent input grid noise of
4 uV, somewhat noisy really when some good tubes measure 1uV
with dc heaters, then your noise will be 80uV at the output.

But you're lucky. A preamp may not be any better, and
produce 50uV, and this converts to 1,000 uV, or 1 mV.

Relative to an average signal level of 1 Vrms you'd have an SNR of only
60dB unweighted.
But that's good enough for most folks though; they simply cannot hear
that 1mV of noise, ie, hiss and PS hum.
Many SS amps fail to be as quiet as ppl think they mostly are.

But with better than 60dB unweighted, most tube amps are fine about
noise.

In fact the howl from the OPT caused by the magnetic currents at audio F
are in fact at a much higher sonic level than the noise buried within
the signal.
SE amps are the worser in this regard.

The best OPT have been potted to reduce their howl.

Try connection of a dummy R load and turning up the gain with a music
signal
and you'll see what I mean.

The noise of the OPT is as unwanted as are the vibrations from speaker
cabinets excited by sound waves inside the cabs.

Audio gear that isn't meant to have any sound during operation
needs careful design!

My latest 845 amp creations tested with less than 1mV of hum in the
signal
but I sure had to pot the OPT.
Then I found the PT was a bit hummy with so many rectifiers on it that
have had to place that on a separate chassis and pot it very well.
Mains is turned on by a relay in the PSU chassis so NO mains wires
go into the power amp chassis and no ac hums in rails either,
and no very subtle vibration from the mains tranny shaking the
845 cathodes or other tubes.
In such a set up in my 845s, or in my 300 watters as seen at
http://www.turneraudio.com.au/300monobloc.html
there cannot be star grounding, but noise figures are extremely low, and
good.




Patrick Turner.





Regards to all
Iain

[Iain Churches[_2_]]

"Patrick Turner" wrote in message
...


Iain Churches wrote:

Patrick posted some interesting facts about ground buss
connections, which I have extracted from another thread
and pasted here, because I think the subject is important
enough to warrant its own thread.

He wrote:

The 0V rail of the preamp should be a short buss wire about 100mm long
with ends connected to the RCA plug 0V bodies at inputs and outputs.
ALL parts with OV connections should be made to this buss,
and the CHASSIS or CASE connected via a 5 watt 27 ohm R, and the case
taken to the green/yellow wire to the wall socket so the case can't
become live to mains or the B+. There should be NO direct connection of
the OV buss to the case.
--

I ask:

In other words the mains supply case should be bonded to the case,
and the 0V (signal grounds) taken to the ground point via a 27 Ohm
5W resistor?

Why is this?

Because chassis can have magnetically induced voltages in them,
they should never be used for the 0V rail.

And why 25W?

Iain

[Patrick Turner]

Iain Churches wrote:

"Patrick Turner" wrote in message
...


Iain Churches wrote:

Patrick posted some interesting facts about ground buss
connections, which I have extracted from another thread
and pasted here, because I think the subject is important
enough to warrant its own thread.

He wrote:

The 0V rail of the preamp should be a short buss wire about 100mm long
with ends connected to the RCA plug 0V bodies at inputs and outputs.
ALL parts with OV connections should be made to this buss,
and the CHASSIS or CASE connected via a 5 watt 27 ohm R, and the case
taken to the green/yellow wire to the wall socket so the case can't
become live to mains or the B+. There should be NO direct connection of
the OV buss to the case.
--

I ask:

In other words the mains supply case should be bonded to the case,
and the 0V (signal grounds) taken to the ground point via a 27 Ohm
5W resistor?

Why is this?

Because chassis can have magnetically induced voltages in them,
they should never be used for the 0V rail.

And why 25W?

I said 5W, but 25W would be OK.

Because you don't want that R to go open, ever, or the whole audio
circuit
IS NOT REFERENCED TO THE CHASSIS AND EARTH, something I feel is
important.

If the B+ becomes shorted to the chassis, you want the fuse to blow
because of that short.
You DON'T want a 27 ohm x 1/4 watt R to fuse open in an instant, leaving
the 0V rail at +500V,
including the OV rail and the speaker wires....

Hope for the best with your amps, but ALWAYS prepare for the worst!

Patrick Turner.




Iain

[John Byrns]

In article ,
Patrick Turner wrote:

Iain Churches wrote:

And why 25W?

I said 5W, but 25W would be OK.

Because you don't want that R to go open, ever, or the whole audio
circuit
IS NOT REFERENCED TO THE CHASSIS AND EARTH, something I feel is
important.

If the B+ becomes shorted to the chassis, you want the fuse to blow
because of that short.
You DON'T want a 27 ohm x 1/4 watt R to fuse open in an instant, leaving
the 0V rail at +500V,
including the OV rail and the speaker wires....

I am having trouble getting my mind around this. I am standing on my
head trying to get a good perspective on the question. Wouldn't it be
-500V on the "OV rail and the speaker wires" if the B+ shorted to the
chassis, or does it just look that way to me because I am standing on my
head?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Eeyore]

John Byrns wrote:

Patrick Turner wrote:
Iain Churches wrote:

And why 25W?

I said 5W, but 25W would be OK.

Because you don't want that R to go open, ever, or the whole audio
circuit
IS NOT REFERENCED TO THE CHASSIS AND EARTH, something I feel is
important.

If the B+ becomes shorted to the chassis, you want the fuse to blow
because of that short.
You DON'T want a 27 ohm x 1/4 watt R to fuse open in an instant, leaving
the 0V rail at +500V,
including the OV rail and the speaker wires....

I am having trouble getting my mind around this. I am standing on my
head trying to get a good perspective on the question. Wouldn't it be
-500V on the "OV rail and the speaker wires" if the B+ shorted to the
chassis, or does it just look that way to me because I am standing on my
head?

You are correct.

Graham

[Patrick Turner]

John Byrns wrote:

In article ,
Patrick Turner wrote:

Iain Churches wrote:

And why 25W?

I said 5W, but 25W would be OK.

Because you don't want that R to go open, ever, or the whole audio
circuit
IS NOT REFERENCED TO THE CHASSIS AND EARTH, something I feel is
important.

If the B+ becomes shorted to the chassis, you want the fuse to blow
because of that short.
You DON'T want a 27 ohm x 1/4 watt R to fuse open in an instant, leaving
the 0V rail at +500V,
including the OV rail and the speaker wires....

I am having trouble getting my mind around this. I am standing on my
head trying to get a good perspective on the question. Wouldn't it be
-500V on the "OV rail and the speaker wires" if the B+ shorted to the
chassis, or does it just look that way to me because I am standing on my
head?

Regards,

John Byrns

Indeed you are right, but if the 27R went open, and B+ shorted to the
chassis, then the chassis would try to go +ve, and 0V rail and speakers
etc would try to go
very negative. BUT, if you had a preamp attatched, with coaxial RCA
cable connecting the power amp 0V to preamp 0V, and there was a similar
27 ohms in the preamp
to its chassis and Earth, then the preamp's "ground lifting resistance"
of 27ohms
might also fuse open, and you'd get a high -Ve voltage at the RCA 0V
terminal and speakers
so if you touched this or speakers and the chassis which IS at earth
potential,
you'd get a bad shock.

So hence the need for the ground lift R to be rugged enough so when such
a B+ to ground short
occurs, a mains fuse will blow because of the low load on the power
supply.

Its very unlikely you'd ever get the B+ shorting to the chassis.
Its much more likely that a B+ short to 0V would occur, through a
stuffed output tube,
or from P to S on the OPT, or from an arc across from pin 3 to pin 2 on
octal sockets.
So its likely that the 27R isn't ever exposed to a sudden amount of high
current.

But **** happens, so prepare for it.

The point I was making is that all chassis should be well connected to
EARTH,
and then if ground lift between chassis and 0V rail is the standard way
to lower noise,
then for safety use a high wattage low value
ground lift R which still has MUCH more resistance than the coax outer
shield of an interconnect
to some other component such as preamp or cd player, tuner etc.

Patrick Turner.


--
Surf my web pages at, http://fmamradios.com/

[Peter Wieck]

On Mar 2, 8:33*am, Patrick Turner wrote:

Good Stuff.

Patrick, reducing your and Iain's post to a very few salient points,
am I correct in deriving "best practice" as follows:

a) The chassis must be grounded to the mains ground
b) The circuit ground should be separate and isolated from the chassis/
case, connected via the 27ohm@5W resistor.
c) The circuit ground should be as short as possible and loops (such
as connecting signal-shields at both ends) are to be avoided.

I see safety addresssed by grounding the chassis directly to the mains
ground. I see any excess potentials within the circuit bleeding to the
case. I also see isolating the circuit from the case helping when
other components are connected (and grounded).

It seems that this solution is the one that was actually put into
place on the humming pre-amp...

Thanks in advance.

Peter Wieck
Wyncote, PA

[Iain Churches[_2_]]

"Peter Wieck" wrote in message
...
On Mar 2, 8:33 am, Patrick Turner wrote:

Good Stuff.

Patrick, reducing your and Iain's post to a very few salient points,
am I correct in deriving "best practice" as follows:

a) The chassis must be grounded to the mains ground

Most books seem to stress this, and the amp builders
I have know seem to have always paid particular attention to it.
It is critical for safety.

b) The circuit ground should be separate and isolated from the chassis/
case, connected via the 27ohm@5W resistor.

I have seen boards in a setero amp with the grounds separated
by a 10 Ohm resistor, but this is the first time I recall hearing about
this excellent 27 Ohm 5W solution. I would like to try it.


c) The circuit ground should be as short as possible and loops (such
as connecting signal-shields at both ends) are to be avoided.

A friend of mine in the UK was I was young was a prototype
wireman. He used to make up all sort of interesting circuits for
the studio where he worked. He taught me that the input wirirng
should be grounded at the input connector (connector isolated
from the chassis)

I see safety addresssed by grounding the chassis directly to the mains
ground. I see any excess potentials within the circuit bleeding to the
case. I also see isolating the circuit from the case helping when
other components are connected (and grounded).

There seem to be several ways to build a quiet hum-free amp.
Most people seem to be happy with an amplifier with no hum
or hiss audible from the listening position. With careful work,
it is possible to build an amplifier which is dead silent even with
your ear against the speaker.

http://www.kolumbus.fi/iain.churches...em/C50_002.jpg


Regards to all
Iain

[Eeyore]

Iain Churches wrote:

"Peter Wieck" wrote

Good Stuff.

Patrick, reducing your and Iain's post to a very few salient points,
am I correct in deriving "best practice" as follows:

a) The chassis must be grounded to the mains ground

But it doesn't have to be if your transformer and other mains wiring meets
Class II.

Bear in mind that safety earthing isn't universal even in Europe. I gather
that Denmark ? in particular has many unearthed outlets.

Graham

[John Byrns]

In article ,
Eeyore wrote:

Iain Churches wrote:

"Peter Wieck" wrote

Good Stuff.

Patrick, reducing your and Iain's post to a very few salient points,
am I correct in deriving "best practice" as follows:

a) The chassis must be grounded to the mains ground

But it doesn't have to be if your transformer and other mains wiring meets
Class II.

Bear in mind that safety earthing isn't universal even in Europe. I gather
that Denmark ? in particular has many unearthed outlets.

What does Europe have to do with this issue, I thought that the presence
of "safety earthing", or lack thereof, was mostly an issue of how old
the building is, or are you saying that in Europe there was a directive
that all outlets without "safety earthing" must be upgraded?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Peter Wieck]

On Mar 4, 8:24*am, "Iain Churches" wrote:

With careful work,
it is possible to build an amplifier which is dead silent even with
your ear against the speaker.

Aren't they all supposed to be that way?

Peter Wieck
Wyncote, PA

[Iain Churches[_2_]]

"Peter Wieck" wrote in message
...
On Mar 4, 8:24 am, "Iain Churches" wrote:

With careful work,
it is possible to build an amplifier which is dead silent even with
your ear against the speaker.

Aren't they all supposed to be that way

Indeed they are "supposed" to be.
Iain

[Ian Iveson]

Iain Churches wrote:

My experience with ground buss amps is limited. I have
never been
able to make them quiet enough. I found that the exact
position in
which a wire was placed on the buss was critical, and that
a difference
was audible.It may be there is something lacking in my
implementation
of the buss.

I guess the order in which connections are made along a bus
is significant. If you think of the bus as a resistor, then
a high-current return placed furthest from the ground will
produce a voltage gradient along the bus. If the next
connection is, say, the signal ground from the first gain
stage, that voltage could be significant.

OTOH, if the connections to the bus are made in order of
highest current, the voltages they produce will be
minimised.

But perhaps there is countervailing argument? If a sensitive
connection is close to the ground, then a voltage produced
by a high-current connection further along will be
attenuated. So perhaps the order is important, but it
doesn't matter to which end of the bus the ground is
connected? What you don't want is a high-current connection
and a sensitive connection both distant from ground.

I find a genuine star earth is hard to implement if there
are many ground connections to make. Exactly how do you
fashion a star?

The signal ground must be safe to touch if it is brought out
to exposed external connectors. If a resistance is placed
between the 0V and chassis ground, then it should be a low
enough value and high enough power to ensure that the fuse,
and not the resistor, will blow quickly if the signal ground
becomes live due to some fault. Perhaps some statutory
regulations apply?

Not a "pro", or an "expert", as usual, thankfully.

Ian

[Iain Churches[_2_]]

"Ian Iveson" wrote in message
.uk...
Iain Churches wrote:

My experience with ground buss amps is limited. I have never been
able to make them quiet enough. I found that the exact position in
which a wire was placed on the buss was critical, and that a difference
was audible.It may be there is something lacking in my implementation
of the buss.

I guess the order in which connections are made along a bus is
significant. If you think of the bus as a resistor, then a high-current
return placed furthest from the ground will produce a voltage gradient
along the bus. If the next connection is, say, the signal ground from the
first gain stage, that voltage could be significant.

OTOH, if the connections to the bus are made in order of highest current,
the voltages they produce will be minimised.

But perhaps there is countervailing argument? If a sensitive connection is
close to the ground, then a voltage produced by a high-current connection
further along will be attenuated. So perhaps the order is important, but
it doesn't matter to which end of the bus the ground is connected? What
you don't want is a high-current connection and a sensitive connection
both distant from ground.


Very interesting. Thanks.
Next time I build a prototype, I will try this out.

I find a genuine star earth is hard to implement if there are many ground
connections to make. Exactly how do you fashion a star?

My stars are not symnmetrical with the ground point in the
middle if that what you mean. On a power amp I put the
chassis bonding terminal close to the AC socket, and on
a preamp close to input 1.

I usually make up the star on the bench, as a cableform,
and then fit, trim the loose ends and solder.

The signal ground must be safe to touch if it is brought out to exposed
external connectors. If a resistance is placed between the 0V and chassis
ground, then it should be a low enough value and high enough power to
ensure that the fuse, and not the resistor, will blow quickly if the
signal ground becomes live due to some fault. Perhaps some statutory
regulations apply?

Not a "pro", or an "expert", as usual, thankfully.

Ditto. But thanks for your thoughts, Ian. This is an
interesting business.

Regards
Iain

[Henry Pasternack[_2_]]

This is something I found on the Web. It was apparently posted on the
usenet, perhaps to this group or maybe rec.audio.tech, many years ago,
althought I'm unable to find any evidence of the article in the Google
archives.

I offer the article without comment, and don't make any claims as to
its accuracy. Perhaps there is some value to what is written, as quite
a few people have linked to or reposted copies on their websites. The
author has left his phone number and email address in the signature. If
you have any issues, you may wish to contact him there. I would, in fact,
be very interested in hearing if anyone manages to contact him that way.

-Henry

--- BEGIN REPOSTED ARTICLE ---

Someone suggested I write an article on power and grounding techniques
for equipment construction. This is a topic I can't really do justice to;
whole books have been written on the subject. In the spirit of reckless
misinformation, I'll try to summarize a few hints. Consider this an
introduction for advanced beginners, but bear in mind there is room for
expanding and improving the information contained below.

-Henry

* * * * * * *

If circuits worked exactly as they are drawn on schematics, there'd
be no need to worry about power and ground topologies or wire routing.
Instead, we could just wire up all the components willy-nilly making
sure only that all the specified connections were complete. In the
real world of electromagnetics, things aren't quite so convenient:

1) Ground isn't really ground. Ideally, ground is a zero-voltage
reference that never varies. In fact, every ground bus that
carries current has small voltage variations across its length
due to small but significant resistance.

2) Stray capacitance. Two parallel conductors form a capacitor
across which unexpected AC currents can flow.

3) Electromagnetic induction. By definition, every circuit forms
a loop. When a changing magnetic flux (due, perhaps, to the
strong field from a transformer or choke) exists in the loop,
a current will be induced.

Now I'll talk briefly about the consequences of these real-world effects.

Ground Loops.

A ground loop occurs when a ground circuit encloses a loop and a
source of energy causes current to flow through the loop. If the flow
of current causes a voltage drop in a sensitive gain stage, the
voltage can be amplified and appear as noise. A typical ground loop
occurs in the amplifiers I just built. Because I use grounded power
cords, the chassis of my monoblocks are joined electrically at the
power outlet. The signal grounds are connected (via the input jacks
and interconnect cable shields) at the preamp output terminals. The
signal grounds are also connected to chassis ground internally in each
amplifier. The result is a loop that picks up inductive noise or
leakage currents and couples them into the amplifier gain circuitry,
causing an audible hum in the speakers. The quick solution is to
break the loop by using a three-to-two wire converter on one power
cord. A better fix is to "lift" the internal connection between
signal and chassis ground in one or both amplifiers and install a 10
Ohm resistor. The resistor is a significant obstacle to the flow of
current compared to the stout power cords and effectively breaks the
loop.

Another sort of ground loop occurs internal to equipment, but for
a different reason. In any circuit, one can trace the flow of power
from the supply, out to various circuits, and back to ground. Each
power supply typically provides current to more than one circuit
branches. Topologically speaking, the branches form intermeshing loops
that originate and terminate at the power supply. In the regions
where the loops overlap (share common conductors), voltage drops in
one loop can impose unwanted signals in another.

When a circuit loop overlaps on the supply side of a power source,
the designer will use parallel capacitors and/or series resistors or
inductors to block or shunt away signal currents on the supply rails.
The series components keep unwanted signals from leaving their circuit
branches, and the parallel caps redirect those that escape to ground.
Purifying the supply rails in this manner is called "decoupling".
Decoupling also helps to rid the rails of noise that creeps in due
to magnetic or electrostatic fields (more on theis later).

On the ground side, it's very important to keep the return currents
separate from one another as they work their way back to the common
power supply terminal. Practically speaking, we want to minimize
overlapping loops in the ground circuit. This is done by using a
short, thick ground bus of very low resistance and connecting all
ground wires to it. The most effective solution is to provide
separate conductors for each ground current source and return them all
to a single point; this is known as "star" grounding and is standard
practice in audio design. In tube gear wired point-to-point, it may
be sufficient to route a heavy ground wire around the edge of the
circuit and make all connections directly to it at the closest
convenient point.

Inductive and Capacitive Coupling.

Every conductor carrying a signal current generates an electromag-
netic field that can couple to other circuit elements. In addition,
the environment in which equipment is used is loaded with power line
and radio frequency fields that can get into sensitive circuits and
cause noise and distortion. I'll give some very quick information on
minimizing these problems.

Electrostatic fields and capacitive coupling can be reduced by
distance and shielding. A grounded metal shield stops a static field
in its tracks by imposing an equipotential barrier. To keep the field
from sneaking past the shield, the sensitive circuit must be
completely enclosed. Capacitance decreases as the reciprocal of the
distance between conductors, so separating sensitive wires as much as
possible is the other solution to stray electrostatic coupling.
Keeping circuit impedances low will help a great deal by raising the
frequency at which the coupling becomes a problem (hopefully beyond
the bandwidth of the circuit or offending signal source).

Shielding with non-ferrous metals is useless against magnetic
induction. The answer to induced hum of magnetic origin is to keep
circuit loop area to a minimum. The smaller the loop, the smaller the
volume of magnetic flux enclosed and the lower the induced current.
For this reason, power and signal wires should be twisted tightly with
their ground conductors whenever possible. This increases capacitance
between the conductors, so watch out in high-impedance signal
circuits. Plan the layout of hum-sensitive circuits so that the
enclosed area is kept to a minimum. Place transformers, chokes, and
high-current conductors as far as possible from these circuits. Iron
or mu-metal shields may be of some help, but I wouldn't count on them.
It may be better to put the power supply in a separate box for
sensitive preamps.

In most cases it is good advice to keep wire runs short, to twist
conductors carrying opposite currents together (signal and ground,
power supply lines, filament wires, etc), to route wires near the
chassis, and to physically separate high-gain stages from components
and wires that carry high currents.

Practical Advice.

When laying out your circuit, look at the schematic and identify
all of the separate current loops from supply to circuit to ground.
Then come up with a scheme to keep these loops as separate as possible
on the ground side. The biggest source of ground current in most
amplifiers is the power supply ripple in the main filter capacitor.
This current, which contains noisy, high-current rectifier current
spikes, usually flows back to the power transformer through the
secondary center tap. A good strategy is to connect this lead
directly to the filter capacitor common terminal. Then run a short
stub (could be a half inch) to a second point that will serve as a
star ground for the signal circuitry. Another source of high current
ground flow in a power amplifier is the common lead from the speaker
terminals. You'll want to make sure the low-level signal star ground
does not have output ground currents flowing through it or you'll
increase the possibility of instability. What I'm describing here
is really a "star of stars" grounding scheme. If you view every
conductor as a resistor and try to keep associated voltage drops
from crossing loops, you'll end up with the best ground scheme.

Here's the grounding topology in my tube power amps:

The main electrolytic filter caps and driver decoupling caps are
all mounted on one circuit board. The three decoupling caps share
a common, wide circuit board ground trace. The ground for the main
filter cap, for the transformer center tap, and for the decoupling
caps all come together in one small area of the circuit board. The
driver stage ground points are located close together near the central
ground, but "out of the way" of the rectifier current flow. I slotted
the copper strategically to "steer" the charging current current away
from the driver-stage grounds (defining the stub conductor described
above).

The following wires attach to the driver-stage ground area on
the filter cap board:

1) A single ground wire from a local "star ground" on the driver
board that connects the input jack shield, global feedback
cable shield, and the input stage bias resistors grounds.

2) A single ground wire carrying the return current from the
B- supply. This supply is floating and connected to the
driver board by a tightly twisted pair. B- is bypassed
locally by electrolytic and film capacitors. A second
"star ground" on the driver board connects all the bypass
caps. The rationale is that low frequency hum currents
are handled by the electrolytics and don't make it off
the filter circuit board. Local bypass caps keep RF
signals on the supply lines from getting onto the driver
board. The current-sourced differential design greatly
reduces the coupling of the input and driver signal currents,
in the ground leads, justifying the use of a single B- supply
and ground wire. I agonized over this layout for a while,
but it seems to work quite well.

3) A ground wire from the negative bias board. The bias supply
is also floating and connected to the bias board (which also
holds the output coupling capacitors) via a twisted pair.
There is a 0.47uF film capacitor bypass on the bias board.

The common lead from the output tube cathodes connects to a
ground point that runs directly to the main star ground without
passing through the driver ground node. The power transformer
center tap comes in on its own stub directly to the main capacitor
common terminal.

The two B+ wires to the driver stage are very short and connect
directly to the driver board. The output stage B+ is supplied to
the output transformer primary center tap from a circuit area close
to the main filter cap positive terminal. The power cord ground
wire is connected to the chassis at a convenient lug near the back
panel AC socket. The filter cap board has a ground wire to a lug
on the chassis as well (and perhaps this is why I have a ground loop;
I need to experiment with the location of my connection from signal
ground to chassis ground).

A note on solid-state Class AB amplifiers and power rail routing.

The current drawn by the two halves of a Class AB output stage
is rectified and has heavy harmonic components. Because solid-state
amps draw a lot of current from the rails, there is a good chance of
inducing signal-related noise in low-level circuitry unless careful
layout is used. A good technique is to twist the positive and
negative rail leads together and route them directly to the output
devices, keeping them away from low-level conductors. The rails are
usually bypassed on the circuit board by electrolytic capacitors
which should have a dedicated ground wire for their common terminals.
This wire should be kept apart from the small signal ground lead.
Care should be taken to keep the negative feedback connection, which
typically connects to a node near the output output transistors, from
coupling to the power leads. A sophisticated design will use multiple
electrolytic capacitors mounted right at the output devices and
clever circuit board layout. I believe the famous Analog Devices
application note on a wideband current feedback amplifier has some
useful notes on this problem (does anyone have a reference?).

--

Henry A. Pasternack
Member Scientific Staff (514) 761-8734 (phone)
Bell Northern Research, Montreal (514) 761-8509 (fax)

[John Byrns]

I remember the guy that originally posted that article, he used to post
on the usenet newsgroup "rec.audio.high-end", it seems unlikely you
would have found it on the web.


Regards,

John Byrns


In article ,
Henry Pasternack wrote:

This is something I found on the Web. It was apparently posted on the
usenet, perhaps to this group or maybe rec.audio.tech, many years ago,
althought I'm unable to find any evidence of the article in the Google
archives.

I offer the article without comment, and don't make any claims as to
its accuracy. Perhaps there is some value to what is written, as quite
a few people have linked to or reposted copies on their websites. The
author has left his phone number and email address in the signature. If
you have any issues, you may wish to contact him there. I would, in fact,
be very interested in hearing if anyone manages to contact him that way.

-Henry

--- BEGIN REPOSTED ARTICLE ---

Someone suggested I write an article on power and grounding techniques
for equipment construction. This is a topic I can't really do justice to;
whole books have been written on the subject. In the spirit of reckless
misinformation, I'll try to summarize a few hints. Consider this an
introduction for advanced beginners, but bear in mind there is room for
expanding and improving the information contained below.

-Henry

* * * * * * *

If circuits worked exactly as they are drawn on schematics, there'd
be no need to worry about power and ground topologies or wire routing.
Instead, we could just wire up all the components willy-nilly making
sure only that all the specified connections were complete. In the
real world of electromagnetics, things aren't quite so convenient:

1) Ground isn't really ground. Ideally, ground is a zero-voltage
reference that never varies. In fact, every ground bus that
carries current has small voltage variations across its length
due to small but significant resistance.

2) Stray capacitance. Two parallel conductors form a capacitor
across which unexpected AC currents can flow.

3) Electromagnetic induction. By definition, every circuit forms
a loop. When a changing magnetic flux (due, perhaps, to the
strong field from a transformer or choke) exists in the loop,
a current will be induced.

Now I'll talk briefly about the consequences of these real-world effects.

Ground Loops.

A ground loop occurs when a ground circuit encloses a loop and a
source of energy causes current to flow through the loop. If the flow
of current causes a voltage drop in a sensitive gain stage, the
voltage can be amplified and appear as noise. A typical ground loop
occurs in the amplifiers I just built. Because I use grounded power
cords, the chassis of my monoblocks are joined electrically at the
power outlet. The signal grounds are connected (via the input jacks
and interconnect cable shields) at the preamp output terminals. The
signal grounds are also connected to chassis ground internally in each
amplifier. The result is a loop that picks up inductive noise or
leakage currents and couples them into the amplifier gain circuitry,
causing an audible hum in the speakers. The quick solution is to
break the loop by using a three-to-two wire converter on one power
cord. A better fix is to "lift" the internal connection between
signal and chassis ground in one or both amplifiers and install a 10
Ohm resistor. The resistor is a significant obstacle to the flow of
current compared to the stout power cords and effectively breaks the
loop.

Another sort of ground loop occurs internal to equipment, but for
a different reason. In any circuit, one can trace the flow of power
from the supply, out to various circuits, and back to ground. Each
power supply typically provides current to more than one circuit
branches. Topologically speaking, the branches form intermeshing loops
that originate and terminate at the power supply. In the regions
where the loops overlap (share common conductors), voltage drops in
one loop can impose unwanted signals in another.

When a circuit loop overlaps on the supply side of a power source,
the designer will use parallel capacitors and/or series resistors or
inductors to block or shunt away signal currents on the supply rails.
The series components keep unwanted signals from leaving their circuit
branches, and the parallel caps redirect those that escape to ground.
Purifying the supply rails in this manner is called "decoupling".
Decoupling also helps to rid the rails of noise that creeps in due
to magnetic or electrostatic fields (more on theis later).

On the ground side, it's very important to keep the return currents
separate from one another as they work their way back to the common
power supply terminal. Practically speaking, we want to minimize
overlapping loops in the ground circuit. This is done by using a
short, thick ground bus of very low resistance and connecting all
ground wires to it. The most effective solution is to provide
separate conductors for each ground current source and return them all
to a single point; this is known as "star" grounding and is standard
practice in audio design. In tube gear wired point-to-point, it may
be sufficient to route a heavy ground wire around the edge of the
circuit and make all connections directly to it at the closest
convenient point.

Inductive and Capacitive Coupling.

Every conductor carrying a signal current generates an electromag-
netic field that can couple to other circuit elements. In addition,
the environment in which equipment is used is loaded with power line
and radio frequency fields that can get into sensitive circuits and
cause noise and distortion. I'll give some very quick information on
minimizing these problems.

Electrostatic fields and capacitive coupling can be reduced by
distance and shielding. A grounded metal shield stops a static field
in its tracks by imposing an equipotential barrier. To keep the field
from sneaking past the shield, the sensitive circuit must be
completely enclosed. Capacitance decreases as the reciprocal of the
distance between conductors, so separating sensitive wires as much as
possible is the other solution to stray electrostatic coupling.
Keeping circuit impedances low will help a great deal by raising the
frequency at which the coupling becomes a problem (hopefully beyond
the bandwidth of the circuit or offending signal source).

Shielding with non-ferrous metals is useless against magnetic
induction. The answer to induced hum of magnetic origin is to keep
circuit loop area to a minimum. The smaller the loop, the smaller the
volume of magnetic flux enclosed and the lower the induced current.
For this reason, power and signal wires should be twisted tightly with
their ground conductors whenever possible. This increases capacitance
between the conductors, so watch out in high-impedance signal
circuits. Plan the layout of hum-sensitive circuits so that the
enclosed area is kept to a minimum. Place transformers, chokes, and
high-current conductors as far as possible from these circuits. Iron
or mu-metal shields may be of some help, but I wouldn't count on them.
It may be better to put the power supply in a separate box for
sensitive preamps.

In most cases it is good advice to keep wire runs short, to twist
conductors carrying opposite currents together (signal and ground,
power supply lines, filament wires, etc), to route wires near the
chassis, and to physically separate high-gain stages from components
and wires that carry high currents.

Practical Advice.

When laying out your circuit, look at the schematic and identify
all of the separate current loops from supply to circuit to ground.
Then come up with a scheme to keep these loops as separate as possible
on the ground side. The biggest source of ground current in most
amplifiers is the power supply ripple in the main filter capacitor.
This current, which contains noisy, high-current rectifier current
spikes, usually flows back to the power transformer through the
secondary center tap. A good strategy is to connect this lead
directly to the filter capacitor common terminal. Then run a short
stub (could be a half inch) to a second point that will serve as a
star ground for the signal circuitry. Another source of high current
ground flow in a power amplifier is the common lead from the speaker
terminals. You'll want to make sure the low-level signal star ground
does not have output ground currents flowing through it or you'll
increase the possibility of instability. What I'm describing here
is really a "star of stars" grounding scheme. If you view every
conductor as a resistor and try to keep associated voltage drops
from crossing loops, you'll end up with the best ground scheme.

Here's the grounding topology in my tube power amps:

The main electrolytic filter caps and driver decoupling caps are
all mounted on one circuit board. The three decoupling caps share
a common, wide circuit board ground trace. The ground for the main
filter cap, for the transformer center tap, and for the decoupling
caps all come together in one small area of the circuit board. The
driver stage ground points are located close together near the central
ground, but "out of the way" of the rectifier current flow. I slotted
the copper strategically to "steer" the charging current current away
from the driver-stage grounds (defining the stub conductor described
above).

The following wires attach to the driver-stage ground area on
the filter cap board:

1) A single ground wire from a local "star ground" on the driver
board that connects the input jack shield, global feedback
cable shield, and the input stage bias resistors grounds.

2) A single ground wire carrying the return current from the
B- supply. This supply is floating and connected to the
driver board by a tightly twisted pair. B- is bypassed
locally by electrolytic and film capacitors. A second
"star ground" on the driver board connects all the bypass
caps. The rationale is that low frequency hum currents
are handled by the electrolytics and don't make it off
the filter circuit board. Local bypass caps keep RF
signals on the supply lines from getting onto the driver
board. The current-sourced differential design greatly
reduces the coupling of the input and driver signal currents,
in the ground leads, justifying the use of a single B- supply
and ground wire. I agonized over this layout for a while,
but it seems to work quite well.

3) A ground wire from the negative bias board. The bias supply
is also floating and connected to the bias board (which also
holds the output coupling capacitors) via a twisted pair.
There is a 0.47uF film capacitor bypass on the bias board.

The common lead from the output tube cathodes connects to a
ground point that runs directly to the main star ground without
passing through the driver ground node. The power transformer
center tap comes in on its own stub directly to the main capacitor
common terminal.

The two B+ wires to the driver stage are very short and connect
directly to the driver board. The output stage B+ is supplied to
the output transformer primary center tap from a circuit area close
to the main filter cap positive terminal. The power cord ground
wire is connected to the chassis at a convenient lug near the back
panel AC socket. The filter cap board has a ground wire to a lug
on the chassis as well (and perhaps this is why I have a ground loop;
I need to experiment with the location of my connection from signal
ground to chassis ground).

A note on solid-state Class AB amplifiers and power rail routing.

The current drawn by the two halves of a Class AB output stage
is rectified and has heavy harmonic components. Because solid-state
amps draw a lot of current from the rails, there is a good chance of
inducing signal-related noise in low-level circuitry unless careful
layout is used. A good technique is to twist the positive and
negative rail leads together and route them directly to the output
devices, keeping them away from low-level conductors. The rails are
usually bypassed on the circuit board by electrolytic capacitors
which should have a dedicated ground wire for their common terminals.
This wire should be kept apart from the small signal ground lead.
Care should be taken to keep the negative feedback connection, which
typically connects to a node near the output output transistors, from
coupling to the power leads. A sophisticated design will use multiple
electrolytic capacitors mounted right at the output devices and
clever circuit board layout. I believe the famous Analog Devices
application note on a wideband current feedback amplifier has some
useful notes on this problem (does anyone have a reference?).

--

Henry A. Pasternack
Member Scientific Staff (514) 761-8734 (phone)
Bell Northern Research, Montreal (514) 761-8509 (fax)

--
Surf my web pages at, http://fmamradios.com/

[Henry Pasternack[_2_]]

"John Byrns" wrote in message
...
I remember the guy that originally posted that article, he used to post
on the usenet newsgroup "rec.audio.high-end", it seems unlikely you
would have found it on the web.

http://ai.kaist.ac.kr/~suh/DIY/ground

[Andre Jute]

Porno Pas wrote:

This is something I found on the Web.

SNIP some soppy crap

The
author has left his phone number and email address in the signature. If
you have any issues, you may wish to contact him there. I would, in fact,
be very interested in hearing if anyone manages to contact him that way.

-Henry

--- BEGIN REPOSTED ARTICLE ---

Someone suggested I write an article on power and grounding techniques
for equipment construction.

SNIP some stuff probably more at home on rec.audio.opinion.

--

Henry A. Pasternack
Member Scientific Staff (514) 761-8734 (phone)
Bell Northern Research, Montreal (514) 761-8509 (fax)

Isn't he the fellow who was fired by Bell not too long after that? I
wonder why. Considering the article posted, it is not difficult to
guess.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Andre Jute]

A star ground is just a circular bus or a very short bus. Grounding is
is tricky and tiresome in inverse proportion to the amount of thought
you give it, so I do something between what Iain does and what Patrick
does, and I call it a "star-point". Here you can see my star point
http://members.lycos.co.uk/fiultra/K...0T68MZ417A.jpg
on my T68bis "Minus Zero" amp. It is the short piece of stiff wire
sticking up at the right hand side of the aluminium cased resistor
behind the battery boxes in the centre of the top right hand
photograph. It's the bleeder resistor to the power supply and the star
point is at its 0V end. Notice how the convenitonally drawn schematic
http://members.lycos.co.uk/fiultra/t...17acircuit.jpg
tells you nothing of this, leaving you to work it out for yourself.
All the 0V wires are dropped over this stiff wire and soldered on.
Even on such a short bus I take care of the order of the wires as I
put them on. From this point a wire is taken to main's earth. The case
is connected to mains earth by a wire from very sturdy bolt held in
with serrated washers and nuts, which is placed as near as possible to
the mains socket; unfortunately it is not too clear in the photograph,
but it is just below the switch, near the top right hand corner of the
righthand output transformer in the picture.

Most schematics don't tell you enough about earthing. Here, for
instance:
http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
I've shown the star earth being implemented but have not said anything
about connecting the case to earth. Mind you, on some of the Lundahl
Modular Series 300B schemos I showed all the 0V connections in order,
with a note saying "mind the order of the grounding connections", and
two people wrote me letters saying that DIYers are not idiots who need
their hands held. (I was, when I started, and I'm very grateful to
people who made 90 mile round trips to come check over my
constructions before I fired them up.)

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

On Mar 2, 12:39*pm, "Iain Churches" wrote:
Patrick posted some interesting facts about ground buss
connections, which I have extracted from another thread
and pasted here, because I think the subject is important
enough to warrant *its own thread.

He wrote:
The 0V rail of the preamp should be a short buss wire about 100mm long
with ends connected to the RCA plug 0V bodies at inputs and outputs.
ALL parts with OV connections should be made to this buss,
and the CHASSIS or CASE connected via a 5 watt 27 ohm R, and the case
taken to the *green/yellow wire to the wall socket so the case can't
become live to mains or the B+. There should be NO direct connection of
the OV buss to the case.

--

I ask:

In other words the mains supply case should be bonded to the case,
and the 0V (signal grounds) taken to the ground point via a 27 Ohm
5W resistor?

Why is this?

My experience with ground buss amps is limited. I have never been
able to make them quiet enough. I found that the exact position in
which a wire was placed on the buss was critical, and that a difference
was audible.It may be there is something lacking in my implementation
of the buss.

I prefer to use a star ground, as follows. *Earth (ground) connection
from the supply - the only green yellow wire in the amplifier is taken
straight to the chassis bonding screw. *The input and output RCA
signal connectors I used are the isolated type (Neutrik NF2D)

http://www.neutrik.com/uk/en/audio/2...-0_detail.aspx

I run a separate wire (black) from each of the RCA input and output
ground tags to the star ground. Signal wires on the input side have
their shields connected at the RCA socket end only.

On the psu, I run separate grounds (heavier wire) from each cap
separately to the star. They are not linked. *The only exception to
this is the 1st (reservoir) electrolytic , which is connected directly
to the neg terminal of the FW bridge, and then to the star.

This is a topology I have seen used on amps that perform well,
and has been taught to me as a good solution.
It seems to work. My 50W power amp has only 80µV
of noise (-108dB) and no audible hum even with the ear
against the speaker (Tannoy Gold 15 inch)

Regards to all
Iain

[Henry Pasternack[_2_]]

Andre Jute wrote:

A star ground is just a circular bus or a very short bus.

Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.

Grounding is is tricky and tiresome in inverse proportion to the
amount of thought you give it.

I would say the opposite is true. The less you think about grounding,
the less tricky it seems. With no thought at all, it becomes as simple
as pie. Or fruit tart, for that matter. Just connect all the ground
connections together any way you like, and don't worry. It's only
when you start to think about it that it truly becomes tricky.

Here you can see my star point [URL deleted].

You may be able to see it, but to my eyes the picture is impossibly
tiny to reveal any useful details. But, you know I have this problem
with photographs.

Most schematics don't tell you enough about earthing. Here, for
instance: [URL deleted]. I've shown the star earth being implemented
but have not said anything about connecting the case to earth.

Attempting to connect all the grounds together like that, willy-nilly,
is not the right approach. That's because in practice it's nearly
impossible to achieve a true equipotential connection for all those
wires. Also, there are other performance issues having to do with
all those long ground connections running about the amplifier.

... I showed all the 0V connections in order, with a note saying
"mind the order of the grounding connections", and two people wrote
me letters saying that DIYers are not idiots who need their hands
held.

Then the DIYers were idiots, because the subject is quite worthy of
elaboration. The problem I see with everything you say here is that
you fail to address the most important meat of the problem, which is
precisely how to determine the "order of the grounding connections"
and how this translates into a practical wiring and ground layout.

My opinion on this subject is there are many ways to wire an amplifier
to minimize hum and noise. Star grounding (and its variants) and
bus wiring are two common solutions. Rather than posting fuzzy
pictures and vague generalities, if you would like to help your
readers, you should teach them the principles involved (you do
know them, right?) so they can work out the optimum grounding
scheme for each project by themselves.

Of course, being a lying psychopath pornographic scumbag, I may
not really know what I'm talking about! Feel free to ignore
everything I say. In fact, I strongly urge you to do so! :-)

-Henry

[Ian Thompson-Bell]

Henry Pasternack wrote:
Andre Jute wrote:

A star ground is just a circular bus or a very short bus.

Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.


The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point
IS the 0V point of the PSU i.e the ground of the input filter cap.#

In power amps this is relatively easy to achieve and running a thick bus
from the PSU 0V past the power section to the preamp section should work
just a s well since the power currents will not flow through any of the
preamp sections of the bus.

In separate pre-amps or mic pre-amps or tube mixers where the supply is
remote from the pre-amp this is clearly not possible and there is the
added problem of separating power currents from input/output signal
currents (unless floating transformer inputs and outputs are used). One
solution I have seen is to have a local pre-amp power supply - indeed
this was very common practice in many tube based recording mixers of the
50s and 60s. Each pre-amp would have its own mains transformer and PSU
along with balanced floating inputs and outputs. All earth loop problems
were therefore local to the pre-amp and you could connect them together
however you liked to build a mixer without ever having to worry about
ground loops. An expensive option to be sure, but one that worked very well.

Cheers

ian

[Eeyore]

Ian Thompson-Bell wrote:

Henry Pasternack wrote:
Andre Jute wrote:

A star ground is just a circular bus or a very short bus.

Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.


The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point
IS the 0V point of the PSU i.e the ground of the input filter cap.#

In power amps this is relatively easy to achieve and running a thick bus
from the PSU 0V past the power section to the preamp section should work
just a s well since the power currents will not flow through any of the
preamp sections of the bus.

But still a compromise.


In separate pre-amps or mic pre-amps or tube mixers where the supply is
remote from the pre-amp this is clearly not possible and there is the
added problem of separating power currents from input/output signal
currents (unless floating transformer inputs and outputs are used). One
solution I have seen is to have a local pre-amp power supply - indeed
this was very common practice in many tube based recording mixers of the
50s and 60s. Each pre-amp would have its own mains transformer and PSU
along with balanced floating inputs and outputs. All earth loop problems
were therefore local to the pre-amp and you could connect them together
however you liked to build a mixer without ever having to worry about
ground loops. An expensive option to be sure, but one that worked very well.

Far simpler is to have 2 (or more) stars and use these to direct current flow.
In particular, the PSU should have its own star and this is where ALL ripple
currents must flow. This can now be tied to the input 'star' with a
*non-current-carrying conductor* (or at least carrying only the B- smoothed DC).

It is *essential* to keep power and signal paths separate for hum free
operation.

Graham

[Ian Thompson-Bell]

Eeyore wrote:

Ian Thompson-Bell wrote:

Henry Pasternack wrote:
Andre Jute wrote:

A star ground is just a circular bus or a very short bus.
Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.

The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point
IS the 0V point of the PSU i.e the ground of the input filter cap.#

In power amps this is relatively easy to achieve and running a thick bus
from the PSU 0V past the power section to the preamp section should work
just a s well since the power currents will not flow through any of the
preamp sections of the bus.

But still a compromise.


In separate pre-amps or mic pre-amps or tube mixers where the supply is
remote from the pre-amp this is clearly not possible and there is the
added problem of separating power currents from input/output signal
currents (unless floating transformer inputs and outputs are used). One
solution I have seen is to have a local pre-amp power supply - indeed
this was very common practice in many tube based recording mixers of the
50s and 60s. Each pre-amp would have its own mains transformer and PSU
along with balanced floating inputs and outputs. All earth loop problems
were therefore local to the pre-amp and you could connect them together
however you liked to build a mixer without ever having to worry about
ground loops. An expensive option to be sure, but one that worked very well.

Far simpler is to have 2 (or more) stars and use these to direct current flow.
In particular, the PSU should have its own star and this is where ALL ripple
currents must flow. This can now be tied to the input 'star' with a
*non-current-carrying conductor* (or at least carrying only the B- smoothed DC).


Presumably you mean no *signal* current carrying conductor.

This still leaves a common mode conductor carrying output signal current
which is of course supplied by the power supply. I am not clear how
multiple local stars solve the problem.

It is *essential* to keep power and signal paths separate for hum free
operation.


Which can only be achieved with transformers?

Cheers

Ian

[Henry Pasternack[_2_]]

"Ian Thompson-Bell" wrote in message
...
The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point IS
the 0V point of the PSU i.e the ground of the input filter cap.#

True. But a better practical arrangement is to create a "star of stars".
The real key, IMHO, is to start with the schematic and draw out all
of the current loops in the circuit, from power supply out to the signal
circuitry and back, and also the input and output currents. Then you
find places where separate current loops share common paths, and
then separate out these loops so they meet at (to the greatest extent
possible) single points.

The connection to the chassis is done for electrostatic shielding. It's
done at a single point on the circuit's ground net. Where that point
should be is a subject for debate. To understand the implications, you
have to visualize the effects of currents flowing though and in the
chassis walls due to external potentials and electrostatic/electromagnetic
fields. Not easy if you really want to take it to the "next level". And
that's why that fellow in the article reposted said whole books can be
written on the subject.

If you try to follow a single technique from rote and vague instructions,
your results may be hit-and-miss. Always better, I say, to understand
the problem from first principles.

-Henry

[Eeyore]

Henry Pasternack wrote:

"Ian Thompson-Bell" wrote

The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point IS
the 0V point of the PSU i.e the ground of the input filter cap.#

True. But a better practical arrangement is to create a "star of stars".
The real key, IMHO, is to start with the schematic and draw out all
of the current loops in the circuit, from power supply out to the signal
circuitry and back, and also the input and output currents. Then you
find places where separate current loops share common paths, and
then separate out these loops so they meet at (to the greatest extent
possible) single points.

100% correct.


If you try to follow a single technique from rote and vague instructions,
your results may be hit-and-miss. Always better, I say, to understand
the problem from first principles.

I couldn't agree more. With grounding it's almost all about directing current
flow in an appropriate way.

Graham

[Ian Thompson-Bell]

Henry Pasternack wrote:
"Ian Thompson-Bell" wrote in message
...
The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point IS
the 0V point of the PSU i.e the ground of the input filter cap.#

True. But a better practical arrangement is to create a "star of stars".
The real key, IMHO, is to start with the schematic and draw out all
of the current loops in the circuit, from power supply out to the signal
circuitry and back, and also the input and output currents. Then you
find places where separate current loops share common paths, and
then separate out these loops so they meet at (to the greatest extent
possible) single points.


The problem I see with that is that all output currents must flow from
the power supply, through the load and back to the PSU 0V but they share
a common ground with the inputs. How do you separate these?

The connection to the chassis is done for electrostatic shielding. It's
done at a single point on the circuit's ground net. Where that point
should be is a subject for debate. To understand the implications, you
have to visualize the effects of currents flowing though and in the
chassis walls due to external potentials and electrostatic/electromagnetic
fields. Not easy if you really want to take it to the "next level". And
that's why that fellow in the article reposted said whole books can be
written on the subject.

If you try to follow a single technique from rote and vague instructions,
your results may be hit-and-miss. Always better, I say, to understand
the problem from first principles.

No argument about that!

Cheers

Ian

[John Byrns]

In article ,
Ian Thompson-Bell wrote:

Henry Pasternack wrote:
Andre Jute wrote:

A star ground is just a circular bus or a very short bus.

Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.


The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point
IS the 0V point of the PSU i.e the ground of the input filter cap.#

In my experience it is not the input filter cap that is important here,
but rather that it is the final filter cap in the main PSU filter that
must be connected to the "star point" or its equivalent.

In power amps this is relatively easy to achieve and running a thick bus
from the PSU 0V past the power section to the preamp section should work
just a s well since the power currents will not flow through any of the
preamp sections of the bus.

In separate pre-amps or mic pre-amps or tube mixers where the supply is
remote from the pre-amp this is clearly not possible and there is the
added problem of separating power currents from input/output signal
currents (unless floating transformer inputs and outputs are used). One
solution I have seen is to have a local pre-amp power supply - indeed
this was very common practice in many tube based recording mixers of the
50s and 60s. Each pre-amp would have its own mains transformer and PSU
along with balanced floating inputs and outputs. All earth loop problems
were therefore local to the pre-amp and you could connect them together
however you liked to build a mixer without ever having to worry about
ground loops. An expensive option to be sure, but one that worked very well.

And in other 50s and 60s systems a whole rack full of microphone preamps
were powered from a common power supply without problems because only
power currents flowed through the wires from the power supply, the
signal input and output currents were isolated from the common power
wires by input and output transformers.

Oops on proof reading, I see that you already mentioned this in
parenthesis, oh well.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Ian Thompson-Bell]

John Byrns wrote:
In article ,
Ian Thompson-Bell wrote:

Henry Pasternack wrote:
Andre Jute wrote:

A star ground is just a circular bus or a very short bus.
Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.

The key phrase here is 'reducing the resistance of the common ground bus
to zero'. it is all very well connecting all grounded leads to a single
point but if you then connect that by a single wire to the zero volts
point of the power supply you have immediately introduced a long no zero
common ground bus. So a star ground really only works if the star point
IS the 0V point of the PSU i.e the ground of the input filter cap.#

In my experience it is not the input filter cap that is important here,
but rather that it is the final filter cap in the main PSU filter that
must be connected to the "star point" or its equivalent.

In power amps this is relatively easy to achieve and running a thick bus
from the PSU 0V past the power section to the preamp section should work
just a s well since the power currents will not flow through any of the
preamp sections of the bus.

In separate pre-amps or mic pre-amps or tube mixers where the supply is
remote from the pre-amp this is clearly not possible and there is the
added problem of separating power currents from input/output signal
currents (unless floating transformer inputs and outputs are used). One
solution I have seen is to have a local pre-amp power supply - indeed
this was very common practice in many tube based recording mixers of the
50s and 60s. Each pre-amp would have its own mains transformer and PSU
along with balanced floating inputs and outputs. All earth loop problems
were therefore local to the pre-amp and you could connect them together
however you liked to build a mixer without ever having to worry about
ground loops. An expensive option to be sure, but one that worked very well.

And in other 50s and 60s systems a whole rack full of microphone preamps
were powered from a common power supply without problems because only
power currents flowed through the wires from the power supply, the
signal input and output currents were isolated from the common power
wires by input and output transformers.


I am not clear about that. The output signal currents (internal to the
transformer isolated circuit) flow from the psu through the output stage
and transformer primary and thence to the PSU 0V, so presumably each
needs a separate connection to/from the PSU?

Oops on proof reading, I see that you already mentioned this in
parenthesis, oh well.


Sort of, except I was assuming separate PSUs rather than one feeding a
rack of mic preamps.

Cheers

Ian

Regards,

John Byrns

[Andre Jute]

Here we go with the old Magnequest Scum methods again. What happens is
that Porno Pas, unable technically to fault what I write, rephrases
what I say in a slightly different manner and then pretends that what
I say is wrong. It's bull****. And the rest is just Porno Pas claiming
that whatever I say is white is really black. It is beneath contempt,
not worth answering. That's quite aside from the fact that I don't
hold cosy chats with child molesers. -- Andre Jute

Henry "Porno" Pasternack wrote:
Andre Jute wrote:
A star ground is just a circular bus or a very short bus.

Not really, ANDRE. *A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. *It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.

Grounding is is tricky and tiresome in inverse proportion to the
amount of thought you give it.

I would say the opposite is true. *The less you think about grounding,
the less tricky it seems. *With no thought at all, it becomes as simple
as pie. *Or fruit tart, for that matter. *Just connect all the ground
connections together any way you like, and don't worry. *It's only
when you start to think about it that it truly becomes tricky.

Here you can see my star point [URL deleted].

You may be able to see it, but to my eyes the picture is impossibly
tiny to reveal any useful details. *But, you know I have this problem
with photographs.

Most schematics don't tell you enough about earthing. Here, for
instance: [URL deleted]. *I've shown the star earth being implemented
but have not said anything about connecting the case to earth.

Attempting to connect all the grounds together like that, willy-nilly,
is not the right approach. *That's because in practice it's nearly
impossible to achieve a true equipotential connection for all those
wires. *Also, there are other performance issues having to do with
all those long ground connections running about the amplifier.

... I showed all the 0V connections in order, with a note saying
"mind the order of the grounding connections", and *two people wrote
me letters saying that DIYers are not idiots who need their hands
held.

Then the DIYers were idiots, because the subject is quite worthy of
elaboration. *The problem I see with everything you say here is that
you fail to address the most important meat of the problem, which is
precisely how to determine the "order of the grounding connections"
and how this translates into a practical wiring and ground layout.

My opinion on this subject is there are many ways to wire an amplifier
to minimize hum and noise. *Star grounding (and its variants) and
bus wiring are two common solutions. *Rather than posting fuzzy
pictures and vague generalities, if you would like to help your
readers, you should teach them the principles involved (you do
know them, right?) so they can work out the optimum grounding
scheme for each project by themselves.

Of course, being a lying psychopath pornographic scumbag, I may
not really know what I'm talking about! *Feel free to ignore
everything I say. *In fact, I strongly urge you to do so! *:-)

-Henry

[Eeyore]

Andre Jute wrote:

Here we go with the old Magnequest Scum methods again. What happens is
that Porno Pas, unable technically to fault what I write, rephrases
what I say in a slightly different manner and then pretends that what
I say is wrong.

It's nothing like what you wrote you bloody idiot.

Henry actually understands the fine detail of what he's talking about instead
of posting 'design by rote' guides.

Graham

[Andre Jute]

Poopie Stevenson (who would rather be known as a braying ass) wrote:
Andre Jute wrote:
Here we go with the old Magnequest Scum methods again. What happens is
that Porno Pas, unable technically to fault what I write, rephrases
what I say in a slightly different manner and then pretends that what
I say is wrong.

It's nothing like what you wrote you bloody idiot.

Well then, sonny, explain in detail what is wrong with what I do.
Meanwhile we'll note that what I do is pretty much accepted practice,
is what everyone does, is what is recommended in trusted textbooks, is
legal, is approved by my local hams (who surely all have more hands-on
HT experience than you and Pasternack together). Let's hear a wrong
detail, not just an inane overage fat schoolboy called Poopie
screeching "bloody idiot" in a squeaky voice.

There may be better ways than what I do, and what Patrick and Iain do,
but it'll be a cold day in hell when we hear them from you or Porno
Pas.

Henry actually understands the fine detail of what he's talking about instead
of posting 'design by rote' guides.

Your sainted child molester Porno Pas has just posted a "design by
rote" guide, which we suspect got its author fired from Bell Northern.

Graham

What do you say to that, Poopie? Don't you think you're being just a
wee bit hypocritical, dear old Poopster?

Andre Jute
Always happy to entertain the lower classes

[Patrick Turner]

Henry Pasternack wrote:

Andre Jute wrote:

A star ground is just a circular bus or a very short bus.

Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.

Don't you mean more hum than silence?

Grounding is is tricky and tiresome in inverse proportion to the
amount of thought you give it.

I would say the opposite is true. The less you think about grounding,
the less tricky it seems.

It depends on what knowledge is in the thinker's mind and how good at
thinking they are.

With no thought at all, it becomes as simple
as pie. Or fruit tart, for that matter. Just connect all the ground
connections together any way you like, and don't worry. It's only
when you start to think about it that it truly becomes tricky.

Oh my Gord, while your at it, just connect all components up to randomly
chosen circuit points and tube socket pins.
Avoid all thought, and never check what you are doing.

Turn it on with bravado, and cheer as the smoke rises and parts fry to
death.
But maybe it doesn't hum, so mission accomplished.

That other re-posted advice does ahve lots of good stuff people should
realise
and practice automatically while thinking about how to make their amp.

So we won't take you seriously always and we will keep smiling...

Here you can see my star point [URL deleted].

You may be able to see it, but to my eyes the picture is impossibly
tiny to reveal any useful details. But, you know I have this problem
with photographs.

Most schematics don't tell you enough about earthing. Here, for
instance: [URL deleted]. I've shown the star earth being implemented
but have not said anything about connecting the case to earth.

Attempting to connect all the grounds together like that, willy-nilly,
is not the right approach. That's because in practice it's nearly
impossible to achieve a true equipotential connection for all those
wires. Also, there are other performance issues having to do with
all those long ground connections running about the amplifier.

... I showed all the 0V connections in order, with a note saying
"mind the order of the grounding connections", and two people wrote
me letters saying that DIYers are not idiots who need their hands
held.

Then the DIYers were idiots, because the subject is quite worthy of
elaboration. The problem I see with everything you say here is that
you fail to address the most important meat of the problem, which is
precisely how to determine the "order of the grounding connections"
and how this translates into a practical wiring and ground layout.

That does take practised skills which are best learnt by trial and error
by diyers in their own shed. All the discussions in the world
about grounding on new groups won't stop diyers getting things wrong a
few times unless they learn,
and some cannot, or simply will not, because its cheaper to go to a tech
person to sort their mistakes.

Even when I point out they ARE ABLE to work it out and learn, and that
they DO HAVE
the time, they won't learn, and won't use the time, and prefer to
do such dumb**** things as attend pubs and watch TV and have reams of
useless small talk with
others around them.

So urging Andre, or myself, or to give a diagram of how-to-do yourself
will have almost zero effect on the hum found in diyer first attempts.

I had to teach myself. And I built test gear for measuring low mV level
signal volts and currents so I needed to know how to make circuits
quiet.
At first they were hopelessly too noisy, but gradually I got really good
at
eliminating noise.

It took days and weeks of practice.





My opinion on this subject is there are many ways to wire an amplifier
to minimize hum and noise. Star grounding (and its variants) and
bus wiring are two common solutions.

Well, starring is the most predictable. It usually gives a fair result.
But you end up using more hook up wire than you'd like to so
avoiding lengthy wires from PS cap 0V terminals to a point near the
input is investigated.
Finally, the idea of referencing is formed in the diyer's mind, and
ideas about never
allowing a PS supply wire carrying heavy ac or dc to appear commom to
other 0V wires
which may produce some noise at the input.


Pictures and vague generalities, if you would like to help your
readers, you should teach them the principles involved (you do
know them, right?) so they can work out the optimum grounding
scheme for each project by themselves.

Well, for any given amp, very few variations of the 0V path
will give noise free operation.
determined diyers will find them through their own efforts at
educating themselves on the basics about circuit currents flowing around
the bloody
circuits they are building. But its a big expectation to expect people
to
prove anything to themselves; many people prefer chocolate to apples,
and bull**** to truth....


Of course, being a lying psychopath pornographic scumbag, I may
not really know what I'm talking about! Feel free to ignore
everything I say. In fact, I strongly urge you to do so! :-)

I have never found you to be a clueless scumbag full of porno
and don't have the time to determine if its true or not.
Porno is art to many folks, unless its porking 1 year olds,
and thankfully we don't have images allowed at r.a.t, where no doubt a
small
minority would make use of the binaries ability to post
inappropriate images which may be distracting to tube craft.

I find it difficult to think about sex and +700 V at the same time.

If you sent me an image of yourself or even myself porking Queen
Elizabeth II,
I'd be mildly amused, and know there was no accounting for taste, eh.

I have Nicole K and Kylie M here this minute to mow my lawns
because they get so tired of the work they do.

I also want them to clip the hedges, and they are having a little argy
bargy
about who gets up the ladder, and who holds the ladder steady...

I'll bring them a nice cup of tea when they finish and we'll have a nice
swim in the pool
after. About 50 laps should tire them out naturally.

r.a.t is democracy without regulation, and its a lot better than
elsewhere....

Patrick Turner.




-Henry

[Andre Jute]

On Mar 3, 10:57*am, Patrick Turner wrote:
Henry Pasternack wrote:

Andre Jute wrote:

A star ground is just a circular bus or a very short bus.

Not really, ANDRE. *A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. *It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.

Don't you mean more hum than silence?

Porno Pas has built two or three tube amps in his entire life, total,
max, final count. What he says is hardly ever specific enough to be
useful, and my experience is that he tailors the truth about
electronics according to who he speaks to. In short, Henry Pasternack
is unreliable, often dangerous.

I have no problem believing that a Pasternack amp produces "more hum
than silence". Why, even Jon Yaeger, hardly the most discriminating
tubie, broke up one of Pasternack's amps, presumably because it was
too noisy to use or sell on.

Pasternack can't even keep his story straight in a single letter. He
contradicts himself repeatedly in the letter you're replying to.

Andre Jute
"I was at a board meeting for the LA Chapter of the Audio Engineering
Society last night on XM Satellite radio audio and data transmission.
Sadly, we missed you there, and at the SMPTE and Acoustical Society
recent meetings as well. Everyone was asking, 'Where is that wonderful
Andre Jute? The world just doesn't rotate without him...'" -- John
Mayberry, Emmaco


Grounding is is tricky and tiresome in inverse proportion to the
amount of thought you give it.

I would say the opposite is true. *The less you think about grounding,
the less tricky it seems.

It depends on what knowledge is in the thinker's mind and how good at
thinking they are.

With no thought at all, it becomes as simple
as pie. *Or fruit tart, for that matter. *Just connect all the ground
connections together any way you like, and don't worry. *It's only
when you start to think about it that it truly becomes tricky.

Oh my Gord, while your at it, just connect all components up to randomly
chosen circuit points and tube socket pins.
Avoid all thought, and never check what you are doing.

Turn it on with bravado, and cheer as the smoke rises and parts fry to
death.
But maybe it doesn't hum, so mission accomplished.

That other re-posted advice does ahve lots of good stuff people should
realise
and practice automatically while thinking about how to make their amp.

So we won't take you seriously always and we will keep smiling...





Here you can see my star point [URL deleted].

You may be able to see it, but to my eyes the picture is impossibly
tiny to reveal any useful details. *But, you know I have this problem
with photographs.

Most schematics don't tell you enough about earthing. Here, for
instance: [URL deleted]. *I've shown the star earth being implemented
but have not said anything about connecting the case to earth.

Attempting to connect all the grounds together like that, willy-nilly,
is not the right approach. *That's because in practice it's nearly
impossible to achieve a true equipotential connection for all those
wires. *Also, there are other performance issues having to do with
all those long ground connections running about the amplifier.

... I showed all the 0V connections in order, with a note saying
"mind the order of the grounding connections", and *two people wrote
me letters saying that DIYers are not idiots who need their hands
held.

Then the DIYers were idiots, because the subject is quite worthy of
elaboration. *The problem I see with everything you say here is that
you fail to address the most important meat of the problem, which is
precisely how to determine the "order of the grounding connections"
and how this translates into a practical wiring and ground layout.

That does take practised skills which are best learnt by trial and error
by diyers in their own shed. All the discussions in the world
about grounding on new groups won't stop diyers getting things wrong a
few times unless they learn,
and some cannot, or simply will not, because its cheaper to go to a tech
person to sort their mistakes.

Even when I point out they ARE ABLE to work it out and learn, and that
they DO HAVE
the time, they won't learn, and won't use the time, and prefer to
do such dumb**** things as attend pubs and watch TV and have reams of
useless small talk with
others around them.

So urging Andre, or myself, or to give a diagram of how-to-do yourself
will have almost zero effect on the hum found in diyer first attempts.

I had to teach myself. And I built test gear for measuring low mV level
signal volts and currents so I needed to know how to make circuits
quiet.
At first they were hopelessly too noisy, but gradually I got really good
at
eliminating noise.

It took days and weeks of practice.

My opinion on this subject is there are many ways to wire an amplifier
to minimize hum and noise. *Star grounding (and its variants) and
bus wiring are two common solutions.

Well, starring is the most predictable. It usually gives a fair result.
But you end up using more hook up wire than you'd like to so
avoiding lengthy wires from PS cap 0V terminals to a point near the
input is investigated.
Finally, the idea of referencing is formed in the diyer's mind, and
ideas about never
allowing a PS supply wire carrying heavy ac or dc to appear commom to
other 0V wires
which may produce some noise at the input.

Pictures and vague generalities, if you would like to help your
readers, you should teach them the principles involved (you do
know them, right?) so they can work out the optimum grounding
scheme for each project by themselves.

Well, for any given amp, very few variations of the 0V path
will give noise free operation.
determined diyers will find them through their own efforts at
educating themselves on the basics about circuit currents flowing around
the bloody
circuits they are building. But its a big expectation to expect people
to
prove anything to themselves; many people prefer chocolate to apples,
and bull**** to truth....



Of course, being a lying psychopath pornographic scumbag, I may
not really know what I'm talking about! *Feel free to ignore
everything I say. *In fact, I strongly urge you to do so! *:-)

I have never found you to be a clueless scumbag full of porno
and don't have the time to determine if its true or not.
Porno is art to many folks, unless its porking 1 year olds,
and thankfully we don't have images allowed at r.a.t, where no doubt a
small
minority would make use of the binaries ability to post
inappropriate images which may be distracting to tube craft.

I find it difficult to think about sex and +700 V at the same time.

If you sent me an image of yourself or even myself porking Queen
Elizabeth II,
I'd be mildly amused, and know there was no accounting for taste, eh.

I have Nicole K and Kylie M here this minute to mow my lawns
because they get so tired of the work they do.

I also want them to clip the hedges, and they are having a little argy
bargy
about who gets up the ladder, and who holds the ladder steady...

I'll bring them a nice cup of tea when they finish and we'll have a nice
swim in the pool
after. About 50 laps should tire them out naturally.

r.a.t is democracy without regulation, and its a lot better than
elsewhere....

Patrick Turner.



-Henry

[Iain Churches[_2_]]

"Patrick Turner" wrote in message
...


Henry Pasternack wrote:

Andre Jute wrote:

A star ground is just a circular bus or a very short bus.

Not really, ANDRE. A star ground is the abstract notion of a purely
equipotential (equal voltage) single point connection that eliminates
ground loops by reducing the resistance of the common ground bus to
zero. It's impossible to achieve in practice, though, and trying to
take the approach too literally is likely to cause more harm than
good.

Don't you mean more hum than silence?

Grounding is is tricky and tiresome in inverse proportion to the
amount of thought you give it.

I would say the opposite is true. The less you think about grounding,
the less tricky it seems.

In my experience, the layout and ground scheme can make or
break and amp. The schematic only tells half the story. As far
as tube amps go, careful examination of mil spec equipment, or
units built for studio use, can tell you a lot. The bean-counters
had a lot less influence over their design than they would have had
over equipment made for the domestic market.

Then the DIYers were idiots, because the subject is quite worthy of
elaboration. The problem I see with everything you say here is that
you fail to address the most important meat of the problem, which is
precisely how to determine the "order of the grounding connections"
and how this translates into a practical wiring and ground layout.

That does take practised skills which are best learnt by trial and error
by diyers in their own shed. All the discussions in the world
about grounding on new groups won't stop diyers getting things wrong a
few times unless they learn,
and some cannot, or simply will not, because its cheaper to go to a tech
person to sort their mistakes.

ISTM there are two ways to learn about this kind of thing.
You can do it the hard way, and make the same mistake over and
over again, gradually implementing changes which lead to improvement,
or: You can listen to people with experience, and gain info from
books and looking at real-world examples. I have done some of
both. But still I have a lot to learn.

So urging Andre, or myself, or to give a diagram of how-to-do yourself
will have almost zero effect on the hum found in diyer first attempts.

I had to teach myself. And I built test gear for measuring low mV level
signal volts and currents so I needed to know how to make circuits
quiet.
At first they were hopelessly too noisy, but gradually I got really good
at
eliminating noise.

It took days and weeks of practice.

It's taken me forty years - so far:-)

Iain

[West]

"Andre Jute" wrote in message
...
A star ground is just a circular bus or a very short bus. Grounding is
is tricky and tiresome in inverse proportion to the amount of thought
you give it, so I do something between what Iain does and what Patrick
does, and I call it a "star-point". Here you can see my star point
http://members.lycos.co.uk/fiultra/K...0T68MZ417A.jpg
on my T68bis "Minus Zero" amp. It is the short piece of stiff wire
sticking up at the right hand side of the aluminium cased resistor
behind the battery boxes in the centre of the top right hand
photograph. It's the bleeder resistor to the power supply and the star
point is at its 0V end. Notice how the convenitonally drawn schematic
http://members.lycos.co.uk/fiultra/t...17acircuit.jpg
tells you nothing of this, leaving you to work it out for yourself.
All the 0V wires are dropped over this stiff wire and soldered on.
Even on such a short bus I take care of the order of the wires as I
put them on. From this point a wire is taken to main's earth. The case
is connected to mains earth by a wire from very sturdy bolt held in
with serrated washers and nuts, which is placed as near as possible to
the mains socket; unfortunately it is not too clear in the photograph,
but it is just below the switch, near the top right hand corner of the
righthand output transformer in the picture.

Most schematics don't tell you enough about earthing. Here, for
instance:
http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
I've shown the star earth being implemented but have not said anything
about connecting the case to earth. Mind you, on some of the Lundahl
Modular Series 300B schemos I showed all the 0V connections in order,
with a note saying "mind the order of the grounding connections", and
two people wrote me letters saying that DIYers are not idiots who need
their hands held. (I was, when I started, and I'm very grateful to
people who made 90 mile round trips to come check over my
constructions before I fired them up.)

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

Great illustration. Did you have those schematics/illustrations
professionally made or is there a particular program you used? Thanks.

west

[Peter Wieck]

On Mar 2, 2:13*pm, "West" wrote:
"Andre Jute" wrote in message

...
A star ground is just a circular bus or a very short bus. Grounding is
is tricky and tiresome in inverse proportion to the amount of thought
you give it, so I do something between what Iain does and what Patrick
does, and I call it a "star-point". Here you can see my star pointhttp://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
on my T68bis "Minus Zero" amp. It is the short piece of stiff wire
sticking up at the right hand side of the aluminium cased resistor
behind the battery boxes in the centre of the top right hand
photograph. It's the bleeder resistor to the power supply and the star
point is at its 0V end. Notice how the convenitonally drawn schematichttp://members.lycos.co.uk/fiultra/t68mzwe417acircuit.jpg
tells you nothing of this, leaving you to work it out for yourself.
All the 0V wires are dropped over this stiff wire and soldered on.
Even on such a short bus I take care of the order of the wires as I
put them on. From this point a wire is taken to main's earth. The case
is connected to mains earth by a wire from very sturdy bolt held in
with serrated washers and nuts, which is placed as near as possible to
the mains socket; unfortunately it is not too clear in the photograph,
but it is just below the switch, near the top right hand corner of the
righthand output transformer in the picture.

Most schematics don't tell you enough about earthing. Here, for
instance:http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
I've shown the star earth being implemented but have not said anything
about connecting the case to earth. Mind you, on some of the Lundahl
Modular Series 300B schemos I showed all the 0V connections in order,
with a note saying "mind the order of the grounding connections", and
two people wrote me letters saying that DIYers are not idiots who need
their hands held. (I was, when I started, and I'm very grateful to
people who made 90 mile round trips to come check over my
constructions before I fired them up.)

Andre Jute
Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

Great illustration. Did you have those schematics/illustrations
professionally made or is there a particular program you used? Thanks.

west

Pillock:

You can do all of that using "Word" and the extra symbols chart. Most
word-processing programs are capable of all of that and more. On a
Mac, it is that much easier. So, you could finally furnish that long-
promised schematic on your "Slow B+" as the wherewithall is likely
already resident on your computer.

Peter Wieck
Wyncote, PA

[Andre Jute]

On Mar 2, 7:13*pm, "West" wrote:
"Andre Jute" wrote in message

...
A star ground is just a circular bus or a very short bus. Grounding is
is tricky and tiresome in inverse proportion to the amount of thought
you give it, so I do something between what Iain does and what Patrick
does, and I call it a "star-point". Here you can see my star pointhttp://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
on my T68bis "Minus Zero" amp. It is the short piece of stiff wire
sticking up at the right hand side of the aluminium cased resistor
behind the battery boxes in the centre of the top right hand
photograph. It's the bleeder resistor to the power supply and the star
point is at its 0V end. Notice how the convenitonally drawn schematichttp://members.lycos.co.uk/fiultra/t68mzwe417acircuit.jpg
tells you nothing of this, leaving you to work it out for yourself.
All the 0V wires are dropped over this stiff wire and soldered on.
Even on such a short bus I take care of the order of the wires as I
put them on. From this point a wire is taken to main's earth. The case
is connected to mains earth by a wire from very sturdy bolt held in
with serrated washers and nuts, which is placed as near as possible to
the mains socket; unfortunately it is not too clear in the photograph,
but it is just below the switch, near the top right hand corner of the
righthand output transformer in the picture.

Most schematics don't tell you enough about earthing. Here, for
instance:http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
I've shown the star earth being implemented but have not said anything
about connecting the case to earth. Mind you, on some of the Lundahl
Modular Series 300B schemos I showed all the 0V connections in order,
with a note saying "mind the order of the grounding connections", and
two people wrote me letters saying that DIYers are not idiots who need
their hands held. (I was, when I started, and I'm very grateful to
people who made 90 mile round trips to come check over my
constructions before I fired them up.)

Andre Jute
Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

Great illustration. Did you have those schematics/illustrations
professionally made or is there a particular program you used? Thanks.

west

Good golly, no, I don't send out for simple art. Graphic arts is one
of my professions, though at the higher levels we called typopgraphers
or reprographers because it as much about technicalities as about art.
Here are some introductory books in a series of which I am general
editor:
http://members.lycos.co.uk/fiultra/T...%20GDitCA.html
and see also my key text for advanced designers "Grids" (Rotovision,
Switzerland, 1996) he
http://members.lycos.co.uk/fiultra/T...re%20Jute.html

The programme I use for schematics is QuarkXPress, a professional page
makeup programme; I just drew the symbols in it and duplicate them on
the "pasteboard". It really isn't worth buying QXP--- it is a fair
chunk over a thousand dollars in price --- or investing the
substantial time necessary to master the programme, just to draw
schematics. Try Microsoft Word's drawing module.

Andre Jute
"I was at a board meeting for the LA Chapter of the Audio Engineering
Society last night on XM Satellite radio audio and data transmission.
Sadly, we missed you there, and at the SMPTE and Acoustical Society
recent meetings as well. Everyone was asking, 'Where is that wonderful
Andre Jute? The world just doesn't rotate without him...'" -- John
Mayberry, Emmaco

[Eeyore]

Andre Jute wrote:

The programme I use for schematics is QuarkXPress

And if you were s serious audio practioner you'd use a proper CAD schematic program.

Just typical of your amatuerism to use the wrong tools for the job.

Graham

[Andre Jute]

On Mar 3, 1:05*am, Eeyore
wrote:
Andre Jute wrote:
The programme I use for schematics is QuarkXPress

And if you were s serious audio practioner you'd use a proper CAD schematic program.

It's always the little sucker-fish who rant on about how "serious" and
"professional" they are. I just use what is to hand, and my great
skill makes the tool fit the job at hand. Yo, Poopie, where
appropriate, of course I use a CAD programme -- for instance when
precise measurements in the design of my bicor horn were the point, I
sent out drawings in CAD formats to those RATs who asked for them. But
you really want to be less rigid, Poopie, if you want us to take you
seriously; lateral thinking, even a little of it, is a sign of human
intelligence.

Just typical of your amatuerism to use the wrong tools for the job.

The fastest tool that does the job right, is what I say. Why bother
with slow, obstructive tools for a simple job when I've already bent
another professional tool to my will? Especially when the result
always draws compliments.

Graham

Always nice to hear from you, Poopie. Let's hope that this time your
provide evidence that you're human, rather than a chimpanzee with
typing skills.

Andre Jute
My chimp as called MiniAndre. Who is missing a chimp called Poopie?