[John Byrns]

In article ,
"Iain Churches" wrote:

"Patrick Turner" wrote in message
...


Andre Jute wrote:

Iain Churches wrote:

c) this active load cathode follower.

In listening tests, people chose C.

Shh! Allen Wright will come demand a royalty. That's the big secrets
his guru passed on to him, to use cathode followers and to tie the
wright (sic -- heh-heh!) currents down tight.

I think perhaps you could be guessing about what is in Iain's preamp.

He has avoided giving us a schematic.

He started off saying it was generic 6SN7 used as a gain stage followed
by cathode follower,
as Tremaine may have described in 1963, but then talks about listening
tests
using vastly fifferent topolgies, and just what is in the box is a
complete mystery.

Tremaine 4th edition dates from 1975.

No mystery Patrick. I stated clearly that it is an active load cathode
follower, which was chosen after comparison with a mu-follower and
a cascode.

I have no schematic drawn. It can be found in any one of a dozen
books


Perhaps he don't want to give away copyable secrets.

Copyable secrets? LOL. People have been using this topology
for 50 years:-)) It was used in line and distribution amps in studios
and broadcast everywhere. I can remember seeing racks and racks
of 'em.

OK, the circuit was used in studios and broadcast everywhere, is the
circuit anything like the 12BH7 output stage in this device?

http://www.waltzingbear.com/Schemati...Urei_LA-2A.JPG


Regards,

John Byrns

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

[Peter Wieck]

On Apr 11, 10:07 am, John Byrns wrote:
In article . com,
"Peter Wieck" wrote:

On Apr 10, 4:20 pm, "Iain Churches" wrote:
"Peter Wieck" wrote in message

ups.com...

On Apr 10, 3:51 am, "Iain Churches" wrote:

http://www.kolumbus.fi/iain.churches...ier/252.02.jpg

Wowsers... looks vaguely like:

http://www.radfordaudio.co.uk/ mid-page right.

Is yours the chicken or the egg?

How do you tell, which came first, the chicken or the egg? My wild
guess would be that Ian's amp was the "egg".

Regards,

John Byrns

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

The chicken is the egg's excuse for another egg.

Peter Wieck
Wyncote, PA

[John Byrns]

In article ,
"Ian Iveson" wrote:

Iain:

http://www.kolumbus.fi/iain.churches/Preamp/203A.html

It's a joint effort together with my pal Markus.
He is a very skilled metal worker and made the
casework, and also laser-cut the stainless steel
top grille.

We decided to do as much possible ourselves.
Any comments would be of interest.

Nice power plugs.

Screws holding the grill spoil the plot IMHO, more than your
accustomed eyes might suggest.

I think you have nailed what bothered me about the grilles.


Regards,

John Byrns

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

[John Byrns]

In article ,
"Iain Churches" wrote:

I have received as many replies and comments re
this preamp, by e.mail direct as I have on the NG,
and people off-list are usually much
more helpful and constructive.

The emails are doubtlessly helpful and constructive to you, but they are
useless to the rest of us who would like to learn something from the
various projects presented on this forum. Unfortunately there are those
who don't like to share, perhaps they lack confidence in their ideas,
and revert to email. Both the best and the worst comments seem to be
reserved for email.


Regards,

John Byrns

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

[Patrick Turner]

Andre Jute wrote:

Patrick Turner wrote:
Andre Jute wrote:

Iain Churches wrote:

c) this active load cathode follower.

In listening tests, people chose C.

Shh! Allen Wright will come demand a royalty. That's the big secrets
his guru passed on to him, to use cathode followers and to tie the
wright (sic -- heh-heh!) currents down tight.

I think perhaps you could be guessing about what is in Iain's preamp.

He has avoided giving us a schematic.

He started off saying it was generic 6SN7 used as a gain stage followed
by cathode follower,
as Tremaine may have desribed in 1963, but then talks about listening
tests
using vastly fifferent topolgies, and just what is in the box is a
complete mystery.

Perhaps he don't want to give away copyable secrets.
This is not very nice. At r.a.t we are supposed to be a free tube-craft
information outlet for the WWW.
I have 18mB at a website and page after page of schematics which anyone
is free to use.

But Allan Wright's special super cathode follower is only just that, and
whether
it dramatically increases sonic heaven's enthralling qualities is a moot
point.

Patrick Turner

RAT is a voluntary association. Everyone publishes what he likes in
whatever form he likes, and whatever he chooses to share with us is a
favour. We have no right to demand any more.

Indeed we have no rights to demand, and we won't, well, not at gun
point.
So we are left with time to ask, persuade or cajole.

That is about all I have time for, and if what is asked for does not
turn up, so be it, there are plenty of other things to move along to.


Your demand in another post that anyone who wants to post an amp on
RAT should document it fully, *and be prepared to defend it*,
encourages exactly the sort of adversarial procedure that has made RAT
the sewer it is.

Full presentation of the facts about what one has done might have the
opposite
effect, and lead to less adversarials.

I don't believe it ever has been possible during the last 3 million
years of
human evolution for people not to be adversarial, and conduct
challenging
discussions. Such heated discussions have led to where there might be
game was when it came time for a hunt, or how best to go about it,
and how best to divide the hunt results, and who the leader of the next
hunt should be.
There has always been a world where people fight over some darn thing.
Humans have the most unenviable record for fighting amoung
themselves and it seems to be a function of warped intelligence, until
you realise how warrior
mode was related to survival, and in the hunter gatherer world, you have
to kill
the next tribe if they steal water or game on your side of the mountain.
When people became agricultural and civilised, they had to defend
themselves
against raiders.
For hundreds of millions of years the dinosaurs fought amoung
themselves, the old
animal rules of tooth and claw, and all about survival and who you get
to ****.
How come that lot of lizards didn't evolve an intelligent reptile?
Were they too cunning to let themselves drift to intelligence?
Well, if they had evolved, we wouldn't be here.
So in fact there is "fight" in all species, even amoung trees in a
forest
for dominance, and its always been like this.
So our traits go back to the first organic molecule, many hundreds of
millions of years.

Jesus came with a message of love, compassion, and hope and forgiveness.
Most have ignored him; how do you change human nature that took 400
million years to form in 3 years?
Jesus needed to stay many more years to get anywhere against the idea of
an eye for an eye,
and no forgiveness, and all that hard old **** in the Old
Testament.......
Did not Jesus find a rabble to contend with?

There are many humans who actually like sewers, like rats do.
I personally don't like wars, sewers or rats,
but I would fight for truth and undertstanding, and the abolition of BS
wherever its level tries to rise above the gumboots.

I wonder if amoung the millions of other planets where life did evolve,
is still evolving,
or will evolve in future there are planets where competition does not
evolve.
Would a planet based on caring and sharing and never a harsh word be one
that could evolve?
And don't tell me such a place would be feminine, I only have to think
of Margaret Thatcher
to believe it entirely probable that females were the first to develop
weapons
to whomp a bad man when he was asleep, and certainly females
can be fiesty, and live by the idea that the end justifies the means.

Patrick Turner.


Andre Jute

[Patrick Turner]

Andre Jute wrote:

Phil Allison wrote:
"Andre Jute"


I know, Iain. I was making a joke about the way Allen in his book
makes it sound as if his guru received the cathode follower and the
constant current source from the finger of God himself.

** Well, as a life long Scientologist - he would imply that, wouldn't he.

Only the "God" in question was his implanted, operating Thetan.

Anyway, you're not ready to be an audio guru yet. You're too young and
you have too much hair. Allen Wright and Holger Stein and Dieter
Ennemoser and I decided long ago that the only people who are
qualified to build good audio equipment are over fifty and going light
on top -- like us.

** Whaaaaattt ???

Kiwi ex pat Scientologist " Alien " Wright was going very thin on top way
back in 1980.

Naw, he didn't see the light about the best designers being over fifty
until he was himself over fifty... The minute he explained it to me, I
saw it too, probably because I'd just turned fifty.

Didn't Allan discover tubes rather late after spending all that time
with HP working with SS?

Like all passionates, he's a mix of ideas, some good, some bad.

Looked a like some demented woman's idea of Yul Brynner.

I know, cos I briefly worked for the shonky idiot and met his various "
ladyfriends ".

LOL !!

Allen's a guy of sudden enthusiasms, which is a kind way of saying
eccentric. I wonder how he goes down in Germany.

Didn't the German Government conduct and win a major court case against
Scientology?

I decided Scientology wasn't for me about as soon as I became aware of
it,
and it seemed to be just another looney belief system amoung so many
that one does well to stay clear of.

While giving thought about Allan being a scientologist in Germany,
one wonders how much if any harm he does to others under the German
situation and history.

Some ppl must have what appears to me to be an irrational
need to believe in all sorts of things I think are BS.
They are quite unhappy without such beliefs, and how it is that so many
people with logical and genuinely scientific minds can
spend time being illogical and irrational is beyond me.

A few of them know something rather than nothing about tube audio,
and that is the most relevant thing to me.
I am not offended by their religion, sexual orientation, skin colour,
voting habits,
criminal record, how much filthy money they have, or their poor dress
sense.

There are some very obvious false notions about concerning audio;
Shakti Stones were a classic example of in-your-face quackery.

But in life as we look outward broadly, there are to be seen many more
and far worse odious
false notions presented to us day to day than some galloot
trying to sell us a few rocks to make the sound better,
or someone telling a story about using tubes, and including a modicum of
BS.

Patrick Turner.




....... Phil

Thanks for the giggle, Phil.

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

[Iain Churches]

"John Byrns" wrote in message
...
In article ,
"Ian Iveson" wrote:

Iain:

http://www.kolumbus.fi/iain.churches/Preamp/203A.html

It's a joint effort together with my pal Markus.
He is a very skilled metal worker and made the
casework, and also laser-cut the stainless steel
top grille.

We decided to do as much possible ourselves.
Any comments would be of interest.

Nice power plugs.

Screws holding the grill spoil the plot IMHO, more than your
accustomed eyes might suggest.

I think you have nailed what bothered me about the grilles.

The user has to be able to remove these, if tube replacement
is required. The screws are cap-head, and so can also be removed
without tools if required. They could easily be replaced by a low
profile cheese-head screw, or even countersunk.

Regards
Iain

[Iain Churches]

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

http://www.kolumbus.fi/iain.churches/Preamp/203A.html


Nice power plugs.

Do you mean the DC connectors?

Screws holding the grill spoil the plot IMHO, more than your accustomed
eyes might suggest.

The rest of the panels are fixed with tamper-proof screws.
Only the grille has cap- head screws which can be removed with
a hex key or by finger, (if the user has no tools) to change the
tubes.

Things I build for myself, I try to style like weird science, rather than
engineering from the days of Edison, and your use of a double skin chassis
is well OTT.

Have you ever talked to people to ask what they think of
current design?

The use of the copper inner chassis means that the inner parts
of the amp can be pre-assembled. This was something that was
widely done in analogue studio equipment.

As something styled for market, it would be interesting to know which.
These days, reliability and precision are hardly associated with
weightiness. People have learned the opposite.

Hmm. Interesting. I gained a totally different impression when
talking to dealers, musicians, and people interested in high end
audio. It seems that PQ (perceived quality) is regarded as
important.


Look at Border Patrol, or Audio Note. Chunky is out, svelte is in, for the
longer view.

It would be easy to copy any of the above. Don't you think
it is interesting to do something a little different? We did, so
we have:-)



Regards
Iain

[Iain Churches]

"Peter Wieck" wrote in message
ups.com...
On Apr 10, 4:20 pm, "Iain Churches" wrote:
"Peter Wieck" wrote in message

ps.com...

On Apr 10, 3:51 am, "Iain Churches" wrote:

http://www.kolumbus.fi/iain.churches...ier/252.02.jpg

Wowsers... looks vaguely like:

http://www.radfordaudio.co.uk/ mid-page right.

Is yours the chicken or the egg?


More than *vaguely like*:-)
It's an STA25 MkII. I updated it to Mk III later.
But it could have been anything, the layout is so
sensible.

While at Decca, we had close contact with Radford,
and I managed to get a complete set of iron from them.



Regards
Iain

[Iain Churches]

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

I have received as many replies and comments re
this preamp, by e.mail direct as I have on the NG,
and people off-list are usually much
more helpful and constructive.

The emails are doubtlessly helpful and constructive to you, but they are
useless to the rest of us who would like to learn something from the
various projects presented on this forum. Unfortunately there are those
who don't like to share, perhaps they lack confidence in their ideas,
and revert to email. Both the best and the worst comments seem to be
reserved for email.

Hello John.

Many of those who keep in touch by e.mail are former
subscribers to this and other Usenet groups. Most
of them can be found on closed groups to which the
lunatic fringe (in our case PA and AK) are denied
access. The discussion on such fori is well-informed
and constructive. Pics and schematics can be posted.
I have access to two such groups, which are divided
by general topic into several sub groups, broadcast,
studio practice, studio engineering, music performance,
audio teknik (which includes tube amps) etc etc
There are sometimes a total of 200 posts, all on
topic in 24 hrs.

No wonder so many eschew the bar-room brawl
that RAT has become.

Iain

PS Just had a mail from a pal who read your post.
He says "Closed groups are like large condenser
microphones. The only people who don't like them
are those that do not have access to them":-)

[Iain Churches]

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

No mystery Patrick. I stated clearly that it is an active load cathode
follower, which was chosen after comparison with a mu-follower and
a cascode.

I have no schematic drawn. It can be found in any one of a dozen
books

The cathode follower part sounds straight forward enough, but the
"active load" part could be anyone of a number of things. Is the
circuit what I think is called a "White" cathode follower?

The White CF is similar, except that the anode of the bottom
triode and the cathode of the upper triode are usually at the
same potential. The grid of the top triode is biased by a pair
of resistors from the B+ to ground, with the junction of these two
Rs connected to the grid.

On the ALCF the grid of the lower tube is biased in this
way. The anode of the lower tube and the cathode of the
upper tube are separated by a resistor of about 1k2 to
give a differential of about 2V between them.
1M is then connected from anode 1 to grid 2 for bias
(rather like the mu-follower)

Best regards
Iain

[Iain Churches]

"Andre Jute" wrote in message
ups.com...

Iain Churches wrote:
"Andre Jute" wrote in message
ups.com...
Iain Churches wrote:

This is not the Wright Schematic, but the generic active load
cathode follower which can be found in many textbooks.

I know, Iain. I was making a joke about the way Allen in his book
makes it sound as if his guru received the cathode follower and the
constant current source from the finger of God himself.

:-) Yes, I got the joke:-)

Anyway, you're not ready to be an audio guru yet. You're too young and
you have too much hair.

Old enough, but I do still have a full head of hair, and weight in at
80kgs!

Allen Wright and Holger Stein and Dieter
Ennemoser and I decided long ago that the only people who are
qualified to build good audio equipment are over fifty and going light
on top -- like us.

And Peter Walker:-)

I also teach recording arts to young musicians mainly classical
players, at Academy level. It is important for them to understand
what goes on and what is expected of them in the recording
studio environment. Most never get studio gigs because
they have no experience. And they can't get experience without
doing some gigs! It's very highly paid work, and so orchestral
agents book only the top players.

Back in the 70s, string sections on pop records were common.
These days, real strings are seldom used, or real drums
for that matter, so anyone who knows how to set up a
string section or a rock or jazz kit has achieved guru status:-))

Best regards
Iain

[Iain Churches]

"Andre Jute" wrote in message
ups.com...

Patrick Turner wrote:
Andre Jute wrote:

Iain Churches wrote:

c) this active load cathode follower.

In listening tests, people chose C.

Shh! Allen Wright will come demand a royalty. That's the big secrets
his guru passed on to him, to use cathode followers and to tie the
wright (sic -- heh-heh!) currents down tight.

I think perhaps you could be guessing about what is in Iain's preamp.

He has avoided giving us a schematic.

He started off saying it was generic 6SN7 used as a gain stage followed
by cathode follower,
as Tremaine may have desribed in 1963, but then talks about listening
tests
using vastly fifferent topolgies, and just what is in the box is a
complete mystery.

Perhaps he don't want to give away copyable secrets.
This is not very nice. At r.a.t we are supposed to be a free tube-craft
information outlet for the WWW.
I have 18mB at a website and page after page of schematics which anyone
is free to use.

But Allan Wright's special super cathode follower is only just that, and
whether
it dramatically increases sonic heaven's enthralling qualities is a moot
point.

Patrick Turner

RAT is a voluntary association. Everyone publishes what he likes in
whatever form he likes, and whatever he chooses to share with us is a
favour. We have no right to demand any more.

Your demand in another post that anyone who wants to post an amp on
RAT should document it fully, *and be prepared to defend it*,
encourages exactly the sort of adversarial procedure that has made RAT
the sewer it is.

Andre Jute

Andre, as a long term poster here, I am sure you have noticed how many
interesting people have abandoned this NG and Usenet in general. After the
demise of Pinkerton, there was some hope that things would improve.

As I mentioned in a reply to Patrick, I posted this link to relieve the
monotony of Arny's OT drivel, and Phil's autistic cut-and-paste.
Perhaps I should not have bothered:-)

Best regards
Iain

[Iain Churches]

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

Removing the stainless steel grille to change the tubes
reveals what appears like an empty compartment with
just the tubes and the tube bases set horizontally into a
4mm bulkhead. There is a "false floor" under which
the cable harness runs to the input selector and
switched attenuators at the front.

Wouldn't it be better to eliminate the false floor and provide a steel
grille on the bottom to provide improved air circulation for better
cooling?

John. There are cooling slats in the base plate.
The air is vented through the lower edges of the bulkhead.

Maybe I shouldn't even suggest that as the steel grille on top is the
one design element that doesn't look quite right to my eye, although I
am not sure why.

Perhaps the pic does not do it justice? Most people who
have seen the unit are of the opinion that the laser etched grille
together with the stainless steel dials sets off the whole
appearance of the unit beautifully.


Best regards
Iain

[Iain Churches]

"Patrick Turner" wrote in message
...

Eventually, we will coax a schematic from the man, and why the noise is
so high.

Hello Patrick,

I will draw it when I have time.
In actual fact we have established that the noise is not high, but my
method of measurement erroneous.

As soon as this unit comes back from a demo tour, my pals
at Swedish Broadcast have promised to measure the noise floor.
My best AC voltmeter (Marconi) has 300µV as the lowest
range, so perhaps the resolution is not good enough to measure
this unit accurately.

Best regards
Iain

[John Byrns]

In article ,
"Iain Churches" wrote:

"John Byrns" wrote in message
...


For the first time in a long time I have to agree with Phil, something
just doesn't add up here. By the way, where did these specs. come from,
did I miss a link on Ian's page?

Morning John.

Last night, I listened to Shostakovich 2nd Symphony (Op 14)
the excellent interpretation by Gothenburg Symphony Orchestra
conducted by Neeme Järvi.

I turned up the level so that I could not stay in the room.
Then, using the remote, I put the CD player onto pause,
and returned to my listening chair. There was silence, so I
think the performance of the preamp is as it should be.

There are two possibilities here.
a) The pair of tubes I have fitted (RCA cleartops) are noisy
(possible but unlikely)

b) My noise measurement methods are incorrect (much
more likely)

The preamp has been packed up now, and shipped off
to the first of several people who want to hear it. So I
shall not be able to investigate further for a while.

What sort of a SNR (A weighted) should I expect
from an active loaded cathode follower?

Hi Iain,

There are two issues here, first what sort of unweighted SNR you should
expect, and second what effect will A weighting have on the SNR. Taking
the A weighting issue first, I would think the effect would depend on
what the dominant noise source is in your preamp, is it noise due to
random processes in the components used, or is it due to line frequency
harmonics from the power supply? How was the input terminated for the
SNR measurements?

With respect to the noise you should expect, assuming all the line
frequency related noise has been dealt with, we should be able to
calculate that. Unfortunately I don't do those calculations on a daily
basis, so I would have to root around in my files to find the relevant
formulas. Perhaps while I am searching, someone else has the necessary
formulas right at their finger tips, and can provide the answer more
quickly than I ccould?

When Phil said your output noise level was too high I started wondering
could he be correct? My first thought was my "Power Amplifier Without
Power Transformer", which uses a 12SN7 driver stage. This amplifier has
an output noise level greater than 80 dB below 1 Watt output, without
negative feedback. I thought I would do a quick calculation to estimate
what the noise level at the output of the 12SN7 stage might be. I did
the calculations with a calculator, and without writing anything down,
and found the noise level at the output of of the 12SN7 to be in the
same general ballpark as your preamp. This did not seem to be a
promising result relative to your preamp, as my PAWPT uses a series
heater string across the power line, and a half-wave rectifier directly
off the power line, with the output stage B supply filtered only by the
main filter capacitor, not necessarily a recipe for low noise. I will
have to run through the calculations again, writing down the steps, to
be sure I didn't skip a digit somewhere.

Another way to look at the preamp output noise is to consider what would
happen if you feed a 120 uV noise source into a power amp with a typical
gain of 20X. For an 8 Ohm load that would give an output noise level
only about 61 dB below 1 Watt, not exactly a top rank result.

Only the actual calculation, which I will try to do later, will tell us
what sort of noise level you should expect. I would hope for 40 uV of
noise at worst, and would prefer less than 12 uV of noise, although I
don't know if that is possible.


Regards,

John Byrns

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

[robert casey]

Comments were interesting. Most people were averse to
the ubiquitous silver anodised equipment that seems to
adorn every hi fi shop. Most preferred filament indicator
lamps to LEDs (when someone bothered to show them
the difference)

That's just styling decoration, which has no effect on the sound (unless
someone does something that removes shielding to a sensitive part of the
circuit, or such). But I do admit to not liking the current fashion
that has the tubes sticking outside the "cabinet" without any metal cage
or such to enclose them. Tubes get hot, and I don't like burning myself
on them... But a cage should have lots of holes for ventilation, so
you still get to see the cool looking heater glow!

Most preferred engraved panels to silk screen.
All preferred our laser etched dials to either of the
other two possibilities.

I prefer the silver box over a black box, if for the only reason that I
can actually see the black markings on the silver panel a lot better
than white (or gray) markings on a black panel. I have a few black
boxes, and I always have to look closely at the markings to see which
button to press. PITA!

[robert casey]

Eventually, we will coax a schematic from the man, and why the noise is
so high.



I will draw it when I have time.

Please understand that the most valuable document in a DIY forum or NG
is the schematic circuit diagram. Otherwise we won't really comprehend
exactly what you did. Photos of the completed boxes are pretty, but
don't really tell us much.

[robert casey]

How was the input terminated for the
SNR measurements?


I'm no expert in SNR measurement methods, but I'd think that the input
jack should have a resistor to ground, and the value of that resistor be
the same as the Thevinan equivalent impedance of the expected sources.
Like 47K if it's a phone cart, but this isn't a phono preamp. And other
sources' impedances are all over the map, so we should pick something
that makes for "worst case" conditions. Probably a higher resistance
value. 100K?

[Phil Allison]

"Iain Churches"


As soon as this unit comes back from a demo tour, my pals
at Swedish Broadcast have promised to measure the noise floor.
My best AC voltmeter (Marconi) has 300µV as the lowest
range, so perhaps the resolution is not good enough to measure
this unit accurately.


** Hey ****wit.

If you wanna measure low level noise - first you gotta * amplify * it !!!

A flat response gain stage, with one or two op-amps, will provide 100 or
even 1000 times gain.

Then you attach an audio band filter and finally a wide band millivolt
meter.



......... Phil

[Phil Allison]

"robert casey"

I'm no expert in SNR measurement methods, but I'd think that the input
jack should have a resistor to ground, and the value of that resistor be
the same as the Thevinan equivalent impedance of the expected sources.


** For a CD player or similar, that is about 250 ohms.

But even that is pointless, as all active sources have their own output
noise - way above that of the impedance alone.


Like 47K if it's a phone cart,


** ********.

A phono cartridge in an inductance, so has a source impedance that rises
with frequency.

A 47 kohm resistor is fitted to the pre-amp as a LOAD for that cartridge.

With NO cartridge connected, the noise level from a typical phono pre-amp
is 10 to 20 dB higher than when one is connected.

Are you so asinine you have never noticed this ???



And other sources' impedances are all over the map,


** No they are not - you bull****ting ass.

The expected source are all active and have very low impedances.




........ Phil

[Patrick Turner]

Iain Churches wrote:

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

I have received as many replies and comments re
this preamp, by e.mail direct as I have on the NG,
and people off-list are usually much
more helpful and constructive.

The emails are doubtlessly helpful and constructive to you, but they are
useless to the rest of us who would like to learn something from the
various projects presented on this forum. Unfortunately there are those
who don't like to share, perhaps they lack confidence in their ideas,
and revert to email. Both the best and the worst comments seem to be
reserved for email.

Hello John.

Many of those who keep in touch by e.mail are former
subscribers to this and other Usenet groups. Most
of them can be found on closed groups to which the
lunatic fringe (in our case PA and AK) are denied
access. The discussion on such fori is well-informed
and constructive. Pics and schematics can be posted.
I have access to two such groups, which are divided
by general topic into several sub groups, broadcast,
studio practice, studio engineering, music performance,
audio teknik (which includes tube amps) etc etc
There are sometimes a total of 200 posts, all on
topic in 24 hrs.

No wonder so many eschew the bar-room brawl
that RAT has become.

Iain

PS Just had a mail from a pal who read your post.
He says "Closed groups are like large condenser
microphones. The only people who don't like them
are those that do not have access to them":-)

I must be the exception. I have access to a bunch of little secret
groups
and won't take part in any of them.

I have visted some of these groups but rarely felt a need to reply to
anything I read,
or I would have shown them more interest.
But I only get to talk to maybe one or two people who often don't know
very much and who
hate their pet theories being challenged.
I'd much rather post to the widest pssible audience.

I would say that there are a large number of people in the minor groups
who keep their eye
on what is said here, but are afraid to take part because they would
just get treated as fools or
idiots. But because this is an unmoderated group, ie, is like a beach
without a shark net,
one has to be concise and truthful and knowledgeable to take a swim in
these waters,
and be quite prepared to proove what you say, and say a lot in
explanation, not just some dumb one liner.
So there is an imperative to bring one's technical competence up to a
certain level
BEFORE trying to discuss matters with authority, and unless you have
studied and done your homework,
ridicule greets you if you come here unprepared.

All these little groups have HORRIBLE access paths and their site all
don't work as easy and simply
as a usernet group, with the groups listed in my inbox, and one click
brings me to the day's postings with header titles, and I can review
everything posted for the recent past.
Another click brings me whatever post i want to reply to.
one more click is for reply, and I get a full page to type into,
not some STOOPID 100mm x 50mm section of the screen.

My intelligence is insulted by the outright display of incompetence
promulgated by all these
little discussion groups; they'd like me there, I have been invited,
but they want me to eat a **** sandwich before and while I take part.

They know where I am, and where I post. Why can't they be real men and
expose
their ideas to the whole world without fear like I do?
They don't like the heat of being challenged, they expect to get away
with believeing their own BS,
and most have no passion about anything.

I am not going to waste my precious time yabbering at dumbos via
rottenly set up group formats.
I wouldn't mind being able to take part, but its all got to be easier to
use.

Patrick Turner.

[robert casey]

Like 47K if it's a phone cart,



** ********.

A phono cartridge in an inductance, so has a source impedance that rises
with frequency.

A 47 kohm resistor is fitted to the pre-amp as a LOAD for that cartridge.

With NO cartridge connected, the noise level from a typical phono pre-amp
is 10 to 20 dB higher than when one is connected.

Are you so asinine you have never noticed this ???

:-)
Well, then, maybe I should use an actual phono cart (housed inside a
shielded box to avoid external noise pickup). Been a while since I've
messed with record players.




And other sources' impedances are all over the map,



** No they are not - you bull****ting ass.

The expected source are all active and have very low impedances.

:-)
Okay, but I was thinking of sources like a vintage vacuum tube FM tuner,
which tend to have higher output impedances.

(wouldn't be suprised to have having had another brain fart, I've done
it before...) :-)

[west]

"Iain Churches" wrote in message
. fi...
Andre asks what all the tubeheads are doing.
You can see what this tubehead is doing at:

http://www.kolumbus.fi/iain.churches/Preamp/203A.html

It's a joint effort together with my pal Markus.
He is a very skilled metal worker and made the
casework, and also laser-cut the stainless steel
top grille.

We decided to do as much possible ourselves.
Any comments would be of interest.

Regards to all
Iain

Did Marcus and you do all the metal work in your lab or did he do any of it
at his work place? If done at your lab, that leads me to another question
.... Knowing little about metal work, can an individual buy all the needed
equipment (perhaps you can list all the needed equipment) and diy or is this
strictly left to the professional metal worker? I bet Marcus doesn't know
Greek or Latin. ;-)

Cordially,
west

[Patrick Turner]

Iain Churches wrote:

"Patrick Turner" wrote in message
...

Eventually, we will coax a schematic from the man, and why the noise is
so high.

Hello Patrick,

I will draw it when I have time.
In actual fact we have established that the noise is not high, but my
method of measurement erroneous.

As soon as this unit comes back from a demo tour, my pals
at Swedish Broadcast have promised to measure the noise floor.
My best AC voltmeter (Marconi) has 300µV as the lowest
range, so perhaps the resolution is not good enough to measure
this unit accurately.

Best regards
Iain

To measure noise below 300uV, you need a low noise amplifier
to raise its level to work a meter or display it on a CRO or both.

So you need to make a wide band amp, at least 10Hz to 20kHz with gain of
up to 1,000
for noise measurements, but gain able to be varied between say 10 and
1,000.
So if noise = 3uV, it is amplified to 3mV after the amp, and able to be
measured/displayed
by gear you have already.

Its so darn easy, but takes time and understanding, and you are short of
both.

There are many opamps good enough to raise a small signal to a larger
one for measurement
and without adding any substantial noise&distortion of their own.

I became frustrated with my limitations on what I could measure
while I taught myself to answer the myriad of questions I asked of
myself
in years spent locked in my shed before I dared to go online
where I might be ridiculed for not doing/understanding very much.

So amoung the simple test gear I did build was a millivolt meter with 6
ranges 1mV to 1,000Vrms with 2Hz to 1MHz bandwidth.
They are based on discrete solid state devices and opamps, no need for
tubes.
A wide band amp, 10Hz to 30MHz with two 2N222 with gain of 20 raises
signals a bit if I need to.
For measuring noise in input tubes, ie, establishing what the grid input
noise is of any given sample triode,
a 20Hz to 20kHz 3 stage tube amp with max gain = 1,600 is used. Its like
a very quiet microphone amp.
These are not pretty, but have worked fine for 10 years so far,
and building them taught me a heck of a lot.
I expect you'll do similar if you really want to learn something.
When something you design yourself doesn't work, you have to learn more
and apply the knowhow until it works
better than the text books say it should. Then you proove that to
yourself.
You should then be able to proove to others the method behind the
madness is all OK.
Then you have arrived.
If you have not done exercizes like the ones I have outlined, you can't
do much
except copy everyone else, and hope for the best, and put up with lots
of your own mistakes.

I have posted previously on noise and its measurement here at r.a.t
Were you asleep? Did it all go in one ear and out the other?

Noise should be measured with the gain turned up and input grounded.
It should be described as figure without any signal present.
A normal well chosen 6DJ8, 6CG7, perhaps 6SN7, 12AY7, and many others
should have
no more than 2uV at the grid when grounded. It is generated by the
equivalent input resistance which is a figure for any device and you
have yet to comprehend
such technical issues.
But suppose you have a common cathode mode 6CG7 with well bypassed
cathode, ( 2k plus 2,200 uF ),
RL = 50k, then at 4mA for Ia, perhaps gain = 16. You want to test its
noise.
The grid is taken to ground with a lead not exceeding 25mm.
DC is used on the heater to avoid hum, which may well be much above the
hiss, or wide band noise we wish to measure.
If there is 1uV of hiss noise at the grid, you get 16uV noise at the
anode, and when amplified
by a subsequent tube amplifier of similar tubes the noise at the anode
of the tube under test
will well dominate the measurements because noiase voltages
when added are the square root of the sum of voltages squared, something
else you need to know.
So when two cascaded stages of 6SN7 are added after the DUT tube, the
16uV is amplified
256 times to 4,096uV, or 4.1mV, and easily measured or seen.
Hum will perhaps obscure what noise you are measuring, so you MUST
specify what sort of noise it is that you are measuring.
Is the 120uV of noise from your CF "preamp" hum? or is is wide band
hiss, like pink noise?
Technically, what you have built isn't a preamp, its an integrated
buffer, because it does not have
any gain, and so amplifies nothing.

Therefore if the grid uput noise was 1uV, the cathode output should also
be 1uV
Even at 1mV of output signal the SNR would be -60dB, and at a volt of
output
SNR should be -120dB.
In practice this is not all that easy to achieve.
But it is where competent designers aim for.


We all look forward to a schematic of your latest creation.
In another of your posts, your verbal explanations about the schematic
to Mr Byrns
were about as clear as a beer bottle full of mud,
and if you do attempt to explain a schematic in words in future, please
show more respect to your fellow group members with more concise
terms, double check what you have said, make it simple and easy and
unambiguous,
to avoid us wasting so much of our precious time to de-cyphering WTF you
have tried to say,
and getting knowhere.

Patrick Turner.

[Patrick Turner]

Iain Churches wrote:

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

No mystery Patrick. I stated clearly that it is an active load cathode
follower, which was chosen after comparison with a mu-follower and
a cascode.

I have no schematic drawn. It can be found in any one of a dozen
books

The cathode follower part sounds straight forward enough, but the
"active load" part could be anyone of a number of things. Is the
circuit what I think is called a "White" cathode follower?

The White CF is similar, except that the anode of the bottom
triode and the cathode of the upper triode are usually at the
same potential. The grid of the top triode is biased by a pair
of resistors from the B+ to ground, with the junction of these two
Rs connected to the grid.

On the ALCF the grid of the lower tube is biased in this
way. The anode of the lower tube and the cathode of the
upper tube are separated by a resistor of about 1k2 to
give a differential of about 2V between them.
1M is then connected from anode 1 to grid 2 for bias
(rather like the mu-follower)

Best regards
Iain


Unfortunately, I have no idea what Iain is talking about at all.

Maybe Iain doesn't know either.

Patrick Turner.

[John Byrns]

In article ,
"Iain Churches" wrote:

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

No mystery Patrick. I stated clearly that it is an active load cathode
follower, which was chosen after comparison with a mu-follower and
a cascode.

I have no schematic drawn. It can be found in any one of a dozen
books

The cathode follower part sounds straight forward enough, but the
"active load" part could be anyone of a number of things. Is the
circuit what I think is called a "White" cathode follower?

The White CF is similar, except that the anode of the bottom
triode and the cathode of the upper triode are usually at the
same potential. The grid of the top triode is biased by a pair
of resistors from the B+ to ground, with the junction of these two
Rs connected to the grid.

On the ALCF the grid of the lower tube is biased in this
way. The anode of the lower tube and the cathode of the
upper tube are separated by a resistor of about 1k2 to
give a differential of about 2V between them.
1M is then connected from anode 1 to grid 2 for bias
(rather like the mu-follower)

OK, Thanks, I think I understand. The bias sounds like it is done the
same way as the circuit at the link I posted. It is not clear from your
description if the bottom triode serves simply as a passive load for the
cathode follower, or if a signal is applied to the grid of the lower
triode making it an active load?


Regards,

John Byrns

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

[John Byrns]

In article ,
"Iain Churches" wrote:

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

Removing the stainless steel grille to change the tubes
reveals what appears like an empty compartment with
just the tubes and the tube bases set horizontally into a
4mm bulkhead. There is a "false floor" under which
the cable harness runs to the input selector and
switched attenuators at the front.

Wouldn't it be better to eliminate the false floor and provide a steel
grille on the bottom to provide improved air circulation for better
cooling?

John. There are cooling slats in the base plate.
The air is vented through the lower edges of the bulkhead.

Maybe I shouldn't even suggest that as the steel grille on top is the
one design element that doesn't look quite right to my eye, although I
am not sure why.

Perhaps the pic does not do it justice? Most people who
have seen the unit are of the opinion that the laser etched grille
together with the stainless steel dials sets off the whole
appearance of the unit beautifully.

Yes, it is very beautiful, especially the dials, except the screws that
hold the grilles on are a sort of discordant note, I would prefer that
they were recessed, but that is just one man's opinion. Absolute
perfection is difficult to achieve.

Speaking of perfection, did you ever consider building a matching
equalizer to go with the preamp?


Regards,

John Byrns

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

[Iain Churches]

"Patrick Turner" wrote in message
...

I must be the exception. I have access to a bunch of little secret
groups
and won't take part in any of them.

I think you are mistaken Patrick.The groups to which you refer
are moderated but not closed groups. That's a totally different
thing altogether.

Closed groups, for example the broadcast and recording group
to which I have access, are used by professionals. If they are not
members of the university, institute or company which runs the
group, they are there strictly by invitation only.

Your are correct in saying that people do keep an eye on RAT.
Recruiting to closed groups is not uncommon, and I have never
met anyone who has refused the invitation:-)

You bump into lot of familiar and respected names. Have
you ever wondered why, with the exception of yourself, no
other professional audio designer or manufacturer has a
presence here?

Regards
Iain

[bassett[_2_]]

Well I,ve read all the posts about your little project, And it does look
the part, At least you have used proper wood, and not MDF with plastic
veneer. tell me it's proper wood. It's a wonder someone's not commented
on the inner resenance of the wood causing ground noise, or some such
bull****.

Anyway, after all the pro's and con's , in's and out's, chicken's and
egg's , asking as a consumer of this sort of stuff, Just what does it
sound like, and is it any good.

Iv'e found that simply because it looks the part, does not mean it will
deliver, I had a mate come up the other weekend with a lambo Countach,
dunno where he got it, but hopyfully he took the thing back, load of
rubbish, and when you consider the price , when it was new. So looks
mean nothing, performance is what counts.

I also could not find any info on what the output or your amp was,
but then I wasn't really looking.

And regardless of what you might have used or not used, the bottom line is
the results it can produce, completely regardless of measurements, data,
or other total rubbish, that might look very respectable on paper, but
does absolutely nothing to the end product, which is the sound it
produces.

You say that you tested it , and had the volume turned up, so you
could no longer stay in the room, but failed to say for how long was it
running, Was it 10 minutes, a couple of hours, a day, a week, or until the
thing self-destructed. So as you could then work out what had failed and
replaced it with something bigger and stronger.. You also failed to say
how big the room was..
You may be surprised to learn, that some people do run there stuff at
maximum volumes, to the point where crossover coils melt, and catch fire.

Finally, your plugs are nothing special, I can get the same things from
WES a lot cheaper then there quoting.
bassett

[bassett[_2_]]

"Patrick Turner" wrote in message by e.mail are
former

I must be the exception. I have access to a bunch of little secret
groups
and won't take part in any of them.

I have visted some of these groups but rarely felt a need to reply to
anything I read,
or I would have shown them more interest.
But I only get to talk to maybe one or two people who often don't know
very much and who
hate their pet theories being challenged.
I'd much rather post to the widest pssible audience.

I would say that there are a large number of people in the minor groups
who keep their eye
on what is said here, but are afraid to take part because they would
just get treated as fools or
idiots. But because this is an unmoderated group, ie, is like a beach
without a shark net,
one has to be concise and truthful and knowledgeable to take a swim in
these waters,
and be quite prepared to proove what you say, and say a lot in
explanation, not just some dumb one liner.
So there is an imperative to bring one's technical competence up to a
certain level
BEFORE trying to discuss matters with authority, and unless you have
studied and done your homework,
ridicule greets you if you come here unprepared.

All these little groups have HORRIBLE access paths and their site all
don't work as easy and simply
as a usernet group, with the groups listed in my inbox, and one click
brings me to the day's postings with header titles, and I can review
everything posted for the recent past.
Another click brings me whatever post i want to reply to.
one more click is for reply, and I get a full page to type into,
not some STOOPID 100mm x 50mm section of the screen.

My intelligence is insulted by the outright display of incompetence
promulgated by all these
little discussion groups; they'd like me there, I have been invited,
but they want me to eat a **** sandwich before and while I take part.

They know where I am, and where I post. Why can't they be real men and
expose
their ideas to the whole world without fear like I do?
They don't like the heat of being challenged, they expect to get away
with believeing their own BS,
and most have no passion about anything.

I am not going to waste my precious time yabbering at dumbos via
rottenly set up group formats.
I wouldn't mind being able to take part, but its all got to be easier to
use.

Patrick Turner.


Well if I wasn't depressed before, I am now. Your the sort of
person who would complain about the cab fare to the bridge, you were going
to jump off.

Mate, get a grip, go out and buy yourself a good root, you might just
feel a bit better.
If you where happy, you would complain about the cost of breathing, and
the time it took out of your day.
bassett

[Iain Churches]

"west" wrote in message
newsVgTh.5927$SK3.3050@trnddc03...

"Iain Churches" wrote in message
. fi...
Andre asks what all the tubeheads are doing.
You can see what this tubehead is doing at:

http://www.kolumbus.fi/iain.churches/Preamp/203A.html

It's a joint effort together with my pal Markus.
He is a very skilled metal worker and made the
casework, and also laser-cut the stainless steel
top grille.

We decided to do as much possible ourselves.
Any comments would be of interest.

Regards to all
Iain

Did Marcus and you do all the metal work in your lab or did he do any of
it
at his work place? If done at your lab, that leads me to another question
... Knowing little about metal work, can an individual buy all the needed
equipment (perhaps you can list all the needed equipment) and diy or is
this
strictly left to the professional metal worker? I bet Marcus doesn't know
Greek or Latin. ;-)


Hi West. One of the big advantages of sharing a
workshop with three other guys is that they all bring
something to the party, in the shape of radial drill presses,
a milling machine, a linisher, a fly press, a turret press
punches, taps and dies etc. So then most work can
be done in house. CNC machining, laser cutting and lettering
is the exception.

My pal is a highly skilled tool-maker, but just as you surmise he
reads neither Greek nor Latin, neither can he play the Rachmaninoff
piano concerto or transcribe a 5 part saxophone riff to manuscript
paper:-)) I very much enjoy working with other people, hearing
their ideas, and discussing with them. Each and everyone of us
has a unique skill set, some are good at the visual concept, some
can solder and wire to mil spec. Others make great coffee:-)

If you are thinking of making chassiswork for hobby projects,
perhaps it would be better, and time saving, to take your ideas
and drawings to a third party metal-shop. If you can find a small
place, a proto shop, with someone who is interested in what you
are doing, then so much the better. You don't need incredibly
small tolerances. These days, most metal shops use CNC machines
and can drill punch and bend to 0.01mm with ease. The trouble
is they need CAD generated files to make anything, and are not
really interested in small quantities so a small old fashioned shop
with a guillotine and a hydraulic folding press is what you are
looking for:-)

The other possibility is of course a pre fabricated chassis.
Hammond have a good range, and the old ubiquitous
battleship-grey has been augmented by a very smart black
powder coated range. They also have tube cages to match.
You can see the 1441 series and the 1454 cages at:

http://www.hammondmfg.com/scpgMET.htm

I have also been looking into the possibility of making PCBs,
I currently use turret boards. Believe it or not, it is a lot cheaper
to buy copper clad board, and have a PCB shop etch the
copper away for you than buy plain board. But there are
advantages in being able to design a ground plane on the
reverse side of the board.

Reading the replies to my question on this subject of PCBs
here on RAT, one would get the impression that it was a
waste of time even to try to get professional results. I had
e-mails from several people, who described in detail their
methods. One even sent some excellent pics of his work,
on 2.4mm board, lacquered and silk screened. Another
fellow who lives on the other side of the world, has offered
to help me get started. People are generally pretty decent.

Regards
Iain

[Iain Churches]

"bassett" wrote in message
...


Well I,ve read all the posts about your little project,

Hardly "little". I wouldn't like to estimate the number of man
hours from first concepts to completion. It has been about
two years, although we did have a prototype running about a
yeara ago then someone bought it.


And it does look the part, At least you have used proper wood, and
not MDF with plastic veneer. tell me it's proper wood.

Yes - solid teak. 25mm. People have also asked about
walnut or Scandinavian pine.

It's a wonder someone's not commented on the inner resenance of the wood
causing ground noise, or some such bull****.

There is still time:-)

Anyway, after all the pro's and con's , in's and out's, chicken's and
egg's , asking as a consumer of this sort of stuff, Just what does
it sound like, and is it any good.

About fifty people have hard it up to now. Many of these are audio
pros. No-one could find anything negative to say about the sound. There
have been a couple of comments about styling, but that's a personal thing
anyway, and you can't hope to please everyone:-)


Iv'e found that simply because it looks the part, does not mean it
will deliver, I had a mate come up the other weekend with a lambo
Countach, dunno where he got it, but hopefully he took the thing back,
load of rubbish, and when you consider the price , when it was new. So
looks mean nothing, performance is what counts.

Indeed.

I also could not find any info on what the output or your amp was,
but then I wasn't really looking.

It's a unity gain preamplifier.

And regardless of what you might have used or not used, the bottom line
is the results it can produce, completely regardless of measurements,
data, or other total rubbish, that might look very respectable on
paper, but does absolutely nothing to the end product, which is the
sound it produces.

Personally I agree with Morgan Jones who writes that no preamplifier
is better than any preamplifier, so at home I have my CD player
plugged straight into my power amp (sensitivity 0dBV for 50W) with
a pair of stepped attenuators at the front end.

But when you have more than one source, even though you may not need
extra gain, some sort of a preamp with multiple inputs is required.

You say that you tested it , and had the volume turned up, so you
could no longer stay in the room, but failed to say for how long was
it running, Was it 10 minutes, a couple of hours, a day, a week, or until
the thing self-destructed. So as you could then work out what had failed
and replaced it with something bigger and stronger.. You also failed
to say how big the room was..

We were discussing the noise floor. I mentioned that I turned the system to
a level at which one could not stay in the room. Then, using the remote,
I put the CD player onto pause, and went back to the listening position
to evaluate the system noise. There was none.

This was not a test of durability. The build quality of this amp and the
quality of components used make me think that it will be totally reliable
Time will tell. Many have reservations about lead-free solder!

The tubes are running at fairly low current, with regulated current for
heater and regulated voltage for HT. They should run for 10 000 hrs
before needing to be replaced.

Finally, your plugs are nothing special, I can get the same things
from WES a lot cheaper then there quoting.

I did not claim they were anything special. They are the industry standard
studio and broadcast unbalanced analogue connector.

Best regards
Iain

[Iain Churches]

"John Byrns" wrote in message
...

Speaking of perfection, did you ever consider building a matching
equalizer to go with the preamp?


Regards,

John Byrns


Gosh, John. You must have a crystal ball:-)
But first comes the matching RIAA stage, a grounded
grid cascode which will run from the same psu.

Then I thought about an equaliser, a subtle three-band
-3dB, 0, +3dB at LF MF and HF.

Plus of course an ME (eye tube) to indicate level:-))

Iain

[Iain Churches]

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

"John Byrns" wrote in message
...
In article ,
"Iain Churches" wrote:

No mystery Patrick. I stated clearly that it is an active load
cathode
follower, which was chosen after comparison with a mu-follower and
a cascode.

I have no schematic drawn. It can be found in any one of a dozen
books

The cathode follower part sounds straight forward enough, but the
"active load" part could be anyone of a number of things. Is the
circuit what I think is called a "White" cathode follower?

The White CF is similar, except that the anode of the bottom
triode and the cathode of the upper triode are usually at the
same potential. The grid of the top triode is biased by a pair
of resistors from the B+ to ground, with the junction of these two
Rs connected to the grid.

On the ALCF the grid of the lower tube is biased in this
way. The anode of the lower tube and the cathode of the
upper tube are separated by a resistor of about 1k2 to
give a differential of about 2V between them.
1M is then connected from anode 1 to grid 2 for bias
(rather like the mu-follower)

OK, Thanks, I think I understand. The bias sounds like it is done the
same way as the circuit at the link I posted. It is not clear from your
description if the bottom triode serves simply as a passive load for the
cathode follower, or if a signal is applied to the grid of the lower
triode making it an active load?


Just as in the White topology, the input to the ALCF is taken to
the grid of the upper tube. The lower triode is a CCS.

Iain

[Iain Churches]

Hello John,

Just a brief "top" reply to your post. Thanks very much for
your comments - greatly appreciated.

I am off on a recording trip tomorrow. I wil print out
your post, and take it with me for careful reading.

As I mentioned in my earlier post, there is no audible noise
from the listening position, so I think that the performance of
the amplifier is as it should be, but my measuring technique
leaves something to be desired:-)

Many thanks again for your input.
Best regards

Iain





"John Byrns" wrote in message
...

Hi Iain,

There are two issues here, first what sort of unweighted SNR you should
expect, and second what effect will A weighting have on the SNR. Taking
the A weighting issue first, I would think the effect would depend on
what the dominant noise source is in your preamp, is it noise due to
random processes in the components used, or is it due to line frequency
harmonics from the power supply? How was the input terminated for the
SNR measurements?

With respect to the noise you should expect, assuming all the line
frequency related noise has been dealt with, we should be able to
calculate that. Unfortunately I don't do those calculations on a daily
basis, so I would have to root around in my files to find the relevant
formulas. Perhaps while I am searching, someone else has the necessary
formulas right at their finger tips, and can provide the answer more
quickly than I ccould?

When Phil said your output noise level was too high I started wondering
could he be correct? My first thought was my "Power Amplifier Without
Power Transformer", which uses a 12SN7 driver stage. This amplifier has
an output noise level greater than 80 dB below 1 Watt output, without
negative feedback. I thought I would do a quick calculation to estimate
what the noise level at the output of the 12SN7 stage might be. I did
the calculations with a calculator, and without writing anything down,
and found the noise level at the output of of the 12SN7 to be in the
same general ballpark as your preamp. This did not seem to be a
promising result relative to your preamp, as my PAWPT uses a series
heater string across the power line, and a half-wave rectifier directly
off the power line, with the output stage B supply filtered only by the
main filter capacitor, not necessarily a recipe for low noise. I will
have to run through the calculations again, writing down the steps, to
be sure I didn't skip a digit somewhere.

Another way to look at the preamp output noise is to consider what would
happen if you feed a 120 uV noise source into a power amp with a typical
gain of 20X. For an 8 Ohm load that would give an output noise level
only about 61 dB below 1 Watt, not exactly a top rank result.

Only the actual calculation, which I will try to do later, will tell us
what sort of noise level you should expect. I would hope for 40 uV of
noise at worst, and would prefer less than 12 uV of noise, although I
don't know if that is possible.


Regards,

John Byrns

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

[Iain Churches]

"Patrick Turner" wrote in message
...


To measure noise below 300uV, you need a low noise amplifier
to raise its level to work a meter or display it on a CRO or both.

So you need to make a wide band amp, at least 10Hz to 20kHz with gain of
up to 1,000
for noise measurements, but gain able to be varied between say 10 and
1,000.
So if noise = 3uV, it is amplified to 3mV after the amp, and able to be
measured/displayed
by gear you have already.

Ok. Understood. Thanks for that. I have a good selection of op-amps
used in prof recording consoles. I can get something put together without
too much trouble. A "lurker" on RAT sent me an e-mail with the same
info as you supplied, and offered to make such a measurement amp, so
that is also an option.

Its so darn easy, but takes time and understanding, and you are short of
both.

For me this is a hobby. I devote as much time to it as I am able.
Don't be too pretentious about "understanding" You are a professional
amp builder, one would expect you to know the detail. My skillset
and training is totally different. I am currently editing a 24 track big
band recording from a full score. Would you know where to start,
Patrick? :-)

The remainder of your post contains much interesting info.
Thanks. I have printed it out for careful study.

Best regards
Iain

[Iain Churches]

"Patrick Turner" wrote in message
...


Iain Churches wrote:

Tremaine 4th edition dates from 1975.

No mystery Patrick. I stated clearly that it is an active load cathode
follower, which was chosen after comparison with a mu-follower and
a cascode.

I have no schematic drawn. It can be found in any one of a dozen
books

Hardly any of us have a copy of Tremaine's 4th Edition, Audio
Encyclopedia.

That's probably because its name is Audio Cyclopedia:-))

There IS a MYSTERY.

How can we talk about your amp details without a schematic????????

It will be just bull****ting into the wind without one.

You may indeed have a nice device, but here you have to proove it.

No Patrick. I don't have to *proove* (sic) anything to anyone, here.
This is not the Spanish Inquisition. Neither is it a professional group
(if it were, you would be the sole member:-) As I understand it,
RAT is a recreational (hobby) group.

Against the wished of my pal with whom I shared this project, I
started this thread on RAT to relieve the monotony of Arny's
OT drivel and Phil's cut-and-paste invective.

Here is where when someone says something, it better be right,
and reasons given, or its deemed to be wrong.
When you show something, its prudent to offer the full story
with a schematic.

Few hobbyists can meet your expectations. That is probably
why so few project threads appear. If you set the threshold too
high you will end up with a pleasant but fast-shrinking band of
tubeheads, plus one autistic Australian toaster repairer, and a
Born Again tambourine basher from Michigan:-)


Iain

[Patrick Turner]

Iain Churches wrote:

"Patrick Turner" wrote in message
...

I must be the exception. I have access to a bunch of little secret
groups
and won't take part in any of them.

I think you are mistaken Patrick.The groups to which you refer
are moderated but not closed groups. That's a totally different
thing altogether.

OK, you make a further important distinction.
The "little" groups I refer to are the ones the public is free to read,
but you have to subscribe, use a pass word, and obey rules or
get banned. I have nothing against all these things,
its just that I find most of the groups are clumsy to use and read and
there simply isn't enough content for me to become involved with.


Closed groups, for example the broadcast and recording group
to which I have access, are used by professionals. If they are not
members of the university, institute or company which runs the
group, they are there strictly by invitation only.

They wouldn't like me being around then.



Your are correct in saying that people do keep an eye on RAT.
Recruiting to closed groups is not uncommon, and I have never
met anyone who has refused the invitation:-)

I recall I have subscribed to a few, been accepted, made one post,
and never returned. I read a dozen posts later and not feel I could say
much
that wasn't already being said about the trivial / beginner issue
being discussed.

If they had any questions, they know where I am.

Some weeks I get several private queries from around the world, and some
guys
are building things and need the help, and deserve it, because rather
than
just sit typing BS, they are soldering and measuring and calculating
their way through a project.



You bump into lot of familiar and respected names. Have
you ever wondered why, with the exception of yourself, no
other professional audio designer or manufacturer has a
presence here?

Because they are thin skinned, and when skinned alive here
they die fast after shrivelling up.

Their high profile name rests on a delicate ego.

They are very choosy about who they sit next to in
the railway carriage of discussions, and as you know, r.a.t
is a bit like a Bombay train full of noisy smelly
workers going home for the day after sundown.
If they don't like Hindu morons, they better keep quiet.
If they can afford it, they go in the 1st Class carriage,
and talk about the weather, politics, and the economy.
There is no kudos to be gained when talking to the masses,
unless you want them to vote for you,
and then you tell them what they want to hear, even in
the 1st class carriage. If you start asking questions,
making criticisms, they might throw you off the train.

Many "well respected" ppl's ideas can certainly be challenged,
questioned,
ridiculed, parodied, and their elete status can be reduced to being
fairly ordinary. Here there are NO SACRED COWS!!
Everything and anything is fair game for comment.
If someone survives here, they are fit, agile, and
durable indeed, and truly one who belongs to all manner of people, at
home in a pub,
or in court of a king.

I once tried rec.audio.hi-end, and found it had the the most
stultifying atmosphere. To be someone of influence there
I should have become far wealthier from audio, after starting 40 years
ago.
I felt I was very much a johnny come lately there.
And they didn't like tube gear much, let alone boutique DIY.
So after a few weeks I found I just didn't enjoy r.a.h-e

My ego fell off the back of a truck 20 years ago, and
being from a building worker background, I got use to spending all day
working hard down some hell hole with mud up to my knees, until the job
is done.
When confronted with unruly people around me I wasted no time dealing
with them.
I don't have to be too rugged too long, and they get the drift.

I don't have a "high profile" worth keeping mud free.
I'm just a bloke who enjoys audio and making gear and I have some ideas
about it worth
sharing. So I have written a website to make sure everyone knows what i
know
if they want to read something.
So I save having to repeat what is mainly common sense.

If people follow my reasoning, they will find good music.

When I was about 25, I was working as a sub-foreman on a
large multi-storey building at NSW University. I'd begun there
after being drawn from ranks of my peers as being worth being trained
for such large complex works.
I had a tendency to waffle on, and not compose language properly.
A seriously no-nonsense project general foreman once told me
"Look here mate, say only what you mean, and mean what you say, OK!"
The othe boss in charge was the project manager, and once had me run to
the
17th floor with messages for people or to find something, or find out
about something
4 times before morning tea one day. I just tried to obey,
and he must have been impressed, because I was quick and efficient, and
showed no strain.
But he told me plainly, "Spit it out man!, which do you mean? don't
speak
to me in riddles!", after I'd given a contradictory answer to his
questions.
In the trades, there can only be one answer.
I was somewhat overwhelmed at first by the size of the job, and could
easily be distracted,
and it took me a month to stop bull****ting, and make each word count
especially when addressing my superiors,
so I had to start each day commanding myself to be a Better Builder
Today!, OK.
I needed to ask more questions, and observe more thouroughly.
I became a better builder indeed, and years later I could thank the
hardened task masters for their
NO BS approach to all they did. When others were sacked, I was retained.
Apprentices sent to me for training
didn't have a picnic either, they actually had to work,
and sometimes motivation meant some very heated discussions
with a deal of acrimony about the sloppy, untidy, un-timely,
incompetent efforts they presented while they still expected to be paid
the same wages. Luckily this didn't happen often, and I had a good
reputation for
running peaceful productive sites with a low panic level and good safety
record.
I could see trouble coming, and didn't provoke it.
One foreman the company had who'd been an Olympic rower in '56 and who
was
the most rugged and powerful person once hung an apprentice over a
balcony
of a 14 storey building by holding onto only one ankle to impress upon
the lad
that misbehaviour was not going to occur again, and if it did, another
session
over the balcony would occur, only he would let go. "Big Dennis" as we
called him
was otherwise a very fine foreman we all liked.

I don't plan to enforce learning here like Dennis tried then. Too
over-the-top!

In other areas of my life, such as personal relationships, I've tried to
have the same
NO BS approach, and I've always preferred to back truth, even if it
embarrassed mates, or a succession of females. I was damn honest, and
although some office managers
and shielas sometimes didn't like it during disputes, they could respect
it.

When I come here, I naturally expect competent standards, and will try
to help anyone get there who isn't there yet.

Many in other groups are not very prolific, and just want to sit around
and
chat without any great goal in mind, and that's all fine,
but I like to see things achieved after a day's efforts.

Patrick Turner





Regards
Iain

[Patrick Turner]

I am not going to waste my precious time yabbering at dumbos via
rottenly set up group formats.
I wouldn't mind being able to take part, but its all got to be easier to
use.

Patrick Turner.

Well if I wasn't depressed before, I am now. Your the sort of
person who would complain about the cab fare to the bridge, you were going
to jump off.

No, I'd drive myself; no whingeing.


Mate, get a grip, go out and buy yourself a good root, you might just
feel a bit better.
If you where happy, you would complain about the cost of breathing, and
the time it took out of your day.
bassett

Be a nice doggie Bassett, and do try to finish your bowl of Chum.

Do not bassett hounds always look depressed? those long droopy ears,
legs way to short to run with?

I'd sure be depressed if I was a bassett.
I'd smell a bitch in heat and not be able to run after her.
When I got to her many hours later, mounting her would be impossible,
because where I wanna go would be way UP there.....

Patrick Turner.