[Arny Krueger]

"Patrick Turner" wrote in message

John Byrns wrote:

In article ,
Patrick Turner wrote:

Denon invented the MC way back in 1949, and the DL103R
cart is still available and still well regarded, and I
have one. Radio stations preferred the MC because of
better noise figures and possibly lower THD and I sure
found it better than MM Shure V15.

Are you sure the MC cartridge wasn't around before 1949?
I built my first MC cartridge as a teenager in the mid
1950s.

I am 99% sure that Denon invented the MC. Maybe a google
search will proove me wrong though.

This google search supports your claim:

https://shop.mantra-audio.co.uk/acat...artridges.html

"Denon built the world's first stereo moving coil cartridge in 1951 and have
been masters of the art of cartridge design ever since."

[Phil Allison]

"Arny Krueger"
"Patrick Turner"

I am 99% sure that Denon invented the MC. Maybe a google
search will proove me wrong though.

This google search supports your claim:

https://shop.mantra-audio.co.uk/acat...artridges.html

"Denon built the world's first stereo moving coil cartridge in 1951 and
have been masters of the art of cartridge design ever since."


** A Google search also DESTROYS that same, idiotic, unsourced and
unsupported claim.

" Early LP recordings were monaural, but stereo LP records became
commercially available in 1957. "

http://en.wikipedia.org/wiki/LP_album



...... Phil

[Patrick Turner]

flipper wrote:

On Wed, 5 Nov 2008 09:36:43 +1100, "Phil Allison"
wrote:


"Arny Krueger"
"Patrick Turner"

I am 99% sure that Denon invented the MC. Maybe a google
search will proove me wrong though.

This google search supports your claim:

https://shop.mantra-audio.co.uk/acat...artridges.html

"Denon built the world's first stereo moving coil cartridge in 1951 and
have been masters of the art of cartridge design ever since."


** A Google search also DESTROYS that same, idiotic, unsourced and
unsupported claim.

" Early LP recordings were monaural, but stereo LP records became
commercially available in 1957. "

http://en.wikipedia.org/wiki/LP_album

OK, don't ask me who invented or made the first monaural MC cart.

I searched awhile, and didn't find who.

But my DL103R Denon has been around a long time, and works for me.

Patrick Turner.





..... Phil


Are you guys arguing about MC or *stereo* MC? Mono MC carts were
around before the later.

Grado is credited with inventing the stereo MC and I presume that's
patent # 3040136 filed Jan 1959 (issued 1962).

http://www.pat2pdf.org/

[Ian Bell[_2_]]

Patrick Turner wrote:


snip


If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian

[Phil Allison]

"Ian Bell"

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types.


** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise - noise
from the valve will always be waaaay higher .



However, I am having trouble finding sources for 100K and 39K wire wound
types at anything less than 5W rating which is something of an overkill.
Do you know any good sources of high value low wattage wire wound
resistors (preferable non-inductive of course)?


** ROTFLMAO




........ Phil



Cheers

Ian

[Patrick Turner]

Ian Bell wrote:

Patrick Turner wrote:


snip


If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian

Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Patrick Turner.

[Patrick Turner]

Phil Allison wrote:

"Ian Bell"

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types.

** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise - noise
from the valve will always be waaaay higher .

Suppose noise generated by the V1 tube as 30uV at the output.
If total noise was 50uV, then you have to add far more than 20uV to 30uV
to get a total of 50uV,
because the total of a bunch of noise sources is the sq.rt of the total
of each voltage squared.

Interested ppl in such noise problems are advised to study theory more
deeply because its impossible for those of us who do manage to make amps
with excellent SNR to spend the time to repeat all we have said in the
past yet again.


However, I am having trouble finding sources for 100K and 39K wire wound
types at anything less than 5W rating which is something of an overkill.
Do you know any good sources of high value low wattage wire wound
resistors (preferable non-inductive of course)?

** ROTFLMAO

So impolite Phil, but I can see why you are laughing when there are
sources of highish values of wire wound around.

And as you say, why not metal film?

Patrick Turner.

....... Phil


Cheers

Ian

[Phil Allison]

"Patrick Turner"
Phil Allison wrote:
"Ian has Bats in his Belfry "

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise.
The solution seems to be to replace metal film resistors with wire
wound
types.

** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise - noise
from the valve will always be waaaay higher .

Suppose noise generated by the V1 tube as 30uV at the output.
If total noise was 50uV, then you have to add far more than 20uV to 30uV
to get a total of 50uV,
because the total of a bunch of noise sources is the sq.rt of the total
of each voltage squared.

Interested ppl in such noise problems are advised to study theory more
deeply because its impossible for those of us who do manage to make amps
with excellent SNR to spend the time to repeat all we have said in the
past yet again.


However, I am having trouble finding sources for 100K and 39K wire
wound
types at anything less than 5W rating which is something of an
overkill.
Do you know any good sources of high value low wattage wire wound
resistors (preferable non-inductive of course)?

** ROTFLMAO

So impolite Phil, but I can see why you are laughing when there are
sources of highish values of wire wound around.


** Not what I was laughing at - the bit about " non-inductively wound was
very funny.

How much L does it take to make a 100 kohm, WW resistor have say 101 Kohms
of impedance at 20 kHz ??

The answer is 113 mH !!!!!!!

The resistance wire would have to be wound on a Mu-Metal core to get such a
value.

Do the math.



...... Phil

[Ian Bell[_2_]]

Phil Allison wrote:
"Ian Bell"

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types.


** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise

Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise. With
150V across an anode resistor that an extra 15uV of noise I can well do
without.

Can you cite a supplier that quotes a lower figure?


Cheers

Ian

[Ian Bell[_2_]]

Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
snip

If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian

Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Patrick Turner.

[Ian Bell[_2_]]

Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
snip

If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian

Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.



Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?


Cheers

Ian
Patrick Turner.

[Phil Allison]

"Ian Bell"
Phil Allison wrote:
"Ian Bell"

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types.


** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise

Are they? Most metal film resistor suppliers that actually bother to spec
this usually put a figure of about 0.1uV/V for excess noise.


** What measurement bandwidth - eh ??

What resistance value - eh ??

Got no ****ig clue - have you.

You ****ING **** WIT




........ Phil

[Phil Allison]

"Ian Bell"


Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of resistor
type.


** No it is not - you hee hawwwing ASS





...... Phil

[Patrick Turner]

Phil Allison wrote:

"Patrick Turner"
Phil Allison wrote:
"Ian has Bats in his Belfry "

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise.
The solution seems to be to replace metal film resistors with wire
wound
types.

** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise - noise
from the valve will always be waaaay higher .

Suppose noise generated by the V1 tube as 30uV at the output.
If total noise was 50uV, then you have to add far more than 20uV to 30uV
to get a total of 50uV,
because the total of a bunch of noise sources is the sq.rt of the total
of each voltage squared.

Interested ppl in such noise problems are advised to study theory more
deeply because its impossible for those of us who do manage to make amps
with excellent SNR to spend the time to repeat all we have said in the
past yet again.


However, I am having trouble finding sources for 100K and 39K wire
wound
types at anything less than 5W rating which is something of an
overkill.
Do you know any good sources of high value low wattage wire wound
resistors (preferable non-inductive of course)?

** ROTFLMAO

So impolite Phil, but I can see why you are laughing when there are
sources of highish values of wire wound around.

** Not what I was laughing at - the bit about " non-inductively wound was
very funny.

How much L does it take to make a 100 kohm, WW resistor have say 101 Kohms
of impedance at 20 kHz ??

The answer is 113 mH !!!!!!!

The resistance wire would have to be wound on a Mu-Metal core to get such a
value.

Do the math.

I've never noticed a hugely worrying amount of L in higher value wire
wound R.

Then there is is the self capacitance of the wound turns.

I have not often used WW R for dc supply loads, but when I have its been
with low Ra triodes so the poles caused by reactances have been at
fairly high F.

I have not experienced problem with stability with use of WW R for anode
loads even when GNFB is used.

Non inductive WW R are available, with turns wound in two directions to
cancel out the inductance, but I've only ever seen low value types,
never high values.

Let me see now, XL of 0.113H at 20kHz = 0.113 x 20,000 x 6.28 = approx
15kohms.

So the Z (R + L) would be only very slightly greater than the 100k at 1
kHz.

But there are lots of turns.

I've never bothered to measure such things.

Patrick Turner.




..... Phil

[Patrick Turner]

Ian Bell wrote:

Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
snip

If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian

Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.


Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?

I've never noticed it in amps i have built. If I'd found that the noise
measurements didn't seem to add up, then I'd have been the one to reason
why.

I've usually used Welwyn or Beyshlag metal film R for most circuits.
Noise is negligible.

Patrick Turner.

Cheers

Ian
Patrick Turner.

[Eeyore]

Ian Bell wrote:

Phil Allison wrote:

Metal film resistors are near as damn it free of voltage noise

Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise. With
150V across an anode resistor that an extra 15uV of noise I can well do
without.

Can you cite a supplier that quotes a lower figure?

All the more reason to use solid state circuitry with lower voltages.

Graham

[Patrick Turner]

Eeyore wrote:

Ian Bell wrote:

Phil Allison wrote:

Metal film resistors are near as damn it free of voltage noise

Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise. With
150V across an anode resistor that an extra 15uV of noise I can well do
without.

Can you cite a supplier that quotes a lower figure?

All the more reason to use solid state circuitry with lower voltages.

Graham

15uV of noise isn't a heck of a lot to worry about if its after stage 1
of the amp, or at the output.

The use of a mic step up transformer should produce a good enough SNR
with a tube amp.

No need to use all SS.

But I like a j-fet at the input to drive a cathode of a grounded grid
triode.

It is of course an inherently quiet cascode circuit. No drain or cathode
resistance to be seen, and gain of such a stage 200.

So if input is 1mV, you get 200mV output, and if noise at the output was
20uV, you can work out the SNR at -80dB, unweighted.

Patrick Turner.

[Ian Bell[_2_]]

Phil Allison wrote:
"Ian Bell"

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of resistor
type.


** No it is not - you hee hawwwing ASS



Simple negation is no argument. I presently have about 65uV of noise
from the circuit under test. Eliminating a 15uV component of it is
worthwhile.

Cheers

Ian

[Ian Bell[_2_]]

Phil Allison wrote:
"Ian Bell"
Phil Allison wrote:
"Ian Bell"

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types.

** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise
Are they? Most metal film resistor suppliers that actually bother to spec
this usually put a figure of about 0.1uV/V for excess noise.


** What measurement bandwidth - eh ??

What resistance value - eh ??

Got no ****ig clue - have you.

You ****ING **** WIT


Sounds like you are back pedalling, Phil. You of all people will know
exactly how excess noise is specified (which includes the bandwidth). I
happen to have a 100K resistor in one anode which, from one
manufacturers graph, shows its excess noise is 0.1V/V.

As a said before, show me a manufacturer that quotes less.

CHeers

Ian



....... Phil

[Ian Bell[_2_]]

Patrick Turner wrote:

Phil Allison wrote:
"Patrick Turner"
Phil Allison wrote:
"Ian has Bats in his Belfry "

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise.
The solution seems to be to replace metal film resistors with wire
wound
types.
** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise - noise
from the valve will always be waaaay higher .
Suppose noise generated by the V1 tube as 30uV at the output.
If total noise was 50uV, then you have to add far more than 20uV to 30uV
to get a total of 50uV,
because the total of a bunch of noise sources is the sq.rt of the total
of each voltage squared.

Interested ppl in such noise problems are advised to study theory more
deeply because its impossible for those of us who do manage to make amps
with excellent SNR to spend the time to repeat all we have said in the
past yet again.

However, I am having trouble finding sources for 100K and 39K wire
wound
types at anything less than 5W rating which is something of an
overkill.
Do you know any good sources of high value low wattage wire wound
resistors (preferable non-inductive of course)?
** ROTFLMAO
So impolite Phil, but I can see why you are laughing when there are
sources of highish values of wire wound around.
** Not what I was laughing at - the bit about " non-inductively wound was
very funny.

How much L does it take to make a 100 kohm, WW resistor have say 101 Kohms
of impedance at 20 kHz ??

The answer is 113 mH !!!!!!!

The resistance wire would have to be wound on a Mu-Metal core to get such a
value.

Do the math.

I've never noticed a hugely worrying amount of L in higher value wire
wound R.

Then there is is the self capacitance of the wound turns.

I have not often used WW R for dc supply loads, but when I have its been
with low Ra triodes so the poles caused by reactances have been at
fairly high F.

I have not experienced problem with stability with use of WW R for anode
loads even when GNFB is used.

Non inductive WW R are available, with turns wound in two directions to
cancel out the inductance, but I've only ever seen low value types,
never high values.

Let me see now, XL of 0.113H at 20kHz = 0.113 x 20,000 x 6.28 = approx
15kohms.

So the Z (R + L) would be only very slightly greater than the 100k at 1
kHz.

But there are lots of turns.

I've never bothered to measure such things.

Patrick Turner.



..... Phil


Morgan did these tests and the results are in his book. He concluded
that for 10K the inductance is negligible and the equivalent parallel
capacitance is about 3pF. Low resistance values have high inductances
because of the use of thicker wire.

Cheers

IAn

[Ian Bell[_2_]]

Eeyore wrote:

Ian Bell wrote:

Phil Allison wrote:
Metal film resistors are near as damn it free of voltage noise
Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise. With
150V across an anode resistor that an extra 15uV of noise I can well do
without.

Can you cite a supplier that quotes a lower figure?

All the more reason to use solid state circuitry with lower voltages.

Graham


All the more reason for you to disappear and go post on a semiconductor
news group. What are you doing here, Graham??

Cheers

Ian

[Ian Bell[_2_]]

Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
snip

If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian
Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?

I've never noticed it in amps i have built. If I'd found that the noise
measurements didn't seem to add up, then I'd have been the one to reason
why.

I've usually used Welwyn or Beyshlag metal film R for most circuits.
Noise is negligible.

I'll check out Welwyn and Beyshlag specs, thanks

Cheers

IAn

Patrick Turner.
Cheers

Ian
Patrick Turner.

[Ian Bell[_2_]]

Ian Bell wrote:
Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
snip

If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about
30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it
without
much complexity and cost.
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise.
The solution seems to be to replace metal film resistors with wire
wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage
wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian
Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and
the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its
shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?

I've never noticed it in amps i have built. If I'd found that the noise
measurements didn't seem to add up, then I'd have been the one to reason
why.

I've usually used Welwyn or Beyshlag metal film R for most circuits.
Noise is negligible.

I'll check out Welwyn and Beyshlag specs, thanks

Cheers

IAn

Welwyn MFR5 types specify a maximum excess noise of 0.1uV/v per decade
of frequency. I have been unable to find a spec for this parameter on
any of type of theirs other than the MFR series.

I have looked at several Vishay (Beyschlag) data sheets and the best
they can do is to say 'low noise' whatever that means.

So I am still unconvinced that metal film resistors do not produce a
significant amount of excess noise for low level low noise applications.

Cheers

Ian



Patrick Turner.
Cheers

Ian
Patrick Turner.

[Phil Allison]

"Ian Bell = utterly STUPID ****WIT "


One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise. The solution seems to be to replace metal film resistors with
wire wound types.

** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise
Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise.


** What measurement bandwidth - eh ??

What resistance value - eh ??

Got no ****ing clue - have you.

You ****ING **** WIT


Sounds like you are back pedalling, Phil. You of all people will know
exactly how excess noise is specified (which includes the bandwidth).


** Then YOU need to post the link - ****HEAD.

Since that is the ONLY evidence you have.


As a said before, show me a manufacturer that quotes less.


** The figure you quoted ( without ANY kind of link or reference ) is simply
not a spec at all.





...... Phil

[Phil Allison]

"Ian Bell = LIAR "

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.


** No it is not - you hee hawwwing ASS



Simple negation is no argument.


** An totally unsupported assertion is NOT a case and requires NO
DISPROOF !!


I presently have about 65uV of noise from the circuit under test.
Eliminating a 15uV component of it is worthwhile.


** Another ****ING RIDICULOUS unsupported assertion = typical Bell
puke.

FYI, you arrogant ****head:

Noise voltages DO NOT ADD !!!





....... Phil

[Patrick Turner]

Ian Bell wrote:

Phil Allison wrote:
"Ian Bell"

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of resistor
type.


** No it is not - you hee hawwwing ASS



Simple negation is no argument. I presently have about 65uV of noise
from the circuit under test. Eliminating a 15uV component of it is
worthwhile.

Cheers

Ian

OK, you have 65uV of noise. I think you said your amp has a gain of
about 15.

Suppose the input signal was 4.3 mV, then output signal would be 65mV,
and SNR = -60dB unweighted.

Removing 15uV of the noise won't make a significant SNR improvement.

If the output signal is to be fed into a typical power amp needing 1Vrms
for clipping at 50W/6 ohms, then the power amp gain = 17.3x, 25dB,
and 65uV of applied noise will become 1.124mV not something that would
be improved by lowering to 0.87mV if 15uV was removed.

65mV of signal at the power amp becomes 1.124Vrms, enough to make 0.21
watts into a 6 ohm speaker, and if the 6 ohm speaker sensititivity is
90dB for 1 watt with 2.45Vrms, then the 0.21 watts gives about 83dB SPL
and is loud enough for most ppl, and allows a considerable headroom.

I suggest you work out the whole basic working of your system and amps
using a block diagram with signal levels or else quit mucking around
theorizing, and just build it and see if its quiet enough. After than
you can tweak things to make things more silent.
Or raise the signal level before feeding it to a power amp via an
attenuator.

Patrick Turner.

[Patrick Turner]

Ian Bell wrote:

Patrick Turner wrote:

Phil Allison wrote:
"Patrick Turner"
Phil Allison wrote:
"Ian has Bats in his Belfry "

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise.
The solution seems to be to replace metal film resistors with wire
wound
types.
** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise - noise
from the valve will always be waaaay higher .
Suppose noise generated by the V1 tube as 30uV at the output.
If total noise was 50uV, then you have to add far more than 20uV to 30uV
to get a total of 50uV,
because the total of a bunch of noise sources is the sq.rt of the total
of each voltage squared.

Interested ppl in such noise problems are advised to study theory more
deeply because its impossible for those of us who do manage to make amps
with excellent SNR to spend the time to repeat all we have said in the
past yet again.

However, I am having trouble finding sources for 100K and 39K wire
wound
types at anything less than 5W rating which is something of an
overkill.
Do you know any good sources of high value low wattage wire wound
resistors (preferable non-inductive of course)?
** ROTFLMAO
So impolite Phil, but I can see why you are laughing when there are
sources of highish values of wire wound around.
** Not what I was laughing at - the bit about " non-inductively wound was
very funny.

How much L does it take to make a 100 kohm, WW resistor have say 101 Kohms
of impedance at 20 kHz ??

The answer is 113 mH !!!!!!!

The resistance wire would have to be wound on a Mu-Metal core to get such a
value.

Do the math.

I've never noticed a hugely worrying amount of L in higher value wire
wound R.

Then there is is the self capacitance of the wound turns.

I have not often used WW R for dc supply loads, but when I have its been
with low Ra triodes so the poles caused by reactances have been at
fairly high F.

I have not experienced problem with stability with use of WW R for anode
loads even when GNFB is used.

Non inductive WW R are available, with turns wound in two directions to
cancel out the inductance, but I've only ever seen low value types,
never high values.

Let me see now, XL of 0.113H at 20kHz = 0.113 x 20,000 x 6.28 = approx
15kohms.

So the Z (R + L) would be only very slightly greater than the 100k at 1
kHz.

But there are lots of turns.

I've never bothered to measure such things.

Patrick Turner.



..... Phil

Morgan did these tests and the results are in his book. He concluded
that for 10K the inductance is negligible and the equivalent parallel
capacitance is about 3pF. Low resistance values have high inductances
because of the use of thicker wire.

You are not quite correct.

Low WW R may have L which can affect circuit performance when used in
speaker crossovers or series current FB resistors between source and
load or 0V in SS amps. The amount of L for a low value R is lower than
for a high value R.

The actual R is always taken to be in series with the amount of L, but
the full model of a WW R needs your inspection. There are far more turns
in a 47k WW R than in a 4r7 resistance. L is higher in the 47k, but the
series R is enough so that the L does not significantly increase the
load impedance driven by the active device, so the response stays flat
at least between dc and 20kHz.

In a 0.22 source or emitter resistance in an SS amp, the small amount of
L in such a low impedance circuit can mean the impedance at say 500kHz
is rising and inductive and can cause oscillations in the circuit. The
answer is to use non inductive WW resistances which are sold at many
outlets.

I've never seen a non inductive 47k R, but probably because there is no
need.

Patrick Turner.


Cheers

IAn

[Patrick Turner]

Ian Bell wrote:

Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
snip

If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian
Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?

I've never noticed it in amps i have built. If I'd found that the noise
measurements didn't seem to add up, then I'd have been the one to reason
why.

I've usually used Welwyn or Beyshlag metal film R for most circuits.
Noise is negligible.

I'll check out Welwyn and Beyshlag specs, thanks

Cheers


Noise is mainly the product of the resistance value. It should not
matter what the R is made from. If properly made from any resistive
material the number of ohms is the main issue, then temperature. I don't
expect Welwyn or Beyshlag or Mills or Cadock or anything else from the
Vishay Resistor Mafia to be much different.

Metal film do have low noise, and noise below old fashioned carbon
composition types. I have a box full ot NOS from the mid 1930s which are
carbon rods with brass end shells clamped on and painted. They are in
good condition but I doubt they will be noiser than later carbon
compostion types which were notorious for change of value and moisture
ingress and chemical corrosion and decomposition over time. Quad used
these horrible R in the Quad-II and 22 control units. All may have been
fine when installed. I'm sure Peter Walker would have checked all this
out. But maybe they were not so quiet after 55 years...

The circuit resistances in most old ancient tube amps including Quad
junk and others was always on the high side. EG, Quad 22 volume control
is 500k.

Using say 100k instead of 1M to bias a tube reduces noise by 1/3.16, but
is true only if there isn't anything else shunting such R.

Noise in smaller R is proportional to 1 / sq.rt of the reduction of
resistance.

Or if you had 1uV noise in 1k for a given bandwidth, then noise with 10k
= 3.16uV, 100k gives 10uV, and 1M gives 31.6uV.
10M gives 100uV, and is a typical value used to bias a tube with grid
leak biasing as in a radio.
But there is usually some other R shunting the 10M, like a 1M volume
control, so noise is less at the output.


Patrick Turner.



Patrick Turner.
Cheers

Ian
Patrick Turner.

[Patrick Turner]

Ian Bell wrote:

Ian Bell wrote:
Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
snip


snip,

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?

I've never noticed it in amps i have built. If I'd found that the noise
measurements didn't seem to add up, then I'd have been the one to reason
why.

I've usually used Welwyn or Beyshlag metal film R for most circuits.
Noise is negligible.

I'll check out Welwyn and Beyshlag specs, thanks

Cheers

IAn

Welwyn MFR5 types specify a maximum excess noise of 0.1uV/v per decade
of frequency. I have been unable to find a spec for this parameter on
any of type of theirs other than the MFR series.

I have looked at several Vishay (Beyschlag) data sheets and the best
they can do is to say 'low noise' whatever that means.

So I am still unconvinced that metal film resistors do not produce a
significant amount of excess noise for low level low noise applications.

From the data you have seen, what is the worst case amount of noise you
coud expect in your circuit?

What happens to noise when you change resistance brands/types in your
circuit?

Ya gotta try things.

Patrick Turner.

[Ian Bell[_2_]]

Phil Allison wrote:
"Ian Bell = utterly STUPID ****WIT "

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise. The solution seems to be to replace metal film resistors with
wire wound types.
** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise
Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise.

** What measurement bandwidth - eh ??

What resistance value - eh ??

Got no ****ing clue - have you.

You ****ING **** WIT

Sounds like you are back pedalling, Phil. You of all people will know
exactly how excess noise is specified (which includes the bandwidth).


** Then YOU need to post the link - ****HEAD.

Since that is the ONLY evidence you have.


This is not a trial in court - I don't need to post 'evidence' it was
simply a request for information.


As a said before, show me a manufacturer that quotes less.


** The figure you quoted ( without ANY kind of link or reference ) is simply
not a spec at all.


Really, well the Welwyn metal film resistors Patrick recommended can be
found he

http://www.welwyn-tt.co.uk/products/...&Submit=Search

Check out the pdf file for their MFR range which states simply 0.1uV/V
max per decade. FInd me one significantly better than that and I'll
happily use it.

Cheers

Ian




..... Phil

[Ian Bell[_2_]]

Phil Allison wrote:
"Ian Bell = LIAR "
Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

** No it is not - you hee hawwwing ASS


Simple negation is no argument.


** An totally unsupported assertion is NOT a case and requires NO
DISPROOF !!


I presently have about 65uV of noise from the circuit under test.
Eliminating a 15uV component of it is worthwhile.


** Another ****ING RIDICULOUS unsupported assertion = typical Bell
puke.

FYI, you arrogant ****head:

Noise voltages DO NOT ADD !!!



No, their powers do. I made no statement either way about how they add.

Cheers

Ian

[Ian Bell[_2_]]

Patrick Turner wrote:

Ian Bell wrote:
Phil Allison wrote:
"Ian Bell"

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of resistor
type.

** No it is not - you hee hawwwing ASS


Simple negation is no argument. I presently have about 65uV of noise
from the circuit under test. Eliminating a 15uV component of it is
worthwhile.

Cheers

Ian

OK, you have 65uV of noise. I think you said your amp has a gain of
about 15.

Suppose the input signal was 4.3 mV, then output signal would be 65mV,
and SNR = -60dB unweighted.

Removing 15uV of the noise won't make a significant SNR improvement.

Of course not. But it is just one of two such sources and I am simply
taking your recommendation of identifying each source in turn and
addressing them in turn.

Cheers

Ian

If the output signal is to be fed into a typical power amp needing 1Vrms
for clipping at 50W/6 ohms, then the power amp gain = 17.3x, 25dB,
and 65uV of applied noise will become 1.124mV not something that would
be improved by lowering to 0.87mV if 15uV was removed.

65mV of signal at the power amp becomes 1.124Vrms, enough to make 0.21
watts into a 6 ohm speaker, and if the 6 ohm speaker sensititivity is
90dB for 1 watt with 2.45Vrms, then the 0.21 watts gives about 83dB SPL
and is loud enough for most ppl, and allows a considerable headroom.

I suggest you work out the whole basic working of your system and amps
using a block diagram with signal levels or else quit mucking around
theorizing, and just build it and see if its quiet enough. After than
you can tweak things to make things more silent.

That is EXACTLY what I have done. The thing is on my bench now and the
output noise I quoted is as measured. You recommended I identify each
noise source and tackle them in turn which is just what I am trying to
do. I have fixed the low frequency noise as described in other posts and
now I am looking at other sources. Excess noise is just one of them.
From looking at metal film resistor specs it seemed they could be a
contributory factor and that wirewound types would be significantly
quieter. The only problem is finding them in the high values I need;
hence my original question on this topic, to which you and others
replied either that metal film resistors are not noisy or that the
noise they contribute is not significant.

Cheers

Ian

Or raise the signal level before feeding it to a power amp via an
attenuator.

Patrick Turner.

[Ian Bell[_2_]]

Patrick Turner wrote:

Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
snip

If you have 50uV of noise at the output and gain is 15x, and input is
grounded, then you could have a total of 2uV grid input noise if the
input tube is a real good one. 2uV gets amplified to make about 30uV at
the output, and some of that is LF noise. where does the rest of the
noise come from? By observation you should be able to see where the
noise is being generated and how, and find ways of stopping it without
much complexity and cost.
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types. However, I am having trouble finding sources for 100K and 39K
wire wound types at anything less than 5W rating which is something of
an overkill. Do you know any good sources of high value low wattage wire
wound resistors (preferable non-inductive of course)?

Cheers

Ian
Suppose you had 30uV of noise due to the input tube at the output of
your amp with gain = 15x.

And total noise = 50uV. Say you have Ra of the input tube = 20k, and the
load resistor for dc in parallel to the following stage bias R might be
50k. The 50k 20Hz ro 20k noise can be calculated, but the its shunted by
Ra = 20k and thus attenuated. The excess noise would also be shunted,
but unlikely to be as high as the V1 tube noise, even if its a poor
quality R. Its the value of R in ohms which gives rise to noise, and
usually 90% of the noise at the output of a mic amp is due to the
broadand noise of V1, and all following R and tubes have little
contribution unless the output of V1 is a tiny voltage.

I think you should just build it and then try things to make it silent.
Wire wound would appear to be blameless, and getting a high value one
may mean you series a few. A 47k WW type will at least make the
predicted amount of noise because its the ohms than make the noise.
Any other type of R, metal film, carbon film also will make similar
noise you should find unless they are faulty.

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?
I've never noticed it in amps i have built. If I'd found that the noise
measurements didn't seem to add up, then I'd have been the one to reason
why.

I've usually used Welwyn or Beyshlag metal film R for most circuits.
Noise is negligible.
I'll check out Welwyn and Beyshlag specs, thanks

Cheers


Noise is mainly the product of the resistance value. It should not
matter what the R is made from. If properly made from any resistive
material the number of ohms is the main issue, then temperature. I don't
expect Welwyn or Beyshlag or Mills or Cadock or anything else from the
Vishay Resistor Mafia to be much different.

I hear what you say Patrick but Morgan Jones and the manufacturers data
sheets I have seen do not support that view.

For example the Johnson noise in a 20KHz bandwidth at room temperature
for a 39K resistor is ABOUT 3.6uV. If it is in an anode circuit with
150V across it then the excess noise of a typical metal film resistor
will be about 15uV per decade.

In low voltage circuits I agree Johnson noise predominates but I am not
sure it does in anode circuits.

Cheers

Ian

Metal film do have low noise, and noise below old fashioned carbon
composition types. I have a box full ot NOS from the mid 1930s which are
carbon rods with brass end shells clamped on and painted. They are in
good condition but I doubt they will be noiser than later carbon
compostion types which were notorious for change of value and moisture
ingress and chemical corrosion and decomposition over time. Quad used
these horrible R in the Quad-II and 22 control units. All may have been
fine when installed. I'm sure Peter Walker would have checked all this
out. But maybe they were not so quiet after 55 years...

The circuit resistances in most old ancient tube amps including Quad
junk and others was always on the high side. EG, Quad 22 volume control
is 500k.

Using say 100k instead of 1M to bias a tube reduces noise by 1/3.16, but
is true only if there isn't anything else shunting such R.

Noise in smaller R is proportional to 1 / sq.rt of the reduction of
resistance.

Or if you had 1uV noise in 1k for a given bandwidth, then noise with 10k
= 3.16uV, 100k gives 10uV, and 1M gives 31.6uV.
10M gives 100uV, and is a typical value used to bias a tube with grid
leak biasing as in a radio.
But there is usually some other R shunting the 10M, like a 1M volume
control, so noise is less at the output.


Patrick Turner.


Patrick Turner.
Cheers

Ian
Patrick Turner.

[Ian Bell[_2_]]

Patrick Turner wrote:

Ian Bell wrote:
Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
Ian Bell wrote:
Patrick Turner wrote:
snip


snip,

Read up from RDH4 about noise and equivalent input resistance and noise
in R and summing of noise voltages.

Thanks for the input Patrick. I know about Johnson noise and in plate
resistors it is not much of an issue as it is swamped by other noise
sources. What I am concerned about is excess noise which is voltage
dependent. In the few places I have seen this specified it is typically
0.1uV/V so with a plate resistor with 150V across it there is possibly
15uV of noise due to this effect - enough to warrant a change of
resistor type.

Are you saying that regular metal film resistors do not suffer from
excess noise?
I've never noticed it in amps i have built. If I'd found that the noise
measurements didn't seem to add up, then I'd have been the one to reason
why.

I've usually used Welwyn or Beyshlag metal film R for most circuits.
Noise is negligible.
I'll check out Welwyn and Beyshlag specs, thanks

Cheers

IAn
Welwyn MFR5 types specify a maximum excess noise of 0.1uV/v per decade
of frequency. I have been unable to find a spec for this parameter on
any of type of theirs other than the MFR series.

I have looked at several Vishay (Beyschlag) data sheets and the best
they can do is to say 'low noise' whatever that means.

So I am still unconvinced that metal film resistors do not produce a
significant amount of excess noise for low level low noise applications.

From the data you have seen, what is the worst case amount of noise you
coud expect in your circuit?

15uV per decade


What happens to noise when you change resistance brands/types in your
circuit?


Pass, but my original idea was to substitute wirewound types because
they have very much lower levels of excess noise, but I found it
difficult to find 39K and 100K wirewound types that were not huge -
hence my original question about sources of wirewound types.

I thought I would buy some wirewound types anyway and try them but
thought is was a good idea to cheack the group wisdom before parting
with my cash.

Cheers

Ian
Ya gotta try things.

Patrick Turner.

[Phil Allison]

"Ian Bell = utterly STUPID ****WIT "

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise. The solution seems to be to replace metal film resistors with
wire wound types.
** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise
Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise.

** What measurement bandwidth - eh ??

What resistance value - eh ??

Got no ****ing clue - have you.

You ****ING **** WIT

Sounds like you are back pedalling, Phil. You of all people will know
exactly how excess noise is specified (which includes the bandwidth).


** Then YOU need to post the link - ****HEAD.

Since that is the ONLY evidence you have.


This is not a trial in court - I don't need to post 'evidence'


** Merely asking for a link to the data you are quoting.

So we see it in CONTEXT - you dumb ass !!!

So we can see if you are MISQUOTING or MISINTERPRETING it.



** The figure you quoted ( without ANY kind of link or reference ) is
simply not a spec at all.


Really, well the Welwyn metal film resistors Patrick recommended can be
found he

http://www.welwyn-tt.co.uk/products/...&Submit=Search

Check out the pdf file for their MFR range which states simply 0.1uV/V max
per decade.


** Which is not what it ACTUALLY says at all.





...... Phil

[Phil Allison]

"Ian Bell = LIAR "


I presently have about 65uV of noise from the circuit under test.
Eliminating a 15uV component of it is worthwhile.


** Another ****ING RIDICULOUS unsupported assertion = typical
Bell puke.

FYI, you arrogant ****head:

Noise voltages DO NOT ADD !!!



No, their powers do. I made no statement either way about how they add.


** Yes you ****ing did !!!

Do the math correctly as see what the result is.

Then **** OFF - you VILE LYING PIG .




........ Phil

[Paul G.]

On Sun, 09 Nov 2008 08:07:26 +0000, Ian Bell
wrote:

Phil Allison wrote:
"Ian Bell"
Phil Allison wrote:
"Ian Bell"

One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total noise.
The solution seems to be to replace metal film resistors with wire wound
types.

** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise
Are they? Most metal film resistor suppliers that actually bother to spec
this usually put a figure of about 0.1uV/V for excess noise.


** What measurement bandwidth - eh ??

What resistance value - eh ??

Got no ****ig clue - have you.

You ****ING **** WIT


Sounds like you are back pedalling, Phil. You of all people will know
exactly how excess noise is specified (which includes the bandwidth). I
happen to have a 100K resistor in one anode which, from one
manufacturers graph, shows its excess noise is 0.1V/V.

As a said before, show me a manufacturer that quotes less.

CHeers

Ian



....... Phil








Vishay sells bulk foil resistors
http://www.vishay.com/company/press/...08/080507foil/ , and
according to "JIS C5202 5.9" method of measurement, they are at -40db,
where 0db is 1 uv/v, and I assume it is for 1Hz bandwidth, since I
can't find any details of what this standard uses (without paying for
it). That means the -40db would give you about .01uv/v (10 nv/v)
voltage noise. My guess is that this resistor is as good as you'll
get. I've been told that most wirewounds are typically -38db. Metal
film resistors often use this spec, and typical values for good
resistors (100kohms) are about -20 db using JIS C5202 5.9.

From an article promoting Vishay resistors:
http://www.planetanalog.com/features...leID=177105460
"Current noise is the bunching and releasing of electrons associated
with current flow. The amount of current noise (or lack thereof)
depends largely on the resistor technology employed, and it is
measurable and is expressed as a function of the input voltage. The
magnitude is microvolts per volt applied. A noise index is expressed
in decibels, and the equation converting µV/V to dB is:
dB = 20 x log (noise voltage [in µV]/DC voltage [in V]).
For example, 0 dB equates to 1.0 µV/V, and 15 dB equates to 5.6 µV/V."
(end of quotation)
Read the article.... it answers a lot of questions, and poses some
possible audio nuttyness.

Current noise has a 1/f frequency distribution. Bear that in mind when
you read the above article.... The frequency of the artifacts is very
low, and the oscilloscope pictures suggest a problem that is really
not as audibly bad as presented.

Carbon resistors have "contact noise", which is an additional very
significant noise. You should avoid carbon resistors, especially the
composition carbon ones (cheapo resistors).

The Johnson noise for the 100K resistor is about 41 nv (bw=1Hz),
or about 128 nv for the decade (I don't know why manufacturers specify
a decade when 1 Hz is more specific). It is wide band noise, not 1/f
noise. The different frequency distributions (1/f and wideband) make
judgements difficult, especially with the ear's sensitivity vs.
frequency. It's going to take a lot of 1/f noise to be noticed
compared to the wideband Johnson noise.

Wirewound and bulk film resistors are considered best for noise,
even by Phil Allison http://sound.westhost.com/project66.htm "Metal
film resistors are about the best only bettered by wire wound which is
a bit impractical"

You must also be careful of wirewound resistors, since they can
inductively pick up AC magnetic fields, especially the precision
bobbin types of resistors.
The resistor noise voltage generated, is on the anode circuit for
your tube, if you use the input noise voltage for a typical low noise
tube (12AX7), you have about 450nv (bw=1Hz) effectively at the grid.
Considering typical gains of 10-100, that gives a noise (bw=1Hz) at
4.5uv to 45uv at the anode. The tube noise will completely swamp the
noise of the resistor! Make sure to use the correct bandwidth when
making the comparison.

At the very low level signal levels you seem to want, you will
probably get more satisfaction by using some of the more recent low
noise op-amps, and then amplify to get the voltage levels required by
your tube circuits. Vacuum tubes DO have considerable 1/f noise
(Johnson, John B, "The Schottky effect in low frequency circuits,"
Physical Review, July 1925, pg 71.). That's 1925! Not that I have much
against tube circuitry.... but they are not appropriate for low level
signal amplification (IMHO).

Paul G.

[Phil Allison]

"Paul G."


Wirewound and bulk film resistors are considered best for noise,
even by Phil Allison http://sound.westhost.com/project66.htm "Metal
film resistors are about the best only bettered by wire wound which is
a bit impractical"


** No way did I suggest " bulk film " resistors had low DC voltage noise -
quite then opposite, I warned specifically against them. The full quote is:

" Where a resistor has significant DC voltage imposed on it in high gain
circuits always use low noise types. Metal film resistors are about the best
only bettered by wire wound which is a bit impractical. Avoid cermet, metal
glaze, and very old carbon composition types. "

FYI

Cermet and "Metal Glaze" are thick or " bulk film " resistors - notorious
for having high and variable amounts of DC voltage noise.


..... Phil

[Ian Bell[_2_]]

Phil Allison wrote:
"Ian Bell = utterly STUPID ****WIT "
One of the potential sources I have discovered is excess noise in the
anode resistors. This could account for 20uV or more of the total
noise. The solution seems to be to replace metal film resistors with
wire wound types.
** Where does this LUNATIC get these wacky ideas from ??

Metal film resistors are near as damn it free of voltage noise
Are they? Most metal film resistor suppliers that actually bother to
spec this usually put a figure of about 0.1uV/V for excess noise.
** What measurement bandwidth - eh ??

What resistance value - eh ??

Got no ****ing clue - have you.

You ****ING **** WIT

Sounds like you are back pedalling, Phil. You of all people will know
exactly how excess noise is specified (which includes the bandwidth).

** Then YOU need to post the link - ****HEAD.

Since that is the ONLY evidence you have.

This is not a trial in court - I don't need to post 'evidence'


** Merely asking for a link to the data you are quoting.

So we see it in CONTEXT - you dumb ass !!!

So we can see if you are MISQUOTING or MISINTERPRETING it.



** The figure you quoted ( without ANY kind of link or reference ) is
simply not a spec at all.

Really, well the Welwyn metal film resistors Patrick recommended can be
found he

http://www.welwyn-tt.co.uk/products/...&Submit=Search

Check out the pdf file for their MFR range which states simply 0.1uV/V max
per decade.


** Which is not what it ACTUALLY says at all.





..... Phil




Very helpful Phil. The sheet I saw read 'Noise. (in a decade of
frequency) uV/V' and then under the column labelled 'Max' it said 0.1.

Cheers

Ian

[Ian Bell[_2_]]

Phil Allison wrote:
"Ian Bell = LIAR "

I presently have about 65uV of noise from the circuit under test.
Eliminating a 15uV component of it is worthwhile.

** Another ****ING RIDICULOUS unsupported assertion = typical
Bell puke.

FYI, you arrogant ****head:

Noise voltages DO NOT ADD !!!


No, their powers do. I made no statement either way about how they add.


** Yes you ****ing did !!!


No I did not. I said eliminating 15uV component was worthwhile.



Cheers

Ian