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Default Pultec EQP clone problem

Don Pearce wrote:
================

** You sure about "any" ?

Square waves have cascading, odd numbered harmonics.
The ringing one would merely be out of step with the others.

Nothing to do with the frequency of the wave or its harmonics. Each
ringing event is separate and is triggered by the broadband energy of
the rising or falling edge.


** Gobbledegook.

The frequency of the ring is determined by
the LC circuit that is being struck by that edge.


** So a linear circuit with a resonance creates a new frequency ?

Does not do so with a sine sweep.



...... Phil
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On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "
wrote:

Nothing to do with the frequency of the wave or its harmonics. Each
ringing event is separate and is triggered by the broadband energy of
the rising or falling edge.


** Gobbledegook.


Don't be so hasty. I know this is not instantly intuitive, but it is
exactly what happens.


The frequency of the ring is determined by
the LC circuit that is being struck by that edge.


** So a linear circuit with a resonance creates a new frequency ?

No. If you do an FFT on an edge, you will find a broad spectrum, not a
discrete one. THere will be energy at whatever frequency the resonant
circuit causing the ringing works at.

Does not do so with a sine sweep.


If you do a sine sweep you will find the resonant frequency of the
ring. That is the frequency you will see when you strike it with a
fast rising edge. Think of it like a bell. If you keep hitting it, you
will hear the individual strikes, but the frequency that comes out
will be that of the bell, and nothing to do with how quickly you hit
it.

d

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Default Pultec EQP clone problem

wrote:
Don Pearce wrote:

The frequency of the ring is determined by
the LC circuit that is being struck by that edge.


** So a linear circuit with a resonance creates a new frequency ?

Does not do so with a sine sweep.


You bet it does! You get close to the resonance and it kicks off... you
don't need to be right on the resonance, you only need to be in the
ballpark.

This is the basic principle that makes bandpass speaker enclosures do
what they do. You don't need to put that one bass note into it... any
bass going into it will come out as that one note.
--scott
--
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Default Pultec EQP clone problem

On Saturday, 27 February 2021 at 16:57:06 UTC, Scott Dorsey wrote:
wrote:
Don Pearce wrote:

The frequency of the ring is determined by
the LC circuit that is being struck by that edge.


** So a linear circuit with a resonance creates a new frequency ?

Does not do so with a sine sweep.

You bet it does! You get close to the resonance and it kicks off... you
don't need to be right on the resonance, you only need to be in the
ballpark.

This is the basic principle that makes bandpass speaker enclosures do
what they do. You don't need to put that one bass note into it... any
bass going into it will come out as that one note.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."




Well I think I might go for the mod of 100 ohms in series with 0.01uF, as this seems to best address the obvious catastrophic ringing this unit has, even though I have been unable to recreate the 90 Hz oscillations the customer encountered when connecting the unit via a patchbay.

Fortunately, the unit has an XLR output and a parallel TRS output, so the mod can be incorporated into a TRS jack, so the customer can insert the mod or remove it at will.
The mod does have a slight HF rolloff, so perhaps if the 90Hz problem is not happening, he can at least get his full frequency response back.

Seems to me this is a serious design issue that was overlooked, the mod is a sticking plaster.

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Don Pearce wrote:
================

Nothing to do with the frequency of the wave or its harmonics. Each
ringing event is separate and is triggered by the broadband energy of
the rising or falling edge.


** Gobbledegook.


Don't be so hasty. I know this is not instantly intuitive, but it is
exactly what happens.


** No it ain't.

The frequency of the ring is determined by
the LC circuit that is being struck by that edge.


** So a linear circuit with a resonance creates a new frequency ?

No.


** You are here claiming it does.

If you do an FFT on an edge,


** Not the situation.

The *square wave* can be band limited to just a few times the ringing frequency.
Only needs ONE harmonic close enough to that frequency to get a damped sine result.

Does not do so with a sine sweep.


If you do a sine sweep you will find the resonant frequency of the ring.


** But not *create* it - the maximum is at the exact same frequency as the input sine.

That is the frequency you will see when you strike it with a
fast rising edge.


** Not the case with a normal, square wave test.



...... Phil




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Scott Dorsey wrote:
================


The frequency of the ring is determined by
the LC circuit that is being struck by that edge.


** So a linear circuit with a resonance creates a new frequency ?

Does not do so with a sine sweep.

You bet it does! You get close to the resonance and it kicks off..


** No new frequency appears, the input is simply boosted.

This is the basic principle that makes bandpass speaker enclosures do
what they do. You don't need to put that one bass note into it... any
bass going into it will come out as that one note.


** Filters do NOT do frequency shifting.


...... Phil
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Default Pultec EQP clone problem

On Sat, 27 Feb 2021 15:20:57 -0800 (PST), "
wrote:

Don Pearce wrote:
================

Nothing to do with the frequency of the wave or its harmonics. Each
ringing event is separate and is triggered by the broadband energy of
the rising or falling edge.

** Gobbledegook.


Don't be so hasty. I know this is not instantly intuitive, but it is
exactly what happens.


** No it ain't.

The frequency of the ring is determined by
the LC circuit that is being struck by that edge.

** So a linear circuit with a resonance creates a new frequency ?

No.


** You are here claiming it does.

If you do an FFT on an edge,


** Not the situation.

The *square wave* can be band limited to just a few times the ringing frequency.
Only needs ONE harmonic close enough to that frequency to get a damped sine result.

Does not do so with a sine sweep.


If you do a sine sweep you will find the resonant frequency of the ring.


** But not *create* it - the maximum is at the exact same frequency as the input sine.

That is the frequency you will see when you strike it with a
fast rising edge.


** Not the case with a normal, square wave test.



..... Phil


Phil, you need to think. Forget square waves and harmonics for a
moment. You can trigger ringing with a single transient edge. No
repetition or harmonics needed.

d

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Don Pearce wrote:
=================


Phil, you need to think.


** No way, YOU do - ****head.


Forget square waves and harmonics for a moment.


** No way - cos THAT IS ACTUALLY the topic here.

FYI:

I suspect you know you are wrong, by dint of being in the wrong context.
You favorite hiding hole, for the last 20 plus years.

Along with all the other smelly, know nothing, usenet rodents.

**** off.


....... Phil
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On 28/02/2021 09:46, wrote:

Along with all the other smelly, know nothing, usenet rodents.

**** off.

Genuine question. If your opinion of us is so low, why in heaven do you
keep posting here?

Your posts are always framed in unhelpful ways and insult the
intelligence of the poster you are replying to. This does not impress
anyone, least of all the person you are insulting.

This is why you are in many people's killfiles, so we only see your
potty mouthed outpourings when someone replies to them.


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gareth magennis wrote:

This Pultech clone has "catastophic ringing" with a 1kHz square wave, almost identical to the example posted.


Assuming that you are doing this with the EQ out of circuit (controls set
flat), then the output transformer is garbage.

A 600 ohm resistor alone reduces level by almost half, but the ringing remains at the same proportion of the square wave amplitude.


This is how a normal Pultec would be expected to operate. 600 ohm source,
600 ohm load.

A 100ohm resistor in series with 10nF reduces the catastophing ringing initial spikes hugely, but nowhere near to "mild ringing", and has a slight rolloff on a sine wave at 10 and 20 kHz but not 1kHz.
A 100ohm resistor with 68 nF has way too much hf rolloff, but the ringing is eliminated entirely with a sloping squarewave wavefront showing the hf cut.
A 100 ohm resistor with 4.4nF to 1nF causes full amplitude oscillation, very bad.

The 10nF seems to be the most useful. Anything higher does eventually elliminate the ringing, but with unacceptable rolloff.


A well-designed transformer might ring a little bit, but it won't ring as
severely as in that picture. More importantly, it will ring somewhere in
the 100kc-200kc range so that you can add a zobel network to notch it out
without affecting the response in the audible range.

It sounds to me like your transformer is ringing close to or even within
the audible range, and so the only way to get it to stop is with a very
low frequency network. This will have audible consequences.

Out of curiosity, who makes their output transformer? I want to make sure
I never use one of those.
--scott
--
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gareth magennis wrote:

So it might be possible that the company's mod advice of 100 ohms in parallel with 0.1uF should really be 100 ohms in series with 0.01uF?


Something is very wrong at this company. See if you can speak with an
actual engineer. Do they have any, even?
--scott
--
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wrote:
Scott Dorsey wrote:

This is the basic principle that makes bandpass speaker enclosures do
what they do. You don't need to put that one bass note into it... any
bass going into it will come out as that one note.


** Filters do NOT do frequency shifting.


Don't think of it as frequency shifting. Think of it as a mass-spring system.
--scott
--
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Default Pultec EQP clone problem

On Sunday, 28 February 2021 at 15:55:54 UTC, david gourley wrote:
(Scott Dorsey) :
gareth magennis wrote:

So it might be possible that the company's mod advice of 100 ohms in

parallel with 0.1uF should really be 100 ohms in series with 0.01uF?

Something is very wrong at this company. See if you can speak with an
actual engineer. Do they have any, even?
--scott

They offer Cinemag transformers.

I had a great response from Scott Stone at Warm Audio, so request him in
any service communications. If he can't answer, he'll find someone who
will. I had a pilot lamp issue with my WA-251 (nice enough mic with a GOOD
figure of eight null BTW), and he sent a replacement to me within a week.

david
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I have been in contact with Scott.

It was Scott who gave the customer the info: 100 ohms, 0.1uF in parallel.


I have twice asked him to confirm what the mod should be, he has not got back.

That is why I gave up and posted here.
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John Williamson wrote:
==================

Genuine question.


** Like hell it is.

If your opinion of us is so low,


**Who is "us" and when did you get elected to represented them ??

why in heaven do you keep posting here?


** Why do you ? You don't seem to know anything.

Your posts are always framed in unhelpful ways


** On the contrary - my posts are VERY helpful.

and insult the intelligence of the poster you are replying to.


** I never insult intelligence - only stupidity and arrogance.


This is why you are in many people's killfiles,


** Using the killfile is like burying your head in the sand.
Have to be an ostrich to do that.

FYI Pearce is a bull****ting idiot and massive fake.


....... Phil




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Scott Dorsey wrote:
================

This is the basic principle that makes bandpass speaker enclosures do
what they do. You don't need to put that one bass note into it... any
bass going into it will come out as that one note.


** Filters do NOT do frequency shifting.


Don't think of it as frequency shifting.


** Fraid I cannot do that, double think does not come naturally to me.

Think of it as a mass-spring system.


** That is your dumb mistake.



....... Phil
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Scott Dorsey wrote:
===============

Something is very wrong at this company. See if you can speak with an
actual engineer.


** They never agree to speak with complainers.

Do they have any, even?


** Not bloody likely.

Even operations as big as Fender and QSC have no-one worth speaking with.


...... Phil



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On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "
wrote:

Don Pearce wrote:
================

** You sure about "any" ?

Square waves have cascading, odd numbered harmonics.
The ringing one would merely be out of step with the others.

Nothing to do with the frequency of the wave or its harmonics. Each
ringing event is separate and is triggered by the broadband energy of
the rising or falling edge.


** Gobbledegook.

The frequency of the ring is determined by
the LC circuit that is being struck by that edge.


** So a linear circuit with a resonance creates a new frequency ?

Does not do so with a sine sweep.



..... Phil


Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d

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gareth magennis
:

On Sunday, 28 February 2021 at 15:55:54 UTC, david gourley wrote:
(Scott Dorsey)
:
gareth magennis wrote:

So it might be possible that the company's mod advice of 100 ohms in

parallel with 0.1uF should really be 100 ohms in series with 0.01uF?

Something is very wrong at this company. See if you can speak with an
actual engineer. Do they have any, even?
--scott

They offer Cinemag transformers.

I had a great response from Scott Stone at Warm Audio, so request him
in any service communications. If he can't answer, he'll find someone
who will. I had a pilot lamp issue with my WA-251 (nice enough mic with
a GOOD figure of eight null BTW), and he sent a replacement to me
within a week.

david
--
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I have been in contact with Scott.

It was Scott who gave the customer the info: 100 ohms, 0.1uF in
parallel.


I have twice asked him to confirm what the mod should be, he has not got
back.

That is why I gave up and posted here.


I'm sorry you didn't have a better experience. IIRC they're in Texas, and
they just had a lot of problems, power and otherwise, due to weather. I
would keep trying, or ask for Bryce, but that's just me.

Good luck.

david
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On Sunday, 28 February 2021 at 20:21:06 UTC, david gourley wrote:
gareth magennis
:
On Sunday, 28 February 2021 at 15:55:54 UTC, david gourley wrote:
(Scott Dorsey)
:
gareth magennis wrote:

So it might be possible that the company's mod advice of 100 ohms in
parallel with 0.1uF should really be 100 ohms in series with 0.01uF?

Something is very wrong at this company. See if you can speak with an
actual engineer. Do they have any, even?
--scott
They offer Cinemag transformers.

I had a great response from Scott Stone at Warm Audio, so request him
in any service communications. If he can't answer, he'll find someone
who will. I had a pilot lamp issue with my WA-251 (nice enough mic with
a GOOD figure of eight null BTW), and he sent a replacement to me
within a week.

david
--
This email has been checked for viruses by Avast antivirus software.
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I have been in contact with Scott.

It was Scott who gave the customer the info: 100 ohms, 0.1uF in
parallel.


I have twice asked him to confirm what the mod should be, he has not got
back.

That is why I gave up and posted here.

I'm sorry you didn't have a better experience. IIRC they're in Texas, and
they just had a lot of problems, power and otherwise, due to weather. I
would keep trying, or ask for Bryce, but that's just me.

Good luck.

david


Thanks David, yeah, maybe I should be more patient, these are difficult times for sure, but I'd like to get this sorted and back to customer, it's been a while now I've had it.

Still, it's good to post here as you always get more info than you bargained for.

And the bunfights.


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Default Pultec EQP clone problem

wrote:
Scott Dorsey wrote:
================

This is the basic principle that makes bandpass speaker enclosures do
what they do. You don't need to put that one bass note into it... any
bass going into it will come out as that one note.

** Filters do NOT do frequency shifting.


Don't think of it as frequency shifting.


** Fraid I cannot do that, double think does not come naturally to me.

Think of it as a mass-spring system.


** That is your dumb mistake.



...... Phil


Explain Raman spectroscopy then. Hit a sample with light from a
monochromatic laser and light at different (non-harmonically related)
frequencies comes back.

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On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "



Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff
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geoff wrote:

=============

I think a spectrum analyser display would have been more relevant.


** Understatement of day.

I have run such a test with an input transformer using FFT and found no new frequency.
The run down of decaying, odd harmonics gets a lump in the middle when the output is unloaded.

Odds on Don's scope has FFT built in.

Wonder if he knows???


....... Phil

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On Mon, 1 Mar 2021 12:48:16 +1300, geoff
wrote:

On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "



Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff


No it would not. The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on. That would have resulted
in a beat walking through the ring. A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?

d

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On Sun, 28 Feb 2021 15:55:15 -0800 (PST), "
wrote:

geoff wrote:

=============

I think a spectrum analyser display would have been more relevant.


** Understatement of day.

I have run such a test with an input transformer using FFT and found no new frequency.
The run down of decaying, odd harmonics gets a lump in the middle when the output is unloaded.

Odds on Don's scope has FFT built in.

Wonder if he knows???


...... Phil


For quite a few years I was principal engineer for Marconi
Instruments, and in that time I designed signal generators and a
metrology grade spectrum analyser. I understand both measurement and
results presentation. Now, enough of your nonsense. It's time for once
in your life to man up and admit you got something wrong.

d

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On 1/03/2021 8:43 pm, Don Pearce wrote:
On Mon, 1 Mar 2021 12:48:16 +1300, geoff
wrote:

On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "



Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff


No it would not. The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on. That would have resulted
in a beat walking through the ring. A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?

d


I would be curious to see the oredrs of harmonics and if they altered
over freq.

geoff
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Default Pultec EQP clone problem

On 1/03/2021 8:46 pm, Don Pearce wrote:
On Sun, 28 Feb 2021 15:55:15 -0800 (PST), "
wrote:

geoff wrote:

=============

I think a spectrum analyser display would have been more relevant.


** Understatement of day.

I have run such a test with an input transformer using FFT and found no new frequency.
The run down of decaying, odd harmonics gets a lump in the middle when the output is unloaded.

Odds on Don's scope has FFT built in.

Wonder if he knows???


...... Phil


For quite a few years I was principal engineer for Marconi
Instruments, and in that time I designed signal generators and a
metrology grade spectrum analyser. I understand both measurement and
results presentation. Now, enough of your nonsense. It's time for once
in your life to man up and admit you got something wrong.

d


Can you fix my 2955 ? ;- )

geoff
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On Mon, 1 Mar 2021 20:59:42 +1300, geoff
wrote:

On 1/03/2021 8:46 pm, Don Pearce wrote:
On Sun, 28 Feb 2021 15:55:15 -0800 (PST), "
wrote:

geoff wrote:

=============

I think a spectrum analyser display would have been more relevant.


** Understatement of day.

I have run such a test with an input transformer using FFT and found no new frequency.
The run down of decaying, odd harmonics gets a lump in the middle when the output is unloaded.

Odds on Don's scope has FFT built in.

Wonder if he knows???


...... Phil


For quite a few years I was principal engineer for Marconi
Instruments, and in that time I designed signal generators and a
metrology grade spectrum analyser. I understand both measurement and
results presentation. Now, enough of your nonsense. It's time for once
in your life to man up and admit you got something wrong.

d


Can you fix my 2955 ? ;- )

geoff


Very likely. the 2030 and 2040 range of ultra low phase noise gens
were my era.

d

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On Mon, 1 Mar 2021 20:58:52 +1300, geoff
wrote:

On 1/03/2021 8:43 pm, Don Pearce wrote:
On Mon, 1 Mar 2021 12:48:16 +1300, geoff
wrote:

On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "


Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff


No it would not. The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on. That would have resulted
in a beat walking through the ring. A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?

d


I would be curious to see the oredrs of harmonics and if they altered
over freq.

geoff


They would. The same mechanism that produces ringing also makes a
tuned impedance changing network. That would produce a lift in
harmonic level in the same frequency range as the ringing. But that in
itself would no be ringing - just a raised harmonic level.
The word ringing is not an accident. The analogy with a bell being
struck is accurate.

d

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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Pultec EQP clone problem

On Mon, 01 Mar 2021 08:09:00 GMT, (Don Pearce) wrote:

On Mon, 1 Mar 2021 20:58:52 +1300, geoff
wrote:

On 1/03/2021 8:43 pm, Don Pearce wrote:
On Mon, 1 Mar 2021 12:48:16 +1300, geoff
wrote:

On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "


Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff

No it would not. The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on. That would have resulted
in a beat walking through the ring. A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?

d


I would be curious to see the oredrs of harmonics and if they altered
over freq.

geoff


They would. The same mechanism that produces ringing also makes a
tuned impedance changing network. That would produce a lift in
harmonic level in the same frequency range as the ringing. But that in
itself would no be ringing - just a raised harmonic level.
The word ringing is not an accident. The analogy with a bell being
struck is accurate.

d


Just a further thought. If the mechanism were selective harmonic
boosting, the ringing wave would be continuous - it would not die away
after the edge. The harmonics in a square wave don't come and go with
time. They are there all the way through the wave.

d

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[email protected] palli...@gmail.com is offline
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Default Pultec EQP clone problem

Don Pearce wrote:
==============
geoff

Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

I think a spectrum analyser display would have been more relevant.

geoff


No it would not.


** The original question was about the* look( of the spectrum.

" Any idea what the catastrophic ringing harmonics would look like on a spectrum
analyzer."


The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on.


** Bull**** it did. *

That would have resulted
in a beat walking through the ring.


** Absurd.

A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?


** There was none, fake test no result.


........ Phil
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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Pultec EQP clone problem

On Mon, 1 Mar 2021 00:15:32 -0800 (PST), "
wrote:

Don Pearce wrote:
==============
geoff

Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

I think a spectrum analyser display would have been more relevant.

geoff


No it would not.


** The original question was about the* look( of the spectrum.

" Any idea what the catastrophic ringing harmonics would look like on a spectrum
analyzer."


The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on.


** Bull**** it did. *

That would have resulted
in a beat walking through the ring.


** Absurd.

A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?


** There was none, fake test no result.


....... Phil


Phil, you truly are the world's most miserable, clueless ****.

d

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[email protected] palli...@gmail.com is offline
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Default Pultec EQP clone problem

Don Pearce wrote:
================

geoff wrote:

=============

I think a spectrum analyser display would have been more relevant.

** Understatement of day.

I have run such a test with an input transformer using FFT and found no new frequency.
The run down of decaying, odd harmonics gets a lump in the middle when the output is unloaded.

Odds on Don's scope has FFT built in.

Wonder if he knows???

For quite a few years I was principal engineer for Marconi
Instruments, and in that time I designed signal generators and a
metrology grade spectrum analyser.


** Time for you to present the *spectrum* of a ringing square wave.
In the frequency domain.
Not one, tiny, leading cycle on a scope trace.

Cos that was NEVER the question and YOU know it.

BTW:

Your fake Concerto for solo trumpet was removed, cos it hurt my ears.

..... Phil

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Default Pultec EQP clone problem

geoff wrote:
===========

I think a spectrum analyser display would have been more relevant.


I would be curious to see the oredrs of harmonics and if they altered
over freq.


** They do, ones near the ringing frequency are all pumped up.

Fraid no * steady * one in sight as you move the test wave



....... Phil
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Default Pultec EQP clone problem

Don Pearce wrote:
===============

Just a further thought. If the mechanism were selective harmonic
boosting, the ringing wave would be continuous


** Boosting happens in the *frequency domain*.
Better keep time out of it ............

Arrange for a more pronounced ringing on the square wave
& turn your ****ing FFT on.


...... Phil


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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Pultec EQP clone problem

On Mon, 1 Mar 2021 00:21:11 -0800 (PST), "
wrote:


** Time for you to present the *spectrum* of a ringing square wave.
In the frequency domain.
Not one, tiny, leading cycle on a scope trace.

Cos that was NEVER the question and YOU know it.


That "one tiny leading cycle" IS the ringing. It is all of the
ringing. There is no more. The mechanism doesn't create more. It shows
ringing in the domain in which it happens - time.

d

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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Pultec EQP clone problem

On Mon, 1 Mar 2021 20:58:52 +1300, geoff
wrote:

On 1/03/2021 8:43 pm, Don Pearce wrote:
On Mon, 1 Mar 2021 12:48:16 +1300, geoff
wrote:

On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "


Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff


No it would not. The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on. That would have resulted
in a beat walking through the ring. A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?

d


I would be curious to see the oredrs of harmonics and if they altered
over freq.

geoff


I've taken an FFT showing all the harmonics up to and beyond the
ringing frequency. The harmonic at the ringing frequency is marked.
Make of it what you will.

http://www.soundthoughts.co.uk/look/ringing.gif

The ring itself is of very short duration so despite its amplitude, it
contains very little energy compared to the harmonics which are
continuous. That is why it won't show up in the frequency domain
(unless the Q is so high that it continues at considerable amplitude
all the way to the next excitation). To see such a low energy signal
you have to choose the appropriate domain, the one in which it can be
isolated. That of course is time. I'm really disappointed that I have
to go though these hoops - they should not be necessary for a
technical audience.

d



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gareth magennis gareth magennis is offline
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Default Pultec EQP clone problem

On Monday, 1 March 2021 at 10:12:40 UTC, Don Pearce wrote:
On Mon, 1 Mar 2021 20:58:52 +1300, geoff
wrote:

On 1/03/2021 8:43 pm, Don Pearce wrote:
On Mon, 1 Mar 2021 12:48:16 +1300, geoff
wrote:

On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "


Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff

No it would not. The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on. That would have resulted
in a beat walking through the ring. A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?

d


I would be curious to see the oredrs of harmonics and if they altered
over freq.

geoff

I've taken an FFT showing all the harmonics up to and beyond the
ringing frequency. The harmonic at the ringing frequency is marked.
Make of it what you will.

http://www.soundthoughts.co.uk/look/ringing.gif

The ring itself is of very short duration so despite its amplitude, it
contains very little energy compared to the harmonics which are
continuous. That is why it won't show up in the frequency domain
(unless the Q is so high that it continues at considerable amplitude
all the way to the next excitation). To see such a low energy signal
you have to choose the appropriate domain, the one in which it can be
isolated. That of course is time. I'm really disappointed that I have
to go though these hoops - they should not be necessary for a
technical audience.
d



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These are screenshots of the Pultec clone ringing:
https://imgur.com/Ou0BGml

and with 100 Ohms in series with 0.01uF:
https://imgur.com/jaLv5Dz


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Don Pearce[_3_] Don Pearce[_3_] is offline
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Default Pultec EQP clone problem

On Mon, 1 Mar 2021 06:01:58 -0800 (PST), gareth magennis
wrote:

On Monday, 1 March 2021 at 10:12:40 UTC, Don Pearce wrote:
On Mon, 1 Mar 2021 20:58:52 +1300, geoff
wrote:

On 1/03/2021 8:43 pm, Don Pearce wrote:
On Mon, 1 Mar 2021 12:48:16 +1300, geoff
wrote:

On 1/03/2021 8:55 am, Don Pearce wrote:
On Sat, 27 Feb 2021 04:31:33 -0800 (PST), "


Since you won't get off your lazy arse and do the work, I've done it
for you. Of course I knew precisely what the result would be before I
started, but it was a boring Sunday evening so here goes.

https://youtu.be/-hQgI0eCO08

d



I think a spectrum analyser display would have been more relevant.

geoff

No it would not. The screen I showed illustrated perfectly that there
was no selective harmonic boosting going on. That would have resulted
in a beat walking through the ring. A rock-solid, edge-induced ring is
what I intended to show, and that is exactly what I did show. Now, how
about addressing the result?

d


I would be curious to see the oredrs of harmonics and if they altered
over freq.

geoff

I've taken an FFT showing all the harmonics up to and beyond the
ringing frequency. The harmonic at the ringing frequency is marked.
Make of it what you will.

http://www.soundthoughts.co.uk/look/ringing.gif

The ring itself is of very short duration so despite its amplitude, it
contains very little energy compared to the harmonics which are
continuous. That is why it won't show up in the frequency domain
(unless the Q is so high that it continues at considerable amplitude
all the way to the next excitation). To see such a low energy signal
you have to choose the appropriate domain, the one in which it can be
isolated. That of course is time. I'm really disappointed that I have
to go though these hoops - they should not be necessary for a
technical audience.
d



--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus



These are screenshots of the Pultec clone ringing:
https://imgur.com/Ou0BGml

and with 100 Ohms in series with 0.01uF:
https://imgur.com/jaLv5Dz


Did you get those backwards? The one with the 100 ohms is much worse.
That first one though - pretty much identical to my tests. The FFT
would look identical for sure. I think I nailed it.

d
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david gourley[_6_] david gourley[_6_] is offline
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Default Pultec EQP clone problem

-snippage-
I had a great response from Scott Stone at Warm Audio, so request
him in any service communications. If he can't answer, he'll find
someone who will. I had a pilot lamp issue with my WA-251 (nice
enough mic with a GOOD figure of eight null BTW), and he sent a
replacement to me within a week.

david
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I have been in contact with Scott.

It was Scott who gave the customer the info: 100 ohms, 0.1uF in
parallel.


I have twice asked him to confirm what the mod should be, he has not
got back.

That is why I gave up and posted here.

I'm sorry you didn't have a better experience. IIRC they're in Texas,
and they just had a lot of problems, power and otherwise, due to
weather. I would keep trying, or ask for Bryce, but that's just me.

Good luck.

david


Thanks David, yeah, maybe I should be more patient, these are difficult
times for sure, but I'd like to get this sorted and back to customer,
it's been a while now I've had it.

Still, it's good to post here as you always get more info than you
bargained for.

And the bunfights.


Agreed. You may want to also try Gearslutz too. Bryce is posting there
(CEO IIRC), or at least you can PM him. I only have a couple of their
products, but have been happy with them.

But please post results at the end -thanks!

david
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