Pultec EQP clone problem

gareth magennis wrote:

===================
>
>
> Maybe there never was any "motorboating", this notion came from the customer in his email to the company.

** So you OP here was an entire pile of bull crap.

> I never found any, despite adding caps on the output like Mike suggested.

** So what the **** were you trying to *fix* ?????

Dear Mr Magennis,

your total lack of insight & professionalism is appalling.
If I were your employer, I would hand you broom and tell you sweep the floor.


......... Phil

On Wednesday, 3 February 2021 at 12:06:07 UTC, wrote:
> gareth magennis wrote:
>
> ===================
> >
> >
> > Maybe there never was any "motorboating", this notion came from the customer in his email to the company.
> ** So you OP here was an entire pile of bull crap.
> > I never found any, despite adding caps on the output like Mike suggested.
> ** So what the **** were you trying to *fix* ?????
>
> Dear Mr Magennis,
>
> your total lack of insight & professionalism is appalling.
> If I were your employer, I would hand you broom and tell you sweep the floor.
>
>
> ........ Phil


I think it is obvious I fixed an incorrect modification instruction from the company.

I felt strongly enough that this instruction was just not right, that I felt the need to post my concerns here, where I might get some vaulable insight into whether these concerns bore any weight, or perhaps I was missing something.

As usual, it turned out worthwhile.

Both Don and yourself explained the motorboating phenomenon in a system without negative feedback.
Thanks, that is valuable education indeed, and I appreciate that.

It doesn't really matter that the alleged motorboating may have turned out to be a red herring, I think we all learned something from that.
I said from the outset I was unable to recreate it, it was reported as such by the customer.



My only concern now is that I return the unit to the customer with the proper mod in place, to find it really does have a motorboating problem I can't recreate on the bench, as the mod actually seems to be a low pass filter to stop hf oscillations, not to stop a motorboating issue.

gareth magennis wrote a pile of self serving drivel:

===========================================
> My only concern now is that I return the unit to the customer with the proper mod in place,

** Which does next to nothing.

> to find it really does have a motorboating problem I can't recreate on the bench,

** There is another way a piece of audio gear can be made to " motor boat " at a low frequency.

You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.

Bet your dopey customer has done that by missconnecting the patch bay.

Try it and see if what YOU get matches with their story.


...... Phil

On Wednesday, 3 February 2021 at 22:36:33 UTC, wrote:
> gareth magennis wrote a pile of self serving drivel:
>
> ===========================================
> > My only concern now is that I return the unit to the customer with the proper mod in place,
> ** Which does next to nothing.
> > to find it really does have a motorboating problem I can't recreate on the bench,
> ** There is another way a piece of audio gear can be made to " motor boat " at a low frequency.
>
> You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.
>
> Bet your dopey customer has done that by missconnecting the patch bay.
>
> Try it and see if what YOU get matches with their story.
>
>
> ..... Phil




Funny, that's what I just said, but in a different language.

On Wednesday, 3 February 2021 at 23:09:36 UTC, gareth magennis wrote:
> On Wednesday, 3 February 2021 at 22:36:33 UTC, wrote:
> > gareth magennis wrote a pile of self serving drivel:
> >
> > ===========================================
> > > My only concern now is that I return the unit to the customer with the proper mod in place,
> > ** Which does next to nothing.
> > > to find it really does have a motorboating problem I can't recreate on the bench,
> > ** There is another way a piece of audio gear can be made to " motor boat " at a low frequency.
> >
> > You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.
> >
> > Bet your dopey customer has done that by missconnecting the patch bay.
> >
> > Try it and see if what YOU get matches with their story.
> >
> >
> > ..... Phil
> Funny, that's what I just said, but in a different language.


I think we are actually on the same page here.

gareth magennis is a massive narcissist :

------------------------------------------------------------------------
> > You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.
> >
> > Bet your dopey customer has done that by missconnecting the patch bay.
> >
> > Try it and see if what YOU get matches with their story.
> >
>
> Funny, that's what I just said, but in a different language.


** You said *nothing of the sort* - you pathetic bull**** artist.

Got a broom handy - know how to use it?

....... Phil

On Wednesday, 3 February 2021 at 23:20:53 UTC, wrote:
> gareth magennis is a massive narcissist :
>
> ------------------------------------------------------------------------
> > > You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.
> > >
> > > Bet your dopey customer has done that by missconnecting the patch bay.
> > >
> > > Try it and see if what YOU get matches with their story.
> > >
> >
> > Funny, that's what I just said, but in a different language.
> ** You said *nothing of the sort* - you pathetic bull**** artist.
>
> Got a broom handy - know how to use it?
>
> ...... Phil



Oh well, I tried.

gareth magennis wrote:

=====================
>
> > ------------------------------------------------------------------------
> > > > You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.
> > > >
> > > > Bet your dopey customer has done that by missconnecting the patch bay.
> > > >
> > > > Try it and see if what YOU get matches with their story.
> > > >
> > >
> > > Funny, that's what I just said, but in a different language.
>>
> > ** You said *nothing of the sort* - you pathetic bull**** artist.
> >
> > Got a broom handy - know how to use it?
> >
>
> Oh well, I tried.

** ROTFL !!!!

The only thing this tedious prick " tried " was to bull**** his way out of admitting his massive incompetency.




...... Phil

On Thursday, 4 February 2021 at 00:21:30 UTC, wrote:
> gareth magennis wrote:
>
> =====================
> >
> > > ------------------------------------------------------------------------
> > > > > You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.
> > > > >
> > > > > Bet your dopey customer has done that by missconnecting the patch bay.
> > > > >
> > > > > Try it and see if what YOU get matches with their story.
> > > > >
> > > >
> > > > Funny, that's what I just said, but in a different language.
> >>
> > > ** You said *nothing of the sort* - you pathetic bull**** artist.
> > >
> > > Got a broom handy - know how to use it?
> > >
> >
> > Oh well, I tried.
>
> ** ROTFL !!!!
>
> The only thing this tedious prick " tried " was to bull**** his way out of admitting his massive incompetency.
>
>
>
>
> ..... Phil


OK, briefly,

I talked at length to the customer today.
His experience of this "motorboating" was an oscillation around 90 Hz.

I had an email converation with the company today.
They say they had problems with the first batch of units that would oscillate around 90 Hz when connected to a remote patchbay.
They designed this mod to combat this occasional 90Hz problem, and made circuit revisions thereafter.

I was incorrect in assuming this mod was to guard against HF oscillations.



If you refer back to the Gearslutz thread I referred to, you will find this problem described thus:

2. The thing with the added capacitors and resistors is to properly load the output stages, which would solve a buzz you might hear if you run long output cables.

link to thread again he
https://www.gearslutz.com/board/so-m...fications.html

On Thursday, 4 February 2021 at 23:17:09 UTC, gareth magennis wrote:
> On Thursday, 4 February 2021 at 00:21:30 UTC, wrote:
> > gareth magennis wrote:
> >
> > =====================
> > >
> > > > ------------------------------------------------------------------------
> > > > > > You mentioned there is a "patch bay" the unit plugs into. If somehow enough output signal gets back to the input, positive feedback results in low frequency oscillation - typically a sub sonic square wave at high level.
> > > > > >
> > > > > > Bet your dopey customer has done that by missconnecting the patch bay.
> > > > > >
> > > > > > Try it and see if what YOU get matches with their story.
> > > > > >
> > > > >
> > > > > Funny, that's what I just said, but in a different language.
> > >>
> > > > ** You said *nothing of the sort* - you pathetic bull**** artist.
> > > >
> > > > Got a broom handy - know how to use it?
> > > >
> > >
> > > Oh well, I tried.
> >
> > ** ROTFL !!!!
> >
> > The only thing this tedious prick " tried " was to bull**** his way out of admitting his massive incompetency.
> >
> >
> >
> >
> > ..... Phil
> OK, briefly,
>
> I talked at length to the customer today.
> His experience of this "motorboating" was an oscillation around 90 Hz.
>
> I had an email converation with the company today.
> They say they had problems with the first batch of units that would oscillate around 90 Hz when connected to a remote patchbay.
> They designed this mod to combat this occasional 90Hz problem, and made circuit revisions thereafter.
>
> I was incorrect in assuming this mod was to guard against HF oscillations.
>
>
>
> If you refer back to the Gearslutz thread I referred to, you will find this problem described thus:
>
> 2. The thing with the added capacitors and resistors is to properly load the output stages, which would solve a buzz you might hear if you run long output cables.
>
> link to thread again he
> https://www.gearslutz.com/board/so-m...fications.html


I haven't been able to experience this problem, but it is starting to look like it is not a full blown oscillation at full volume, but rather some background noise problem, where a 90Hz tone gets added to the audio.
Dunno, this is work in progress I guess.