View Single Post
  #20   Report Post  
Posted to rec.audio.pro
gareth magennis gareth magennis is offline
external usenet poster
 
Posts: 73
Default Pultec EQP clone problem

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.