An oldie. Maybe a goodie? - Page 5

sakis · 26th January 2009, 10:54 AM

Perreaux factory tour

thats they way i like to make amps .... no mater if cost effective or not .....

SpeakerScott · 26th January 2009, 01:31 PM

Quote:

Originally posted by sakis
but your answers dont look really enough ......

what i mean is ....How come an amp like that runing at so much high rails doesnt requier CCS and out resistors ????

Sakis,

Matched transistors and lateral mosfets which have a negative temperature coefficient. Personally, at those power levels, with that number of transistors even with matched lateral devices....I wouldn't do it. But I'm an overly cautious sort. I would strongly recommend against running without degeneration resistors with hexfets or bipolar transistors.

As far as CCS...proper dominant pole compensation and most likely higher distortion...and it'll be fine.

I bought a BGW amp at a pawn shop and proceded to spend over a year fixing someone elses "fixes" on a previously blown channel. When something as a time constant of an hour or two there are only sooo many tests you can run in one night. The BGW used Motorola bipolar output devices, 10 per channel with .22 ohm emitter degeneration resistors. I eventually traced it down to the previous repair tech did not adequately tighten 2 of the transistors to the sink.

Scott

Steve Dunlap · 26th January 2009, 03:20 PM

Quote:

Originally posted by jacco vermeulen
The static killed them ?

The 80s fashion of restamping or making output devices incognito was pretty amusing, as if there was a vast array of different devices to pick from.

The static killed them. They were using a wire wheel on a grinder.

ungie · 15th February 2009, 08:02 PM

Things have been very hectic at work over the past couple of weeks, so I have not had a chance to continue working on the PMF5550. I will likely start with replacing all of the front end electros and see if that improves the DC offset.
I also had a very nice reply to an e-mail I sent to Perreaux service.
In his response he said that the correct output bias is 50ma per device. This applies to all Perreaux amplifiers.
Also, interesting enough, their current service people do not really know what effect RV2 has on audible performance and indeed it has nothing to do with DC offset.
Apparently it's an adjustment to improve measured performance in some way, but I am told that they usually set it so that +6.2V appears at the wiper.

26th January 2009, 10:54 AM	#41
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	triple woaw !!!!!!! Perreaux factory tour thats they way i like to make amps .... no mater if cost effective or not ..... __________________ SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

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15th February 2009, 08:02 PM	#44
ungie diyAudio Member Join Date: Dec 2002 Location: Ontario, Canada	Things have been very hectic at work over the past couple of weeks, so I have not had a chance to continue working on the PMF5550. I will likely start with replacing all of the front end electros and see if that improves the DC offset. I also had a very nice reply to an e-mail I sent to Perreaux service. In his response he said that the correct output bias is 50ma per device. This applies to all Perreaux amplifiers. Also, interesting enough, their current service people do not really know what effect RV2 has on audible performance and indeed it has nothing to do with DC offset. Apparently it's an adjustment to improve measured performance in some way, but I am told that they usually set it so that +6.2V appears at the wiper.