Building Bryston amps from the service manuals

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Bias setting for Bryston amps

I have been playing about with the 7B-SST schenatic in spice. Does anyone have one of these (or any other SST amp from bryston) and knows what the bias currents are set to? Reviewing schematics for all SST amps, the double VBE muliplyer is subtley different in each amp.
Maybe there is a "setup or service manual" around which states how these amps are setup?
 
I owned an older 4B for a short time and i can tell you with my Hales Revelation 3's the amp just grabbed the bottom end! almost as if it added an entire octave on the low end to my speakers. I had heard these amps were good for bass but dang! wow!!

I had been using modified soundcraftsmens up until then and the differences are dramatic! besides the bottom ended being cleaner and lower in extension, the top was much clearer, but a bit harsh with the rev 3's. overall the amp was very clear sounding.

The clip indicators arent very good. when those lights come on, your already into clipping. and there calibrated from the factory at 8 ohms....

The Soundcraftsmen amps seem to have a much more accurate clip indicator in them. i highly reccomend anyone wanting to add a clip light to check out the PCR-800 scematics for a really good clip indicator.

I sent my 4B in for updates just before the warranty expired and they replaced the 2 big can caps for 4x 10,000uf caps with a smaller package size.

While i liked the amp, something about it combined with my rev 3's was fatiguing. i ended up selling it. i hear the newer designs are much better sounding.

At some point i want to buy a used Krell KSA-250 or Classe 200 or 400 amp.


Zero Cool :Pumpkin:
 
There arent anyone having a bryston 7BSST available and can take a close photo inside it?

It is really good data on this amp and if one should build a powerful amp this is probbably one of the best choices, and skip all the crap about LEDS, balanced inputs and such things :)

Best regards
Jonas
 
Hi
this thread has gone quiet.
Are you all analysing & building Brystons and going to publish results in a couple of months?
Just a few thoughts on Bryston's schematics;
the discrete opamp at the front end seems to be an add on to give bal & unbal options with a switched gain option.
I don't think it helps the sound of the overall kit. but it may do no harm ( see later).
The LTP complementary pairs run with resistor load and resistor sources from regulated rails. This could be why they sound quite good (no mirrors seems to be the preferred option for good sound).
The LTP run without degeneration resistors. Perceived wisdom from others (Cherry , Leach, Linsley-Hood & others) is that the input must not overload the LTP. Bryston run at upto 4v into the LTP!!! Two solutions seem to be; keep the global gain high or add large degen. Could this be why some are finding that Brystons sound a bit bright or harsh at the top(TID) due to hi freq overload?
Bryston have used miller cap (Cdom) around the VAS. could this be improved by running a local feedback from the output stages to VAS input? (but I believe the times 3 would have to come out).
Bryston have a times three voltage multiplier between the LTP/VAS and output stage. is this good for sound? is the benefit of running the VAS at lower voltage (more voltage swing = more distortion) greater than the loss of the x3?
The quad complementary is new to me but seems an elegant way of combining the EF and CFP output stages. Does it eliminate the errors as Bryston claim or does it combine the worst of both i.e. the temp sensitivity of the EF and the sharp changeover of the CFP.
Current protection on the CFP & EF seems to be more complicated to calculte than normal. any thought on analysing?
How do you set/calculate the VAS stage bias current when you have VBE multiplier and top & tail VAS transistors?
Let the knowledge bank answer back!!!!
Oh and finally I'm thinking leach front end & Bryston quad output( 1quad for class AB into 4r, 2 quad for ClassA or into 2r0)
regards
Andrew T.
 
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