Bryston 4B SST clone

Yes, very similar to 4Bsst with four extra pairs of output devices per channel.. The input board isn't as self contained and easy to mount in the chassis as those for the 4Bsst. Doesn't have the +/-33V power supplies on board either.
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I'm tempted but it's a costly project, oh by the way the output board is running smoothly, at trafo primary it's idling at 70 watts,
 
Good to know design is ok before I build my output boards - thanks. By the way what voltage are you running the boards at? As you say the 28B sst2 project would be costly - the power supply and output transistors alone would cost a substantial amount. In my experience if you're tempted then at some point you're gonna do it - that's why I have a lab full of power amps that I rarely use!!
 
I ran the output today at +/- 50 volts, I only used the bench psu, and it maxed out at 50, but ran it for 15 minutes at 50 volt 1khz and lowered it to 40volts for a good hour, heatsink temp stabilized at 38 degrees Celsius, with around 200w output, so I'm happy, the toroid for final build is +/÷ 65volt.
Regarding the bryston 28b I have parts now for the complete power supply 90 volts 2kw, so biggest cost is a massive chassis and transistors,
Think we're a bit alike, I don't build for the end result having a high-end setup, I build because it's fun, so I guess you have a bunch of DIY stuff lying around, sell it to collect money for new stuff?
 
Assembly finally..!

Putting together the bryston, it's an old chassis and I have to make a new rear plate to accommodate the input board, but think it's coming along nicely.
 

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Looking good! Is the main transformer underneath the power supply/protection board?
Chalky you have good insight in the bryston amps, regarding the final bias adjustment, what would be your approach? Follow guidelines...adjust for minimum crossover distortion..what your view?. I read several places that there's no need for running them to hot, environmental and it's lifespan.
And another thing I've been thinking of, is it possible to run the boards of say +/÷ 90 volts?
The mje182/72 come out of SOA ?? Can they be replaced by say mjl15030/31 with higher volt rating.
 
Amplitude, if you have a spectrum analyzer then I'd adjust for minimum THD, otherwise the documentation that came with the pcbs looks sensible. As regards the +/-90V power supply I'd have to take a closer look I assume that all of your elcos are rated for 100V? No mje172/82 in power amp module??
 
Had another look at the power amp module schematic. No problems with the driver board at +/-90V main supply voltage. I tend to be a bit conservative so I'd experiment with replacing the 2N5401/5551s with MPSA42/92s and the MJE15030/31 with MJE15032/3 in the power section just to be on the safe side ( both substitutions have higher Vce0 ratings ).
 
Hi.
Unfortunately I have no acces to a spectrum analyzer, so just followed instructions , all good, booth channels running, but still need to finish rear plate drilling, regarding the 90 volts it was because I have several transformers from old pa amps, many running 60 to 70 volts AC out, so if I were to build a second I could use the transistors you mentioned and off course larger volt caps.
So chalky have you powered up yet? I'm curious to hear your opinion on sound quality.
Ohh by the way I couldn't resist buying those 28b sst boards, so must yet again start sourcing components.
 
Just finished building my four SSRs to replace the loudspeaker relays on the power supply boards. I've ordered the parts for the power amp boards and should be able to start on them soon. Its school holiday time so we're looking after grandchildren all day - not too much energy left after that!
 
Just finished building my four SSRs to replace the loudspeaker relays on the power supply boards. I've ordered the parts for the power amp boards and should be able to start on them soon. Its school holiday time so we're looking after grandchildren all day - not too much energy left after that!
Also just had 14 days of holiday that's why I made good progress, enjoy time with the grand children that's better,
 
I just noticed that you've added some extra off board smoothing caps to the power supply. What is your total capacitance per rail now? Saw your "nearly completed" pics in the gallery -very nice work!

Hi..
The extra capacitance is because of the amp chassis history, at first it was a proto type for a Danish high end brand, it shorted a lot of to3, and I doomed it dead, then it became a blameless by a guy here named Carlos (destroyer dx), well then the itch started and it became the bryston, so extra caps always been in chassis, total capacitance is 114000uf per rail.
Is there a company that can make rear plate costumized, preferably not to expensive?
Pic is of the original amp.
 

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If you look on CNC Zone you should be able to find someone fairly local who will do the machining for you ( there's a section for posting work required ). Most big cities have at least one anodising shop so the finish shouldn't be a problem.
I will do some research cause backplane looks like Swiss cheese, been fiddling with on/off for the amp, front panel has a cutout of 4cm by 10cm, I want to put frosted glass in and a capacitive switch for on/off , using a 555 for latching relay
 
Finished

Today I finished the amp, rear plate is fine enough, no need to spend a gazillion on that, I tried a capacitive switch in front panel as on/off switch, through a piece of glass , I couldn't get it to react stable so I went for the good old rocker switch.
 

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