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Old 13th September 2005, 04:29 AM   #1
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Default Bryston 3B SST, enyone interested?

Searching on the Diyaudio site also googling the web pages related amplifiers, I wondered why no one showed any interest in cloning Bryston amps. They are not just ordinary audiophile me too amps, but are excellent choice amongst professionals, were building quality and reliability are sometimes more important then the good sound. I will add great reviews in magazines; they are on recommended list in “Stereophile” for last decade, not to mention their original output stage and excellent spec.

Good reasons for me to clone one of these…

I will go for the “simplest” model, 3B SST, which have two output pairs per channel (MJL21193, 21194), 150watts into 8 ohms, 250 watts into 4 ohms. For me it’s more then enough power, and I don’t like amps with grater number of output transistors, sound wise.

From my research, other models have extra PCB with two more pairs per channel so anyone who wish my go for more power. From one older test in “Stereophile”(October 96), 3B ST has two toroidal transformers rated at 225 VA, and one 10000uF/63V cap per rail, 4 in total. I think the new model is very similar or the same. Rails are +- 55Volts DC.

According previous mentioned “Stereophile” issue, Stuart Taylor had great work to redesign older pcb’s and at the and he managed to lower the noise and THD a lot. That means we must design really good pcb with all the help from all experienced members.

Some usable pictures from `real thing` will be more then helpful!

All schematics can be downloaded at official Bryston site; also there can be found other interesting stuff like explanations about their Quad-Complementary output section.
Everyone opinions are welcome!

Best regards,
Chicco
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Old 13th September 2005, 05:16 AM   #2
MOER is offline MOER  United States
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Default Bryston amps

Not very good amplifiers. Examine the circuits closely. The differential amplifiers have NO local feedback and have no constant current sources driving them but simply resistors to a zener diode. The VAS stages are rather crude also with minimal local feedback and yes they do give low measured THD due to their massive open loop gain and then the tons of global feedback applied. The VAS is a two stage affair with cascaded common emitter amplifiers which further increases open loop gain.

We have worked on sevral models of these amplifiers and found instability in driving reactive loads. The amplifiers are marginally stable.

The cookiest idea is having both emitter followers and collector followers in the output stages. For what reason? The EF configuration gives slightly worse saturation than CF but who cares , add 1-2 volts of rail. I have nothing against CFP output stages BUT they must be compensated with local feedabck to keep them stable. They do have lower measured THD than EF outputs but who cares. It is the nature of the distortion that we care about, not how much.

The use of coils in the speaker circuit is further proof of the unstable nature of these circuits.
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Old 13th September 2005, 01:29 PM   #3
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Hi MOER,

You wrote:
“Bryston amps
Not very good amplifiers.”

Your experience is based from looking in the schematics, servicing them, or owning one for your listening pleasure?
I’m not educated in electronics enough to analyze schematics like you did, but I had opportunity to listen 3B ST and 4B ST in two different systems, driving B&W 802 matrix and Martin Logan SL3. Sound was excellent, and both owners independently told me that after changing a lot of amps, they finally settled with Brystons. Neither of them had “instability problems”.

You wrote:
“We have worked on several models of these amplifiers and found instability in driving reactive loads. The amplifiers are marginally stable.”

“The use of coils in the speaker circuit is further proof of the unstable nature of these circuits.”

As I understand, every Bryston amp has 100 hours burn in at full power before living the factory. Not to mention 20-year transferable warranty…
Will they offer that kind of service for “unstable” or “marginally stable” products? I don’t think so.
They did sell amps in professional market where is a lot of abusing, but from what I read, Bryston amps are very popular amongst professionals.
I will also add that 3B SST selling price in UK is 1725 pounds, about 2500 euros. What’s wrong if one can clone it for 10% of that price???

At the end, can you point other interesting amp worth cloning (bipolar design, two power transistor pairs per channel, which is more stable but more important, with better sound quality) ???

Best regards,
Chicco
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File Type: jpg 3b sst inside.jpg (31.5 KB, 2402 views)
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Old 13th September 2005, 02:24 PM   #4
MOER is offline MOER  United States
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Default Bryston

Dear Chicco,

Yes I look at them from an engineering standpoint and also have compared them in my home system to others. I have a double blind A-B set up that can be installed in my speaker leads. I do this only on the mids and highs.

My subs are servo controlled and not easily A-B compared.

I have Infinity Gammas which are not easy loads to drive. I also always keep an oscilliscope connected so I can see what is going on.

I did a comparison about 6 months ago with a Bryston 4B, an original GAS Ampzilla from 1975 and my own McIntosh MI350 mono tube amplifiers.

The GAS was streets ahead of the 4B and it was quite easy to pick it out time again. The 4B sounds like Crown amplifiers, grainy, clinical and edgy.......... why you may ask? Well high open loop gain massive global feedback low low THD designs tend to sound this way.

The GAS is the opposite in design. Low global feedback, lots of local feedback loops, short signal path.

I am sure the bottom end of the 4B is good due to big power supplies and high damping factor (which I do not place much credence on anyway. Just add in the series R of the speaker coil and effective damping factor becomes 1.3!!!

The 4B against the MI350s was not even a competition. The Macs were light years ahead, yes I am comparing a tube amplifier to a solid state nut never the less. The Macs were also better than the GAS.

There are many other great designs to copy at 10% of the cost I know as I am a manufacturer of amplifiers.

The Leach design is streets ahead of the 4B or 3B just to name one. Copy the original GAS Ampzilla it hold it's own against most modern day designs anyway.


Regards

Steve
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Old 13th September 2005, 03:36 PM   #5
tlf9999 is offline tlf9999  United States
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Default Re: Bryston

Quote:
Originally posted by MOER
The GAS was streets ahead of the 4B
how's the comparison done? If it were done sighted, it would have very limited value.
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Old 13th September 2005, 04:12 PM   #6
anatech is offline anatech  Canada
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Hi Chicco,
I have to agree with MOER here. I've serviced them and listened to them. Nothing special at all. The funny output stage is something Bryston cooked up in a garage years ago. It's part of what a Bryston is and they will not change it. I don't feel they are as reliable as they could be. Possibly the lastest ones are better? I don't know.

I would not bother building an ST or original. A complete waste of a good heatsink. There are other things that sound way better, why not go with an amp from this forum in that case.

The Bryston product would be good to study. I'd approch them from that angle.

-Chris
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Old 13th September 2005, 04:20 PM   #7
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I would give this project a go for the same reason I did the Krellclones, why not? Yes, it may have issues but half the fun of this hobby is trying things out, and certainly, in the UK, Brystons are relatively rare on the S/H market.

Let's face it, the expensive lumps are the case and psu, both of which could be reused for other projects if the Bryston is not deemed worthy. But if you don't build one, you don't know...
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Old 13th September 2005, 05:27 PM   #8
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I've lived with many amps over the years including 3 different Brystons. IMHO there have been very few amps that exceeded the 3B which is not as good sounding as the 4B. The 4B was a bit "edgy" when I first got it hooked up to my speakers but that only lasted a few weeks. I would not characterize its sound as grainy or edgy now. Clinical, maybe, but it also has very good ambience and solid bass. It will expose poor recordings. I think accurate is a better discription in this case.

Reliable? Heck, each of them were/are workhorses that will not quit. And by continuing to offer a 20 year transferable warranty, you know that Bryston knows it as well.

In short, there are far more inferior sounding amps out there than there are better sounding amps to clone.
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Old 13th September 2005, 05:46 PM   #9
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Quote:
The funny output stage is something Bryston cooked up in a garage years ago. It's part of what a Bryston is and they will not change it. I don't feel they are as reliable as they could be. Possibly the lastest ones are better? I don't know.
I think every company has "A unique design approach" which earns him a distinguished identity from rest of the traditional designs or company's and therefore it would not leave that foremost feature so easily which is crafted or created or invented by him with hardwork...whether that feature is good or bad, but when you workhard to achieve something, then its very difficult to believe that the thing at which you are working is worth nothing...it takes a lot of time to accept....but again Time is the greatest Healer...

K a n w a r
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Old 13th September 2005, 05:46 PM   #10
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I work at Universal Music Group headquarters and almost all of the conference rooms are powered with Brystons. They sound very good to me.
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