As well as I know, the patent would probably only be for the output stage. Even then I believe the patent doesn’t stop anybody from building themselves a copy of the amp, so long as they don’t sell it and it doesn’t hurt Bryston in any way.
There are lots of reviews of this amp at www.audioreview.com/ (most however are for the older ST ) if anyone wants to have a look. One of them says Bryston uses a feedback loop to fatten up the bottom end. Could someone point this out to me. Many of those reviews also claim that the sim audio amps are the next step up from the Bryston, at 2.5x the cost they should be. I really wish I had the schematic to one of them.
There are lots of reviews of this amp at www.audioreview.com/ (most however are for the older ST ) if anyone wants to have a look. One of them says Bryston uses a feedback loop to fatten up the bottom end. Could someone point this out to me. Many of those reviews also claim that the sim audio amps are the next step up from the Bryston, at 2.5x the cost they should be. I really wish I had the schematic to one of them.
Hi eupupa,
sorry I don't know your name.
I am trying to get this thread going on analysing Bryston's schematic. I do NOT intend building a copy. My post indicates that I have many reservations about the design decisions adopted by Bryston but I want everyone to have the opportunity to air their views. Bryston might even join in to explain their philosophy. Some of us might end up with a better sounding amp than the original & then the whole community will benefit.
If some of us find a circuit idea that helps solve a problem & then incorporates a version of that idea into their own circuit design then I believe that the design of the new circuit is not breaking the copyright of the originator.
Think about it another way how did we all start using common emitter stages? I guess someone published the circuit and those who recognised its worth put it into their circuits. Soon everyone is using common emitter at some time or other and I hear no one complaining infringement of copyright.
Lets not have copyright blighting a usefull (to some) technical discussion.
regards
Andrew T.
sorry I don't know your name.
I am trying to get this thread going on analysing Bryston's schematic. I do NOT intend building a copy. My post indicates that I have many reservations about the design decisions adopted by Bryston but I want everyone to have the opportunity to air their views. Bryston might even join in to explain their philosophy. Some of us might end up with a better sounding amp than the original & then the whole community will benefit.
If some of us find a circuit idea that helps solve a problem & then incorporates a version of that idea into their own circuit design then I believe that the design of the new circuit is not breaking the copyright of the originator.
Think about it another way how did we all start using common emitter stages? I guess someone published the circuit and those who recognised its worth put it into their circuits. Soon everyone is using common emitter at some time or other and I hear no one complaining infringement of copyright.
Lets not have copyright blighting a usefull (to some) technical discussion.
regards
Andrew T.
Hi Andrew, have you some Bryston's SST family in your hands ? They are excellent amps ( I was tested 4 and 7 for one Czech hifi magazine, this test you can find on Bryston's home page, my name is Pavel Dudek ), but all types have ( in my look ) one disadvantage. They have two stage VAS and because havn't antisaturation circuity, all stages by clipping ( mainly at high frequencys ) are deeply saturated, which caused rise of quinscent current on realy great value ( power consumption on AC side rise from 4 A to more than 8 A ! by only " touch " on clipping by 10 kHz ). It is probably reason, why some listeners hear harsh sound at high frequencys. All other parametres of this amp are realy very good. Pavel
I to would be really interested in improving on this amp. I can’t wait to see somebody build one. I have some questions if anybody would like to try and take a stab at answering them.
1) Does anybody know how to make this amp balanced without using it’s built in preamp board. I don’t understand why they don’t just go directly to the amp. If going I directly to the amp and bypassing the “preamp” stage, should the input resistor values be changed?
2) I thought amps with lots and lots of negative feedback where supposed to sound really bad. This amp is using lots of feedback and yet it gets very good reviews. Am I missing something here?
1) Does anybody know how to make this amp balanced without using it’s built in preamp board. I don’t understand why they don’t just go directly to the amp. If going I directly to the amp and bypassing the “preamp” stage, should the input resistor values be changed?
2) I thought amps with lots and lots of negative feedback where supposed to sound really bad. This amp is using lots of feedback and yet it gets very good reviews. Am I missing something here?
To LBHajdu : Are you asking why is not minus input conected directly to inverting input ? Answer is simply : there is too low input impedance and balanced line in this case will be not work correctly and WILL BE NOT BALANCED. Technics in this firm know very well their job, probably much more better than you know and don't need some stupid advices from amateurs 
. And second notice : once before long time was by very intelligent people make up one very good thing : negative feedback for IMPROVING parametres of equipment. This principle is not " any devil's work ", how again and again says idiots, which don't know whatabout is talking 🙁 . I had heard many amps " without feedback " and in every time they distorted - isn't thruth that they have better sound, amps with best sound was always this ones with feedback, but made by smart people, not by idiots.
. And second notice : once before long time was by very intelligent people make up one very good thing : negative feedback for IMPROVING parametres of equipment. This principle is not " any devil's work ", how again and again says idiots, which don't know whatabout is talking 🙁 . I had heard many amps " without feedback " and in every time they distorted - isn't thruth that they have better sound, amps with best sound was always this ones with feedback, but made by smart people, not by idiots.
The good reviews come from listeners who don't know any better. Ask Upupops if you don't believe me 🙂
Anybody notice the *positive* feedback in the high frequency compenstation? Obviously the amp works, probably because the series R is so large, but ....
Anybody see it?
Anybody see it?
There's 470 pF - 100K from the collector of the first diff amp transistor to the negative input of the diff amp, in the 3B IV schematic. This is positive feedback since the first diff amp collector is inverted relative to the + input, but the 100K R makes it very small.
Is this an attempt to "null out" the Miller capacitance of the neg diff amp transistor?
Anybody know?
Is this an attempt to "null out" the Miller capacitance of the neg diff amp transistor?
Anybody know?
Hi,
pb2 I cannot answer your query, sorry!
But could you look at post 38 & think about some analysis?
regards Andrew T.
pb2 I cannot answer your query, sorry!
But could you look at post 38 & think about some analysis?
regards Andrew T.
I have never listened to a Bryston myself so I can't comment. I have a buddy of mine in Kansas City that installs nothing but Brystons in HT. The big HT systems (>$50K), he says he uses them because they are bullet proof.
For whatever this is worth...
For whatever this is worth...
Hi AndrewT,
I would agree with you about reservations. Do we know who designed this amp? It looks so much like the SWTPC designs that I wonder if it was the same designer or did they "borrow" it and add their patented output stage to claim innovation. It seems to add unnecessary complexity. The output stage looks like they couldn't make up their mind, I kind of laugh when I look at it.
Concerning those who commented about the patent, as I understand it, experimentation with patented designs is encouraged to promote further innovation. And people here do seem to be innovating.
I have many concerns about this design, there are 4 common emitter stages, but the first VAS has so much degeneration that it probably operates almost as common collector. The first VAS has 2.2K emitter degen wonder if it has much voltage gain at all? Then it has a speed up cap across it.
I could go on, but this design does not give me a warm fuzzy feeling.
I would agree with you about reservations. Do we know who designed this amp? It looks so much like the SWTPC designs that I wonder if it was the same designer or did they "borrow" it and add their patented output stage to claim innovation. It seems to add unnecessary complexity. The output stage looks like they couldn't make up their mind, I kind of laugh when I look at it.
Concerning those who commented about the patent, as I understand it, experimentation with patented designs is encouraged to promote further innovation. And people here do seem to be innovating.
I have many concerns about this design, there are 4 common emitter stages, but the first VAS has so much degeneration that it probably operates almost as common collector. The first VAS has 2.2K emitter degen wonder if it has much voltage gain at all? Then it has a speed up cap across it.
I could go on, but this design does not give me a warm fuzzy feeling.
AndrewT,
Have you had a look at the Jensen 990 Discrete OP amp and the AES article covering the design? There's good discussion about LTP degeneration, current mirrors, HF compensation. This was designed by Deane Jensen and shows some excellent engineering:
http://recording.org/users/kev/Jensen_990C_schematic.tif
AES 1980 Jan/Feb Vol 28 Number 1/2
Found the above schematic on this page, not endorsing the page but there are other references to the 990:
http://recording.org/users/kev/discrete_op-amps.htm
Any opinions on the LM394 super matched pair?
Have you had a look at the Jensen 990 Discrete OP amp and the AES article covering the design? There's good discussion about LTP degeneration, current mirrors, HF compensation. This was designed by Deane Jensen and shows some excellent engineering:
http://recording.org/users/kev/Jensen_990C_schematic.tif
AES 1980 Jan/Feb Vol 28 Number 1/2
Found the above schematic on this page, not endorsing the page but there are other references to the 990:
http://recording.org/users/kev/discrete_op-amps.htm
Any opinions on the LM394 super matched pair?
AndrewT wrote:
"Two further comments I omitted.
Is that a pair of caps to slug the hi freq gain of the VAS (100nF C13 C15).
What do C7 & C8 (470p) do? Hi Freq feedback around the local loop output stages?"
C7 and C8 reduce the voltage gain of the driver and output stage to unity as frequency increases.
C13 and C15 offer a frequency dependent load on the VAS to reduce the gain at HF.
Further, C27 and C28 look like Cdom compensation caps but thier not on the VAS, rather their on a current gain stage.
"Two further comments I omitted.
Is that a pair of caps to slug the hi freq gain of the VAS (100nF C13 C15).
What do C7 & C8 (470p) do? Hi Freq feedback around the local loop output stages?"
C7 and C8 reduce the voltage gain of the driver and output stage to unity as frequency increases.
C13 and C15 offer a frequency dependent load on the VAS to reduce the gain at HF.
Further, C27 and C28 look like Cdom compensation caps but thier not on the VAS, rather their on a current gain stage.
Thanks pb2,
You're confirming that the reputed excellent sound of this amp is not down to clever topology. It seems to be carefull selection of various compensation elements or could the whole sound be due to the overiding excellence of the quad output?
PB2 does not agree but I still think it is an elegant combination of EF and CFP.
I plan to modify a quasi output to quad for comparison.
regards Andrew T.
You're confirming that the reputed excellent sound of this amp is not down to clever topology. It seems to be carefull selection of various compensation elements or could the whole sound be due to the overiding excellence of the quad output?
PB2 does not agree but I still think it is an elegant combination of EF and CFP.
I plan to modify a quasi output to quad for comparison.
regards Andrew T.
Actually AndrewT I'm not sure what to make of this amplifier, I had a very good impression of it based on reviews and performance tests, it was a bit of a shock to see how similar it is to the SWTPC designs which I've built.
Then looking at the schematics it does not appear to conform to the keep it simple philosophy since it seems to have HF compensation in every possible location. This does not make a good impression in terms of a straightforward compensation scheme. However, I've taken another look at the performance and it's interesting that it does very well from a distortion perspective even at higher frequencies. This suggests high open loop bandwidth and it's possible that the extensive compensation is there to get the most out of the design. I'd like to see the open loop gain and phase plots versus level and load.
Still it appears as a design that has evolved.
I've seen the discussion of the output stage at their site, but nothing more technical. I noticed someone mention a patent but was unable to find it, have you seen it?
I'd like to hear what others think of this design.
IME, large PSU reserve (big caps) and high output current capability make for tight well controlled bass, assuming a sound basic design. It will be good to hear the results of your experiment.
Then looking at the schematics it does not appear to conform to the keep it simple philosophy since it seems to have HF compensation in every possible location. This does not make a good impression in terms of a straightforward compensation scheme. However, I've taken another look at the performance and it's interesting that it does very well from a distortion perspective even at higher frequencies. This suggests high open loop bandwidth and it's possible that the extensive compensation is there to get the most out of the design. I'd like to see the open loop gain and phase plots versus level and load.
Still it appears as a design that has evolved.
I've seen the discussion of the output stage at their site, but nothing more technical. I noticed someone mention a patent but was unable to find it, have you seen it?
I'd like to hear what others think of this design.
IME, large PSU reserve (big caps) and high output current capability make for tight well controlled bass, assuming a sound basic design. It will be good to hear the results of your experiment.
built versions
Hi,
this thread has run for over a year now.
djmiddelkoop appears to have built something based on at least part of the topology and gave a solution for oscillation.
Has anyone else built any part of it?
Please report on successes or otherwise.
Bryston appear to have included 2 Vbe multipliers; one monitoring the VAS board temp and the other monitoring the output heatsink temp. Can anyone confirm this?
regards Andrew T.
Hi,
this thread has run for over a year now.
djmiddelkoop appears to have built something based on at least part of the topology and gave a solution for oscillation.
Has anyone else built any part of it?
Please report on successes or otherwise.
Bryston appear to have included 2 Vbe multipliers; one monitoring the VAS board temp and the other monitoring the output heatsink temp. Can anyone confirm this?
regards Andrew T.
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