janneman said:
No, I like that chategorization too, although they use different
terminology for the cases in my book. It is just that things
seem to have settled on a particular modern meaning of
the terms VFB and CFB, so I guess it's best to stick to them
to minimize confusion. I was "accused" of being oldfashioned
and sticking to old books by people probably much older than
myself when I brought up a similar discussion recently. Now
we have the confusion of lacking terms for what you and Hugh
call VFB and CFB instead. I guess voltage/current sense are
reasonable terms here, but maybe there are new standard
terms for them, or there never was any agreement at all
on the feedback terminology? I am not arguing with anybody
anyway, just want us to speak the same language, ie.
terminology, whichever one we settle for so we can avoid
confusion.
janneman said:
For your reference, the CFB discussion was here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=22408
Now back to this thread which is about the Stochino amp.
I have a paper copy of the article laying around. Unfortunately I don't have access to a scanner or I would have posted it here.
From what I remember the interesting part about this amp was that he achieved high speed by running the input diff-pair in class AB so that there was more current available to charge/discharge the Miller capacitor around the VAS stage.
The schematic that Christer posted a link to seems correct from what I remember.
I saw this at the AD website.
http://www.analog.com/UploadedFiles/Application_Notes/492001115525484056221917334AN211.pdf
Has anybody ever built and/or listened to one?
ensen.
http://www.analog.com/UploadedFiles/Application_Notes/492001115525484056221917334AN211.pdf
Has anybody ever built and/or listened to one?
ensen.Attachments
I have for a friend long time ago. The amp worked quite nicely but I used other mosfets, don't remember which type IRF???.
QRV-03 is an enhanced Alexander amp. It has the same current feedback section as this
Quote from head-fi.org
7. - Listening QRV-03 - Although it is very subjective and hard to describe my experience in English, Sound
is so clear and rich... In a single word, Excellent!!! This QRV-03 gives me the most satisfaction among what
I have built 19 kinds of DIY Headphone amps.
Words from Hyun Joon Rho, a korean builder.
His amp can be seen here
QRV-03 is an enhanced Alexander amp. It has the same current feedback section as this
Quote from head-fi.org
7. - Listening QRV-03 - Although it is very subjective and hard to describe my experience in English, Sound
is so clear and rich... In a single word, Excellent!!! This QRV-03 gives me the most satisfaction among what
I have built 19 kinds of DIY Headphone amps.
Words from Hyun Joon Rho, a korean builder.
His amp can be seen here
The Alexander CFB seems to be the most popular current feedback basic schematic. I've heard what kind of sound it produces, clean, fast, details are good but if you listen to it for some time it becomes boring. The highs seems tobe more dominant than the lows. Too dry for me.
I tried not to use CFB if possible. What is the secret of making ultra fast power amp using ordinary voltage feedback? What is the original Stochino schematic looks like?
Does anyone knows what is inside MC2 professional amp?
I tried not to use CFB if possible. What is the secret of making ultra fast power amp using ordinary voltage feedback? What is the original Stochino schematic looks like?
Does anyone knows what is inside MC2 professional amp?
Lumanauw,
Masalah ini - tak ada satu rahasia pun. Ada beberapa lagi.
There are at least four very sensitive points in any SS PP amplifier. All have to be very carefully addressed to make the overall sound good.
Remember also that component choice and pcb design play a role; this is as much an art as engineering.
There are some very expensive amplifiers available in high end, yet when you examine their schematics, you find small differences. But it is the small differences which matter, and which command high prices in the audio marketplace.
No manufacturer, including me, will tell you these hard won secrets. It is their living. You just have to go through all the hardship and pay your dues, like John Curl, Nelson Pass, Jonathon Carr, and numerous other luminaries in this field. You are dealing with intellectual property; not highly regarded by some, but jealously guarded by those who know, of which I (perhaps arrogantly) am one.
The input stage, the voltage amplifier, and the output stage are all very important. Lag compensation is vital. Use fast transistors. Keep feedback paths short. Stick to convention. Read all Rod Elliott's website. Absorb it, think about it, build circuits, blow up transistors, try crazy things. After a few years you will know a great deal about high end, and likely will have a beautiful amplifier.
Otherwise, you just have to pay, like the rest of us..........
Is it really any different to any other technology, including medicine, or automotive?
Cheers,
Hugh
Masalah ini - tak ada satu rahasia pun. Ada beberapa lagi.
There are at least four very sensitive points in any SS PP amplifier. All have to be very carefully addressed to make the overall sound good.
Remember also that component choice and pcb design play a role; this is as much an art as engineering.
There are some very expensive amplifiers available in high end, yet when you examine their schematics, you find small differences. But it is the small differences which matter, and which command high prices in the audio marketplace.
No manufacturer, including me, will tell you these hard won secrets. It is their living. You just have to go through all the hardship and pay your dues, like John Curl, Nelson Pass, Jonathon Carr, and numerous other luminaries in this field. You are dealing with intellectual property; not highly regarded by some, but jealously guarded by those who know, of which I (perhaps arrogantly) am one.
The input stage, the voltage amplifier, and the output stage are all very important. Lag compensation is vital. Use fast transistors. Keep feedback paths short. Stick to convention. Read all Rod Elliott's website. Absorb it, think about it, build circuits, blow up transistors, try crazy things. After a few years you will know a great deal about high end, and likely will have a beautiful amplifier.
Otherwise, you just have to pay, like the rest of us..........
Is it really any different to any other technology, including medicine, or automotive?
Cheers,
Hugh
Hugh,
I am sure the large majority of forum members understand and
share your view. Primarily, this forum is, as the name indicates,
a forum for amateurs. Unless they have some suspect reason
for their presence here they are and should be willing to and
interested in sharing their knowledge and experiences with
other members, thus adding to an increased collective
knowledge and understanding of audio equipment.
The presence of commercial audio designers like yourself and
many others is an added bonus. We can ask you for
information and advice, but we cannot demand you or expect
you to tell us anything that is a trade secret. Most of you share
more experience and knowledge with us than we could expect,
and I am sure most of us grateful for that generosity.
(There may be a few commercial designers who are considered,
at least by some, to not act appropriately, but that is a different
story. I am referring to the large majority of them, those who
do behave properly and do not use the forum to promote their
own products.)
I am sure the large majority of forum members understand and
share your view. Primarily, this forum is, as the name indicates,
a forum for amateurs. Unless they have some suspect reason
for their presence here they are and should be willing to and
interested in sharing their knowledge and experiences with
other members, thus adding to an increased collective
knowledge and understanding of audio equipment.
The presence of commercial audio designers like yourself and
many others is an added bonus. We can ask you for
information and advice, but we cannot demand you or expect
you to tell us anything that is a trade secret. Most of you share
more experience and knowledge with us than we could expect,
and I am sure most of us grateful for that generosity.
(There may be a few commercial designers who are considered,
at least by some, to not act appropriately, but that is a different
story. I am referring to the large majority of them, those who
do behave properly and do not use the forum to promote their
own products.)
When you talk ultrafast, how fast do you mean?lumanauw said:
The secrets are: Extremely fast input stage, fast VAS with lot's of current capability (much more than the idle current), not too much open-loop gain.
BTW: I have also heard rumours that CFB is
but I haven't yet come to this conclusion. I think it's more a matter of taste than facts. How come so many prefer 16-bit sound coming from a old TDA1541 (was it the right number?) What about CFB and tubes?So far I really like my two different CFB amps and the latest is really in-listened.
The point is that the differences are very small. Noone yet has noticed that I have different opamps in left right channel in my QRV-04, OPA627, and AD8610. I wonder if anyone of you with golden ears can pick the right opamp?
Yes, you are right, AKSA. As an amateur I only wish for directions, cannot expect a full complete answer. It is what the audio designer's living. Cannot bypass it. They earn their knowledge for decades, with hundreds of thousand workhours. I know if I had reach the stage like you said, maybe I will also behave the same too. Sometimes very short and simple answer have so much meaning for me. Mr.Pass, GRollins, PRR usually do this.
Mr. Peranders, what I mean by fast amp, is like having damping >1000, very high slew rate. (like the rating of MC2 power amp). What is the meaning of "VAS with lot's of current capability (much more than the idle current)". Is it the rating of the transistors?
Very fast differential and VAS, is it about the transistor, or about the circuity?
About the taste of CFB it is 100% my personal subjective. It is wrong for me if I say it is for somebody else. I dont know what other people is thinking.
If anyone don't mind, is it possible for me to know whoever active in this diyaudio.com and knows what is each's commercial product brand? Like Mr.Pass with Pass lab. But I don't know any other example. I just know there are so many comercial product designer involved here. I know this from the quality of the answers. Ordinary hobbyist wouldn't have such a skill.
Mr. Peranders, what I mean by fast amp, is like having damping >1000, very high slew rate. (like the rating of MC2 power amp). What is the meaning of "VAS with lot's of current capability (much more than the idle current)". Is it the rating of the transistors?
Very fast differential and VAS, is it about the transistor, or about the circuity?
About the taste of CFB it is 100% my personal subjective. It is wrong for me if I say it is for somebody else. I dont know what other people is thinking.
If anyone don't mind, is it possible for me to know whoever active in this diyaudio.com and knows what is each's commercial product brand? Like Mr.Pass with Pass lab. But I don't know any other example. I just know there are so many comercial product designer involved here. I know this from the quality of the answers. Ordinary hobbyist wouldn't have such a skill.
Christer,
Your moderate, balanced post moves me to write a little more on this subject.
I once was like Lumanauw, and sought the holy grail of a really good amplifier design. For thirty years I built other people's designs and many were bad, some were OK, a few were good. None in the public domain were what I would consider outstanding. After all, if you pay nothing for it, it's usually worth the money!
When after a military career in the Australian Army I retired after 21 years, I took a well paid job in IT (those are my qualifications). In 1994 I began R&D on amp design, finally, at 43, able to pursue my dream of a better audio amplifier. I used the income from my IT job (which I didn't much enjoy, incidentally) together with my military superannuation, to fund this R&D. It was a very pleasant time in my life; I'm very glad I did it.
Starting with NP's Zen amplifier, I began work on many different topologies. I raided Universities and Tech Institutes around Melbourne, a city of 3.6 million souls, for information. Soon I even began to comb the net. I talked with clever people all over the world; Kevin in Canada, Elmar in Germany, to mention two. My first amplifier was the Glass Harmony, a single ended bipolar/mosfet hybrid with a tube front end, which remains to this day a reference amplifier. It is a wonderful amp which makes people cry, but its efficiency threatens planet Earth...... I even built a 56W SE version which was water cooled and dissipated 620 watts of heat; it sounded like the San Andreas fault in full symphony, but it's inefficiency really began to concern me.
I then moved on to high efficiency; I deplore wastage, and even my cars operate on environmentally friendly liquefied petroleum gas. I look forward to the days when all motorcycles will have diesel engines! I studied all the things related to sonics, including not just the electronics, but the psychoacoustics and structure of music. It was fascinating; in the last five years I feel I've forgotten more than I learned in my first thirty years in hifi!
After about four years of working on the Class AB PP SS amplifier, I had completed the AKSA. It is, surprisingly, very conventional technology, but it is super-refined. It was designed by listening, and confirming with the ears of others. When sonics improved, I would exhaustively go over the engineering, and check the limits above and below the operating points chosen. The reading and research behind the work involved would cover a couple of PhD theses; this is something you'd only do if you were absolutely crazy about a better mousetrap. I identified how it would sound with certain alterations; probably no different to wind tunnel testing a Porsche for all road conditions. Arguably this is only good engineering practice, nothing mystical. There are no pointy rocks, colorful crystals or cosmic triangles in any of this, but there certainly is a lot of exhaustive testing - which costs money, and time, but most of all, passion.
A small but growing hifi company is now my living. I wouldn't do anything else - it is a wonderful life style, I meet lots of other compulsive obsessive audiophiles, and enjoy their company, many over several cups of coffee. Not one of them is a fool; all are intelligent people with a love of technology (and some even like music!!) and it's a pleasure to work amongst and for such people, particularly as I rarely found my fellow officers in the military to be pleasant people, most of them reluctant to think outside the square and intent on political issues rather than technical practicalities.....
You are quite right, Christer. Now that I have something good, I won't give it away. It cost too many years of my life, and too much of my lifeforce! The AKSA is just one of my designs; I have about seven notebooks full of schematics, and as my enterprise grows I will release more of them into the market.
Lumanauw is a committed, interested audiophile. He comes from a country I know well, as I was trained as an Indonesian linguist in the military and have visited the country several times. In fact, my wife and two daughters are travelling to Jakarta for a long holiday in three days (I'm staying behind to run my business!). I well understand his position, and specifically I understand that with limited resources he would like to build a world class amplifier.
I have fielded many inquiries about my AKSA, many offering highly imaginative reasons why I should just send the inquirer the circuit diagram and pcb layout. One from Cuba was notable; an electrical engineer, no less, clever man. But unless there is a technical association and a mutual benefit, this cannot happen without due financial recompense. For most in the Western world, my amplifiers are quite inexpensive, so I lose no sleep over my policy...
An astute observer of human behaviour might ask why I'm here. It's complicated, but here goes.
You guys are very interesting people to me, and some of you, such as Fred, Jackinj, Walt Jung, Jonathon, NP, PRR, etc are a lot smarter than I am and with care and attention I might learn something from them. Secondly, the greatest developments in audio do not come from the big companies; they are driven by accountants and managers and risk is very carefully formulated. No, the big developments come from the little guys with fertile minds and vivid passion. Some of these people are right here, and sharp readers will know who they are....
Thirdly, if I can help without offering up all my trade secrets, I will. And lastly, if I do help someone, and they appreciate it, who knows, one day they might buy my kitset amplifiers!!
Today was a great day. I collected my first batch of laser cut and etched SS baseplates for my new hybrid preamplifier. I also arranged for deep chroming my 1" brass volume and balance knobs (just recently machined right here in Melbourne!) I nearly herniated my spine lifting the the 2mm thick baseplates stacked together, but now they are in my workshop awaiting assembly and they are just superb. You'll be able to drive a small car over them without damage! And the chromed copper domes to cover the trafos are just sensational, something to swoon over.........
Cheers,
Hugh
Your moderate, balanced post moves me to write a little more on this subject.
I once was like Lumanauw, and sought the holy grail of a really good amplifier design. For thirty years I built other people's designs and many were bad, some were OK, a few were good. None in the public domain were what I would consider outstanding. After all, if you pay nothing for it, it's usually worth the money!
When after a military career in the Australian Army I retired after 21 years, I took a well paid job in IT (those are my qualifications). In 1994 I began R&D on amp design, finally, at 43, able to pursue my dream of a better audio amplifier. I used the income from my IT job (which I didn't much enjoy, incidentally) together with my military superannuation, to fund this R&D. It was a very pleasant time in my life; I'm very glad I did it.
Starting with NP's Zen amplifier, I began work on many different topologies. I raided Universities and Tech Institutes around Melbourne, a city of 3.6 million souls, for information. Soon I even began to comb the net. I talked with clever people all over the world; Kevin in Canada, Elmar in Germany, to mention two. My first amplifier was the Glass Harmony, a single ended bipolar/mosfet hybrid with a tube front end, which remains to this day a reference amplifier. It is a wonderful amp which makes people cry, but its efficiency threatens planet Earth...... I even built a 56W SE version which was water cooled and dissipated 620 watts of heat; it sounded like the San Andreas fault in full symphony, but it's inefficiency really began to concern me.
I then moved on to high efficiency; I deplore wastage, and even my cars operate on environmentally friendly liquefied petroleum gas. I look forward to the days when all motorcycles will have diesel engines! I studied all the things related to sonics, including not just the electronics, but the psychoacoustics and structure of music. It was fascinating; in the last five years I feel I've forgotten more than I learned in my first thirty years in hifi!
After about four years of working on the Class AB PP SS amplifier, I had completed the AKSA. It is, surprisingly, very conventional technology, but it is super-refined. It was designed by listening, and confirming with the ears of others. When sonics improved, I would exhaustively go over the engineering, and check the limits above and below the operating points chosen. The reading and research behind the work involved would cover a couple of PhD theses; this is something you'd only do if you were absolutely crazy about a better mousetrap. I identified how it would sound with certain alterations; probably no different to wind tunnel testing a Porsche for all road conditions. Arguably this is only good engineering practice, nothing mystical. There are no pointy rocks, colorful crystals or cosmic triangles in any of this, but there certainly is a lot of exhaustive testing - which costs money, and time, but most of all, passion.
A small but growing hifi company is now my living. I wouldn't do anything else - it is a wonderful life style, I meet lots of other compulsive obsessive audiophiles, and enjoy their company, many over several cups of coffee. Not one of them is a fool; all are intelligent people with a love of technology (and some even like music!!) and it's a pleasure to work amongst and for such people, particularly as I rarely found my fellow officers in the military to be pleasant people, most of them reluctant to think outside the square and intent on political issues rather than technical practicalities.....
You are quite right, Christer. Now that I have something good, I won't give it away. It cost too many years of my life, and too much of my lifeforce! The AKSA is just one of my designs; I have about seven notebooks full of schematics, and as my enterprise grows I will release more of them into the market.
Lumanauw is a committed, interested audiophile. He comes from a country I know well, as I was trained as an Indonesian linguist in the military and have visited the country several times. In fact, my wife and two daughters are travelling to Jakarta for a long holiday in three days (I'm staying behind to run my business!). I well understand his position, and specifically I understand that with limited resources he would like to build a world class amplifier.
I have fielded many inquiries about my AKSA, many offering highly imaginative reasons why I should just send the inquirer the circuit diagram and pcb layout. One from Cuba was notable; an electrical engineer, no less, clever man. But unless there is a technical association and a mutual benefit, this cannot happen without due financial recompense. For most in the Western world, my amplifiers are quite inexpensive, so I lose no sleep over my policy...
An astute observer of human behaviour might ask why I'm here. It's complicated, but here goes.
You guys are very interesting people to me, and some of you, such as Fred, Jackinj, Walt Jung, Jonathon, NP, PRR, etc are a lot smarter than I am and with care and attention I might learn something from them. Secondly, the greatest developments in audio do not come from the big companies; they are driven by accountants and managers and risk is very carefully formulated. No, the big developments come from the little guys with fertile minds and vivid passion. Some of these people are right here, and sharp readers will know who they are....
Thirdly, if I can help without offering up all my trade secrets, I will. And lastly, if I do help someone, and they appreciate it, who knows, one day they might buy my kitset amplifiers!!Today was a great day. I collected my first batch of laser cut and etched SS baseplates for my new hybrid preamplifier. I also arranged for deep chroming my 1" brass volume and balance knobs (just recently machined right here in Melbourne!) I nearly herniated my spine lifting the the 2mm thick baseplates stacked together, but now they are in my workshop awaiting assembly and they are just superb. You'll be able to drive a small car over them without damage! And the chromed copper domes to cover the trafos are just sensational, something to swoon over.........
Cheers,
Hugh
lumanauw, you must specify your data first than you will get the rest.
Max output power at which load?
Power bandwidth at the specified load? (gives you the slew rate)
Minimum damping factor? (50-100 is realistic and a good start)
If you know these three parameters you can start to design.
All (almost) parameters are tied together so you can't really choose freely, slew rate, damping factor, distorstion etc.
Let me also tell you that a fast amp can cause you trouble also.
Current feedback is one (rather easy) way to create a fast amp. Voltage feedback is more challenging. Pcb layout is very important.
Hugh, I have seen the schematics of your AKSA amp (got it from you) and I think you are doing the right thing to keep it non-public. If the amp had been really complicated like Alaskan Audio's monster, it would be very hard to copy so it would be easier just to buy the pcb from you.
Max output power at which load?
Power bandwidth at the specified load? (gives you the slew rate)
Minimum damping factor? (50-100 is realistic and a good start)
If you know these three parameters you can start to design.
All (almost) parameters are tied together so you can't really choose freely, slew rate, damping factor, distorstion etc.
Let me also tell you that a fast amp can cause you trouble also.
Current feedback is one (rather easy) way to create a fast amp. Voltage feedback is more challenging. Pcb layout is very important.
Hugh, I have seen the schematics of your AKSA amp (got it from you) and I think you are doing the right thing to keep it non-public. If the amp had been really complicated like Alaskan Audio's monster, it would be very hard to copy so it would be easier just to buy the pcb from you.
The spec for MC2 is :
Output Power (Watts RMS) per channel : . MC1250 .
16 ohms 400
8 ohms 750
4 ohms 1250
2 ohms 1800
Mono Bridged
8 ohms @ 1khz 2500
4 ohms @ 1khz 3600
THD @ rated power into 4 ohms
1 kHz <0.008%
20Hz-20kHz <0.03%
Input CMRR >80 dB
Hum & Noise -105 dB
Gain 33 db
Sensitivity for rated output, 4 ohms + 6 dBu 1.54 v
Damping Factor 1 kHz, 8 ohms >1000
Frequency Response 20Hz-20kHz +0/-0.5 dB
Input Impedance (actively balanced) 10k ohms
Dimensions 3U(mm) 130 x 480 x 460
Weight 32 kgs
Power Requirement 230 VAC @ 20.0 amps max.
or
120 VAC @ 38.0 amps max.
I really dont need that kind of power rating. 100 or 200W is enough. But the quality of MC2 is what I'm curious.
What kind of circuit can do this? I've looked inside it. It is using few parts, compared to other professional amp. But the sound is much better.
Output Power (Watts RMS) per channel : . MC1250 .
16 ohms 400
8 ohms 750
4 ohms 1250
2 ohms 1800
Mono Bridged
8 ohms @ 1khz 2500
4 ohms @ 1khz 3600
THD @ rated power into 4 ohms
1 kHz <0.008%
20Hz-20kHz <0.03%
Input CMRR >80 dB
Hum & Noise -105 dB
Gain 33 db
Sensitivity for rated output, 4 ohms + 6 dBu 1.54 v
Damping Factor 1 kHz, 8 ohms >1000
Frequency Response 20Hz-20kHz +0/-0.5 dB
Input Impedance (actively balanced) 10k ohms
Dimensions 3U(mm) 130 x 480 x 460
Weight 32 kgs
Power Requirement 230 VAC @ 20.0 amps max.
or
120 VAC @ 38.0 amps max.
I really dont need that kind of power rating. 100 or 200W is enough. But the quality of MC2 is what I'm curious.
What kind of circuit can do this? I've looked inside it. It is using few parts, compared to other professional amp. But the sound is much better.
Lumanauw,
All this impressive spec tells you nothing of how it sounds. For that you need a schematic, a few pics of the componentry and layout inside, and of course, a two week long audition.
You can't go wrong with Rod Elliott's simple 60W amplifier. It's very good, and the design is both simple and free. My amplifier is similar, but for its sonic improvements, more costly of course. You decide. You are clearly motivated by a desire to have best of breed technology; for this, like anything, you must pay something.
You need to decide how much power; a 100W amp sounds powerful with 90dB/watt/metre speakers, and you never know, for your application, 60W @ 8R (around 90-100W @ 4R) is probably more than enough.
Most of the pro amps, with the obvious exception of the Crown, use simple, double differential, complementary circuits. That is, there are four differential pairs; two complementary input pairs, and two (sometimes one) complementary voltage amplifier pairs. Be aware that high power requires high voltage rails, and the stability of the amp becomes much more difficult than with modest power ratings. The consequence of this is that the lag compensation needs to be heavily stapled down for unconditional stability, and this slows and muffles the sound. Power is seldom available with glory, and smaller is often better.......
Cheers,
Hugh
All this impressive spec tells you nothing of how it sounds. For that you need a schematic, a few pics of the componentry and layout inside, and of course, a two week long audition.
You can't go wrong with Rod Elliott's simple 60W amplifier. It's very good, and the design is both simple and free. My amplifier is similar, but for its sonic improvements, more costly of course. You decide. You are clearly motivated by a desire to have best of breed technology; for this, like anything, you must pay something.
You need to decide how much power; a 100W amp sounds powerful with 90dB/watt/metre speakers, and you never know, for your application, 60W @ 8R (around 90-100W @ 4R) is probably more than enough.
Most of the pro amps, with the obvious exception of the Crown, use simple, double differential, complementary circuits. That is, there are four differential pairs; two complementary input pairs, and two (sometimes one) complementary voltage amplifier pairs. Be aware that high power requires high voltage rails, and the stability of the amp becomes much more difficult than with modest power ratings. The consequence of this is that the lag compensation needs to be heavily stapled down for unconditional stability, and this slows and muffles the sound. Power is seldom available with glory, and smaller is often better.......
Cheers,
Hugh
Hugh
I had the idea, quite a few years ago to first build the best possible class A amp that I could possibly achieve and then go on to see if I could get a class AB to match it. So I was interested to read the above extract.
I 'm still on the class A phase !
My starting point was the JLH simple class A although now it is almost unrecognisable. So far so good. The next one should be about as good as I can get it..... after a few months of experimentation
Do you feel that class AB can ever match the smooth and natural sound of a good class A ?
what is you view, having done both ?
mike
AKSA said:
I had the idea, quite a few years ago to first build the best possible class A amp that I could possibly achieve and then go on to see if I could get a class AB to match it. So I was interested to read the above extract.
I 'm still on the class A phase !
My starting point was the JLH simple class A although now it is almost unrecognisable. So far so good. The next one should be about as good as I can get it..... after a few months of experimentation
Do you feel that class AB can ever match the smooth and natural sound of a good class A ?
what is you view, having done both ?
mike
Mike,
Class A designs sound wonderful, but all too often they lack dynamics. They do, however, have a wonderful tonal structure (or harmonic spectrum, perhaps a better descriptions). The down side is the horrific energy consumption and the low power.
Class AB designs do not have quite the same harmonic spectrum, but with careful design of the diff pair and VAS it can be quite close. The output stage crossover distortion and the interaction with the VAS is, I believe, the key. Stability is a huge factor, and lag compensation must be used sparingly.
So, yes, I think an AB can come very close to an A. However, what is lacking in harmonic spectrum is more than compensated by dynamics. A good AB is outrageously dynamic, something which in a very different way makes them sound much more powerful than their rating.
You must use two completely separate power supplies. That is important, as is a very short, compact feedback loop.
Hope this helps!
Cheers,
Hugh
Class A designs sound wonderful, but all too often they lack dynamics. They do, however, have a wonderful tonal structure (or harmonic spectrum, perhaps a better descriptions). The down side is the horrific energy consumption and the low power.
Class AB designs do not have quite the same harmonic spectrum, but with careful design of the diff pair and VAS it can be quite close. The output stage crossover distortion and the interaction with the VAS is, I believe, the key. Stability is a huge factor, and lag compensation must be used sparingly.
So, yes, I think an AB can come very close to an A. However, what is lacking in harmonic spectrum is more than compensated by dynamics. A good AB is outrageously dynamic, something which in a very different way makes them sound much more powerful than their rating.
You must use two completely separate power supplies. That is important, as is a very short, compact feedback loop.
Hope this helps!
Cheers,
Hugh
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