Hi John,
The devices i use for vas are 200mhz devices, The 33pf is lead compensation. From my limited understanding lead compensation wont annihilate the slew rate like strictly high miller would. As far as oscillations go, I have not tested for these with any test equipment, the output zobel resistor remains coolt at all times, bias current remains steady. When i laid out the copper board i have paid very close attention to high current traces/width, and signal path traces in my best effort to try and avoid parasitics by keeping the signal traces narrow/short and as direct as possible in a forward momentum. The global feedback loop is a mere 1cm, the length of a 1/4 wattresistor. The speaker lead terminates at the mouth of this resistor at a single point in a physical geometry. signal grounds and power grounds are sperate and take off from their individual points and flow into a vast singuar copper pool for signal and power from which i take off into the main star ground/centertap. judging by the computer pcb payouts this could not be done as i have with software. Very time consuming but sonically worth all the trouble. Ihavent tried a lower value lead, i have had no problems with sonics that have led me to believe that this could be any more beneficial at this point, could be, i will deifinately try, I have a couple 22pf silver micas hanging around. Just fi nishes 2 new boards with vas overcurrent protection, just need to wait for my drivers..
Colin
The devices i use for vas are 200mhz devices, The 33pf is lead compensation. From my limited understanding lead compensation wont annihilate the slew rate like strictly high miller would. As far as oscillations go, I have not tested for these with any test equipment, the output zobel resistor remains coolt at all times, bias current remains steady. When i laid out the copper board i have paid very close attention to high current traces/width, and signal path traces in my best effort to try and avoid parasitics by keeping the signal traces narrow/short and as direct as possible in a forward momentum. The global feedback loop is a mere 1cm, the length of a 1/4 wattresistor. The speaker lead terminates at the mouth of this resistor at a single point in a physical geometry. signal grounds and power grounds are sperate and take off from their individual points and flow into a vast singuar copper pool for signal and power from which i take off into the main star ground/centertap. judging by the computer pcb payouts this could not be done as i have with software. Very time consuming but sonically worth all the trouble. Ihavent tried a lower value lead, i have had no problems with sonics that have led me to believe that this could be any more beneficial at this point, could be, i will deifinately try, I have a couple 22pf silver micas hanging around. Just fi nishes 2 new boards with vas overcurrent protection, just need to wait for my drivers..
Colin
Hi everybody
I think an explanation is in order about the answer I gave some posts ago to a question from aquantesoda (funny name coming from Argentina). Very coincidental, my mother was born in Argentina, Buenos Aires and I kind of have some connection with this country...
But let's go back to what I meant to say about that "acid" nothing I gave as a response to his question.
I always loved this forum, I think it's a way of learning, always learning
about this intricate world of diy audio. We learn and sort out what we
like or dislike, we take advantage of the kindness of some very well versed people, a lot of knowledgeable people that so graciously
give to all of us.
It so happens that lately this forum is going to a status that is
boring me so much that I thought I would give it up completely. That day was particularly bad for me, I was in such a bad mood that I was forced to
say something drastic like "nothing"....
Not in a despising tone, no, but as a disappointment because
with so much rambling I get frustated of this resistor being 10 ohms instead of 12, that cap should 330uF as opposed to 220 and so on
and on. I realize everybody has the right to say whatever they
please, but com'on guys there are other more construtive ways
to use this space that the forum gives us.
I guess I should apologize for that "acid" answer...but my mood
would be an excuse for that....
I'll probably get away fro this forum until it gets to be again a way
to learn and discuss seriously the state of solid state audio.
I think an explanation is in order about the answer I gave some posts ago to a question from aquantesoda (funny name coming from Argentina). Very coincidental, my mother was born in Argentina, Buenos Aires and I kind of have some connection with this country...
But let's go back to what I meant to say about that "acid" nothing I gave as a response to his question.
I always loved this forum, I think it's a way of learning, always learning
about this intricate world of diy audio. We learn and sort out what we
like or dislike, we take advantage of the kindness of some very well versed people, a lot of knowledgeable people that so graciously
give to all of us.
It so happens that lately this forum is going to a status that is
boring me so much that I thought I would give it up completely. That day was particularly bad for me, I was in such a bad mood that I was forced to
say something drastic like "nothing"....
Not in a despising tone, no, but as a disappointment because
with so much rambling I get frustated of this resistor being 10 ohms instead of 12, that cap should 330uF as opposed to 220 and so on
and on. I realize everybody has the right to say whatever they
please, but com'on guys there are other more construtive ways
to use this space that the forum gives us.
I guess I should apologize for that "acid" answer...but my mood
would be an excuse for that....
I'll probably get away fro this forum until it gets to be again a way
to learn and discuss seriously the state of solid state audio.
Some fundamental "big picture" questions come to mind. Forgive me if these have already been beaten to death in times past.
Where is it written that a "perfect" amplifier won't cause listener fatigue over time? In fact, if you had continuous live music in your living room for days on end, would it be wonderful, or would it become irritating? Worse, some mixes just are irritating. Noise is often added, and listener fatigue probably wasn't a consideration.
So, how do you evaluate an amplifier alone? IMO, the best system may not have perfectly flat response, and may not exhibit zero compression. Since the system is made up of many components and interfaces, not to mention speaker drivers, how do you sort it out? More importantly, if the signal is to be modified, where's the best place to do it?
My experience with Doug Self's design philosophy is that he comes as close to electrical perfection as anyone. Done properly, a nearly perfect signal can be reproduced, with any imperfections well below what can be heard, and almost below what can be measured. Note however, that using his guidelines is no guarantee of anything- you can still build a lousy amplifier if some subtlety is missed along the way.
Personally, I go for flawless reproduction of electrical signals- what comes out has to mirror what goes in over a wide bandwidth and with as little addition of noise and phase shift as possible (though the audibility of phase shift is debatable). Then, because I like to fool with speakers, I match the sound to the room via adjustments to the active crossovers, and to the room itself. BTW, I believe there are problems with reverb times and standing waves that are more important than response, and cannot be fixed with any amount of fiddling with the system, only the room.
Bottom line- if you want flat low distortion electrically excellent amps, Self's guidelines are the way to go. The question is, do you (and I don't mean anyone in particular) have the confidence and courage to say that isn't what you want, because the overall system sounds better with something different?
Where is it written that a "perfect" amplifier won't cause listener fatigue over time? In fact, if you had continuous live music in your living room for days on end, would it be wonderful, or would it become irritating? Worse, some mixes just are irritating. Noise is often added, and listener fatigue probably wasn't a consideration.
So, how do you evaluate an amplifier alone? IMO, the best system may not have perfectly flat response, and may not exhibit zero compression. Since the system is made up of many components and interfaces, not to mention speaker drivers, how do you sort it out? More importantly, if the signal is to be modified, where's the best place to do it?
My experience with Doug Self's design philosophy is that he comes as close to electrical perfection as anyone. Done properly, a nearly perfect signal can be reproduced, with any imperfections well below what can be heard, and almost below what can be measured. Note however, that using his guidelines is no guarantee of anything- you can still build a lousy amplifier if some subtlety is missed along the way.
Personally, I go for flawless reproduction of electrical signals- what comes out has to mirror what goes in over a wide bandwidth and with as little addition of noise and phase shift as possible (though the audibility of phase shift is debatable). Then, because I like to fool with speakers, I match the sound to the room via adjustments to the active crossovers, and to the room itself. BTW, I believe there are problems with reverb times and standing waves that are more important than response, and cannot be fixed with any amount of fiddling with the system, only the room.
Bottom line- if you want flat low distortion electrically excellent amps, Self's guidelines are the way to go. The question is, do you (and I don't mean anyone in particular) have the confidence and courage to say that isn't what you want, because the overall system sounds better with something different?
Really...days listening may be a torture...and nothing...nothing will be good to
listen continuously this way....if the guy scape from the madness during this torture...at least..will have a flat B-- when finish.
hehe
Happy that i have found someone that can makes things more "extreme" than i usually can.
BTW...as i have perceived from past posts...John Mateus is a very nice guy...so nice that he explained to us his reasons...nice from you Mr. Mateus.
regards Conrad.
Carlos
listen continuously this way....if the guy scape from the madness during this torture...at least..will have a flat B-- when finish.
hehe
Happy that i have found someone that can makes things more "extreme" than i usually can.
BTW...as i have perceived from past posts...John Mateus is a very nice guy...so nice that he explained to us his reasons...nice from you Mr. Mateus.
regards Conrad.
Carlos
Conrad and all,
Now we have a discussion pending! (John might even linger a little).
Conrad, yes, good point. But you supply the answer yourself a little later on in some way. The system listener fatigue you refer to initially is possible, of course - but to me that is different from what we are discussing here. A blameless amplifier will never give listener fatigue, simply per the definition of the term as I understand it, because an unlimited time element is included. (As one grows older
one's ears begin to provide the listener fatigue of course!) I (also) strive to make each component in the chain as good as possible. There are also some "audio philosophers" out there (mercifully so far not referring to members of this site/forum) who make pious sweeping statements regarding synergy. (Only they never seem to tell designers how to exactly achieve it and for whom, do they now - do we replace all our resistors with pots and twiddle until "it" sounds right? Sorry! 
)
So, to stay with amplifiers, one strives for inaudibility of all disturbances as much as possible - back to Douglas Self. For the rest: Ditto, each per itself. As far as the funny mixes on the market .... again.
Regards
Now we have a discussion pending! (John might even linger a little).
Conrad, yes, good point. But you supply the answer yourself a little later on in some way. The system listener fatigue you refer to initially is possible, of course - but to me that is different from what we are discussing here. A blameless amplifier will never give listener fatigue, simply per the definition of the term as I understand it, because an unlimited time element is included. (As one grows older
one's ears begin to provide the listener fatigue of course!) I (also) strive to make each component in the chain as good as possible. There are also some "audio philosophers" out there (mercifully so far not referring to members of this site/forum) who make pious sweeping statements regarding synergy. (Only they never seem to tell designers how to exactly achieve it and for whom, do they now - do we replace all our resistors with pots and twiddle until "it" sounds right? Sorry! )So, to stay with amplifiers, one strives for inaudibility of all disturbances as much as possible - back to Douglas Self. For the rest: Ditto, each per itself. As far as the funny mixes on the market ....
again.Regards
ok.... here's my $0.02.....
there's a few things i do in sim testing, and later in real testing, that tell me rather quickly whether a design is stable or will oscillate.
first, i run a frequency response sweep. in the sim, i set the input amplitude to a level that produces nearly full undistorted output and sweep 10hz to 10Mhz. in real circuits, i run the sweep at 1 watt. the sim returns freq response and phase curves. pay attention to the rlationship between these. if the phase goes to or crosses 180 degrees below the unity gain frequency, you have a stability problem. the phase can be displayed on an o-scope by either comparing waveforms on a dual trace scope, or by x-y comparison on a scope. this is done with a purely resistive load. either an 8 ohm/2 watt carbon comp, or a dale noninductive load, with very short leads to minimize capacitance. most of the time, if you have instability, you will also notice a "hump" in the frequency response near the unstable frequency.
second i run both the sim, and later the real circuit to clipping at 20khz with a capacitive load. if there's a tendency toward oscillation it usually shows up here.
third (and this will sometimes reveal oscillation that gets missed by method two), i run the sim and the real circuit into a capacitive load at 1 watt 20khz, and go from no output bias to full bias. i have seen oscillation that begins at the crossover point and continues toward or beyond the waveform peak, and then extinguishes, leaving a clean waveform until the next zero crossing.
there's a few things i do in sim testing, and later in real testing, that tell me rather quickly whether a design is stable or will oscillate.
first, i run a frequency response sweep. in the sim, i set the input amplitude to a level that produces nearly full undistorted output and sweep 10hz to 10Mhz. in real circuits, i run the sweep at 1 watt. the sim returns freq response and phase curves. pay attention to the rlationship between these. if the phase goes to or crosses 180 degrees below the unity gain frequency, you have a stability problem. the phase can be displayed on an o-scope by either comparing waveforms on a dual trace scope, or by x-y comparison on a scope. this is done with a purely resistive load. either an 8 ohm/2 watt carbon comp, or a dale noninductive load, with very short leads to minimize capacitance. most of the time, if you have instability, you will also notice a "hump" in the frequency response near the unstable frequency.
second i run both the sim, and later the real circuit to clipping at 20khz with a capacitive load. if there's a tendency toward oscillation it usually shows up here.
third (and this will sometimes reveal oscillation that gets missed by method two), i run the sim and the real circuit into a capacitive load at 1 watt 20khz, and go from no output bias to full bias. i have seen oscillation that begins at the crossover point and continues toward or beyond the waveform peak, and then extinguishes, leaving a clean waveform until the next zero crossing.
I feel pretty serious about Solid State Audio.
In a sort of response to Mateus, I can agree to disagree with his staement partly. While I am at a great appreciation that this forum is full of so many audio gurus in my eyes and many others I also happen to know that it could be "some guy" with an idea of 10 or 12 ohms that could also have much to offer even though his degree may be simply soldering some parts on a weekend to experiment. I am of course no engineer or rocket scientist, I am a 28 year old finishing Carpenter by trade, and a musician by birth and at heart ,a drummer for 20+ years playing in two bands and doing session work and a father of two who enjoys everything on here whether mind numbingly insightful or off the wall in craziness and passion. Hey, it could always be worse, atleast we arent discussing the merits of cables
). I am very glad to have this forum, because I can take comfort in knowing I can post any discovery of mine without being lambasted or I can ask a potentially stupid question without being flamed as a jack**s who has no idea what he is doing ;o). DIY audio is for everyone to learn, and there is always something to learn even in the most mundane of topics.
Colin
In a sort of response to Mateus, I can agree to disagree with his staement partly. While I am at a great appreciation that this forum is full of so many audio gurus in my eyes and many others I also happen to know that it could be "some guy" with an idea of 10 or 12 ohms that could also have much to offer even though his degree may be simply soldering some parts on a weekend to experiment. I am of course no engineer or rocket scientist, I am a 28 year old finishing Carpenter by trade, and a musician by birth and at heart ,a drummer for 20+ years playing in two bands and doing session work and a father of two who enjoys everything on here whether mind numbingly insightful or off the wall in craziness and passion. Hey, it could always be worse, atleast we arent discussing the merits of cables
). I am very glad to have this forum, because I can take comfort in knowing I can post any discovery of mine without being lambasted or I can ask a potentially stupid question without being flamed as a jack**s who has no idea what he is doing ;o). DIY audio is for everyone to learn, and there is always something to learn even in the most mundane of topics.Colin
Carlos: you, you, you. 
Off topic:
Geagte Johan,
the MJL numbers are about $5 each in the US, up to $13 overhere.
Ek weet nie of jy die email gelees het. Baie mense syn goed gewees vir my, ook die Suid Afrikaanse mense.
Ek heb die transistore beskikbaar, vir jou geen koste verbonde nie.
Allenig 'n persoonlik briefkaart vir dank. benodig wel 'n kontakadres vir ze an te stuur.
Off topic:
Geagte Johan,
the MJL numbers are about $5 each in the US, up to $13 overhere.
Ek weet nie of jy die email gelees het. Baie mense syn goed gewees vir my, ook die Suid Afrikaanse mense.
Ek heb die transistore beskikbaar, vir jou geen koste verbonde nie.
Allenig 'n persoonlik briefkaart vir dank. benodig wel 'n kontakadres vir ze an te stuur.
Thank You very much for the kind words Carlos, I really enjoy the Charisma and kindness of yourself after all this stuff should be fun such as music itself. I have learned a great deal from these three stage models along with the intelligence and words on these forums, there are truly inspiring people here, I am gracious that I took Hugh Deans suggestion to visit and join here, another intelligent man with wisdom and words that always encourage. On the amplifier side, my new boards are done and ready to install, this time I have mounted the VBE multiplier bjt on top of one of the mjl3281 and increased the 100nf cap to 10uf, bias is much more stable. Added Grahams suggestion of current limiting and 10 ohm resistor on the negative rail also for the front end. will try 22pf lead cap next..
Time to go check the updates on the DX thred..
Colin
Time to go check the updates on the DX thred..
Colin
You are welcome...Hugh Dean is a very special man, in my point of view
he is best designer..as he use his ears too...not only Mathematics...and he understand a lot of Maths too.
I love him very much...he is alike a brother in my heart.
Searching for his bad side i can only say that he has not time enougth to go talking with me all day long..he is very busy..his deffect is this one..works too much.
regards,
Carlos
he is best designer..as he use his ears too...not only Mathematics...and he understand a lot of Maths too.
I love him very much...he is alike a brother in my heart.
Searching for his bad side i can only say that he has not time enougth to go talking with me all day long..he is very busy..his deffect is this one..works too much.
regards,
Carlos
Hugh was a Military Officer and an English language teacher
Retired from the Military Life he decided to go deep into audio...he bougth books and started to read them all... made contact with people that had deep understand about electronics and start his business... his beggining was more than 10 years ago.
His first amplifier was published with that bootstrapped technologie...the same topologie i am using now..when he is using another one now a days...his Aksa has subcircuits and modifications not shown on my amplifier..as those things belongs to Mr. Hugh.
He decided to understand deep the Mathematics involved into audio amplifier designs and have read all the famous designers books.
The better is that he decided to join the instruments with his ear... circuits were tested by ear..by audition and parts substitution and sub circuits were tested..observing effects of waveshape, distortion and spectrum...so..each modern circuit was tested...many amplifiers types checked, built, listened, compared with his units...hardly researched each connection, to "listen" the best possible sound...of course friends have cooperate with him related those evaluations...not a lonely process.
The result was an incredible amplifier, with some sub circuits used that increase sonics quality in a way no other amplifier could match....i have them here...i have compared...i have tested them...and no one could beat his Aksa 55 related sound stage and treble quality reproduction...focusing of instruments and voices quality...... others could be sligtly more powerfull with 35 volts....others had more dinamics....others had stronger bass...but the overall quality is unbeatable.
He has something that i will never have....the patience to catalogue, to take notes of all steps he made.... evaluations about many circuits and subcircuits...effects using types of capacitor and transistors.... all those things he done is something i loose my track .. turning myself lost related the early begining of my researches..I have forgotten what happened with that "yellow" capacitor i have used last year....but Hugh Dean did not loose his track.
He had everything organized...so....he could track the long travel back, to return watching all result of researches made, and joined them together in his amplifiers.
Mathematics and theorical knowledge is, now a days, enougth to discuss with Engineers and to make himself be understood..also enougth to understand the experts.....but more than that...the qualities of a practical researcher he has...the real life experiences made.in the past and still beeing made... the years locked inside his laboratory, researching till he developed repetitive work disease in left arm.... 18 hours each day working years long..day after day.... spending all money he could, to pay parts, to use them till the limit (real limits) and to burn many parts to obtain the needed knowledge of real reliability for his products..... he made an excelent brand, with fidelity related all his customers....and also he is not lazy...to avoid misadjustments...to avoid that constructors make bad constructions...he is doing now a days by himself, soldering each part....constructing the entire unit to preserve quality and to preserve the secrets of knowledge, that costed so expensive to him...not only related money, but also related health and sacrifices he made related his family life.
He is rich now a days...having many cars, motorcicles, enjoyning International travells, having employees and thousands of circuits sold and sounding wonderfull around this world...a humble man he is...even beeing the King of sonics
That's what he have, and all that i do not have dear John
regards,
Carlos
Retired from the Military Life he decided to go deep into audio...he bougth books and started to read them all... made contact with people that had deep understand about electronics and start his business... his beggining was more than 10 years ago.
His first amplifier was published with that bootstrapped technologie...the same topologie i am using now..when he is using another one now a days...his Aksa has subcircuits and modifications not shown on my amplifier..as those things belongs to Mr. Hugh.
He decided to understand deep the Mathematics involved into audio amplifier designs and have read all the famous designers books.
The better is that he decided to join the instruments with his ear... circuits were tested by ear..by audition and parts substitution and sub circuits were tested..observing effects of waveshape, distortion and spectrum...so..each modern circuit was tested...many amplifiers types checked, built, listened, compared with his units...hardly researched each connection, to "listen" the best possible sound...of course friends have cooperate with him related those evaluations...not a lonely process.
The result was an incredible amplifier, with some sub circuits used that increase sonics quality in a way no other amplifier could match....i have them here...i have compared...i have tested them...and no one could beat his Aksa 55 related sound stage and treble quality reproduction...focusing of instruments and voices quality...... others could be sligtly more powerfull with 35 volts....others had more dinamics....others had stronger bass...but the overall quality is unbeatable.
He has something that i will never have....the patience to catalogue, to take notes of all steps he made.... evaluations about many circuits and subcircuits...effects using types of capacitor and transistors.... all those things he done is something i loose my track .. turning myself lost related the early begining of my researches..I have forgotten what happened with that "yellow" capacitor i have used last year....but Hugh Dean did not loose his track.
He had everything organized...so....he could track the long travel back, to return watching all result of researches made, and joined them together in his amplifiers.
Mathematics and theorical knowledge is, now a days, enougth to discuss with Engineers and to make himself be understood..also enougth to understand the experts.....but more than that...the qualities of a practical researcher he has...the real life experiences made.in the past and still beeing made... the years locked inside his laboratory, researching till he developed repetitive work disease in left arm.... 18 hours each day working years long..day after day.... spending all money he could, to pay parts, to use them till the limit (real limits) and to burn many parts to obtain the needed knowledge of real reliability for his products..... he made an excelent brand, with fidelity related all his customers....and also he is not lazy...to avoid misadjustments...to avoid that constructors make bad constructions...he is doing now a days by himself, soldering each part....constructing the entire unit to preserve quality and to preserve the secrets of knowledge, that costed so expensive to him...not only related money, but also related health and sacrifices he made related his family life.
He is rich now a days...having many cars, motorcicles, enjoyning International travells, having employees and thousands of circuits sold and sounding wonderfull around this world...a humble man he is...even beeing the King of sonics
That's what he have, and all that i do not have dear John
regards,
Carlos
Sorry by the off topic Vynil..thing will return to the rails once again after this
last one.
A comment to be made to Johan and Jacoo.
He is so humble...really humble..that he complains when i do those things, those comments about him...also i have pictures of him and he never told me that i can use them.
He use to say:
"I am just a normal man Carlos...i do my best...working hard..but i am not that special guy you are thinking...i have many defects"
He may be talking about our human food processing...well.... we all produce those things.
He is special.... one of the 5 more respectable men i had the pleasure to know in those 56 years of life.
And you cannot imagine how pretty are his daugthers...hehe
regards,
Carlos
...................................................................................................
Nice smilies you found Jacco...final of off topic here....i will not do it again.
....................................................................................................
last one.
A comment to be made to Johan and Jacoo.
He is so humble...really humble..that he complains when i do those things, those comments about him...also i have pictures of him and he never told me that i can use them.
He use to say:
"I am just a normal man Carlos...i do my best...working hard..but i am not that special guy you are thinking...i have many defects"
He may be talking about our human food processing...well.... we all produce those things.
He is special.... one of the 5 more respectable men i had the pleasure to know in those 56 years of life.
And you cannot imagine how pretty are his daugthers...hehe
regards,
Carlos
...................................................................................................
Nice smilies you found Jacco...final of off topic here....i will not do it again.
....................................................................................................
Also then final on this, but ......
(Apology for temporarily hi-jacking your thread, Vynuhl.add.)
I would suggest that on any thread it is never totally off-topic to give praise where praise is deserved. Those people shall not pass on unnnoticed - those from whom we learn or ought to learn if we are not stupid, so that they have not existed in vain.
(Apology for temporarily hi-jacking your thread, Vynuhl.add.)
I would suggest that on any thread it is never totally off-topic to give praise where praise is deserved. Those people shall not pass on unnnoticed - those from whom we learn or ought to learn if we are not stupid, so that they have not existed in vain.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.