AKSA said:
Hello Hugh
Can we just look at the amp, connect to a real loudspeaker, very high frequency (maby the pole frequency) at a scope to see if they oscillated and adjust the lag comp cap value until there is no more oscillation and you go back to half that value and after you adjust the value of the Linsley Hood phase lead cap until there is no more oscillation (since it's effect are combined to the lag comp cap), so we use just half the value of miller cap since, in some ways, the phase lead cap do the other half of the job ?
Btw, many amps do have a 10 to 22 pf cap across the nfb resistor, since it send more of very high frequency signal to the nfb, is it an other way to compensate the use of a smaller value miller cap ?
The more I study into amp making and the more I find that the actual distortion-frequency-phases, etc.. measurements technics give a good ideas but they are not enough to fully give a true ideas of the sonic quality of an amp.
Hi Gaetan,
You wrote:
Yes. You can do this, but you don't need to trigger oscillation with a pole frequency signal. You can do it with a 10KHz square wave; merely examine the ringing patterns to see if transient instability exists. Gross instability is rare; it is usually short term, but it is very non-linear and results in temporary loss of fb control over subsequent signals.
I find a better way is to try 100pF, listen to a dynamic piece of music. This is normally too much, of course, and it will sound slow, and lifeless. Now go to say 22pF. This would normally sound bright, tizzy, fatigueing. Look at the 10KHz square wave on the CRO; it will show the transient instability. Now move up to 33pf, then 47pF, etc. Keep listening carefully; when you know what to listen for the so-called subjective assessment is very effective. Once you have a good sound, no instability, reduce it by around 20%, then pick up the stability again with phase lead.
You need to be methodical, because doing this at random will easily lead you astray. You mention 10-22pF across the fb resistor. This is not quite the same thing as phase lead, because it includes the low impedance output stage in the loop, so the effect is centred on the fb node and includes the phase shift of the output stage. If you take the phase lead cap from the VAS, a high impedance point, then its influence effects both the fb node AND the collector of the VAS, pulling back gain much more effectively while keeping the phase shift of the output stage out of the mix. PL from the VAS is superior, in my view, and makes the amp more load tolerant, whereas a fb cap merely pulls back gain below unity with the LC cap by the pole frequency and can actually promote instability.
I hope this is some help to you,
Hugh
You wrote:
Yes. You can do this, but you don't need to trigger oscillation with a pole frequency signal. You can do it with a 10KHz square wave; merely examine the ringing patterns to see if transient instability exists. Gross instability is rare; it is usually short term, but it is very non-linear and results in temporary loss of fb control over subsequent signals.
I find a better way is to try 100pF, listen to a dynamic piece of music. This is normally too much, of course, and it will sound slow, and lifeless. Now go to say 22pF. This would normally sound bright, tizzy, fatigueing. Look at the 10KHz square wave on the CRO; it will show the transient instability. Now move up to 33pf, then 47pF, etc. Keep listening carefully; when you know what to listen for the so-called subjective assessment is very effective. Once you have a good sound, no instability, reduce it by around 20%, then pick up the stability again with phase lead.
You need to be methodical, because doing this at random will easily lead you astray. You mention 10-22pF across the fb resistor. This is not quite the same thing as phase lead, because it includes the low impedance output stage in the loop, so the effect is centred on the fb node and includes the phase shift of the output stage. If you take the phase lead cap from the VAS, a high impedance point, then its influence effects both the fb node AND the collector of the VAS, pulling back gain much more effectively while keeping the phase shift of the output stage out of the mix. PL from the VAS is superior, in my view, and makes the amp more load tolerant, whereas a fb cap merely pulls back gain below unity with the LC cap by the pole frequency and can actually promote instability.
I hope this is some help to you,
Hugh
Hello
Here a photo of the Aksa showroom at the RMAF, the photo come from audioxsell.com web page.
Gaetan
Here a photo of the Aksa showroom at the RMAF, the photo come from audioxsell.com web page.
An externally hosted image should be here but it was not working when we last tested it.
Gaetan
Yup, that's it all right!! Thank you for posting the photo, Gaetan, much appreciated.
With David Ellis' 1801b floor standers, Frank Van Alstine's Ultra DAC and HK CD player, and my Soraya CB105 power amp, this was 1 fine sounding system and sounded very, very good.
I'm pleased with the way it all went, met a large number of my customers and some impressive engineers in the industry, and made a lot of friends. I hope to return next year!
Sadly I did not have a camera, buying one this week in NYC in fact, but the picture of the system is all you need!
Even hired a car, drove to Aspen Colorado to see the original inspiration of my company name! (And survived driving on the WRONG side of the road!!)
Cheers,
Hugh
With David Ellis' 1801b floor standers, Frank Van Alstine's Ultra DAC and HK CD player, and my Soraya CB105 power amp, this was 1 fine sounding system and sounded very, very good.
I'm pleased with the way it all went, met a large number of my customers and some impressive engineers in the industry, and made a lot of friends. I hope to return next year!
Sadly I did not have a camera, buying one this week in NYC in fact, but the picture of the system is all you need!
Even hired a car, drove to Aspen Colorado to see the original inspiration of my company name! (And survived driving on the WRONG side of the road!!)
Cheers,
Hugh
AKSA said:Yup, that's it all right!! Thank you for posting the photo, Gaetan, much appreciated.
With David Ellis' 1801b floor standers, Frank Van Alstine's Ultra DAC and HK CD player, and my Soraya CB105 power amp, this was 1 fine sounding system and sounded very, very good.
I'm pleased with the way it all went, met a large number of my customers and some impressive engineers in the industry, and made a lot of friends. I hope to return next year!
Sadly I did not have a camera, buying one this week in NYC in fact, but the picture of the system is all you need!
Even hired a car, drove to Aspen Colorado to see the original inspiration of my company name! (And survived driving on the WRONG side of the road!!)
Cheers,
Hugh
Hello Hugh
I've forgot that they drive at other side of the road in Australia
I'm happy that it was good for you at the RMAF
Gaetan
Samuel,
You can imagine my surprise when, at the Aspen/Ellis room, I turned to face someone behind me, and there, with his hand outstretched to meet me, was Nelson Pass - the source of my early inspiration back in, let's see, around 1988 I think, when I built my first Pass amp - a Zen of just 10W!
It turned out we were almost exactly the same age!
He was very nice, we chatted for a moment, and at the end of the Fest I went to say goodbye to him, but sadly did not hear his SEWA and open baffle speaker. I was truly grateful to meet and chat with Nelson, met his son Colin, and enjoyed the chat - oddly, we hardly spoke of amplifiers!
I think that, speaking only for myself, if nothing else happened at RMAF, my chats with Nelson, Frank Van Alstine, Wayne Waananen, Wes Bender and several others were high points, and put me in touch with some of the of the icons and personalities of DIY.
Presently enjoying NYC, wandering aimlessly around the restaurants of Brooklyn with Occam, who is a magnificent host. I have to say that I love this place, and the food is considerably cheaper than Australia, which I'm realising is a very, very isolated and expensive country. But the Americans can't do good coffee, or at least in MOST places this is true.....
Cheers,
Hugh
You can imagine my surprise when, at the Aspen/Ellis room, I turned to face someone behind me, and there, with his hand outstretched to meet me, was Nelson Pass - the source of my early inspiration back in, let's see, around 1988 I think, when I built my first Pass amp - a Zen of just 10W!
It turned out we were almost exactly the same age!
He was very nice, we chatted for a moment, and at the end of the Fest I went to say goodbye to him, but sadly did not hear his SEWA and open baffle speaker. I was truly grateful to meet and chat with Nelson, met his son Colin, and enjoyed the chat - oddly, we hardly spoke of amplifiers!
I think that, speaking only for myself, if nothing else happened at RMAF, my chats with Nelson, Frank Van Alstine, Wayne Waananen, Wes Bender and several others were high points, and put me in touch with some of the of the icons and personalities of DIY.
Presently enjoying NYC, wandering aimlessly around the restaurants of Brooklyn with Occam, who is a magnificent host. I have to say that I love this place, and the food is considerably cheaper than Australia, which I'm realising is a very, very isolated and expensive country. But the Americans can't do good coffee, or at least in MOST places this is true.....
Cheers,
Hugh
Hello
I did look at the stereophile.com web page to see more about the RMAF in their report, there is lot of nice photos, but sadly they don't say or show anything about the Aksa showroom.
stereophile.com are very well know on the Net, it would be very good for Hugh if they talk about Aksa.
Gaetan
I did look at the stereophile.com web page to see more about the RMAF in their report, there is lot of nice photos, but sadly they don't say or show anything about the Aksa showroom.
stereophile.com are very well know on the Net, it would be very good for Hugh if they talk about Aksa.
Gaetan
Yes Gaetan,
That was disappointing, but no one ever said it was easy for the little guys, even if their products were very good.
Perhaps when we go mainstream, do a little advertising, things will improve. Publicity is a fickle mistress!
Nelson,
Thank you for posting the photo. It was a great pleasure to meet you, and I was astonished you knew the works of Richard Brautigan - actually, I was blown away. He is little known, and your awareness of this peculiarly Californian writer of the seventies speaks volumes about the breadth of your interests.
Thank you again for the privilege,
Cheers,
Hugh
That was disappointing, but no one ever said it was easy for the little guys, even if their products were very good.
Perhaps when we go mainstream, do a little advertising, things will improve. Publicity is a fickle mistress!
Nelson,
Thank you for posting the photo. It was a great pleasure to meet you, and I was astonished you knew the works of Richard Brautigan - actually, I was blown away. He is little known, and your awareness of this peculiarly Californian writer of the seventies speaks volumes about the breadth of your interests.
Thank you again for the privilege,
Cheers,
Hugh
AKSA said:
Hello Hugh
I know lot of french writers and only few american writers, and you made me curious about Richard Brautigan, he is very a interesting to know about, I just found a nice web page about him;
http://www.brautigan.net/
Bye
Gaetan
AKSA said:
Hello Hugh
Here a photo of Nelson Pass at the RMAF, I love his Pass Lab shirt and his shoes
Gaetan
An externally hosted image should be here but it was not working when we last tested it.
Hi Gaetan,
Yes, Brautigan was a fascinating, troubled character with enormous talent and a highly original mind. I loved his whimsical, outrageous style of writing and it inspired me when first I read it.
If you look carefully at your picture, Nelson is floating just a few millimetres off the carpet. This is entirely consistent with his fame, and just goes to show anything is possible!! Like Brautigan, NP is understated, whimsical, and very thoughtful.
Thank you for posting the picture,
Hugh
Yes, Brautigan was a fascinating, troubled character with enormous talent and a highly original mind. I loved his whimsical, outrageous style of writing and it inspired me when first I read it.
If you look carefully at your picture, Nelson is floating just a few millimetres off the carpet. This is entirely consistent with his fame, and just goes to show anything is possible!!
Like Brautigan, NP is understated, whimsical, and very thoughtful. Thank you for posting the picture,
Hugh
Hello Hugh
Most of the times wen we find that the loudspeaker and it's passive crossover load made are bit difficult to some power amps we need to use bi-amplification with a good electronics crossover for the best sound, it's not only because of the speaker load since some amp do best at low frequency and other do best at high and it's not alway related to the load, but the load are an important part.
But, by reading a thread at audiocircle.com about the Soraya it seem that your Soraya amp can do the job that most of the time a bi-amplification would be needed for a real high end sound.
http://www.audiocircle.com/circles/index.php?topic=46870.0
Btw, there is a nice photo of you at the audiocircle forum RMAF thread, can I show it here ?
Bye
Gaetan
Most of the times wen we find that the loudspeaker and it's passive crossover load made are bit difficult to some power amps we need to use bi-amplification with a good electronics crossover for the best sound, it's not only because of the speaker load since some amp do best at low frequency and other do best at high and it's not alway related to the load, but the load are an important part.
But, by reading a thread at audiocircle.com about the Soraya it seem that your Soraya amp can do the job that most of the time a bi-amplification would be needed for a real high end sound.
http://www.audiocircle.com/circles/index.php?topic=46870.0
Btw, there is a nice photo of you at the audiocircle forum RMAF thread, can I show it here ?
Bye
Gaetan
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