I red on this forum some time ago that Nelson Pass liked P3A more with active VAS CCS than with bootstrap.
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Sakis is right - generally, people building simple amps have preferred the R+C bootstrap load for the VAS. There are some subtle issues that may or may not be important. I started out building a clone of the AKSA 55 amplifier by Hugh Dean. It took me a bit of time to realize that the bootstrap was critical. It pumps desirable (2nd dominant, falling higher orders) harmonic distortion into the circuit via the imperfect power rail filtering of the input LTP. This is one reason why bootstraps sound different. They may also impact the amount of Cdom required and the value of Cdom affects the sound (if you do the experiments).
That's exactly the reason why I want active CCS, I want to minimize 2nd order harmonic. With my loudspeakers, speaker placement, etc., I do not need more warmth to the sound, but more clarity and brightness. When I want that lush and warm effect, I usually prefer singleton input amps. I know that there is many who prefer bootstrap, but for my taste that's a little too warm and lush sounding.
I prefer amps with push-pull VAS for the same reason, reduced 2nd harmonic. I guess that it also has something to do with loudspeaker distortion. Loudspeaker distortion mixes with the amp distortion to give unique effect. If there is enough of 2nd harmonic in the loudspeaker spectra you don't need more of it in the amp.
I prefer amps with push-pull VAS for the same reason, reduced 2nd harmonic. I guess that it also has something to do with loudspeaker distortion. Loudspeaker distortion mixes with the amp distortion to give unique effect. If there is enough of 2nd harmonic in the loudspeaker spectra you don't need more of it in the amp.
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To be able to choose parts this can only be done through comparison only on a given bias and a given circuit more or less
Please notice that choice of parts and choice of bias can also be a matter of opinion and this is what makes the choice rather complicated .
Example
Listeners that go for piano and a voice will be more happy with plenty of bias while speed will not bother them in this case amplifier can be made with 2N3055
Hard rock listeners will be happy with almost class B operation and very low bias the packet of harmonics and distortions produced is similar to the distortions injected to electric guitars and many people love that ( ?????) (!!!!!!) Mje 340 MJE150XX semis there will sound superb
Listeners like me into soulful house that require a number of instruments inside the program , some of them natural , vocals , crisp highs ,tight and speedy low end will have to go for high speed semis obviously Japanese and a good amount of bias to a level of 70 ma but no more than that .....
Critical
For my active friend ivanlukic !!! ( bigun also why not ) edit !!!
We are in the simulation era .... designers take place infront of a computer examine ideas and simulate the results
Now while simulating and when ever a distortion of any nature appears ( since now we have the computing power to see any of the possible distortions ) So designer now has the power to modify the circuit in order to eliminate any appeared distortion ...
Well Ivan that produces clinic amplifiers without character soul tone or color ....Clearly the P3a due to the nature of built a simple LTP bootstrap VAS and CFP output stage will be an amplifier that includes mistakes character soul and tone ...
There is a question of choice and you have to decide if go for a thing like that ...
Remove the bootstrap and half of the character of p3A is gone ....
Now ...
At east electronics now days we repair an average of 1000 amplifiers per year ...YES we do very well....So feedback from client is a sport here and we actually record everything
Our clients are 40% of no interest they just like some music while the rest 60% is the real hifier that has more than one system in his home plenty of alternative sources or even hybrid HT and HIFI systems
Most of them spend money to upgrade and repair vintage amplifiers only because of the reasons mentioned above ....: tone and character People love that despite the problems related
Remember Ivan amplifier are supposed to play for human ears ....not computers
Best regards
Sakis
Please notice that choice of parts and choice of bias can also be a matter of opinion and this is what makes the choice rather complicated .
Example
Listeners that go for piano and a voice will be more happy with plenty of bias while speed will not bother them in this case amplifier can be made with 2N3055
Hard rock listeners will be happy with almost class B operation and very low bias the packet of harmonics and distortions produced is similar to the distortions injected to electric guitars and many people love that ( ?????) (!!!!!!) Mje 340 MJE150XX semis there will sound superb
Listeners like me into soulful house that require a number of instruments inside the program , some of them natural , vocals , crisp highs ,tight and speedy low end will have to go for high speed semis obviously Japanese and a good amount of bias to a level of 70 ma but no more than that .....
Critical
For my active friend ivanlukic !!! ( bigun also why not ) edit !!!
We are in the simulation era .... designers take place infront of a computer examine ideas and simulate the results
Now while simulating and when ever a distortion of any nature appears ( since now we have the computing power to see any of the possible distortions ) So designer now has the power to modify the circuit in order to eliminate any appeared distortion ...
Well Ivan that produces clinic amplifiers without character soul tone or color ....Clearly the P3a due to the nature of built a simple LTP bootstrap VAS and CFP output stage will be an amplifier that includes mistakes character soul and tone ...
There is a question of choice and you have to decide if go for a thing like that ...
Remove the bootstrap and half of the character of p3A is gone ....
Now ...
At east electronics now days we repair an average of 1000 amplifiers per year ...YES we do very well....So feedback from client is a sport here and we actually record everything
Our clients are 40% of no interest they just like some music while the rest 60% is the real hifier that has more than one system in his home plenty of alternative sources or even hybrid HT and HIFI systems
Most of them spend money to upgrade and repair vintage amplifiers only because of the reasons mentioned above ....: tone and character People love that despite the problems related
Remember Ivan amplifier are supposed to play for human ears ....not computers
Best regards
Sakis
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we are in the era of any possible DAC existing for any taste value wallet and so on
Any body cares to explain me how the **** we had to repair about 650 CD players of the CD 63 Marantz Family ? older younger CD 67 Isiwatta versions se versions and so on ..
Try this: may be they play better ...
Any body cares to explain me how the **** we had to repair about 650 CD players of the CD 63 Marantz Family ? older younger CD 67 Isiwatta versions se versions and so on ..
Try this: may be they play better ...
I can't see any advantage in tinkering with P3a if one's aim is to reduce the harmonic content. Your preference seems more like a cue to consider other conventional and commercial amplifier designs with low distortion rather than strip a known good design back to something more neutral and likely not being able to do that well enough to say it is an improvement.
We have a string of simple but solid designs that have been popular here for many years and the original Symasym series comes to mind as just one of them. Then you have CFA type designs like VSSA that are even simpler but still sound great without seeming to have unnecessarily levels of harmonic distortion.
So, I'd review and consider other designs before trying to hack the P3a as I don't think it will respond particularly well ( based on having listened to P3 and similar forerunners) and I'm sure there are better candidates out there.
We have a string of simple but solid designs that have been popular here for many years and the original Symasym series comes to mind as just one of them. Then you have CFA type designs like VSSA that are even simpler but still sound great without seeming to have unnecessarily levels of harmonic distortion.
So, I'd review and consider other designs before trying to hack the P3a as I don't think it will respond particularly well ( based on having listened to P3 and similar forerunners) and I'm sure there are better candidates out there.
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Joined 2009
Paid Member
Nice project, be very cautious though, I have done a few personal mods of the P3A and the result was not pleasing, after a few months of playing music with it, the oscillation attacks.I do think that adding more parts makes the amp unstable.(even if it shows good results in sim).
My two cents worth.
My two cents worth.
I found P3A dicey to tinker with too. For curiosity, I also reverted to earlier versions like P3 to hear what Rod Elliott meant by his descriptions.
To clarify earlier comments, I referred to mods that reduce the existing sound effects, as Ivan stated for his objective. I suggest that this is not a good starting point because in principle, it would mean taking a complex whole and working backward to some, as yet undefined operating condition. I think perhaps this would rely more on good luck and lots of iterations rather than design intent to lead the way.
The blameless concept design is an obvious starting point but there are others mentioned that are easier to tinker with whilst already producing useful sound effects. I don't say there is only one way - several inspired design ideas are posted here every week so there are plenty - maybe too many ideas already, to choose from..
To clarify earlier comments, I referred to mods that reduce the existing sound effects, as Ivan stated for his objective. I suggest that this is not a good starting point because in principle, it would mean taking a complex whole and working backward to some, as yet undefined operating condition. I think perhaps this would rely more on good luck and lots of iterations rather than design intent to lead the way.
The blameless concept design is an obvious starting point but there are others mentioned that are easier to tinker with whilst already producing useful sound effects. I don't say there is only one way - several inspired design ideas are posted here every week so there are plenty - maybe too many ideas already, to choose from..
I couldn't argue with that and more power to you for the upcoming TGM11-20 series
However, you have considerable engineering skills and used analysis tools effectively in designing your TGM series. Not many DIYs here are likely capable of tackling the critical design issues that arise.
I believe that the key factor here is the bootstrap circuit, I have done a totally different approach while experimenting with my own CFP design that uses a push pull VAS scheme. Bimo, Calvin & Valery helped me out in fine tuning the circuit, and in my observation the oscillation is very critical in the VAS stage, The output cannot tame it efficiently.
I too noticed that P3A is not very tolerant of upgrades when I changed the gain on my P3A built with TIP35C/36C. I raised the gain to 47 times (around 33dB) and noticed very big bandwidth limitation on square waves. In original form amp is tailored for basic specs, not for upgrades. Fortunately higher gain resulted just in lower bandwidth, which was noticable in listening tests, but not in instability.
Hi,
That vas arrangement I got it from D. Self figure f., alternative buffering arrangement uses bootstrapping resistor.The ccs provides 6 ma to vas.I have observed that I need to change the feedback capacitor to 47uf/50 volts to make the treble sound transparent just like the sound of the original bootstrap vas. This is subjective observation.
Thanks,
jromxt
That vas arrangement I got it from D. Self figure f., alternative buffering arrangement uses bootstrapping resistor.The ccs provides 6 ma to vas.I have observed that I need to change the feedback capacitor to 47uf/50 volts to make the treble sound transparent just like the sound of the original bootstrap vas. This is subjective observation.
Thanks,
jromxt
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