People like to push amps, at least once in a while, to see how it behaves at high powers, to "feel the power". My comment was directed to those who will do that. Even at medium power levels, used for prolonged time, voice coil will heat considerably. I used 18 Ohm high power resistors to electrically clean loudspeaker relays in my Yamaha AX592. There was considerable heating though I turned relays on and off just several times at less than 10% rated current using 1kHz sine from test CD. The whole procedure lasted only several seconds and yet resistors were very warm. At higher output levels it's not unusual for voice coil to reach 100-150 degrees C.
Numerous burnt tweeters and even woofers remind us that high power levels are used in homes too. Parties, celebrations, etc. are usual social events, at least here in Serbia. Average user does not have knowledge to estimate when loudspeaker is pushed too hard.
Numerous burnt tweeters and even woofers remind us that high power levels are used in homes too. Parties, celebrations, etc. are usual social events, at least here in Serbia. Average user does not have knowledge to estimate when loudspeaker is pushed too hard.
Last edited:
Member
Joined 2009
Paid Member
With so many good words how can I not build one ?
I have been simulating my own variant of it this week.
I think P3A is already in its simplest form. I expect complicating it will not make it better. Changing the bootstrap with current source for example, will only make it sound clinical. But I have simmed long time ago, that dual output with its own "CFP" pair had better performance than single output. I have always wanted to build it but too busy with other new amps (and speakers).
Member
Joined 2009
Paid Member
There were quite a few experiments done by OSTripper, AKSA and others to compare bootstrap with CCS and they all concluded unanimously that the bootstrap was more musical. I suspect that this conclusion ports over to the P3A.
Bear in mind that the AKSA design was originally on Rods project list and later removed at Hugh's request. For all we know, Rod converted the output to CFP and called it the P3A.
I have no intention of dropping the bootstrap when I build one.
Bear in mind that the AKSA design was originally on Rods project list and later removed at Hugh's request. For all we know, Rod converted the output to CFP and called it the P3A.
I have no intention of dropping the bootstrap when I build one.
Only listening. EF version of the P3A is better on paper but not on listening. So listening for me is more important.
Member
Joined 2009
Paid Member
It was my own amp, not AKSA. What I meant was that numbers is not the same with perception, or I had no idea what "evidence" AndrewT was looking for. Perception is subjective, but numbers is not better either.
And probably there is someone who can "make" the ccs version sound better, I don't know. I have never meant it as a conclusion.
You can have both, bootstraps and CCS.http://www.diyaudio.com/forums/solid-state/186981-bootstrapsccs-t-tmc.html
I have never tried that (is that your idea?) because I don't have depletion mode fets.
With so many good words how can I not build one ?
The more I listen to P3A, the more I like it!
Probably, some assumptions are getting a bit out of date. Don't forget that AKSA designs have moved in several different directions in recent years. About the only common feature of recent products with the design ESP showed, the BAKSA or the AKSA55, is the boostrapped VAS. Newer designs and topologies are strikingly different now. Even though you need to start with topogies that distort with the harmonic emphasis necessary for the various sound qualities needed, there's no point throwing in other topologies whose distortion will counter that and leave a general, wide spectrum distortion mess. The secret sauce of course, is not what you do, but how you go about it. By way of some examples, a LTP is not a good way to promote even harmonics, neither is an output stage using ancient power silcon that screams high order odd harmonics at you.
Using good quality silicon like MJL3281/1302 or 2SC5200/1943 goes a long way to cleaning up these nasty critters in class AB.
TBH, I think rode messed with the P3 design as a cheap utility amplifier design since he was quite young. The fact that it sounds good with overbias was probably a happy coincidence and has little to do with the intent of the original design. A great result that works for everyone who can build it with the correct parts as the P3a version, though.
FWIW AKSA55 was also based on a cheapest possible utility amplifier for general purpose audio use like powered desks, stage sound, instrument amps etc. This was an ordinary sounding amplifier, let me assure you.
Most of you will recall that Greg Erskine systematically went about cloning the AKSA55 and I haven't yet read that he cracked it with a match, soundwise. You can be sure he has the original in some form and listened and compared it a lot.http://www.diyaudio.com/forums/solid-state/168554-based-hugh-deans-aksa-55-a.html
Have others here buit BAKSA to investigate?
Last edited:
I don't know of the advantage of a bootstrap. I thought that the advantage of the bootstrap is the in-existence of the ccs?
So I guess your solution is the midway between full-ccs and full-bs? My solution has been to choose the correct capacitor brand and size by listening, as well as the position of the injection from power supply to get the correct amount of second order distortion or its spectrum (for full-bootstrap).
Okay I understood #2 very well (I believe in distortion spectrum in amplifiers). So #1 is the reason why with bootstrapping (with good quality cap) the bass is better because it is capable of giving short term voltage/current. Instead of seeing the positive side of bootstrap I have seen the negative side of ccs, which is the same thing. Thx.