Class AB .... is it all done ? - Page 2 - diyAudio
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Old 13th January 2012, 06:31 PM   #11
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people you are screwing my thread ha ha ha but that's ok there always something nice to learn listening to the elements of diyaudio !!!!

from commercial integrated amplifiers and the vintage area i would say that most accuphase rock ! also SANSUI AU717 was way too nice Adcoms are fine and here is got to be more these are the first to come in mind
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Old 13th January 2012, 08:10 PM   #12
Bigun is offline Bigun  Canada
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Originally Posted by indianajo View Post
I own 3 transistor amps which are contiunally blowing up all the time.... the St120 blew up the 2nd & 3rd times,...My second amp, the Peavey CS800s, sounded great for 8 months but is blowing the breaker now. ...I've been monkeying with a Peavey PV1.3k split supply amp which has convinced me with burned PC lands how useless diac-triac protection is, and I have gotten one channel to run 20 seconds so far before blowing up again.
Jeez man, you're in the wrong hobby! and I'm not letting you within 10 miles of any of my amplifiers

Class AB - meets the needs of so many and has stood the test of time - I think it will be here for a quite awhile.

But I'm not sure I'm going to be building any more of these Class AB designs - it's a case of diminishing returns for my effort and once I've learned what I wanted to learn the motivation for more starts to fall off. TGM4 and TGM5 could be the last ones for me.


I actually expect Class D to reach a point where it is good enough for hi-if and when the price is attractive enough (no reason why not) then it will be the first choice for many over Class AB. Unfortunately, a lot of the kit-set manufacturers who support this hobby will find it a tough transition.
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Old 13th January 2012, 09:13 PM   #13
Bigun is offline Bigun  Canada
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Originally Posted by sakis View Post
opinions please ?
another vote for Lazycat SSA (or TGM5)
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Old 14th January 2012, 04:08 AM   #14
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Originally Posted by TheShaman View Post
Lack of real arguments is oh so evident when people have to resort to mixing their subjective opinion with facts/objective data in one sentence.
I can only guess about what you mean, and find it appropriate to make few subjective comments (on the basis of amps building practice and listenings at high level system):
- applicability of standard measurements for predicting final sound is overestimated nowdays, since there is no appropriate objective alternative to them, and engineers working at hi-fi industry are forced to protect the basis they are standing on;
- standard measurements serve very good for getting proofs that an amp does not reveal faults like ringing, asymmetrical clipping, bad slew rate etc.;
- perfectioning of sound, unfortunately, is possible only on subjective ground nowdays, and only within commercially unbiased surroundings.
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Old 14th January 2012, 04:55 AM   #15
awpagan is offline awpagan  Australia
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sakis

If you like the P3B
you could always try the Class A version.
25W Class-A Power Amplifier
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Old 14th January 2012, 05:22 AM   #16
system7 is offline system7  United Kingdom
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I remember building an amp (with a current drive output stage) pretty similar to a P3A based on a Maplin kit, but it actually didn't sound that good unless I pushed it into Class A to lower crossover distortion. IIRC it was missing the local voltage feedback at the current drive output stage though. The devil is always in the detail.

Problem for most voltage feedback amps, is that they really have no idea what sort of load they are driving, and it can be quite wild in multi speaker designs. You'd need an element of current feedback to really complete the picture. on the other hand, designing for 8 ohms resistive has gotta be quite easy.

You can do a lot with passive equalisation at the speaker to improve the load as with this Fostex full-range driver example:

Click the image to open in full size.

The bass hump is pure theoretical hell though. I suppose you could add a series RLC circuit to lower it, but that's not easy in practise. Still, bass seems to be the least important amplifier criterion, so maybe let it pass. I have strong views that common-mode (ground noise leakage) rejection matters in amplifiers if you like silence between the musical notes, and I prefer constant impedance stepped attenuators to potentiometers, and the preamp might as well be Class A.

The P3A is really quite nice at many levels though. I want to hear one into a competent speaker. It looks right for a bipolar transistor design, though MOSFETs seem to have more frequency extension and offer some interesting options.

Last edited by system7; 14th January 2012 at 05:44 AM.
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