SAE X25 Class A Amplifier Circuit

Isn't better amps you could use as a reference?

Murphy_t. Any suggestions, the SAE X25A is the only high powered class A amplifier we have available, the valve amplifier is noticeable better in bringing out subtle low level details than any class AB Solid State amplifier we have tested so far. We want to test the valve amplifier against a Solid State amplifier which is guaranteed not to produce any form of crossover artifacts whatsoever, and only a class A amplifier can guarantee this. We believe that crossover artifacts, although virtually impossible to measure by normal tests on a good amplifier, are actually additive on real programme material, particularly on subtle low level stuff, such as choral singing and church organ. The valve amplifier seems to seperate the voices into individual ones, even good Solid State amplifiers does not do this as well. We also want to do some serious tests with different speaker cables. The valve amplifier does not appear to be affected much by various types of speaker cable, and maybe a class A amplifier will show the same characteristics in that regard. Any comments. poulkirk@elan.com.au

Hi. It has been awhile so I hope this gets to you. Just did this whole response offline and lost it trying to post to this site so I am not going to worry too much about errors. You raise some interesting points: 1) Crossover distortion was identified about 25 years ago by David Hafler who called it "notch" distortion so not to confuse it with problems caused by speaker crossovers. I think it is the main reason so many ss amps sound grainy in the high treble. For some reason (the quest for power?) it has been largly ignored bythe audio world. 2) Amp: N.E.W. has a class a amp, HCMaudio has (had) the 120 volt version on sale for $500. Audiovideotoday has the 12 volt version on closeout ($700?, I am not sure). The 12 volt version works off a large rechargeable battery, instantaneous and pure power. Nelson Pass published some class a designs in Audio Amateur magazine, takes a lot to build though. I have a sumo nine class a amp (60 watts a side) that I got used and did some upgrading and mods to. I wouldn't call it reference quality but it is very revealing of every tweek and change I have made. I have tried to salvage some trashed gear and it never seemed to be worth the time and money it takes. Also most good vintage gear gets a cult following and is talked about. I have never heard the SAE, nor have I heard of it. Could be a great amp, I don"t know. 3) Speaker cable: If you are developing cable for your own use then whatever sounds good to you is it. If you are trying to make cable to sell something than is too revealing may not be good. Audioquest makes many cables that punch up the bass and smooth out the highs. Sounds good in a 15 minute store demo so they sell well. Too revealing may not be marketable because of notch distortion. See RJM audio cable web page for more on this. Plus a lot of hype and BS in the cable's ad copy seems to help. Good luck with you project, Tim