Congratulations.... I know you worked hard!
Thanks Generg ! It was you, who got me started, guided and motivated me during this longish J2 expedition.....thanks !!!
(....and we both know how many times we were close to giving up...)
So, it's all your fault
As a compensation, I expect to hear a report of working and nice-sounding Generg-J2 soon.
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I compared 6 Semisouth in 30 different combiations. One SS in upper, the other one in lower position. Measuring THD and 2nd, 3rd harmonics.
The result was really surprising: Regardless of matched or unmatched pairs being measured, the transistors showed very different behaviour in terms of 2nd, 3rd, 4th and 5th harmonics.
It occurs to me, that different Semisouth transistors show different distortion behaviour, and that it is worthwile to select them for the distortion pattern each one of them (or each push-pull pair) generates.
I also would like to emphasize regarding clones (some indicated in this thread):
Semisouth are nowadays almost unobtainable. One element of perfection of FirstWatt amps, is the meticulous selection of transistors from a stock of thousands, so the selected pairs create the desired sound, the designer aims for. In my opinion the selection does not happen only on Idss, Vgs, but also on gate leakage and harmonic distortion spectrum. So, individual diy guys with a large stock of semisouth and a LOT of time might be able to get close. Cloners with the intend to release many amps - forget it - without extreme effort and knowledge it is not possible to reach the same level of perfection.
The result was really surprising: Regardless of matched or unmatched pairs being measured, the transistors showed very different behaviour in terms of 2nd, 3rd, 4th and 5th harmonics.
It occurs to me, that different Semisouth transistors show different distortion behaviour, and that it is worthwile to select them for the distortion pattern each one of them (or each push-pull pair) generates.
I also would like to emphasize regarding clones (some indicated in this thread):
Semisouth are nowadays almost unobtainable. One element of perfection of FirstWatt amps, is the meticulous selection of transistors from a stock of thousands, so the selected pairs create the desired sound, the designer aims for. In my opinion the selection does not happen only on Idss, Vgs, but also on gate leakage and harmonic distortion spectrum. So, individual diy guys with a large stock of semisouth and a LOT of time might be able to get close. Cloners with the intend to release many amps - forget it - without extreme effort and knowledge it is not possible to reach the same level of perfection.
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Hi dsdjoy:
I remember reading a while in the Ba1/3 thread (from Gerd) that did not vary much the sound putting R100 or IRFP240 in the upper position, can you comment something about that?
Thanks ..
Hi gmant123,
At that time I could not measure distortion spectra. I liked the sound with the R100 in the non CCSposition very much. The R100 were only matched for Vgs.
The J2 is a real beast and beauty at the same time..... It will have taken some time for Nelson to produce this sound.
But other babies are also very fine, I enjoy just a F3 clone, easier to manage and besides a little week bass, you have a wonderful panoramic sound.
J2 sounds like being on drugs, F3 like being in a wonderful landscape...
Really starting to paint a picture of your younger day, Generg.
Of Coarse. J2 has virtual Zen Pot built in
....
J2 sounds like being on drugs,......
Really starting to paint a picture of your younger day, Generg.
ya can bet for that .....
I gotta itch to visit Germany
Dark Side of the
Nah, not dark, just obsessed
Feeling a strong itch to make it to Burning Amp SF one day to meet you guys.