Hi Tom,
You are right that there is no measured THD data.
I have built the amp. But I have no instrument such as an AP to measure the THD. I have a 100MHz DSO which prints FFT, but this function is very unreliable to measure THD < 1%. I have done the sine and sq. wave test on this amp, but I did not capture the scope image. I will upload some test photos later after I do that test again. What do you use to measure THD? How much difference do you find the simulation is off the real world results? So far I have to trust the simulation at the design phase and verify the result by listening test with my own ears. I have listened to the amp with my headphone. It sounds good. The noise is merely audible with the input connected to music source. If with the input shorted to ground, the amp is deadly quiet. I consider this a not-bad result in terms of S/N. My scope has a few mVpp noise, thus not good for measuring the S/N.
Thanks for your pointing out the layout concerns. I have some preliminary PCB designs for this amp, which I will release later.
Regards,
Jazz
Hi Bimo,
Waho! That is amazingly good. Could you refer me to the book page where the lameless amp you simulated is based on? Thanks a lot.
With increased LTP current to 2.6mA, the S/R of this amp can reach 60V/us, but THD@10KHz also increase to 0.009%
Jazz
Saying "balanced VAS", I don't mean complementary push-pull, I mean something like this. Fully symmetric, same signal path for both shoulders...
R8 may be a CCS. Bias is set by adjusting its current.
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Q7-Q10 are drawn incorrectly, aren't they? As shown, Q9-10 wouldn't have any collector current.
Hi 
,
Just here to report the latest progress. Have just completed the JC2013 LDO psu for the amp. It is powered by a 800W 37Vx2 toroid, output voltage set to +/-46VDC. With this PSU, and take the time when the kid and her mother is out, the sound test is performed again at higher than usual listenning SPL with a fostex full range BLH speaker. Test CD/sound tracks are 1) The Planets by Gustav Theodore Holst from DG2530102 played by Boston Symphony Orchestra 2) Pictures at an exhibition by Modest Petrovich Moussorgsky from Telarc80296 3) Track No.1&9 by Danny Chan from Dream Lover EMI FX50013 4) You Go To My Head by Diana Krall from Verve UMG LG00383.
I should say that I enjoyed the sound from the speaker this time more than ever😀. If not for that the door bell rang🙁 in the middle of Diana's song, I would like to continue the play.
Two differences can be immediately identified, the background is much cleaner, and there are more fine details at the highs.
Before the listenning test, I re-adjusted the quescent, so that each output transistor had a bias around 210mA. By using a 50KHz sq. ware, I could see that the crossover closed seamless by increasing the current from aound 100mA to 210mA. I also performed the sine wave test. Then, the drawback becomes obvious. It can only output an un-clipped 34Vpp with 46VDC rail voltages, and the amp is running very hot. You cannot touch the sink for more than a split of a second😱. I read 84degree on my infra-red thermal meter aimed at the top the cans.
Jazz
,Just here to report the latest progress. Have just completed the JC2013 LDO psu for the amp. It is powered by a 800W 37Vx2 toroid, output voltage set to +/-46VDC. With this PSU, and take the time when the kid and her mother is out, the sound test is performed again at higher than usual listenning SPL with a fostex full range BLH speaker. Test CD/sound tracks are 1) The Planets by Gustav Theodore Holst from DG2530102 played by Boston Symphony Orchestra 2) Pictures at an exhibition by Modest Petrovich Moussorgsky from Telarc80296 3) Track No.1&9 by Danny Chan from Dream Lover EMI FX50013 4) You Go To My Head by Diana Krall from Verve UMG LG00383.
I should say that I enjoyed the sound from the speaker this time more than ever😀. If not for that the door bell rang🙁 in the middle of Diana's song, I would like to continue the play.
Two differences can be immediately identified, the background is much cleaner, and there are more fine details at the highs.
Before the listenning test, I re-adjusted the quescent, so that each output transistor had a bias around 210mA. By using a 50KHz sq. ware, I could see that the crossover closed seamless by increasing the current from aound 100mA to 210mA. I also performed the sine wave test. Then, the drawback becomes obvious. It can only output an un-clipped 34Vpp with 46VDC rail voltages, and the amp is running very hot. You cannot touch the sink for more than a split of a second😱. I read 84degree on my infra-red thermal meter aimed at the top the cans.
Jazz
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No, they are fine, just two resistors missing - from Q7, Q8 bases to the ground.
It was late and I was in a hurry 🙂
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