no current mirror, current mirror, cascoded current mirror, bjt or jfet VAS?

maxpou · 21st April 2008, 05:00 PM

Hi Guys,
i started my tests with Borbely super buffer topology. But i modified the OLG because i thing that 40dB of feedback is too high and drop to 15dB. I checked hte FFT with my cd player with cd test at 1Khz to 0dB because i don't have a good sine wave generator and he has 0.0068% THD. I have cheap PS with regulator 7812 and 7912. The output for my all test is 2V rms. Any comments is welcome. Thank You! Maxpou

maxpou · 21st April 2008, 05:01 PM

FFT test.

maxpou · 21st April 2008, 05:03 PM

Now I changed the drain resistor to 560ohms.

maxpou · 21st April 2008, 05:06 PM

I changed the drain resistor for current mirror and i have a better result.

maxpou · 21st April 2008, 05:08 PM

sorry the schematic for current mirror.

maxpou · 21st April 2008, 05:15 PM

And if I change the jfet VAS for a cascode bjt and i changed R9, R10 of 270ohms to 75 ohms.

maxpou · 21st April 2008, 05:16 PM

my last test is cascoded current mirror.

maxpou · 21st April 2008, 05:17 PM

and the FFT

peufeu · 21st April 2008, 06:23 PM

Quote:

i thing that 40dB of feedback is too high

Why ?

maxpou · 21st April 2008, 08:40 PM

Hi Peufeu,
because in my experience, i have a better sound when i reduce OLG in my cd player, line stage, power amp and i listen a old audioresearch 100.2 ( 6 dB of feedback) in my friend home and i loved the sound. I listened the Ayre audio system too and my jaw fell to the ground. So because I find it difficult to build a pre-amp without feedback I want to reduce as much as possible. thank you! Maxpou

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21st April 2008, 08:40 PM	#10
maxpou diyAudio Member Join Date: Apr 2006 Location: Québec	Hi Peufeu, because in my experience, i have a better sound when i reduce OLG in my cd player, line stage, power amp and i listen a old audioresearch 100.2 ( 6 dB of feedback) in my friend home and i loved the sound. I listened the Ayre audio system too and my jaw fell to the ground. So because I find it difficult to build a pre-amp without feedback I want to reduce as much as possible. thank you! Maxpou