Simplistic NJFET RIAA - Page 367

merlin el mago · 29th April 2010, 09:39 PM

Quote:

Originally Posted by massimo

Not very good then......

1-0 (and a clear offside)

P.S. It's only a game and not serious staff like audio

Congratulations massimo, your Inter plays the final Europe Champions League, Forza Inter!!!!!

Now plays like your's Milito

merlin el mago · 30th April 2010, 11:45 AM

Arrived the Vishay TX 2575 nude 0.01% & the BG 470uF/50V to upgrade Salas Phono RIAA, some pics for fun:

merlin el mago · 30th April 2010, 07:09 PM

I suppose that is with mine special R6 50 ohms trimmer instead the fixed resistor 27 ohms, I imagine that increasing/decreasing the voltage between Drain Q5 to Gnd can get the same gain in both channels?

Salas · 30th April 2010, 09:11 PM

First stage source resistor trimming is most influential for gain. Second stage for THD.

merlin el mago · 30th April 2010, 09:20 PM

Drain Q2 to Gnd?

Salas · 30th April 2010, 10:44 PM

That is 2nd stage. You got it OK. If you want to play with gain you vary R2 slightly. That one drops more on R1 and ups gain or vice versa. Because the signal level is slight there, THD remains about the same. I don't recommend playing with 2nd stage for gain because it influences the total gain less drastically but changes THD by moving the bias point of the Q5 buffer. You may try optimize the distortion profile to your ears there, 10-11V Q2D-GND is where it measures best in general. Whatever you may like, stays matched between channels on second stage. First stage is much more suitable to balance out any total gain differences between channels. Takes output measurement capability when steady under mV signal is present on input somehow.

RCruz · 1st May 2010, 11:22 AM

Hi Salas

Would you explain how to set the bias on the output buffer, depending on different psu voltages ?

Salas · 1st May 2010, 12:12 PM

Its already set by design. But jfet differences always hover around optimum if you got FFT to see THD or listen critically. The 2nd stage's drain voltage sets it. If you use a trimmer instead of a source resistance in second stage and play, don't exceed the buffer Jfet's Idss judging by the drop on its source resistor/value.

merlin el mago · 4th May 2010, 09:13 PM

Vishay "nude" TX 2575 0.01% subjectively speaking are the best.

RCruz · 4th May 2010, 09:34 PM

Where did you use those ?

30th April 2010, 11:45 AM	#3662
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Arrived the Vishay TX 2575 nude 0.01% & the BG 470uF/50V Arrived the Vishay TX 2575 nude 0.01% & the BG 470uF/50V to upgrade Salas Phono RIAA, some pics for fun:

30th April 2010, 07:09 PM	#3663
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Adjusting gain between channels I suppose that is with mine special R6 50 ohms trimmer instead the fixed resistor 27 ohms, I imagine that increasing/decreasing the voltage between Drain Q5 to Gnd can get the same gain in both channels?

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30th April 2010, 09:11 PM	#3664
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	First stage source resistor trimming is most influential for gain. Second stage for THD.

30th April 2010, 09:20 PM	#3665
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Drain Q2 to Gnd?

30th April 2010, 10:44 PM	#3666
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	That is 2nd stage. You got it OK. If you want to play with gain you vary R2 slightly. That one drops more on R1 and ups gain or vice versa. Because the signal level is slight there, THD remains about the same. I don't recommend playing with 2nd stage for gain because it influences the total gain less drastically but changes THD by moving the bias point of the Q5 buffer. You may try optimize the distortion profile to your ears there, 10-11V Q2D-GND is where it measures best in general. Whatever you may like, stays matched between channels on second stage. First stage is much more suitable to balance out any total gain differences between channels. Takes output measurement capability when steady under mV signal is present on input somehow.

1st May 2010, 11:22 AM	#3667
RCruz diyAudio Member Join Date: Sep 2006 Location: Saxon Blog Entries: 1	Hi Salas Would you explain how to set the bias on the output buffer, depending on different psu voltages ?

1st May 2010, 12:12 PM	#3668
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Its already set by design. But jfet differences always hover around optimum if you got FFT to see THD or listen critically. The 2nd stage's drain voltage sets it. If you use a trimmer instead of a source resistance in second stage and play, don't exceed the buffer Jfet's Idss judging by the drop on its source resistor/value.

4th May 2010, 09:13 PM	#3669
merlin el mago diyAudio Member Join Date: Sep 2009 Location: Catalonia new Europe state	Vishay "nude" TX 2575 0.01% subjectively speaking are the best.

4th May 2010, 09:34 PM	#3670
RCruz diyAudio Member Join Date: Sep 2006 Location: Saxon Blog Entries: 1	Where did you use those ?