Simplistic NJFET RIAA

[massimo]

Another older design by "La Maison de L'Audiophile" was using half 2SK240 (Idss 2mA), R in-to-gnd 100 ohm, 2 kohm on D, S connected to gnd, 1uF o/p cap (no R to gnd) and +12 VDC (Lead Acid Battery bypassed with 10.000uF elcap).
For 2SK240 with higher Idss, they suggested to add 47 ohm from S to gnd

 

[merlin el mago]

Gain x10, how many dB 20?

 

[massimo]

 

[cjcc67]

Thank you that is exactly what i image. very simple. One problem though cannot find the fets in stock. Does anyone have some clues?

 

[merlin el mago]

Thank you that is exactly what i image. very simple. One problem though cannot find the fets in stock. Does anyone have some clues?

Ask Spencer here: http://www.diyaudio.com/forums/swap-meet/131284-toshiba-2sk170bl-sales.html

 

[cjcc67]

excellent you guys are great. While i order the FET i might get some extra to try the Salas RIAA and the analog addicts. Do they nedd to be matched? If so what parameters are matched?

 

[Salas]

IDSS should be matched. Each circuit published in this thread has a note for what IDSS is designed for.

 

[cjcc67]

thanks Salas is that what the 8.5 - 8.7 refers to on the cct diagram of the low MC scheamtic? 8.5 to 8.7 ma Idss?

 

[Salas]

Yes. What is your now MM phono stage you want the MC pre pre for?

 

[merlin el mago]

Gain x10, how many dB 20?

@Salas
How many dBs?

 

[Salas]

Gain x10, how many dB 20?

@Salas
How many dBs?

20dB=x10 times. 30dB=x31.6 times. 40dB=x100 times. 50dB=x316 times. 60dB=x1000 times.

 

[merlin el mago]

20dB=x10 times. 30dB=x31.6 times. 40dB=x100 times. 50dB=x316 times. 60dB=x1000 times.

I will print, another lesson than now I know, thank you Salas.

If need 26dBs can I add other SK170BL in parallel?

 

[Salas]

No, gain isn't fixed like that. Its not power.

 

[merlin el mago]

It's possible do something similar for 26dBs?

 

[Salas]

Yes, you just use 33R for R1, 1k6 for R2, and 12V for V1 battery or whatever. That will give 26dB=x20 times.

 

[merlin el mago]

 

[RCruz]

20dB=x10 times. 30dB=x31.6 times. 40dB=x100 times. 50dB=x316 times. 60dB=x1000 times.

Is there a formulae for that calc ?

 

[Salas]

Gain=20log(Vout/Vin) dB

 

[RCruz]

So is this correct ?

48dB=x251times
57dB=x709times
63dB=x1406times

 

[Salas]

48dB=251, 57dB=708, 63dB=1412 by windows calculator. Yes, correct.