Simplistic NJFET RIAA

[RCruz]

Find it with a trimmer first because it will deviate from theory with available Vds, warm up, your measuring accuracy, things like that.

You are right

Anyway, if I start with only a 500 ohm trimmer can I expect to be able to get 35Vout ?

 

[Salas]

Yes somewhere around mid point if with 30K ref resistor.

 

[RCruz]

Thank you Salas

 

[Salas]

Hi Ricardo,

here are the values I used :
R4=6,790K
C1=46,94nF
C2=15,080nF
C3=47nF
R14=46,93K
R1=180R

I remembered now I had a couple of 47K Z-Foil 0.1%. So I dug them up. No, they are 47K. Its the UT-61E that shows both 46.93K. The LCR meter when in range 2 & 1kHz (calibrated short and open on its Kelvin leads just before), cycles 46.99K and 47.00K every half a second. My 50000 count DMM shows 46.995K when delta zeroed. Check your R4 again too. Caps at 1kHz they must be measured, cycle ranges manually. R.C. he is gonna pull the sims out instantly, I see it coming.

 

[vgeorge]

I did check with my LCR meter and got the same values. Only cross checked with the UT-61E. May I will make a fresh calibration with my LCR and check again.

 

[Salas]

Range 2, 1kHz remember. Gave me surely smack close to 47.00K on both EQU ser par. Those resistors are laser trimmed to 0.1% 0.2ppm grade if you got them from England. They can not really be 46.93K. They can be 47K +/-47 Ohm max. Its the DMM which is 0.5% plus 10 counts at that range (only 4 digits utilized).

 

[vgeorge]

I am sure checked them at 1kHz. Got them from here : Vishay VAR-Series "naked" Z201 Z-FOIL RESISTOR
Still more than 1% now that I think about that.
Will check again.

 

[Salas]

Mine are are 0.1% grade. Still 1% is +/-470 Ohm max error.

 

[merlin el mago]

Mine are are 0.1% grade. Still 1% is +/-470 Ohm max error.

Mine 0,01%

 

[Salas]

They can be produced from 1% down to 0.01%. You are intrepid fox as always. Watched all the details before ordering and bought pricier on the know.

 

[merlin el mago]

Still better ±0.005%, I ordered mine to Michael Percy Audio, when received the resistors marked with TI 0,01%
TI mark best resistors as VAR not as TX2575

 

[Salas]

These are not simply resistors at 0.005% 0.2ppm, they are also calibration instruments.

 

[merlin el mago]

Yes.

 

[vgeorge]

The bug got to me and checked.
With hold2 at the LCR and got 46,98K on both of them.
Hope looks better now.

 

[Salas]

You see, better than in spec. Do the 6.8K and the caps over to make sure.

 

[merlin el mago]

These are not simply resistors at 0.005% 0.2ppm, they are also calibration instruments.

Mine are VAR 0,01% 0,05ppm

 

[vgeorge]

I would also like to mention that big gains in sound quality, sometimes bigger than fancy components on the RIAA, can be gained by clean records!
I can't imagine how I could live so long without a record cleaning machine!

 

[RCruz]

Hehe.... of course I clean my records....

 

[RCruz]

See the small bump at 1hz... it can be cured by lowering the 6790r to 6775 (with some megas in //)

It must sound spectacular as is anyway

 

[vgeorge]

Thanks again Ricardo.
Will check actual values again, but not before Monday and correct if necessary.