Simplistic NJFET RIAA

[RCruz]

Hi Salas

On my 48dB (DL160) build I reduced the 15.72nF cap to 15,33nF as you suggested and I got much better spatiality retaining very detailed bass. Also gained in high freq detail and overall "bite".

I was using SSG-1 15.72nF and now I am using 15n Polystyrene*& Tin Foil 5% (RT) // 330p Smica.... Wonderfull stuff.... I kept it running for 4 hours and it is opening nicely now.

It is drier than with the SSG-1 SM but I like it.

Now I would like your oppinion about the Silver Mica SGM Capacitor from URSS... I have some 7170pF 350V 0.3%... I could use two plus some Cornell Dub.. small SM values to get to 15,33nF

 

[Salas]

It is 15.33n in the PDF for HIMC/MM, yes. USSR SGM are mushier but silkier compared to polystyrene. Its a system tuning thing to play with I guess. All those caps are good quality non the less.

 

[RCruz]

By mushier you mean (thick, soft, and pulpy) right ?

 

[Salas]

Softer, more sentimental side of real. Like from apple to banana.

 

[RCruz]

Perfect definition

I guess I will try another option than.... I have some SSG-1 ~0,012uF 350V 0,5% I will trim with some other smaller SM first. I like the polystyrene sound of the RT but I seem to miss something in the highs.... DIY is a never ending story

 

[DARIO1997]

IRFP9140 or IRFP9140N

Hi Salas,
I have, for shunt regulator, IRFP9140N and no IRFP9140.
Is good for shunt IRFP9140N?
Regards.

 

[Salas]

It has more Crss but it will work. Maybe you got IRFP9240? Better than 9140N.

 

[DARIO1997]

IRFP9140 or IRFP9140N

Hi Salas,
I not have IRFP9240; so if use IRFP9140N, what's problem will the shunt regulator?
Regards

 

[Salas]

No practical problem. Just a bit less bandwidth.

 

[DARIO1997]

IRFP9140 or IRFP9140N

No have problem also RIAA Phono?

 

[Salas]

No have problem also RIAA Phono?

What do you mean? The phono has no Mosfets, the PSU for the phono has. There no problem again, 9140N will work.

 

[DARIO1997]

Yes the phono has no Mosfets, i mean if the Shunt Regulator, with IRFP9140N, can give problems to the phono.

 

[Salas]

No problema.

 

[smpkje]

58.5db vs 63db

 

[smpkje]

left and right channels are ready

 

[Salas]

What kind of input signal level?

 

[smpkje]

Input signal from generator through inverses riaa. Input level is about 2.5mV and ouput level is 3.6V

 

[Salas]

It looks like +6dB rather than +4.5dB. Strong fets in the pre-pre? Just a bit more gain in the next stage can easily multiply to +1.5dB off target OTOH. Is it the same difference @ 0.5mV?

 

[smpkje]

Input jfets are matched at 6.9 mA.
The input level can not measure exactly because on oscilloscope I see just a cloudy signal. Maybe is 3mV not 2.5mV.

I have 15nf capacitor on riaa. I have to add something when listening

 

[Salas]

You will see with your cart anyway. You were after level and it looks very healthy for that. That signal from the generator is strong for such gain. Nice that it does not clip. Its 15.33nF in the 43dB. Not the same as in the 56dB. Notice the left corner of the square wave.

P.S. Average DMM with added capacitance meter function tend to show++ from real. Add xxx pF to ear tuning if you don't have access to a calibrated expensive LCR.