Simplistic NJFET RIAA

[Joshua_G]

I have been experimenting with decoupling caps in my 48dB riaa and I am amazed by the results.... these caps influence tone (I knew that) but they also influence noise...

After replacing the 330u decoupling caps by 680u BG N, the noise went down to the point where I can no longer hear it..... Is it possible or is there any other reason ?

Do you use also Sala's shunt regulator?

 

[RCruz]

Do you use also Sala's shunt regulator?

Hi Joshua

Of course I do.....Salas shunt and Salas riaa go together.... I believe they were designed to work as a complete system.

 

[RCruz]

Ricardo you you have two possibilities depending what are you looking for:

1-Less noise can reached paralleling two BG N "L-Cancelling Pairs" so + one cap to - other cap, look for at the Michael Percy pdf. web

2-N series are very very low noise so very very transparents, if you like more body I will try BG standard 470uF 160V you will be near near heaven

Let me know?

Hi Merlin

I tryed SilmicII 470u and got those nice bass / upper bass but lacking snap in the highs.

Than I used 330u BG std as well as 470u BG std.... very similar results.... maybe 330 is a little faster but noise is equal to the Silmic.

When I swaped for the 680u BGN I got much lower noise.... incredible.... it is so silent I can turn the volume full up and almost hear nothing..... So I am wondering if another nonpolar might do the same.... Nichicon nonpolar are quite inexpensive.... do you know if those are ok ?

 

[RCruz]

Balanced ready to adjust, 1st attempt only with two old regs. V1.0 RS

An externally hosted image should be here but it was not working when we last tested it.

What are those silmics for ?

 

[Salas]

I used Pana FM & Muse KZ & isn't the same.

Weren't they both adequate? Was it noisier with one over another?

 

[merlin el mago]

Hi Merlin

I tryed SilmicII 470u and got those nice bass / upper bass but lacking snap in the highs.

Than I used 330u BG std as well as 470u BG std.... very similar results.... maybe 330 is a little faster but noise is equal to the Silmic.

When I swaped for the 680u BGN I got much lower noise.... incredible.... it is so silent I can turn the volume full up and almost hear nothing..... So I am wondering if another nonpolar might do the same.... Nichicon nonpolar are quite inexpensive.... do you know if those are ok ?

I see you are looking for less noise so only I can suggest do it "L-Cancelling Pairs" with BG N series, you need only 4 caps more to try...

 

[merlin el mago]

Weren't they both adequate? Was it noisier with one over another?

My opinion is subjective but surely are less noise the BG.

 

[merlin el mago]

What are those silmics for ?

I use caps that I have on hand so Nichicon KZ & Elna Silmic II for 1st aproach & set up, once all is going on well I will change for BG.

 

[RCruz]

In your schematic, those silmics serve what purpose ?

 

[Thomo]

Ricardo, have you tried bypassing a Silmic II with a small Polyprop? I like Silmic + Vishay MKP1837 in some places.

One channel of my RIAA finished by the way guys, just haven't had time to test and build the other channel yet.

Cheers, Lee.

 

[RCruz]

Hi Lee

Glad to know you are here again.

I did not bypass the Silmic but I will surely try it soon.

 

[merlin el mago]

In your schematic, those silmics serve what purpose ?

Like you loved red caps

 

[merlin el mago]

BALANCED RIAA MESUREMENTS

I am happy, seems that the balanced RIAA is going on well at first attempt, the set up measurements are in attached Word archive.

 

[Salas]

You better remind your circuit to people too so to can see where your bias measurements apply.

 

[merlin el mago]

I am happy, seems that the balanced RIAA is going on well at first attempt, the set up measurements are in attached Word archive.

 

[Salas]

Are your Q5s stronger than 8.5mA IDSS? They run 9.2-10mA current. Or Q2 less? You must bring Q2 to GND at 8V. Now its over biasing the output.

 

[merlin el mago]

http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-489.html#post2302721

http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-489.html#post2302743

http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-489.html#post2302893

8.51, 8.52, 8.53 & 8.54 for 2nd stage for buffer max. 8.49

Thanks

 

[Salas]

Since the Jfets are measured OK for IDSS as you say, I can't see another way than to arrange proper R6 changes for all channels to match at 8V Q2 drain to earth, so to work right.

 

[merlin el mago]

Thanks, I will do & post new measurements.

 

[merlin el mago]

Hi Lee

Glad to know you are here again.

I did not bypass the Silmic but I will surely try it soon.

I will try with BG standard better than Silmic II.