Simplistic NJFET RIAA

[MASantos]

I have a goldring 1012x mm cart which has an output of 6.5mv at 5seconds which is really high. Which of the low gain versions would be more appropriate? Given the really high output of my cartridge would the 38db schematic be appropriate or could I lower the gain event further?

At the moment I use the integrated phono stage of my rega brio r amp, but I rarely pass the 10 o'clock in the volume as the overall gain is too high.

 

[merlin el mago]

36db-version 7,0-8,0 mA IDSS Post 417 MM 3.5mV

 

[MASantos]

I've seen that one, however the 38 db one seems to have better CSS for the input transistors.

 

[merlin el mago]

Whats your Idss SK170BL stash?

 

[MASantos]

I don't have one. I would try to get some around here if possible already matched, if not I'll buy a few dozens for matching.

 

[merlin el mago]

You can ask a batch of 100 to spencer here in the swap meet:

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

 

[Salas]

I have a goldring 1012x mm cart which has an output of 6.5mv at 5seconds which is really high. Which of the low gain versions would be more appropriate? Given the really high output of my cartridge would the 38db schematic be appropriate or could I lower the gain event further?

At the moment I use the integrated phono stage of my rega brio r amp, but I rarely pass the 10 o'clock in the volume as the overall gain is too high.

That's a rather special category, make this one that will fit better. Your Brio R has 40dB, thus 6dB less will fare better on the volume knob.

 

[MASantos]

That's a rather special category, make this one that will fit better. Your Brio R has 40dB, thus 6dB less will fare better on the volume knob.

Thanks!

My tt is a rega p5 with the rb700 arm so I feel the phono stage is the bottleneck ATM.

Already sent a PM to spencer about the jfets!

 

[Salas]

Alright, let us know if it makes a better combo because I got one too. I may make it a same stage.

 

[AndrewT]

What's the specified output of the 1012?

 

[MASantos]

6.5mv

 

[RCruz]

Hi Salas

Just powered first stage of the "experiment" and got 8v on BC560c emitter... is this ok ?

I am measuring 7.5v at the base so the ccs is working fine.

 

[Salas]

Orientation OK? Emitter towards the Jfets drains underneath? Is there big voltage drop on the resistor between power rail and those drains? That means there is bias to them.

 

[Salas]

P.S. We look for emitter voltage to ground, not Vbe.

 

[RCruz]

Emitter to gnd is now 8.1V... collector to gnd is 4.05v

24.5v Vdrop on the 1k5 resistor (R13)

PS: On the first post I just correctd, I did not have the Gates of the input k170 grounded..... sorry

 

[Salas]

So its ok, no panic for now. Boom and smoke comes a bit later.

 

[Siberia]

Alright, let us know if it makes a better combo because I got one too. I may make it a same stage.

Nick, how do you find the sound of the cartridge? I own the same.

 

[Salas]

Good for Rock, dynamic. It can be tizzy if not a bit nose up on good arm.

 

[RCruz]

Panic ? why should I panic ?

I guess for 7,5V on the base, 8.1v on the emitter is allright no ?

 

[AndrewT]

0.6Vbe, if the polarity is correct, sounds just right.