Puresound P10 RIAA

[merlin el mago]

Only needs to solder the output caps & the suggested RIAA mods, also I need to drill the RIAA chassis & connecte all

 

[RCruz]

Ok

So my first sugestion is:

R17 = 38K9 // 478K = 35973 r

C9//C8 = 2.7nF // 106pF // 180pF = 2.986pF (and because of miller // 38pF = 3.024nF)

C7 = 6nF // 2.2nF // 640pF = 8.84nF

 

[merlin el mago]

SY could be B+ 150V for both tubes? because I want to use only one Salas HV shunt reg for both tubes & the designer Mr. Gay (PureSound) told me that I can do it without change any component.

 

[SY]

Your distortion will certainly be higher with a lower B+. Overload margins will be lower. Why not use 230V as a compromise between the two voltages called out on the schematic? Or bite the bullet and build two regulators?

 

[merlin el mago]

I don't want to use anode resistors for each tube: I prefer connect direct the Salas HV reg also I have only one Bartolucci transformer 150VAC secondary & one 10H Bartolucci choke (both are expensive: best quality), the RIAA is for a friend who has spent a lot of money & I don't want to ask more money.

What about if I reduce E88CC to 80V with a anode resistor? could you tell me the value if OK?

 

[SY]

If you connect the plates directly to the regulator, your playback will be quite silent.

A 240V isolation transformer more than big enough to run that preamp should cost less than 20 euro.

 

[merlin el mago]

That's a good idea, arrives later for my friend but for me can be a cheap alternative for my 26 preamp, could you suggest some 240V isolation transformer with high quality to buy in Europe?

 

[merlin el mago]

Pics

Only for fun a couple of pics

 

[RCruz]

Nice case... what is your source ?

Are you going to put the TX inside also ?

 

[merlin el mago]

Source to buy the case is:

modushop.biz

No, the tx & choke in a separate box (Puresound P10)

 

[RCruz]

Are you going to use this riaa with a step up TX in the input ?

 

[merlin el mago]

No, my friend uses Piccolo pre-pre MC Jim Hagerman ensambled by myself full upgraded BG, Shinkoh, PRP, Dynamicaps, etc. sounds really good.

Last pic one is main tx & the other is 10H choke psu

 

[RCruz]

Can you post the schematic of the Piccolo ?

I would like to study it also

 

[merlin el mago]

You can download PDF, link: http://www.hagtech.com/pdf/piccolo.pdf

 

[Joachim Gerhard]

This is not really a low noise design. The 22 Ohm resistors plus R2 and two Fet`s are in series. S/N against 5mV is -85dB but against 0.5mV what is more common in MC carts it is only -65dB. That is 15dB less then it could be. It should have tremendoes speed though.

 

[RCruz]

I wanted to know what was going to be before the puresound first stage because in this one there is no input cap and I was wondering about first stage tube grid leakeage.

Now I see the cart will be connected to a jfet input... It is safe.

 

[merlin el mago]

Just received Guy answer:

"The internal resistance of an 83 is about 70Kohm which is in parallel with the 120K load resistor giving 44Kohm. This is added to the 330K and the result works in parallel with the 1M0 to ground giving 272K which is the net value used in the Eq calculation. The Miller capacitance of the 88 is 40pF which must be added to the 2n2 and 560pF to get the eq calculation spot on.

rgs

Guy"

 

[merlin el mago]

This is not really a low noise design. The 22 Ohm resistors plus R2 and two Fet`s are in series. S/N against 5mV is -85dB but against 0.5mV what is more common in MC carts it is only -65dB. That is 15dB less then it could be. It should have tremendoes speed though.

It's only a MC pre-pre max 26dBs so needs a MM, I mesured Idss NJFET & all are aprox 14mA, if you know any way to upgrade without changing the SMD NJFETS please be so kind to let me know. Yes have speed, body, resolution, etc that will be perfect combo with a MM tube far better than a step-up tx.

 

[Joachim Gerhard]

Without radically changing the topology i see no possibility to improve SN. When it works for you, fine though.

 

[RCruz]

Just received Guy answer:

"The internal resistance of an 83 is about 70Kohm which is in parallel with the 120K load resistor giving 44Kohm. This is added to the 330K and the result works in parallel with the 1M0 to ground giving 272K which is the net value used in the Eq calculation. The Miller capacitance of the 88 is 40pF which must be added to the 2n2 and 560pF to get the eq calculation spot on.

rgs

Guy"

Now this completely changes my previsions.

I will need some time to digest and soon will post my best bet.