Only needs to solder the output caps & the suggested RIAA mods, also I need to drill the RIAA chassis & connecte all
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
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
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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.
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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?
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?
What about if I reduce E88CC to 80V with a anode resistor? could you tell me the value if OK?
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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.
A 240V isolation transformer more than big enough to run that preamp should cost less than 20 euro.
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?
Attachments
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
Last pic one is main tx & the other is 10H choke psu
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.
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.
Now I see the cart will be connected to a jfet input... It is safe.
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"
"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"
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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.🙂
Without radically changing the topology i see no possibility to improve SN. When it works for you, fine though.
Now this completely changes my previsions.
I will need some time to digest and soon will post my best bet.
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