Problem with led bias on phono preamp...

[mooreamps]

Hi! This is the current scehmatic ... current values.
Please do not consider yesterday's data, slightly different, especially in the B+.
Currently (V2) the voltage value set by the 1n4148 diodes is slightly different from the value obtained with the 2K resistor. I will update it with right diodes.

https://ibb.co/9VWJwz9


Basically it's an "almost" copy of Audioresearch ...

https://ibb.co/QXxrVDc

change R4 and R8 to 100K.

-g

 

[TasoTaso]

100k are values ​​I see in guitar amp schematic!
in the schemes of hifi devices ..... of prestige..no less than 270k.
why your idea? What is the good?

.. are you sure you mean r4 and r8? I think you meant .. r4 (330k) and r5 (330k).

Thanks

 

[leadbelly]

Yet another circle. If you change ANYTHING on V1 you change the RIAA EQ.

EDIT: the more I look at it the more I think it is a waste of time to refine this phonostage. 3 triodes but still uses feedback type EQ, the poorest kind?

 

[mooreamps]

100k are values ​​I see in guitar amp schematic!
in the schemes of hifi devices ..... of prestige..no less than 270k.
why your idea? What is the good?

.. are you sure you mean r4 and r8? I think you meant .. r4 (330k) and r5 (330k).

Thanks

1. looks like clipping to me. changing the plate resistors lowers the gain.
2. has nothing to do with the eq..... just give it a go, and let us know...

 

[TasoTaso]

A stupid question. I have a nagaoka 0s-200 MM cartridge which comes out declared with 4mV. But are they to be understood peak-to-peak or rms or how?
Thanks, it helps me to understand the input levels ...

 

[mooreamps]

Found this on obscure internet forum, for moving magnet phono carriages.
"Shure specs output as millivolts RMS, with sinusoidal groove modulation at 1000 Hz having a PEAK velocity of 5 cm/sec. Other manufacturers probably follow Shure's example."

 

[TasoTaso]

Thanks, so it's RMS ... probably. Ok.