• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Grounded-Grid MC Head Amp for 2x PC900 and Lyra Delos

by the URL
Teflon coupling capacitors & More No-Gain—No-Pain Tube Buffer Circuits
there are to find several variations of such an amplifier stage. Which version is to prefer for a low impedance MC cartridge and 2x PC900/4AH5 ?

I would prefer the topologies from the last four figures (Constant Draw-Current GND-Grid Amplifier with AC+DC Feedback and HF Compensation).

Are there well proven circuits with values (voltage gain 10 times until 20 times) ??
Last edited:
The whole proven circuit/values thing is not exactly what Broskie is describing.

To develop such a circuit, I would start with a high voltage supply composed of batteries, as well as a 6V battery to suffice for heating your tubes. Set up a simple voltage amp with any tubes you think you might want to use, then feed them into your phonostage. Listen to and measure the noise, then move onto the next one.

I would have my doubts about a 12AX7 performing adequately in this circuit without quite a bit of feedback.