• 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.

Modification of 300B SE Amplifier

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Best solution:
remove both srpp (I'm not a big fan), use the 6SN7 ground cathode single triode with 400V plate voltage, 22kOhm plate resistor and the 1,5k cathode resistor bypassed with a film cap of 8 to 10uF.
This has much lower gain (14x) than the product of both srpp, can take high signal at input and can provide all swing needed to drive the 300B, and will sound much better than the origínal project.

If you can make it simpler why make it worst?

Thanks and really a good idea. I will do the trial tonight.
Just to clarifiy your direction is make both stages with a single triode. The input valve with 15k plate resistor / 1.5k cathode (8uF bypass); the driver stage with 22k plate resistor / 1.5k cathode (8uF bypass). Is that correct?

Thanks again!
 
I did an initial trail tonight.

Instead of remove all the SRPP but I keep it at the driver stage as of. I just changed the input stage to one triode with

- 15k ohm Rplate (310Vdc) and keep the 1.5K ohm at cathode (11Vdc), for some reason it does not work at all. No signal go to the driver stage.

- I have then changed the Rplate to 74K ohm (154Vdc) and keep the 1.5K ohm cathode (5.4Vdc).. the same problem of no signal at all.

I just not sure what is the problem or may be the connection error... I have to check it again tomorrow.
 
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