• 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.

12v B+ Tube buffer 12AX7


2010-08-29 1:12 pm
will this circuit provide A little gain but add tube like sound to my amplifier


  • Low B+ Tube Buffer.jpg
    Low B+ Tube Buffer.jpg
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will this circuit provide A little gain but add tube like sound to my amplifier

If you use an ECC81 or ECC82 then yes, it will amplify a bit (not much). It will distort a lot, but I guess that's what you want for a very 'tubey sound'. The ECC83/12AX7 may not work at all at such low voltages, however. (It might work- worth a try)
There seems to be a rash at present of people wanting to add distortion to their sound by running valves from 12V supplies. Does this always happen at this time of year?

If you want to add some "tubey sound" to a line source you can do it with a couple of resistors and a silicon diode, no need for a power supply. Put a resistor in series with the signal, say 4K7. Then from the output put a 10K plus a diode in series to ground. This will gently clip signals above about 600mV, and add some distortion to slightly smaller signals. Low level signals will be unaffected. Roughly the same response as a badly biassed valve, but much cheaper.
R2 shoulda been split and bootstrapped off the output of that op-amp.
Plate voltage already so low, grid leak will either pull the bias negative,
and/or rectify like a diode... plate current will get stOOpid small.

6DJ8 and 6922 heaters are hard wired in series for 6V3. The middle tap
given up to a shield between the triodes. No 12V6 option except drop
the excess voltage somewhere else...

Oh, nevermind... I see now the LM317 0A3 current supply.
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