• 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.

E235L tubes

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> Does any know the E235L tube. Look like a mini EL34?

No, and it doesn't really seem to be a cut-down EL34.

It is scaled for lower Mu, and generally low-voltage low-impedance operation.

The Betriebswerte on the bottom of page 2 shows a perfectly good 30 watt condition. It is very Class B: for hi-fi use you might want to reduce the G1 bias to get the idle current up around 50mA-60mA per tube. Or maybe a 250 ohm common cathode resistor. The 250V Vp and 170Vg2 is a little awkward considering the wide range of G2 current: a regulator may be wise. Or let the G2 live at 250V and increase G1 bias to keep the current down: this gives lower gain but more tolerance for odd-impedance loads like speakers.

If you can't find a 3K transformer, use a 6K and re-label the speaker taps.