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I recently received an Image 34i integrated amplifier (a great sounding amp!)powered with EL-34 tubes.
After a week, I asked a friend to install RFT EL-34 tubes and to set the bias in accordance with the manual (recommended setting is 0.35 - 0.5V).
Today I decided to replace the RFT tubes with used Mullard EL-34 tubes (twin halo getters, xf2 coded), but two of these tubes show low voltage (0.26V and 0.16V, though I turn the adjustment screw clockwise as far as it would go), while other two tubes are stronger.
Does it mean that two of the four Mullard tubes are "low"?
When I tried them with the Cary SLI-80 integrated amp (where the bias is set in milliamps (0.65mA in this particular case), not V), there was no such problem (MAs are quite different).
I will appreciate any comments.
The same happens with "matched" tubes, see thread below...
Antonio Melo Ribeiro
The low readings for the Mullards prolly DOES mean that the tubes are weaker than the RFT's.
But what does low voltage of the two tubes mean? Does it mean that they are weak (much weaker than the other two)?
MA and V in this case are basically the same. In either case, you're measuring voltage across a small cathode resistor. .35-.5 volts over a 10 ohm cathode resistor means 35-50 ma (.35ma is almost 0). Likely, your other amp has a greater range of negative voltage in its adjustment. If you can find a schematic for your amplifier, you can ammend its range for your particular tubes.
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