12ax7 series is this correct??

[prorms]

12ax7 series is this correct??
just wondering if this tube circuit is right

[DougL]

Looking at it quickly, the B+ voltage should be 100V or more, not 10V

R1= R5 so the bias voltage is equal accross both.

Otherwise looks good.

Doug

[prorms]

thxs why when change the volts form 10 to 100 get the same out
amount of ac out?//

should pins 6 7 8 be on top or bottom???

[DigitalJunkie]

I'm not sure if the 12AX7 is terribly linear at 10V. I would also suggest
a higher plate voltage.

It doesn't matter if section one (pins 1,2,3) or section two (pins 6,7,8) are on top. Just be sure to observe the cathode-to-heater ratings.

[kevinkr]

Originally posted by DigitalJunkie
I'm not sure if the 12AX7 is terribly linear at 10V. I would also suggest
a higher plate voltage.

It doesn't matter if section one (pins 1,2,3) or section two (pins 6,7,8) are on top. Just be sure to observe the cathode-to-heater ratings.

The 12AX7A is not linear at 10V at all, in fact the minimum circuit supply voltage for reasonably linear operation with a 12AX7A based mu follower like this is around 200V. The models don't always provide an accurate portrayal of operation at very low voltages.

A 6GM8 operating at around 24V - 36V would work much better if low voltage operation is required, however gain will be only about 14 (23dB) as opposed to nearly 100 (40dB) with the 12AX7A best case.

One other thing to be aware of is the need not to exceed the filament to cathode insulation rating in the upper triode with higher voltage operation than about 200V.. (Use filament supplies biased to a value about midway between the voltages of the lower and upper cathodes - do not exceed the maximum voltage differential to either!)