• 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.

6n7/2a3

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Yes, this combination also works PP:

Here is an old RCA 2A3 amp:
 

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Well,according to my data book I should be getting -5v on the grid @3mA so I was thinking of running it with an 820 or 1k cathode R BUT with a 47k plate resistor this would drop over 200v from my B+ which is 290v .I was looking at dropping more in the region of 40 to 140V so as to run the valve at 150 - 250 v.My calculations bring a cathode R of 1666 ohms so I suppose a 1k5 would be ok yes?This gives about 3.3 mA.
This would mean a plate R to drop 140v of 42.5k so I suppose a pair of 82k in parallel connected to a 1k5 in series be ok.Any comments? Or am I flogging a dead horse and would be better off using a different valve?
 
IMO 6N7 is not a good driver for 2A3 , in fact finding a driver which can provide 90-100V swing from 300V is going to be difficult unless transformer coupling is used . Anyway , here's my suggestion using a 6SN7

cheers

316a
 

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Hi!

The 6N7 works nicely as a driver for tubes like 45 or 2A3. However if fed from the same B+ voltage, the available swing with RC coupling will be very limited. RC coupled it would need more like 450V B+. In a 45 or 2A3 amp with common B+ between output stage and driver LC or transformercoupling is needed for the 6N7. Then it works really nice.

Plates and grids need to be tied together. Another nice touch: a 6J5 will drop in without any changes, even with the same socket wiring. This will prvide less gain and a lower impedance drive in the same environment.

Best regards

Thomas
 
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