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Old 24th August 2007, 06:14 PM   #1
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Default 6n7/2a3

Could anyone tell me if I could use a parallel 6N7 to drive a single-ended 2A3 and if so what component values would I need?
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Old 24th August 2007, 07:48 PM   #2
KaDe is offline KaDe  Germany
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Yes, this combination also works PP:

Here is an old RCA 2A3 amp:
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Old 25th August 2007, 10:10 AM   #3
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I tried this setup with 100k plate resistor and 1k8 cathode R as per rc coupled chart but it didn't work the 100k was dropping too much voltage.I ended up with just 80v across the valve> Any suggestions?
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Old 25th August 2007, 12:09 PM   #4
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OK,Is this worth trying:
Parallel 6N7G
B+ 290v
Plate resistor 10k
Cathode R 1k Bypassed with 10uF
Cap coupled to 2A3 with 0.22 PIO
470k gridleak resistors
Any suggestions/comments welcome.......
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Old 25th August 2007, 12:59 PM   #5
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Quote:
Originally posted by kianbach
...Plate resistor 10k
...Any suggestions/comments welcome.......
Take a little more for the plate resistor ... 47 kOhm (rp of the 6N7 in parallel is 11 kOhm).

Regards Andreas
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Old 25th August 2007, 01:05 PM   #6
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Quote:
Originally posted by AndreasS


Take a little more for the plate resistor ... 47 kOhm (rp of the 6N7 in parallel is 11 kOhm).

Regards Andreas

Won't this drop the B+ a bit much though?
What about the cathode resistors are they ok?
As my previous post I used 100k plate R and this dropped too much of the B+ voltage.
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Old 25th August 2007, 01:34 PM   #7
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hey-Hey!!!,
If the plate load is dropping too much voltage, run less current through it. Increase the cathode resistor, and the plate voltage comes up, yes?
cheers,
Douglas
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Old 25th August 2007, 01:42 PM   #8
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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?
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Old 25th August 2007, 09:25 PM   #9
KaDe is offline KaDe  Germany
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To give it a trial I would just keep the component values in the RCA schematic
and use one 6n7 for both channels with single ended 2A3`s
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Old 25th August 2007, 10:06 PM   #10
316a is offline 316a  England
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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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