[ARC5] 12A6 Audio Output Levels

[Kenneth G. Gordon]

Bill Pileggi wrote:

> In my ARC-5/SCR-274, etc. receivers the 12A6 is biased with the original
> resistors. I simply hook up a 600 ohm to 8 ohm (or equivalent) transformer to
> the existing 600 ohm audio output. The speaker output is quite loud. Not enought
> to shake the walls, but fine for casual listening. The 12A6's all test Very Good
> on the tube tester, RF Gain on MAX, B+ = 50-75vdc. Bill KA3AIS

I use one of those small, cheap Radio Shack 1000 ohms center-tapped 
to 8 ohm transistor transformers. From the looks of them, I would say 
that they probably aren't good for more than about 1 watt.

I use 1/2 the center-tapped side (500 ohms) as the input, and connect a 
speaker to the 8 ohm side.

My ARC-5s provide plenty of speaker volume in a normal room, unless 
one of the kids is playing the piano or violin.

If I need more volume, I use a pair of those amplified computer 
speakers. Then I can even drown out the piano.

I run my ARC-5s at no more than 175 to 180 VDC at most, depending 
on the capacitors.

And I don't dink with the biasing of anything in it. Works fine.

Ken Gordon W7EKB