6080 audio amp?
On Feb 19, 12:22 am, Patrick Turner wrote:
"Bob H." wrote:
A lot of vintage 4k to 5k pp outputs have 16 and even 32 ohm taps.
Putting 8 ohms on the 16 or 32 ohm taps should get you into a better
loading range for 6080's. A lot of PP 7591 output transformers have
pretty low refected impedance, I believe.
Bob H.
This is a solution which could be tried.
However, there is a downside.
A typical old OPT with ratio of 5k:15 will have 10% winding losses, ie
looking into the primary, the total winding resistance will be 500 ohms
of the primary dcr wire resistance and the reflected secondary winding
resistance.
So when you have 8 ohms connected to a 16 ohm tap,
or to a 16 ohm winding which was most common in 1955,
then the primary load is 2k5, but the winding resistance remains at 500
ohms
so losses rise to 20%.
When 4 ohms is connected to the 16 ohm winding, losses = 40%.
The main problem with the 6080/6AS7 tube used for an amp is that once it
is built,
there isn't any other tube that will suit the PS and OPT easily.
With an amp designed for EL34, one can usually fiddle with the
circuit to make it suit 6L6, KT66, KT88, KT90, 6V6, 6CM5, 6DQ6 etc, etc.
Patrick Turner
I'm used to more like 200 to 300 ohm resistance in 7591 primary
windings, and a Heathkit mono 7591 amp on my bench right now shows 220
ohms plate to plate on the output tranny. I'm sure the reflected load
is around 4 to 5k, so the 16 ohm tap would yield around 2 to 2.5 k
impendance.
Bob H.
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