Ideas for a simple 6080/6AS7 Push-Pull amplifier

[Shoog]

That should be about right if you are using 8ohm speakers with the 100V 100mA operating point. The primary needs to be 110V+110V center tapped, with the center tap to B+

Shoog

[Brit01]

That should be about right if you are using 8ohm speakers with the 100V 100mA operating point. The primary needs to be 110V+110V center tapped, with the center tap to B+

Thxs Shoog.

The secondary doesn't need to be center tapped no?
And the larger the iron the better no?
I've got a heater power tranny with a 6.3 and 12.6 secondary and it's a big piece of iron.

I've seen 6.3v trannies 4 times smaller than mine.

Any recommendation on the gauge of the copper also?

[Jeb-D.]

And the larger the iron the better no?

Id suspect the closest to ideal size would be a transformer with a VA rating approximately 3 times the amplifiers power output.

[E.T.]

[My experience was that 6080's work extremely well at 100V and 100mA, so a split rail design with about +/-130V would do the trick. If you are interested i could lash up a schematic of my ideas. The only thing I have not decided on is what driver valve would fit the bill. It would need to work comfortably at about 100V on the plate and sinking about 1-2mA of current and a gain of about 20.

Hi, someone here said that 6as7's get nonlinear below 150V. Is the 6080 a slightly different design? I'm not as interested in perfect specs as in good tube sound, but I'm not sure how the change in linearity might affect that. Also, I'll be using 6as7/6080/ecc80 in van Waarde's SE headphone amp, which doesn't appear to work the power tube very hard. I would rather run it at a Vp of 100V -- that would make the p/s easier and allow audio-grade caps. Any comments would be very much appreciated.

[Brit01]

Some schematics would be great using the 2 x 6080.

I have as drivers, 5687, 6N1P, 6N2P, 6CQ7, 6SN7, 6N6P and some others I can't remember right now.

Id suspect the closest to ideal size would be a transformer with a VA rating approximately 3 times the amplifiers power output.

So if we're looking at a 10watt output VA would be around 14.2 at 100V, 0.143 amps?
14 x 3 = 42 or 0.429 amps.

[Shoog]

I have used a 200VA transformer on a 7watt design with no audible penalty. I would say anything between 50VA and 200VA will do nicely. Remember that core size defines the lowest frequency obtainable, and these transformers are designed for 50hz which means that they will tend to poop out if not oversized.
Using 200VA transformers has allowed me to obtain response down to 10hz.

Shoog

[Jeb-D.]

Using 200VA transformers has allowed me to obtain response down to 10hz.

How is the top-end?

[Shoog]

No issues, good out to 50khz before it starts to drop off. Ringing can be an issue, due to the high interwinding capacitance, and this manifests as a peak at about 50khz and a drop off at low frequencies. Switching primary polarity seems to help.

Shoog

[kenpeter]

I figure 2.5mA at worst, 52K will drop 130 Volts to zilch...
Maximum power transfer would briefly occour some temp
at which grid matches 52K, 0.16W burned at the grid...

There is no capacitor here to store up a "sudden flash" of
higher grid current? What are we worried of here, unseen
traces of gas in the cold tube?

If you really can't sleep knowing 130V might be on G1,
going nowhere, doing nothing, then Zeniers might be
the answer? Just as one would protect the gate of a
MOSFET. Though it seems needless for this circuit.

[kenpeter]

Scuze bad maths... My error on the highside.
Forgettin' half voltage AND half current dropped.
Max power transfer peak = 0.08125W burned at G1.

Assuming driver triodes are ice cold, and the power
triodes at exactly wrong temp for maximum abuse...