OT and tube type

[greiswig]

Hi,

I have an OT with a 3.5k primary, which I typically use with a pair of 6L6's or KT66s. Is there a reason that this could not also be used with 6V6's if the bias change allows? Can someone talk a little more about the interaction between output tubes and OT primary impedance?

Thanks!

[Firestorm]

The published plate-to-plate impedance of a push-pull tube pair is typically the "optimal" point on the tube's transfer curve. It varies with plate voltage and class of operation. As you move away from that sweet spot, you'll usually reduce both bandwidth and output power.
There's pretty much no operating condition where 6V6s will be happy at 3,500 ohms.
But the primary impedance of a transformer isn't a discrete number -- it's a function of the secondary impedance. Assuming your transformer specs are 3,500 ohms primary into an 8-ohm load, just up the load to 16 ohms and your primary impedance will become 7,000 ohms and the 6V6s will be happy campers.

[jjman]

Or hook an 8ohm speaker/cab to the 4 ohm tap.