help with impedance missmatch

[hebaton]

I have an amp with a 4K primary OT running 6L6s. There is a 4 ohm and an 8 ohm tap.

If I run 6v6s ( JJs ) in the amp, which way do I need to missnatch the load ?

Thanks

[WiderGates]

Hello,
8 ohm speaker to 4 ohm tap or
16 ohm speaker to 8 ohm tap.

[cdemike]

Need more information to say for certain. Is the amp fixed or cathode biased? What's your B+? Is it operating in class AB1? Based on a review of the 6L6 datasheet I'd assume you're running with fixed bias in class AB1 with B+ around 350V based on the primary impedance being 4k. If that were true, then under similar conditions Ra-a for 6V6 would be roughly 2x higher, meaning you'd want to double the speaker size compared to what you'd use for 6L6's (e.g., use an 8 ohm load using the 4 ohm tap and 16 ohm load when using the 8 ohm tap). But for your OT's sake, I'd want to know more about the operating conditions.

[hebaton]

Hello,
8 ohm speaker to 4 ohm tap or
16 ohm speaker to 8 ohm tap.

Thank you sir !

[R.G.]

Transformers don't have impedances - transformers have ratios.

Dieter is right - put a higher impedance on as the secondary load, and a higher impedance appears on the primary.

There's another layer of this line of thinking, but the double-the-load idea will get you going.