transformer primary impedance: Princeton reverb/Deluxe reverb

[pula58]

Both the Deluxe Reverb and Princeton reverb use two 6V6 tubes. Then why does the DR OT have a 6.6k primary while a PR OT has a primary impedance of 8k? Is the 6V6 output impedance in the Deluxe rever lower becaue the outout tubes are biased differently (and thus have a lower output impedance see at the plate??)? Or, does the apparent impedance mismatch in the DR help to give it its tone or something?

Thanks!

P.

[RedMan]

That's a good question. Tubes do have different impedances at different operating points. That's one reason why an adjustable plate supply in a power section is really not a good idea. A DR does run at a somewhat higher plate voltage than a PR but that would make it a higher impedance source if the bias was set optimally. In reality there's quite a bit more slop allowed in impedance matching than that 20% or so difference there. Speaker nominal impedances can vary more than that. It is more than likely one of the 1000's of things that makes the amp sound the way it does.

[teleamp]

The 8K OT's were a carry over from the tweed deluxes to the Princeton. But the sonic differences of the PR/DR have more to do with the style of phase inverter that they used.

[pula58]

So,
If I want to put an upgraded OT into my princeton a Deluve Reverb OT wouldn't be quite right would it, because it is 6600 ohms. I should get a 8Kohm primary output transformer, right?


Also, does this mean that an 8 ohm load is actually not the perfect (in terms of power transfer to the speaker) load for a deluxe reverb amplifier? Should it use 6.6 ohms (if there were such a thing)??