Rocket PT 280/250 switch?

[George61]

I am bulding my Rocket and I have a Heyboer HTS-9144 power transformer, which I believe is the correct transformer. It has 250V and 280V taps. I believe that the 'official' wiring is to use the 250VAC taps and a 50 ohm cathode bias resistor. It would not be that hard to use a triple pole, double throw switch to swith the secondary voltage and switch in a different cathode bias resistor (68 ohm with 280VAC tap?). I am fairly new to vacuum tube amps and I am not sure running the amp with 280VAC tranformer taps would change the sound.

How would the higher voltage affect the sound of the amp? Would being able to switch the voltage be a worthwhile mod?

Thanks in advance to anyone who replies.

Solder on,
George

[Roe]

50ohms can work with plate voltages as high as 320v (ac30 specs). however, its hard on the tubes and sometimes you'll get redplating. 50ohm and 315v sound optimal to my ears

[overtone]

Well, I tried it as temporary set up while building a couple of Rockets and did not really notice enough difference on the bench to bother making it permanent.

But, the bench test may not be the best. Using it in anger, in a band situation, would have been a more realistic test, so ymmv!

Somehow adding switches to a Rocket seems to me to run against the purity of the amp. But maybe that is just me, I don't like switches, pedals or even tone stacks!

Enjoy your build and the end result, tony

[Gibsonman63]

My two cents: If you are planning on using a VVR, you might as well use the higher voltage, and just dial it down to taste. Otherwise try each and see which you like best. I don't think there will be enough difference to justify adding another switch.

[George61]

Thanks for the advice. I decided to use the 250 VAC taps because I believe that's how the original amps were built, although, I couldn'd bring myself to cut the 280 VAC leads short.

So far I think I have done a half decent job on the wiring. Wiring the EL84 heaters with 18 AWG 600V wire was not as much fun as I thought it would be but I think I should be OK with what I've got.