Help with power transformer ratings

[Philr228]

Greetings all,

I was hoping for some help with power transformer info, regarding a Dumble overdrive special clone I want to build. I'm intending basing it on either the Ceriatone Overtone Special or #124 but only 50 watts.

Initially I'm thinking a 350-0-350 transformer with 175mA current rating, 5A heater supply, 50V bias tap, with a separate 6V relay transformer, using a 4.2K output transformer rated for 50 watts.

Any comments with this so far?

Ceriatone use larger 150/220k grid stoppers that #124 (100k) I'm assuming because of the different supply voltages 345Vac as opposed to 320Vac, would I be correct?

Anyone have any experience of these?

I look forward to your replies

Cheers

Phil

[Wilder Amplification]

Greetings all,

I was hoping for some help with power transformer info, regarding a Dumble overdrive special clone I want to build. I'm intending basing it on either the Ceriatone Overtone Special or #124 but only 50 watts.

Initially I'm thinking a 350-0-350 transformer with 175mA current rating, 5A heater supply, 50V bias tap, with a separate 6V relay transformer, using a 4.2K output transformer rated for 50 watts.

Any comments with this so far?

Ceriatone use larger 150/220k grid stoppers that #124 (100k) I'm assuming because of the different supply voltages 345Vac as opposed to 320Vac, would I be correct?

Anyone have any experience of these?

I look forward to your replies

Cheers

Phil

Regarding the 150K/220K, are you referring to the "grid load" resistors?

700VAC CT @ 175mA and a 4.2K Zp-p OT load should suffice.

[Philr228]

Hi Jon,

Thanks for your reply. Yes, I was refering to the grid load resistors, not grid stoppers, I hurriedly wrote that out. I guess once I've assembly it I can always change these and try the two different set-ups or mix-and-match!

Cheers

Phil

[Philr228]

Jon,

Actually I mean't the Plate Load resistors dropping the B+ voltage to the pre-amp valves (UK)!

That's if you're still looking at this thread!

Phil

[Wilder Amplification]

Can you post up a layout or a schematic of this circuit?

[MWJB]

"Ceriatone use larger 150/220k grid stoppers that #124 (100k) I'm assuming because of the different supply voltages 345Vac as opposed to 320Vac, would I be correct? - Actually I mean't the Plate Load resistors dropping the B+ voltage to the pre-amp valves (UK)!" No, it's got nothing to do with higher B+, changing the plate load resistor changes the voicing of the amp slightly (darker, grindier, gainier). If you wanted to adjust the preamp plate voltage more transparently you would alter the value of the preamp dropping resistor in the power supply, that feeds the plate resistors.

[Philr228]

Thanks MWJB/ Jon,

I new it it altered the gain structure, but not sure of the effect, I could try it as the Ceriatone values or put 100k in and see what difference I get/like. If I change to 100k having built to Ceriatones values for everything else, should I consider changing the values on the cathodes, for both resistor and capacitor too to be consistant?

Schematics as follows:

124_schematic_182.pdf



The beauty of turret is I can do this relatively easily!

Cheers

Phil

[MWJB]

Changing the cathode resistors will change the voicing further. The 2 amps are voiced a little differently, If you go with the Ceriatone layout, I'd go with the values it states for plates & cathodes, likewise for the #124.

Though, 1.5K to 2.2K cathodes can be mixed and matched with 100K-220K plate resistors depending on what you prefer the sound of.

[Philr228]

Unfortunately I've not heard either of these two amp schematics as such to know whether I prefer one to the other, though I have heard a Ceriatone clip that gave a good mix of the sounds that I'm after so it seems sensible to start there and see what I get. #124 is of course a 100 watt amp.

Nothing is irreversable I guess!!

Phil