What build for these transformers?

[Jay12399]

I bought the transformers and choke from a widow who's husband built amps. They are custom made mercury magnetics. I can't determine what amp he was going to build. He had them mounted in a new head and chassis that looks like a fender twin reverb but the xmers don't seem to be for a twin. What do you think he was going to build? The choke is a 3 Henry and the OT is a 4k. The PT has a 50v bias tap. Here are specs from mercury magnetics. TIA.

[sluckey]

Looks like a small 25 to 30W Fender 6L6 amp, Bandmaster, Tremolux, Vibrolux, etc.

[Phil_S]

The diagrams indicate 30W. The likely sets an upper limit. There is nothing that says you can't go lower.

300-0-300 will get you B+ around 270VDC with a full wave bridge choke input power supply. I'd guess the choke was not meant for a choke input power supply. If you use it like that, it is important to confirm that its mA rating is adequate to carry the load of the whole amp.

Choke input will open up the possibility of using EL84's or 6V6's if you want to go in that direction. With a quad of either, you can use the OT into a 2Ω or 4Ω load. With a pair of output tubes making 15-18W, you are doubling the primary to 8KΩ, so that OT as 4Ω and 8Ω if you did that. This is another world of possibilities: Princeton, AC15, 18W, etc. The point is that you've got lots of choices.

If you need more info about the iron, contact MM. They should have a record of what they made and it seems to me they'd share that with you.

[Jay12399]

Thanks for the info. Keep it coming lol. I would like to use them for a build. When I saw pic of what she was selling I thought the xmers were for a twin reverb. I have some knowledge of amplifiers. So any help on what would be a great build for these please let me know. Thanks

[Jay12399]

Would a bandmaster build be possible or 300v not enough? I think the choke on a bandmaster is 4H but they aren't expensive or is 3H acceptable?

[Phil_S]

Here's the AB763 Bandmaster. http://www.thevintagesound.com/ffg/sche ... _schem.gif It shows 320-0-320. My guess is that it would come out OK and I'd just use the 3H choke. If you fiddle with (reduce) the 4700Ω dropping resistor between take off points C and D in the power supply, you should be able to get the preamp to operate near the stated voltages. This is a very nice project platform. Good luck with it!

[sluckey]

Would a bandmaster build be possible or 300v not enough? I think the choke on a bandmaster is 4H but they aren't expensive or is 3H acceptable?

Sure. That 300-0-300v PT will make 424VDC unloaded.

[didit]

Hello -

Suggest that with all those noval holes suggests following path for a low-power "twin", so aa964 Vibrolux Reverb loose basis to start. Could even forego "normal" channel and put something more interesting into it such as Dumble OD section. To finish off, add matching 2x10" speaker cabinet.

Best .. Ian

[Jay12399]

Ian, that does sound like very cool build. Will look into that.
Thanks for everyone's info and suggestions.

[Smitty]

I would build that exactly like a Twin Reverb and then put four 6V6s in it. About 400V on the plates. PPP 6V6s @ 400V are very happy at 4K plate load.

[Masco]

Would it be too much for MM to put current ratings of the windings and possibly primary Z?

[pdf64]

Perhaps they are reluctant because they’re targeting non techs, who probably wouldn’t understand the concepts of eg how the regulation characteristic affects the windings voltage, how the HT winding’s AC current will be higher than the HT DC etc. Rather they might be put off / confused.
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