Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: J3ona1 on November 17, 2022, 04:48:04 pm

Title: Mod the wave - reverb unit conversion questions
Post by: J3ona1 on November 17, 2022, 04:48:04 pm

Greetings all,
Long time listener...first time poster.

Ive purchased a MOD the wave reverb kit for repair on reverb.com, and I would like the reverb unit to have more drip than stock. I'm thinking of using the parts to create a reverb +tremolo outboard unit or a 6G15 build.

1. Why don't they use a 12AT7 in the stock circuit to drive the reverb tank. Wouldn't the increased current get me closer to drip in the stock circuit?
2. The Hammond 290WX tranny seems to output 1.05A for the filament circuit which JUST meets the current filament circuit requirements for a 6v6 and 2 12ax7's. Is that enough of a margin?
3. The tube complement(3 12ax7's and a 12AT7)/power tranny seems to fit for doing a Princeton like reverb/tremolo circuit. Would it be TONS more work to convert this to a 6G15? If its too much, how would I be able to maximize the drip of this unit with the current tube complement? Line level output is not important to me.

Title: Re: Mod the wave - reverb unit conversion questions
Post by: sluckey on November 17, 2022, 05:16:45 pm

Only the designer knows why he didn't use a 12AT7 driver. If you want to use a 12AT7 just plug it in. Maybe change the cathode resistor to 2.2K.

The filament current requirement for those four tubes is 1.2A. I would not be afraid to use that Hammond 290WX.

This circuit is close to the 6G15 circuit, maybe even better. I don't think it's worthwhile to try to convert to a 6G15. Schematic wise, it's not much work to convert. Layout wise, it could be a bitch.

I think this unit will have plenty of "drip".

Title: Re: Mod the wave - reverb unit conversion questions
Post by: J3ona1 on November 17, 2022, 05:22:53 pm

thanks a million sluckey!!!

Title: Re: Mod the wave - reverb unit conversion questions
Post by: HotBluePlates on November 18, 2022, 06:59:51 am

If the 12AT7 in V2 isn't drippy enough, then try the following:

    - Change the Dwell pot to a 1MΩ Audio.
    - Move the end of the 0.01µF cap feeding the Dwell pot to V1 Pin 1 (other side of the same 100kΩ resistor).

Those 2 things cripple the signal level sent to the Reverb Driver tube.

Title: Re: Mod the wave - reverb unit conversion questions
Post by: J3ona1 on November 18, 2022, 10:16:01 pm

More impedance to ground for the signal going into the grid of V1b, and less resistance for the signal coming from the plate V1a. Makes sense.Thanks HotBluePlates!!!