Dumble clone transformers

[Deafcat]

I need a good suggestion for a transformer to replace the one missing from a Dumble Overdrive Special "clone" that I inherited. Does anyone have any idea what transformer these things used? I hope to find one here in the US but no one seems willing to help when I email the manufacturers of similar amps. They act like it's a huge secret. HELP!!!

[Dave Curtis, dB AudioTech]

Power or output tranny? What are the amp specs? There are a few different ODS models...

[mac1amps]

FWIW, I recall a client of mine bringing me a Dumble that had a very "Fenderesque" design (2x6L6's in a Class AB configuration), and the transformers used in this amp (power AND output) were actual Fender issue transformers, whereas the name Fender had been stamped on the casing. I'm certain that a properly matched Hammond (or certainly a Mercury Mag.) would be "up to par" for one of Mr. Dumble's units.

[Deafcat]

Dumble transformer

Ok. I have a suitable output transformer from a Fender Super. What I need is a power transformer. The amp is actually a Ceriatone Overtone HRM. I think it needs a 6-0 tap.

[Dave Curtis, dB AudioTech]

Okay, the HRM uses 4 6L6s, right? The Super uses 2, IIRC. Your OP tranny is not exactly suitable (at all). You'd be looking for trannies for a Twin Reverb or Showman; one of the 100 watt amps. I've heard that Dumble used Fender trannies, and the circuit is fairly Fender-based.

[Deafcat]

Hrm

The HRM is 2 6L6 40 odd watts. Yes it is fender based.

[Dave Curtis, dB AudioTech]

The HRM is 2 6L6 40 odd watts.

They have a 100 watt version, too. I wasn't sure which one you had.

The Super OPT you have should work OK. You'll need to find a PT that fits with the tube compliment you have.

[Deafcat]

The HRM runs 2 6l6 output tubes and three 12AX7s. There is a pair of relay coils in it that operate the overdrive and preamp boost switching. This means there must be a tap to power the switching as well a the 6.3v heater tap. It looks to me (judging from the schematic) that it is fender based.

Here are some notes on a Dumble clone from Schematics heaven. This schem looks similar to the HRM to me but it says the one in schematic heaven ran 4EL34 tubes.

Here's a description of the power supply:
690 vac from transformer
I think it is full wave rectified with 103Z disc capacitors across the 4 diodes(also oneacross the standby switch).
1st stage: series 200ufd@300v each paralleled with a 470k res - 465volts
2nd stage: series choke
3rd stage: series 47mfd@350v each paralleled with a 470k - 458 volts
4th stage: series wirewound 2980ohm resistor
5th stage: series 47ufd@250v with 470k - 433 volts
6th stage: series 12k resistor carbon film?
7th stage: series 47ufd@250v with 470k - 361 volts
8th stage: series 10k resistor metal film
9th stage: series 47ufd@250v with 470k - 323 volts

[Deafcat]

Some more details

Here are a couple links for the 97 Dumble listed in Schematics Heaven.

Block diagram showing the relays:
http://www.schematicheaven.com/dumbleamps/dblock.pdf

Full schematic (the section of notes I posted are from a "clone" someone built that he states runs "4 EL34" tubes. This only shows 2. It also shows no power for any switching.)
http://www.schematicheaven.com/dumbl...7fullschem.pdf

[Dave Curtis, dB AudioTech]

Here's your layout: http://www.ceriatone.com/images/layo...ut/HRM-50W.jpg

The 2nd schem you posted was drawn by Steve Ahola; I thought I'd seen it somewhere...

[Deafcat]

Thanks

Thanks I printed it last night. Looks good. I think I'm just going to get the transformer set listed on Ceriatone's site. Shipping is outrageous but I haven't found anything in the US nor have I found anyone with any suggestions. The Mercury Magnetics stuff costs more for the output transformer alone than the set of them from Ceriatone.

[martin manning]

Did you check with Brown Note? They sell a 2x 6L6 Dumblesque amp and kits (their "D'Lite 44"), and they sell parts. No transformers listed on their site right now, but you can always ask...

MPM

[Dave Curtis, dB AudioTech]

Thanks I printed it last night. Looks good. I think I'm just going to get the transformer set listed on Ceriatone's site. Shipping is outrageous but I haven't found anything in the US nor have I found anyone with any suggestions. The Mercury Magnetics stuff costs more for the output transformer alone than the set of them from Ceriatone.

You could use the Super OPT that you have, but IIRC, it's 4 ohm only. You could get a Pro Sonic OPT with 4-8-16, which is what I put in my '76 Pro Reverb. Call these guys and find out about a tranny set for a Pro Sonic:

Parts is Parts

Or any other Fender dealer/service center.

[Deafcat]

Power tranny info

Thanks for the help guys!

I did learn that a couple guys who have tried building Dumble clones (whether this is true or not), have had noise problems using the heater tap from a Fender Super tranny to power the switching relay in the D circuit. I can see where this may be a problem, but if your amp is well thought out and your build and grounding scheme is good it shouldn't be a problem, right? Since the one I have is already put together I can't be positive, but the builder was meticulous. The leads aer all perfecly laid out and "bent" at angles instead of just laying "naturally" in the chassis. Maybe there's a reason for this. Maybe he was just anal. Haha. Either way it looks beautiful.

[tedmich]

FYI Edcor has some excellent transformers for the money, much better quality and value than typical guitar amp steel IME.

They have 114 PTs available and their EB site makes it a little hard to find the right one... I have an excel file available

For the Ceriatone HRM as an example, the XPWR029 is an 11lb monster for ~$84 (700V(350-0-350)@400mA, 50V@500mA & 6.3V(3.15-0-3.15)@7.5A)

Their OT are excellent values too.