Not done w/ one, already planning the next - XFMR recommend?

[mlp-mx6]

Hey folks,

I have a ODS-style chassis for my next build. I'm planning a 6V6-based ODS this time around. So I wanted to ask for transformer recommendations.

I was thinking about the Hammond 372JX for power. Voltage is in the right range, has a bias tap, upright mount like I want. Better alternatives?

What about the output? I'd prefer 4/8/16 switchable. Whaddaya like?

Oh, and another question. This chassis is a powder-coated aluminum chassis (1/8" thick!). I'm assuming I will need to scrape away the coating where I put my ground lug(s) to get a good ground connection. Correct?

One last thing. It seems to me that having the tubes right-side up (like a Marshall head) is better for the tubes and the rest of the amp. How bizarre would it be to have an ODS-style chassis "reversed" (left to right) and have the tubes right-side up? (Yeah, this is really an opinion question. I know ODSs and Fenders have run the other way just fine for years...)

Thanks much!
Michael

[llemtt]

Hi Michael

How many 6V6 are you planning 2 or 4? 372JX is huge, you can go with something smaller even with four 6V6, you can try 372FX or the newer 372HX.

Voltage is ok because 372JX-HX-FX gives you 425-430 at idle.

Switching 4/8/16 requires a multi-pole rotary switch, Hammonds don't have 3 separate taps!

Yes you have to scrap coating!! but you should also ground your chassis at 2 places only, one connecting the power cord ground and the other connecting the "signal ground" or "circuit ground" at the greatest distance from it, the nearer to the input jack the better. (all your jacks have to be isolated from chassis too)

Teo

[pedro]

will be good to hear about your 6V6 build

I am about to convert my "plexi 6V6" ( see Mark Huss's site ) to a dumble 6v6 over the next few weeks, so it will be great to compare notes and impressions of the amps.

good luck - will keep you posted on mine.

Rgds
Pete

[mlp-mx6]

Thanks for the replies.

I'm planning a 2-6V6 output section. ODS meets Deluxe/Princeton. All the tone, less volume! (well, a LITTLE less...)

I know the 372JX is huge - but I like huge! I figure overkill on the power xfmr is a good thing - besides, I'll have the heater current to run EL34s if I like. (ODS meets Trainwreck Express!) I may scale back - but the cool thing about the 300-series is the bias tap, which the 200-series lack.

I know about how Hammond outputs are wired - CEDist/AES sells a switch pre-wired to switch Hammond output xfmrs for 4/8/16/20. I wondered if anyone knew of another good choice for 2 6V6s that will go 4/8/16. (Nothing wrong w/ Hammonds - I've used several before, but not for an ODS-style amp. I've always been more than satisfied with Hammond outputs.)

Any opinions on the tube-side-up question?

[ElectronAvalanche]

Hi there,

great project!

I built a 2*EL84 version once and really liked the sound (I built it into a 19" enclosure).

It had a really nice sound, but beware that you will not be able to get any Clean sound out of it in a band situation. An amp like this is very nice for bedroom levels but not for a band situation.

The 372JX is a nice transformer. You might want to use a hefty output transformer as well, otherwise the OT will be saturated easily when blasting away, which IMHO takes away from the Dumble sound.

With the Dumble amps me thinks that the Power section was meant to stay clean pretty long. The sound is made in the preamp, the power amp merely gives the power to be heard.

Cheers,

Dominik

[tictac]

I used a PT from Allen Amps (the one he's got for his 6v6 type kits) It has extra amperage capacity on thte 6.3v heater tap so yo can plug in 6L6's without stressing the PT.

The OT is from Obsolete Electrnics. It's their 2 x EL84 tranny which works great for 6V6's as well. I bought a Delft handwound version but I'm sure the stock one sound great too. They really over build thier stuff.

This amp has the best overdrive I've ever heard, creamy vocal-like Dumbleque and Boogiesque tones, and a sweet clean tone as well.

I think the OT has alot to do with the great tone.

TT

[mlp-mx6]

Anyone else have a 2-6V6 output xfmr recommendation? Again, I'd prefer to be able to switch output impedance 4/8/16.

I looked on the OEI website but did not see the 2-EL84 output xfmr.

[glasman]

Anyone else have a 2-6V6 output xfmr recommendation? Again, I'd prefer to be able to switch output impedance 4/8/16.

I looked on the OEI website but did not see the 2-EL84 output xfmr.

You have a couple of options. You could get the Mercury ToneClone OT FBFD-OM for the Blackface Reverb with 4, 8 & 16 ohm taps for $125.00.

Or you could have Heyboer or Pacific wind you a transformer to you specs (dont even bother with Mercury for custom trannies as they are rediculous in their pricing structure). Heyboer would probably wind a tranny to your specs for less than Mercury's Tone Clone tranny.

Heyboer built several custom transformers for me in the past and they were all well built and met all of the requested specifications. They will be seeing a lot more business from me in the near future!

I would recommend 6600 p/p for the 6V6's.

One last option, if you are looking for 8000 p/p (as what the 2xEL84 tranny mentioned would provide) you could use the universal Fender transformer for the Super Reverb. These normally measure about 3800 p/p with 2, 4 and 8 ohm taps. Using 4 ohm on the 2 ohm , 8 ohm on the 4 ohm and 16 ohm on the 8 ohm tap you would reflect about 7600 p/p. This should work, they are cheap and BEEFY.

Gary

PS> Disclaimer - I am in no way affilated with Heyboer Transformers. The opinions expressed are based on products that I have bought and used.

[mlp-mx6]

Gary,

That's a terrific idea! Especially since I might like to switch between 6V6 and EL34/6L6! 4/8/16 if 6V6, 2/4/8 for the others. Beefy is GOOD! (Beef - it's what's for dinner)

Thanks, bro!
Michael

[glasman]

Gary,

That's a terrific idea! Especially since I might like to switch between 6V6 and EL34/6L6! 4/8/16 if 6V6, 2/4/8 for the others. Beefy is GOOD! (Beef - it's what's for dinner)

Thanks, bro!
Michael

Hi Michael, just make sure that the power supply is up to the job. With 34's or 6L6's it is going to try and produce upwards of 50 watts on the rated tap values.

Gary

[mlp-mx6]

Hammond 372JX (300-0-300 250ma) is the currently slated power xfmr, so no worries! Thanks.

[glasman]

Hammond 372JX (300-0-300 250ma) is the currently slated power xfmr, so no worries! Thanks.

That transformer I was talking about is the 18343 available at Antique or New Sensor as well as most places that sell Fender replacement iron.

Gary

[mlp-mx6]

Right. In fact, 18343 is the same output xfmr (from David Allen) that I am using on my current ODS build. Beefy indeed! (It is also the stock xfmr on my '83 Concert.)

[glasman]

Right. In fact, 18343 is the same output xfmr (from David Allen) that I am using on my current ODS build. Beefy indeed! (It is also the stock xfmr on my '83 Concert.)

I actually have this same transformer in my Superchief Amp (Express inspired) and it works very well with both the EL34's and 6V6's.

Gary

[jelle]

Hi Gary,

nice hearing from you again.

These transformers are for 2x 6V6, right?

What do you guys recommend for 4x 6V6 power and OT?

Thanks,

Jelle
The Netherlands