Transformer specs

[Normster]

Why is it that hardly anyone discusses transformer specs when talking about Dumble amps? As a diversion, I built a Trainwreck Express a few weeks ago and transformer specs are very critical according to the Twreck crowd. (I didn't question them, just ordered trannys with the correct specs.)

Anyway, when it comes to the ODS, I haven't heard much discussion other than Bassman/Super OPT recommendations. Does anyone have tranny specs for grail Dumbles? Does it matter as much as with the 'Wreck?

[glasman]

Looking at many of the pictures I have come across it would seem there is quite a cross section to "grail" transformers for Dr. D's amps.

The 80's style amps (a lot of them) used Fender iron. Many I have seen used a twin reverb output and power tranny. But on the other hand, many later D's used Marshall 100 watt replacement transformers.

I used an NOS (66) twin reverb tranny in my combo and it does sound nice. I had used marshall style in the past and they sound good as well.

Gary

[keithrick]

Well I listened to and considered both of your advice and got the Bassman iron because I have a AB165 laying around. But....the Marshall PT would definatly been easier to use. The Bassman PT eats up alot of chassis room, now I have to get creative to fit in my switching boards!

[Robert]

Great question Normster. I completed my build with a 100 watt Marshall Plexi output transformer and Fender 100 watt PT from Heyboer. I followed the Hybrid A, non HRM OD and the 97 PS. It was Dumbley sounding, but rather aggresively so with mids being a bit in your face and not a very smooth transition from string to string. Any note on the G string jumped out even with controlled playing. At higher volume in OD mode it tended to lose some of the Dumble characteristics and sounded more Marshally. Overall, a very nice sound but just not quite the right Dumble tone to my ears. I recently dropped in a cloned BF Fender Twin ~100 watt OT (Heyboer) without changing anything else and the difference was wonderful. Keep in mind my reference tone would be that of Robben Ford or Larry Carlton. It really smoothed out my eq issues and gave me the tone and behavior I wanted. Unfortunately, I am not able to record yet but it would make for a great comparison set of clips. I was really surprised it needed very little tweaking to sound good. In summary, both OT's are excellent, but different. For the RF, LC tone definitely use the Fender iron. To create your own version of Dumble, the Marshall iron would be an interesting path to pursue.

[jazzyjoepass]

I try to give this discussion a shot.

It seems to me that the o/p trannys give the most character more than the power tranny - marshall tranny with EL34s give you the most marshally sound and fender output iron with 6L6s give a typical fender tone.

The power trannys are there to provide the power to the tubes. Larger irons have better load regulation - will give a stiffer power supply (lesser sag) and hold up at larger volumes.

Filament supplies are better on larger irons especially the marshall iron - could be the reason why Dr D used them.

I use a Twin Reverb power on my bangkok chassis couple with a bassman o/p iron. I can run my heaters for 3 pre + 2 power tubes and 2 x 5V relays on the filaments with proper voltage regulators.

[ayan]

I try to give this discussion a shot.

Filament supplies are better on larger irons especially the marshall iron - could be the reason why Dr D used them.

From what I've seen, he never used Marshall style PTs, while he did use Marshall style OTs. AFAIK, with the exception of some Music Man PTs used in some amps in the 80s (which used no choke), Dumble used Fender style laydown transformers. For the 90s amps, he used the Magic Parts Fender Two PT and and the Plexi 100 OT. The choke was Fender style as well in these amps.

Gil

[Normster]

It looks like there's a pretty broad range of acceptable output transformers. I wish I had the resources to try out a few different brands, styles, primary impedences, etc. I suspect that a good part of what I'm looking for in "my" tone is in the tranny.

[jazzyjoepass]

Come to think of it, I could be wrong on D using Marshall PTs. Those I've seen could have been Musicman PTs, then.

Remember reading somewhere sometime ago that D got hold of a shipment of Musicman PT and he used them for a while.

[Bob-I]

I've tried Fender replacement iron and Marshall replacement. The amp I built using Marshall replacement was for a guy that wanted a Marshall flavor to the tone, and it does have a distinct Marshall tone.

I've had really good success with Mojotone Bassman replacements. I had an amp with a Hoffman Deluxe replacement using 6V6's and it just wasn't quite cutting it. I swapped to a Mojotone Bassman and it's great now, still using the 6V6's.

[Normster]

Bob, Mojotone is Heyboer, right? I've been using Hammonds but maybe I should give them a try.

[Bob-I]

Bob, Mojotone is Heyboer, right? I've been using Hammonds but maybe I should give them a try.

I'm not sure. I've heard other folks say that but there's nothing on the xformer. No doubt in my mind though that these are better than Hammonds.

[glasman]

Bob, Mojotone is Heyboer, right? I've been using Hammonds but maybe I should give them a try.

I'm not sure. I've heard other folks say that but there's nothing on the xformer. No doubt in my mind though that these are better than Hammonds.

I am pretty sure that Heyboer is building the Mojo trannies (at least some of them). They have a link to the Mojo site from their webpages.

If you are buying more than 5 transformers, going to Heyboer is probably the cheaper route.

Gary

[Robert]

The Heyboer guys were great to work with. Call and ask them regarding the Mojo trannys.