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previous: Daver Dave,I've used Hoffman tran... -- 5/23/2000 1:53 AM view thread

Re: Dumble Clone Parts: Trannies etc...

5/23/2000 3:23 AM
Gil Ayan
Re: Dumble Clone Parts: Trannies etc...
Dave, my two dollars worth (inflation!). Dumble has apparently used a number of different things to build his amps over the years... First ones were probably very close to Fender knock offs, and therefore it is reasonable to assume they were Fender parts. Older Dumbles didn't have impedance selector switches and were rated at 4 ohms, so either he didn't bother with other taps, or his transformers were Twin replacements.  
More modern Dumbles reportedly use Fender Twi laydown mains transformer from Magic Parts, Fender Twin choke, and a Magic Parts TF 170 Marshall Plexi otuput transformer. I am a Magic Parts customer and this information was verified by them.  
The more modern amps have an impedance selector switch for 4, 8 and 16 ohms (all of the taps in the TF 170).  
Regarding the Hoffman transformers, the OT sounds very good, but the mains transformer is mechanically noisy (I have to of them in two amps). They do work well, but they are not as beefy as I would like them to be, structurally speaking. Knowing that the rela thing uses Fender Twin mains, you may want to go that route. I have used the New Sensor MPT-100 (plexi 100W) and that thing is great. It has a slightly higher B+ than then Hoffman, but it is built very nicely and is dead quiet -- again, mechanically.  
Regarding the addition of Reverb, anything can be done to any amp and you may end up with a better sound. However, I can guarantee you that the sound will change. Part of the thing about the Dumble circuit is that it is extremely simple, with only four stages before the PI in overdrive mode. If you add reverb to the amp, a la AB 763, you will add another stage to the clean sound and there will be a number of differences:  
1. The dry signal will pass through the 3.3Meg//10pF network, and that may not agree with the lead tone.  
2. AS someone already poited out in another thread today, THAT Fender network allows for the output of the overdrive to travel back to the input of the overdrive via the 3.3Meg resistor. I had built a agin amp (much like a Boogie or Dumble) on a Fender circuit before, and while it ended up singing great, I had a lot of problems fighting oscillations.  
3. Having more stages will inevitably compress the amp some more. Part of the Dumble thing is that it is a very dynamic amp, which kind of sounds like a power section pushed hard, yet, the effect is achieved by using preamp overdrive, to a great extent.  
If I were you, I would wire up the real thing first so that you know what it's supposed to sound like. Then, if you want to "make it better," at least you will have the proper reference to compare the nerw sound to.  
Good luck with your project,  

Peter S I agree with Gil......all of my ear... -- 5/23/2000 5:03 AM
Steve Ahola How about the Dumbleator? -- 5/23/2000 5:35 AM
Dave B. Re: Dumble Clone Parts: Trannies etc... -- 5/23/2000 5:46 AM
andy fuchs Gil: Lets not forget the batch of O... -- 5/24/2000 5:42 PM