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Dumble Amplifiers


 
8/17/1998 5:29 PM
Jason Borders
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Dumble Amplifiers
Would anyone be able to shed some light or know of a good web site that explains why these amps are so sought after. Were they rebuilds of existing amps or built from the ground up. Did he use special transformer, etc. or is just the way it was wired. Thanks.
 
8/17/1998 9:33 PM
Richie
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Jason: I don't know of a web site,but it looks like you have read a little about them.Their is a schematic in the GT book,I guess you know that SRV,Eric Johnson, Robin Ford,and a few others use them,I have read some articles about them,some not so good.They talk about them breaking down alot.I guess then you have to send it to him to fix.The price was a big stopper,5000.oo for a head!A waiting list to get one.I think some bought two, so when ever one was down, they had a backup.Mr. dumble builds these himself,kind of a botique amp.But I would guess if these top players keep using them they must be something to the sound of them.I think in Eric Johnsons vidio you could hear what one sounds like,he said he used the fenders for the clean sound, the dumble for the medium distorted sound, and the marshall for the flat out sound! Hope this helps some. [Richie]
 
 
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8/18/1998 7:26 AM
Jason Borders
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Anyone out there have a scanner that would email me a copy of the Dumble schematic until I get around to ordering the book (from what I've read in various threads, it's a good collection of schematics)?
 
8/18/1998 8:29 AM
Jim S.
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Unfortunately, that diagram in the Groove Tubes book is not really a schematic. It's more of a block diagram and doesn't show the circuit at an individual component level. It's practically worthless for helping find out why Dumble amps can sound so magical (I love Robben Ford's clean and overdriven tones that he gets from his Overdrive Specials).  
 
From what I've read about the Dumble Overdrive Special and hearing how they sound live and on recordings, I believe this model uses a circuit that is based upon Fender blackface amps. Certainly, the clean channel sounds reminiscent of a really great blackface Twin Reverb, but maybe a little bit fatter and sweeter. I have no idea how they acheive such a fantastic overdrive - I can understand why Dumble would try to keep this a secret. To my ears, the overdrive tone has the perfect combination of rawness and refinement. With a PAF-style humbucker equipped guitar, it seems to produce this fantastic "sweet snarl", like from a Tweed Fender from heaven turned all the way up.  
 
I wouldn't be surprised if the Overdrive Special uses a post-phase inverter Master Volume control.  
 
I've heard that it's possible to get close to these tones by modifying an early-80's era Fender Concert (in what way I don't know), but I have not had a chance to experiment with this yet.  
 
Is there anybody out there who has ever had a Dumble amp on their workbench?
 
8/20/1998 5:57 AM
GFR
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What's funny is that the first stage of the Dumble (according to the diagram and to some pictures) is based on a FET! Mr. Dumble seems more like the "if it sounds good, I'll use it" school than an all-tube purist.  
 
I've read a post in Boogie-Talk from someone who played a Dumble. He said that the thing he likes most about the Dumble is that it could easilly go into infinite sustain feedback (like a boogie), but with an almost clean sound (unlike a boogie).  
 
GFR
 
8/20/1998 1:35 PM
GVB
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I seem to recall a thread on a newsgroup about Dumble amps. If I remember correctly, the fet was in a "follower" type setup, so the pickup would not be loaded by the first stage.  
 
It also went on about a "black box" in the amp that was a solid block of epoxy with wires coming out of it. Their were various rants and raves about what was inside, and one person claimed that they had disected one and it was basically a Tube Screamer. I don't know how much truth there is to that, but I can't see someone disecting a $14,000 amp just to see what makes it tick.  
 
GVB
 
8/20/1998 9:02 PM
Carl
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Personally, I've never seen a Dumble in person or even a block diagram. However, after looking at the pictures on that site that Jack posted I'm going to hazard a guess at what's going on.  
First off the part layout seems to indicate a standard Fender style power amp. Now here's where the drive may be coming from. Based on the controls and the relative location of the parts, it may be that there are two tube stages in parallel with the rest of the circuit, similar to a reverb or fx loop. Depending on how you set the thing up, you could easily get an overdrive level as well as a mix to blend it into the dry signal.  
 
Well, does that seem feasable? Running a few simulations could be very telling in this regard.  
 
Carl  
http:/www.angelfire.com/il/summitamps
 
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