What make a Dumble overdrive ?

[godi]

Hi folks, I have very little experience building six tube amps so far, copying layout without really understanding what I'm doing. My next project will be a Dumble with two 5881 tubes, something like a 22 Lite.

Can someone explain to me (and to all other amateurs on this forum) where does the nice overdrive tone full of harmonics come from in that Dumble circuit ?

Thank a lot, Jean

[mad_dog]

Ok I am no expert, but I have found that if you learn to read a schematic as well as just look at the layout, you can follow what happens to you guitar signal a little better than with the layout.

If you look at the schematic and compare it to other classic amps such as Fenders, and Marshalls, I find it is alot easier to see the differences, which there are quite a few.

There is also an article on The Gear Page (before you go to the forums) of all places called "Understanding Gain Structure" which kinda breaks down an amps circuit for Dummies.

[ampdoc1]

The quick answer is the OD gain stages. Dumble gets almost all of the distortion in the preamp, vs an amp like the TrainWreck Express which develops distortion in the output of the amp.

[greenbottle]

Being able to read a schematic circuit diagram enables you to understand what is happening in the cct which you wll not get from a wiring layout.
This means you have got a lot of reading to do.

If you go to the "Londonpower" web site and look up a book called "Ready set go". Print off a list of contents. This will indcate the types of things you need to learn.

I like Kevin O'Connor's books. Others may prefer some body else's books. Perhaps they will post a list of other books for you to read.

Happy reading
Alan

[godi]

Let me clarify my question. My JTM45 clone ( https://tubeamparchive.com/viewtopic.ph ... ight=jtm45 ) have tree 12AX7 preamp tubes, v3 is the PI tube, so there really two preamp tubes left or four gain stages, the Dumble is also design with tree 12AX7 preamp tubes witch one is the PI tube. If both amp have four gain stage, why does the Dumble can overdrive while the JTM45 can't ?

Thank

[ChrisM]

The Dumble cascades gain stages, one into the other, while the JTM45 does not.

[mbeldyga]

There're only two gain stages (+ CF) on jtm45. Dumble has four gain stages while OD section is in the signal path.