Twin Reverb as dumble platform

[pula58]

I have this idea of buying an old Silverface twin reverb and using the first ("normal") channel preamp tube as the dumble overdrive cricuit. Add a relay, and switch the overdrive in or out, and use the same reverb circuit already in-place. How would that work-out? Has anyone tried this? I am sure they must have.

It seem like this would be a very inexpensive way to go. Silverface twins can be had for $800 or so. Re-wire it a little, add the relay circuity and ....what do ya think?

[Zippy]

Sounds simple.

[bepone]

hello pula,
i think that chassis grounding method in fender will make much noise and humm when converting in high gain circuit like on dumble. i would build complete preamp it is not so difficult.. and leave PI, output section without rewiring..

new preamp grounding wiring is essentiall.

here is mine, i converted LAB5 transistor amp in DUMBLE , with transmitting RS1003 tubes , 120 Watter with balls

http://www.youtube.com/watch?v=1JdO9LC6kyM
[IMG:160:120]http://i284.photobucket.com/albums/ll34/bepone/th_110820113786.jpg[/img]
but in my project i must construct everything, from PT, OT to PI to match with those RS transmitting tubes. you will have easy job with fender,, go for it

[Luthierwnc]

Probably on the expensive side. Usually that is a question asked by someone who already has a Twin but eight hundred bucks is close to all the parts for a scratch build. With the Twin, all you've really got are the transformers, chassis and hopefully the tubes are still good. Maybe speakers too but then you still have to carry the thing.

I'm in the drawing stage for a 100w build and think I can bring it in for around seven bills -- and that is all first-rate, new components.

Good luck, Skip

[alvarezh]

Hi pula, think thoroughly on Skip's proposal, sounds like good advise.

But, if you must go the twin route, it would be good to know that it's not considered good building (design?) technic to send your signal backwards (physically) and then forward again on the circuit. I am not saying it can't be done, it's just that you could be getting into interacting signals that could run havoc and you should plan very effectively in order to avoid it. Perhaps if you start out with your input signal on channel one and make channel two's first tube the overdrive glass to bypass, then you are flowing the signal in one direction like almost everyone does.

Best wishes.

[Luthierwnc]

If you really want to work from a donor platform, keep your eyes peeled for a Traynor. For a 50 watt build, the VoiceMaster has about the right amount of holes in the face. For a 100 watter, the YGL series works well. sh

[bcd123]

Hi there - been a long time visitor of the site but this is my first post - would highly recommend using a sf twin reverb as a donor - it means that you can build in the dumbleator and reverb!

I used a super six chassis (essentially a twin reverb) and bought the boards from one of the chaps on the forum and they fit well - it's not finished but there are no issues at all with noise. The paper boards in old Fenders are where most of the noise seems to come from - if you have one that's noisy try running a hot air gun over it until the wax just reflows and this will get the moisture out - be careful not to cook things though javascript:emoticon(':D')

I picked mine up for AU$750 as a working unit - I've copied the #102 build which uses twin iron so why wouldn't it be a good place to start.

As far as layout goes, I used the treble middle & bass on the non-reverb side (ch1) to house the bright, mid boost & rock/jazz switches, the high and low inputs on the that channel became normal and fet and the high and low inputs for the reverb channel became send and receive level pots for the dumbleator. I also used a pull pot to have the option of hard bypassing the effects loop.

The real novelty of having a disguised dumble is that people think you're just playing a twin and can't believe the sound that they are hearing.

My next project will be making ch2 of a Rivera M100 1 X 12 (standard with EVM 12L) into a #183 variant.........it's a lot easier than starting from scratch.

If your main concern is the sound and not the aesthetics this is a good way to go.

[alvarezh]

Interesting bcd123, any gut shots, schematic or layout, by any chance?

Thanks mate,

[Structo]

Here is a long thread about a Fender Twin conversion.

https://tubeamparchive.com/viewtopic.php?t=5396&start=0

[bepone]

I used a super six chassis (essentially a twin reverb) and bought the boards from one of the chaps on the forum and they fit well - it's not finished but there are no issues at all with noise. The paper boards in old Fenders are where most of the noise seems to come from - if you have one that's noisy try running a hot air gun over it until the wax just reflows and this will get the moisture out - be careful not to cook things though javascript:emoticon(':D')

thats my point, new preamp board is cheep (one can choose to buy or DIY), new preamp unit will install in ex fender amp in one, two days. not so difficult to make, also we can't forget most important thing/ challenge

[bcd123]

Some gut shots as requested - sorry about the delay.

As you can see it's a bit messy but the photos are only to show one way of doing this if you are thinking of making a SFTR your starting point.

You can see that I have cut the main PCB in two pieces to separate the phase splitter and preamp sections physically to allow them to be mounted in different places.

Given some of the high quality builds I've seen on this site this is almost embarrassing to post these pics but please bare in mind for me as a practicing muso with a young family it's more about functionality than aesthetics. FET board isn't installed yet but there is room...........just!

The mess in the middle of the amp is basically the dumbleator circuit populated onto the old Fender board.

My intention is to route out a new board at work and install once I've got the design finished to house the components for the dumbleator and reverb - I'm an electronics tech so we have a PCB CAD program and a circuit board router at work for prototyping.

I forgot to mention I have configured the existing bright switches to switch PAB and OD - external f/s is built but rear panel socket isn't installed yet.

Cheers,
Brad

[alvarezh]

Thank you bcd123 for taking your time to illustrate us. I personally like it when people transform and build things with whatever they have available. It is much harder to modify than what most people think, there are problems to solve and inconveniences that need solutions. Buying parts and stacking them together may be a neater way to go, but you don't learn as much, most (if not all) is thought out by someone else already.

Good job really, even if it doesn't look spectacular. As you say, you must have a ball at confusing other musicians on the tone of that "Fender" !

BTW, I have a 1974 Quadreverb which I converted to "black face" specs. It's the amp I use to compare all my amps to on the "clean" tone. It sounds dam good, although I have heard some "real black faces" that I am inclined to say sound just a tad better. Maybe the difference between tube and silicon rectifiers.

Do check the value on those old carbon comp resistors, I have had to change a few on my rig for being way too far off value.

Another thing I have taken notice is that the solder has not flowed well on the eyelets, makes me wonder if your iron is not developing enough heat.

Pretty modern looking rectifier board you have there. I use the normal 1N4007 on mine, you definitively won't have any heat dissipation problems!

White coily cable shielding the signal wires…hmm, wonder if that's from where "Gearmanndude" from "YouTube" got his idea from?

Thanks again for the pictures,

All the best.

[Structo]

bcd123 good effort so far.

On V2 you have the snubber caps, (the ceramics) sticking way up in the air.

They seem to be by the heater wires which is not a good idea because it could pick up some 60 Hz noise.

Shorten those leads so it sits down on the socket and it will sound much better.

Check out the other builds here to see how different people wire their amps.

And look at the layout as it is a good representation of how things should look.

Good luck!

[groovtubin]

If you really want to work from a donor platform, keep your eyes peeled for a Traynor. For a 50 watt build, the VoiceMaster has about the right amount of holes in the face. For a 100 watter, the YGL series works well. sh

Couldn`t agree more! One of my best builds!

[Smitty]

Here's one way to skin that cat:

https://tubeamparchive.com/viewtopic.php?t=20345