Dumble mods for Fender Bassman 50????

[Baddog01]

Hello gentlemen, I'm new to the board and wanted to say hello to everyone here and I hope I can be a good addition to this forum. That being said I was wondering if there are any good Dumble mods that can be applied to a Silverface Bassman 50.

Thanks
Keith

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[ic-racer]

Some documents from Steve Ahola's site that may help you get started.

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[ic-racer]

You may also get some ideas from this thread: https://tubeamparchive.com/viewtopic.php?t=5396&start=0

[Baddog01]

I would have to add a Mid pot to use these mods. Hmm any mods not using a Mid pot?

Thanks
Keith

[wyatt]

I would have to add a Mid pot to use these mods. Hmm any mods not using a Mid pot?

Thanks
Keith

You would just tie them in to the appropriate end of the resistor that sits in place of the Middle pot. That's a 6.8K on the Normal channel. Does the Bass channel have the Deep switch?

[Baddog01]

Here is the schematic for my amp:
http://www.webphix.com/schematic%20heav ... sman50.pdf

I modded the bass channel using something I had in one of my books (see below). I originally wanted to try a Dumble Mod but couldn't find any good info on how to do it. Im just looking around to see what I can find and try.


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[Baddog01]

I think ill try the Deep mod on my bass channel . I can add it to my existing setup mods and check it out. I should have all of the stuff I need to make it happen.

[Mark]

Try the deep switch I like what it does to single coil pickups.

I built two Dumble style amps one being a rebuild of a D'Lite to a #0102 and converting a Boogie SOB into a Bluesmaster, I was surprised at how much the Bluesmaster PI changed the character of the amp. This is worth trying as it will increase the overall gain of the amp. (Actually my first encounter with this PI was when I tried to wire the SOB up per an old Mark 1 Boogie diagram and the gain was over the top, though Boogie does have an extra gain stage.)

As far as the pre-amps go you will have to work out the value of the resistor to replace the mid pot, a high value will mean the bass pot doesn't work that well and a low value will mean the bass control works well but there are any/much mids.

Hope that helps.

[Baddog01]

Thanks for the heads up on the mod and your experiences . I could install a mid pot on the back side of the chassis. Actually I already have hole from a different experiment that didn't work very well.
I'll have to check out the bluesmaster PI and see what it looks like and how it compares to the fender.

Keith

[Baddog01]

Mark,

What's your thought on Dumble amps and there tone? I've only heard them on YouTube and have no personal experience with them. I've built a few amps but most have been Fender amps. I've also built a Carmen Ghia clone, matchless Spitfire , Marshall 18 watt , and an 18watt plexi clone. I mostly use old organ amplifier iron and adapt it to my needs . Not allot of money to spend on a hobby but I make due .

Thanks
Keith

[Mark]

I can't say I've played through a real Dumble, though I have experimented a bit with the various ODS amps.

My personal preference is the HRM amps, though most prefer the non HRM amps, when using a non HRM amp, I really like using a Dumbleator to thicken the tone of the amp, I don't like this thickening effect in the HRM amps though.

I find these amps are particular about valves. The #0102 I built liked a JJ 83S in the first position, a 803AS in the overdrive position (same for HRM and non HRM) and a Sovtek LPS in the PI. The 803S and the LPS are both long plate valves and they sound fatter/bigger.

I seem to recall the JJ were brighter than the Sovtek valves.

The output transformers mattered a lot too. I used the stock D'Lite 33 watt transformer, though later I decided to sub in the Bassman style transformer from my Boogie SOB, to my surprise the Heyboer/D'Lite transformer sounded better, I dare say the quality of the Mesa Boogie transformer wasn't that great. The MB transformer lacked mids and sounded a bit too sterile, the Heyboer transformer had much sweeter mids.

I turned the Boogie into a Bluesmaster and while it sounded good as a Bluesmaster, I don't think it sounded as Dumble intended it to sound. I think there is some debate about the Bluesmaster that it in fact uses 6L6's I used 6L6's in my version as I didn't want to buy EL-34's and the output transformer to use them.

One would think the iron used in organs should be good as the organ does have a greater range than the guitar.

I hope this assists.

Check out the Dumble section, there are guys like Tony Albany and co who've worked extensively on the real thing and built a lot of amps to boot.

[Baddog01]

What does HRM stand for?

Thanks
Keith

[wyatt]

What does HRM stand for?

Thanks
Keith

Hot Rubber Monkey. I kid not.

But I guessing that's not what you meant...

Ultimately it's a Dumble OD channel circuit with an adjustable Marshall-style tone stack added ("adjustable" being relative, the controls were trim pots inside the amp). It resulted in a change in the OD channel, IIRC...more compression, better response to picking dynamics, but people felt it wasn't as fat or as high gain as the earlier (non-adjustable) circuit. People discuss non-HRM vs. HRM, but it's really a matter of pre-HRM (the "Standard" circuit) vs. HRM.

I'm not as well versed on the Dumble history, but this site has whole sections dealing with it and with one post in the Dumble Discussions, you'll probably get more than you need to know. But I would do a little research on Classic, non-HRM, Skyliner, HRM, and Bluesmaster, a Google search should fill you in fine.

[Baddog01]

That helps out allot.

Thanks

[Mark]

I think it takes a bit of time to get use to the HRM circuit, I didn't have an issue with gain particularly when the mega boat is kicked in. I find a lot of people who dislike the HRM circuit didn't turn the tone controls up enough and I suspect this adversely effected the tone of the amp. Once again just my take on it all, and my version was done with the Boogie SOB as a donor amp so there wasn't a lot of bass response to begin with. So turning up the mids and bass wasn't an issue, the greatest issue I've had is telling people I like the hot rubber monkey.

What intensions do you have for this amp?

I have a Bassman 100 and I'll do some of the mods I've mentioned, I'd like to own an amp with reverb again so I'm looking at putting reverb into the Bassman, fortunately there is a lot of room inside these amps which is cool.

I'm considering putting relays into the amp for volume boost and mid boost, these are both good features in a clean amp in my opinion. This will mean another transformer to power the relays though.