OD Reverb #13 (1976)

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oldmacman
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OD Reverb #13 (1976)

Post by oldmacman »

OD Reverb #13 partial schematic, as traced by me from HAD's original layout drawing.

Interesting things to note:

-Values of tonestack
-Method of reverb (tapped off right before V1B -> reverb send -> tank -> reverb recover -> mixed with clean signal from output of attenuation network after V2B)
-NFB loop in reverb recovery/mixer
-Clean/reverberated mix gets sent to the OD stage

NOTE: I don't know if I should put up Dumble's actual hand-drawn layout. I think there might be some copyright violation issues. One of these days, I'll get around to redrawing this.
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Funkalicousgroove
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Re: OD Reverb #13 (1976)

Post by Funkalicousgroove »

Would you be willing to share it privately?
Owner/Solder Jockey Bludotone Amp Works
oldmacman
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Re: OD Reverb #13 (1976)

Post by oldmacman »

Sure.

Shoot me an email at bhs3 (AT) duke.edu
ampdoc1
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Correct #13 Schematic???

Post by ampdoc1 »

oldmanmac

Someone, (maybe you) gave me an electronic copy of this 2-3 years ago. Unfortunately I lost the email after a Windows crash and retained only a copy I had printed, but it is illegible in some areas.
I have made a schematic from it, but some of the values are more guess than anything. If I email this to you, do you think you can correct it? If so, we could post it for all to see!!!!

David Hicks
oldmacman
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Re: OD Reverb #13 (1976)

Post by oldmacman »

Actually, you sent me the blurry layout on a CD, which is where I got this from!

If you send me a schematic, I'd be glad to take a look over it. I've built an OD Reverb based on this, so I have a pretty good idea of what the values should be, or at least the values that I like in there.

Ben
ampdoc1
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Re: OD Reverb #13 (1976)

Post by ampdoc1 »

Hey Ben,...

I've got my layout on AutoCad at work. I've got a busy week, but I'll port it to .bmp or something early next week. Damn!!!! I wish I could figure out who sent me that drawing. I'm sure another generation closer to the original would be much easier to read.

DEH
mlp-mx6
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Re: OD Reverb #13 (1976)

Post by mlp-mx6 »

Consider installing the free CutePDF writer to "print" to a PDF.
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Tdale
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e-mail me?

Post by Tdale »

Oldmacman, can you e-mail me? tommy.dale@c2i.net

I have some questions about the reverb schematics..

Tommy
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Tdale
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Re: OD Reverb #13 (1976)

Post by Tdale »

Does this reverb circuit require 2 or 3 pots?

There is of course a send and return pot in the actual reverb circuit.

But there is also a pot after V1B before the dry signal goes to the mixer. Is it a trim pot?

Tommy
oldmacman
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Re: OD Reverb #13 (1976)

Post by oldmacman »

It's a trim pot. Only 2 reverb controls on the front panel.

Don't know how it's done on later models. I've seen a couple where there's a Reverb control for the OD channel on the back panel.
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Tdale
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Re: OD Reverb #13 (1976)

Post by Tdale »

I managed to find it on the original, although it's a bit unclear scanning.

How do you set that trim? I'd imagine it shouldn't have too much resistance, since that would lower the signal level, and act like a clean-master pot, making the preamp deliver less clean signal than it would without it..?

Tommy
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Tdale
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Re: OD Reverb #13 (1976)

Post by Tdale »

Some of the resistor values has a ? after them. Have you used the values that are printed, and does it work with them?

Tommy
oldmacman
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Re: OD Reverb #13 (1976)

Post by oldmacman »

I haven't looked at that layout in a while, but I've changed a couple of things. The values should work, but no guarantees.

On the reverb return stage, try using 220K/3K3 plate/cathode resistors, and try 220K plate resistors and a 1K5 cathode resistor on the mixer stage. You get a bit more headroom.

The 820K resistor on the NFB loop on the reverb return stage is adjustable. I think I have 2M2 in there now, but I'd have to open it up to be sure.

If you're new to building Dumbles, start with a straight ODS using a layout like the one Gil Ayan and ElectronAvalanche posted recently - Dumble used that one starting in the early '80s. Start with something like a Hybrid-A (be sure to use 220K/100Kpot into the overdrive), use the right parts, and build it right, and you'll be happy.

Ben
fabiosardus
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Layout Question.

Post by fabiosardus »

hi, i'm from italy.

does anyone that give me a complete working layout?
I can use only 4 12ax7 and 2 el34 'cause my trasformer currnt is 120mA.

Oldmacman can you give me a hand made layout privatelly?

Question for relè: what type of relè i can use?

Thanks....(i want..i can...i thank...you....)


OOps...My EMAIL is: faxfux@email.it


Fabio.
PaisleyTube
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Re: OD Reverb #13 (1976)

Post by PaisleyTube »

Hi Ben

Can you email me that one too?
(work: info AT cmwamps DOT com)
Many tia!

Chris
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