Mystery clone

[Lynxtrap]

I'd be grateful to hear any thoughts on this one from all you experts.

This amp is supposed to be kind of a "clone of a clone".

I bought it as an unfinished build. All mounting and wiring in the chassis is finished, but according to the seller there is some oscillation problems that he never got around to fix and then lost interest in the project.

I haven't even tried it yet, I blueprinted the layout (as attached here) and will probably also draw a schematic before I start working on it.
There are some caps with unknown values in the layout as they are mounted in such a way that the label can't be read.

So far I haven't compared it component by component to other ODS versions. There seems to be some similarities to the #183? It has a tube driven effect loop (built in D-lator according to the seller).

What do you make of it?

I'm sure I will have some more particular questions as I start working on it. Are there any particular places you would focus on as possible sources of oscillation?

EDIT: I spotted an error in the layout. There should be a wire from the upper lug of the mid boost switch to the Treble pot input. And of course, the wire to the Volume pot input comes from the middle lug of the Treble pot. There is also a wire missing to the bias pot. There could be other errors as well.

Mystery clone layout rev1.pdf

[jabguit]

Layout looks somewhat incomplete

[Lynxtrap]

Layout looks somewhat incomplete

What are you missing? I'd be very happy to hear about any issues with the layout in case there are errors in the build/circuit.

Except for a few missing or wrongly placed wires, this should be the amp as it is. I tried my best to trace the whole circuit but I guess some mistakes are unavoidable.

The amp does not have a FET input.
The OT is not shown, but all wiring to and from it should be shown or marked in the layout.
I also didn't bother to draw the heater wires.

[ijedouglas]

Other than the PI couplers, bias splitters and no LNFB, I wouldn't really call it close to 183. More like a high-plate skyline with some tweaked values.

More important, how does it sound?

Gut shots?

[Lynxtrap]

Other than the PI couplers, bias splitters and no LNFB, I wouldn't really call it close to 183. More like a high-plate skyline with some tweaked values.
More important, how does it sound?
Gut shots?

OK, thanks!
But it does have LNFB, at V1B?
There seems to be limited interest in this, but I can try to post some gut shots.
Don't know how it sounds yet, but this particular circuit is supposed to sound really great.

Are there known real Dumbles with built in tube D-lators?

[talbany]

Are there known real Dumbles with built in tube D-lators?

Basically No!
I have seen one with a transistor loop built in but the original owner had it later removed. The full (all tube) version of the D-lator has only been sold as a separate add on feature in it's own chassis. AFAIK.

Tony

IMG_2641.jpg

[mojotom]

Layout looks somewhat incomplete

What are you missing? I'd be very happy to hear about any issues with the layout in case there are errors in the build/circuit.

Except for a few missing or wrongly placed wires, this should be the amp as it is. I tried my best to trace the whole circuit but I guess some mistakes are unavoidable.

The amp does not have a FET input.
The OT is not shown, but all wiring to and from it should be shown or marked in the layout.
I also didn't bother to draw the heater wires.

What amp maker build this one ?
Quinn ?

[Lynxtrap]

Basically No!
I have seen one with a transistor loop built in but the original owner had it later removed. The full (all tube) version of the D-lator has only been sold as a separate add on feature in it's own chassis. AFAIK.

Interesting! I'll have to check a schematic of the tube driven D-lator to see if that's what is built in here.

What amp maker build this one ?
Quinn ?

I'm sorry to say I can't answer that as I don't want to cause any trouble for anyone. But it's not Quinn.
This is the circuit, and I will try to make a schematic to put up here if anyone is interested, but I won't name sources.
Kind of ridiculous IMHO, there is nothing sensational here, but that's how it is

[ijedouglas]

But it does have LNFB, at V1B?

Yup, I actually started replying with all the things different from 183 but then changed my mind. No LNFB.. even less like 183

[Lynxtrap]

Yup, I actually started replying with all the things different from 183 but then changed my mind. No LNFB.. even less like 183

I guess my conclusion about the similarities with #183 were a bit premature.
Perhaps a little more similar to #102, but far from identical.

[Charlie Wilson]

Basically No!
I have seen one with a transistor loop built in but the original owner had it later removed. The full (all tube) version of the D-lator has only been sold as a separate add on feature in it's own chassis. AFAIK.

Interesting! I'll have to check a schematic of the tube driven D-lator to see if that's what is built in here.

What amp maker build this one ?
Quinn ?

I'm sorry to say I can't answer that as I don't want to cause any trouble for anyone. But it's not Quinn.
This is the circuit, and I will try to make a schematic to put up here if anyone is interested, but I won't name sources.
Kind of ridiculous IMHO, there is nothing sensational here, but that's how it is

Well I will name the source, Alexander Dumble.
CW

[Lynxtrap]

Well I will name the source, Alexander Dumble.
CW

Absolutely right!
But try that argument with a "big name" clone maker when you make their schematics public.

[Lynxtrap]

OK, so this is the FX loop. Would you call this a D-lator? Notice anything odd?

Mystery FX loop.png

[rootz]

Close to a D-lator at least. 10k tail on CF limits headroom a bit, but I’ve seen anything here from 10k to 27k. No bright switches. I think you’d like those to compensate for cable losses and for the versatility. 3u cap? Not really a std value for a D-lator IIRC. All these things are pretty easy to tweak to taste.

[talbany]

Notice anything odd?

It's a Dumblelator
A few things quick. the 22k RC filter network on the grid of your recovery amp is suppose to be 220K/500pf
on the schematic it's marked 22k but the layout has 220k.
The unmarked bypass cap for recovery (2.7K) says 3uf on the schematic and is marked ? on the layout.
the original is 47uf.


The 2 things that convince me that it's a Dumble design are 220k/500pf grid network and the NFB loop around the recovery amp is classic Dumble trademarks.
BTW the 10k on the cathode of the C.F is used to set the voltage constant at around 30V for optimal frequency response/headroom. Like Rootz says this value can vary depending on the voltages from the P.S
Tony