Dumbleator II build.

[Charlie Wilson]

Hello, I was asked to build a Dumbleator II and here is what I came up with. Had some help from a couple friends.
CW

[Guy77]

So clean. Nice

Cheers
G

[rccolgan]

Oh dang . That's pretty

[Stephen1966]

Very nice, with some period parts as well. What's the choke you are using there?

[Bombacaototal]

Very nice!! Did you design those PCB boards? Which rack chassis did you use?

[jazzbass]

Hi everyone,

first of all "HAPPY EASTER" to you and to the entire TAG community.

I am very interested in building another Dumblator, the first one I made gave a new dimension to the Dumble clones I had built and I consider it an indispensable "accessory" in the sound chain.

Now I'm building a second one starting from the motherboard built by AA Electronics

https://www.aaelectronicspcb.com/produc ... ator-style

The transformer or transformers are my biggest problem. For the first one I solved by buying a toroidal transformer from Tubetown for the first build (TT-T47) , too big for this application, but it worked.
Some members of the TAG forum have suggested other transformers but I would prefer to adopt the "original" transformer, make a more correct choice like the one made by A.H. DUMBLE but which one?

Keep in mind that I live in Europe and here the voltage on the wall is 220/230 Volt, then I have to take into account that it must be outside a U1 rack on the rear side. I'm analyzing Hammond transformers but which one to buy?
I am attaching the layout suggested by Andrea Antonello of AA Electronics, bearing in mind that he lives in England where the voltage on the wall is 120V.

Thanks for any suggestion

A Hug, Franco

[ijedouglas]

Hello, I was asked to build a Dumbleator II and here is what I came up with. Had some help from a couple friends.
CW

Stunning! Bet it sounds great!

[Charlie Wilson]

Thanks guys. For an enclosure I used the same one Dumble used made by LMB Heeger. You can still get them. https://lmbheeger.com/uni-pacuniversalp ... ystem.aspx
They are a bit pricy and for some reason they don't paint the inside of the enclosure anymore but they still are really nice. Circuit boards and choke are from the guy who posted the photos of the Dumbleator II over a decade ago, Brandon (Bludotone). It was very cool of him to help me out with that. Nice old NTE resistors from Ian Douglas who also let me test this thing through his amps so he knows already that it sounds pretty good. Below is a photo of the original.
CW

[Stephen1966]

Thanks guys. For an enclosure I used the same one Dumble used made by LMB Heeger. You can still get them. https://lmbheeger.com/uni-pacuniversalp ... ystem.aspx
They are a bit pricy and for some reason they don't paint the inside of the enclosure anymore but they still are really nice. Circuit boards and choke are from the guy who posted the photos of the Dumbleator II over a decade ago, Brandon (Bludotone). It was very cool of him to help me out with that. Nice old NTE resistors from Ian Douglas who also let me test this thing through his amps so he knows already that it sounds pretty good. Below is a photo of the original.
CW

Please, tell us more about the testing... I must confess, it's a bit of a mystery to me how this thing takes a mono in and gives a stereo out, but that's just a case of following the logic of the circuit. But also, if it alters the bypassed dry tone in any way.

At the time when Brandon posted the internals it appears the choke, a Triad C3X was OOP. They seem to be making them again now though.

triad_c3x_apr22_xonlink.pdf

[Bombacaototal]

Super cool project CW, thanks for the additional details. Congratulations on the beautiful build. Are you going to be using it with a ODS?

[rccolgan]

I'm interested in doing the heavy lifting for designing a PCB, faceplates, etc for this DIY community as we did with SSS #002...

I found the old thread where Brandon uploaded the pics and another member made this schematic. https://ampgarage.com/forum/viewtopic.php?t=5961

How far off do we think this is? Maybe worth its own thread...

I think these could make great transoformers too https://www.mouser.com/c/power/transfor ... series=229

[Charlie Wilson]

Hello, so Stephen I agree this does not fit the definition of a true stereo device. I would like to note that Dumble did not name it Stereo Dumbleator. As far as the choke, I have seen a Dumbleator II with a Triad C-3x choke and actually have an old one sitting on my bench but I do not believe that the one in the photo is a Triad. The Triad is too tall for that single space rack enclosure. Even the one in the photo is gooped most likely to keep the top from rattling against it. rccolgan the schematic is close. The two recovery output pots are 250kA with 270pf bright caps. The bright cap on the 10k send is a big old .027uf bright cap and the the recovery cathode resistors should be 1.5k not 2.1k. I think he read them upside down.
CW

[bepone]

The transformer or transformers are my biggest problem. For the first one I solved by buying a toroidal transformer from Tubetown for the first build (TT-T47) , too big for this application, but it worked.

maybe Piemme elektra - IT?

[Stephen1966]

The Triad is too tall for that single space rack enclosure.

Mmm... you might be right. But if the dimensional drawings are anything to go by the C3X should just about fit. A 1U rack being 1.75" externally and the choke being 1.625" (top to bottom). So a bit of a squeeze maybe, but that's what hammers are for.

the recovery cathode resistors should be 1.5k not 2.1k. I think he read them upside down.

Genius! Sounds like the kind of thing I would do.

I'm interested in the set up, some guys like the idea of running wet alongside dry and with a bit of creative jumpering it might be possible to coax this from the DII. Incidentally, was the Two-Rock "stereo" unit the same circuit? Greg's stereo FX seems a more straightforward proposition for anyone wanting true stereo https://ampgarage.com/forum/viewtopic.p ... 99#p213399

I'm building up an embarrassing surplus of different amps here so I could probably run at least one of the recovery outputs into a different amp's power section but honestly, I should learn to play the guitar first The Dumbleator's I've been building into my amps (two so far) are both series/parallel so it would be overkill, for me. I am interested in the tonal possibilities the regular original Dumbleator offers - a reduced value coupling cap coming off the cathode follower and smaller drive pot - 25k in my case as I'm trying to remember off the top of my head adds a richness to the tone, making it less transparent, but adding what I think is a pleasant extra dimension to the sound. I know asking Charlie about the testing would be like trying to compare apples with pears but the original builds and faithful clones provide invaluable benchmarks when guys like me set out to reinvent the wheel

[rccolgan]

Hello, so Stephen I agree this does not fit the definition of a true stereo device. I would like to note that Dumble did not name it Stereo Dumbleator. As far as the choke, I have seen a Dumbleator II with a Triad C-3x choke and actually have an old one sitting on my bench but I do not believe that the one in the photo is a Triad. The Triad is too tall for that single space rack enclosure. Even the one in the photo is gooped most likely to keep the top from rattling against it. rccolgan the schematic is close. The two recovery output pots are 250kA with 270pf bright caps. The bright cap on the 10k send is a big old .027uf bright cap and the the recovery cathode resistors should be 1.5k not 2.1k. I think he read them upside down.
CW

You're the best, Charlie!

I threw the schematic together and need to review it still. Is C2 really 1UF or is it .1uF? EDIT: I re-read the original thread and it does seem it's 1UF. My guess is it's a lower voltage cap judging on the size

Note, the PORT thing is the in/out of the circuit boards.. Need to clean it up but so far it all checked out in software.