Overdrive Reverb/Steel String Singer Hybrid

[martin manning]

...it’s just one guy naming his creations. No use in getting fixated on what he called an SSS without a post phase inverter cathode followers, or if 121 is an ODS with SSS features or a SSS with ODS features . It just is a thing and has a sound and he happened to call it by whatever . Obviously Dumble was rather loose in the end with what falls under what .

Exactly that, and in both ODS and SSS there was a continuous evolution of the concept going on, influenced by his customer's desires.

[Guy77]

...it’s just one guy naming his creations. No use in getting fixated on what he called an SSS without a post phase inverter cathode followers, or if 121 is an ODS with SSS features or a SSS with ODS features . It just is a thing and has a sound and he happened to call it by whatever . Obviously Dumble was rather loose in the end with what falls under what .

Exactly that, and in both ODS and SSS there was a continuous evolution of the concept going on, influenced by his customer's desires.

Yes I agree with this point as well. " influenced by his customer's desires" In the end the customer is always right! They pay the bills.

Cheers

Guy

[WhopperPlate]

AFAIR Alexander Dumble once commented: If you turn off the OD, it's a SSS.

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[beasleybodyshop]

aha! I knew i remembered it right. Is that from the Dumble Book?

[beasleybodyshop]

Finished up the major wiring. Going to do another circuit audit just in case I missed something. Then it's on to "clipping in a bunch of decade boxes" and setting appropriate plate voltages

I found this cool extruded aluminum enclosure at work that is the perfect size to sit on top of the amp cab for a Solid State dumbleator. I might could fit the tube version in here too. Will make that decision soon.

And lastly, I also found this cool handle that came off an old 70s Acoustic Solid State amp head cab. Considering mounting that on the side to help with lugging this beast around.

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[WhopperPlate]

Finished up the major wiring. Going to do another circuit audit just in case I missed something. Then it's on to "clipping in a bunch of decade boxes" and setting appropriate plate voltages

I found this cool extruded aluminum enclosure at work that is the perfect size to sit on top of the amp cab for a Solid State dumbleator. I might could fit the tube version in here too. Will make that decision soon.

And lastly, I also found this cool handle that came off an old 70s Acoustic Solid State amp head cab. Considering mounting that on the side to help with lugging this beast around.

IMG_20231025_222607868.jpg
IMG_20231025_225626072.jpg
IMG_20231025_225929315.jpg
IMG_20231025_225959050.jpg

Yep dumble book !

Can’t wait to hear the amp !

Has anyone else built something like this yet? I think this is the first I have read .

[beasleybodyshop]

Oh surely it's been done before by others here. Nothing particularly new here, just more pain to build!

[WhopperPlate]

Oh surely it's been done before by others here. Nothing particularly new here, just more pain to build!

Besides Dumble I have not seen one on the forum yet have any experience or opinion one way or another . 121 is all I have heard referenced , and listening to live clips of that amp from Rod Stewart footage I get a similar vibe from my own example . very curious to hear yours and other’s thoughts once you fire it up !

[beasleybodyshop]

Once it's up and running and voltages dialed in I will update the schematic annotations and layout

[WhopperPlate]

This thread reminded me that I hadn’t plugged my amp in for awhile , so I figured I would record some licks with the phone and share them. This is 112 evm12l and definitely loud enough . Ibanez 82’ double cutaway https://youtu.be/oWrzR7i-24Y?si=OVT0K9glOpIUCpEs

[ViperDoc]

This thread reminded me that I hadn’t plugged my amp in for awhile , so I figured I would record some licks with the phone and share them. This is 112 evm12l and definitely loud enough . Ibanez 82’ double cutaway https://youtu.be/oWrzR7i-24Y?si=OVT0K9glOpIUCpEs

Sounds nice! I like the OD tone, it sounds pretty balanced. Which treble cap values did you use in the OD circuit for treble cut?

[WhopperPlate]

This thread reminded me that I hadn’t plugged my amp in for awhile , so I figured I would record some licks with the phone and share them. This is 112 evm12l and definitely loud enough . Ibanez 82’ double cutaway https://youtu.be/oWrzR7i-24Y?si=OVT0K9glOpIUCpEs

Sounds nice! I like the OD tone, it sounds pretty balanced. Which treble cap values did you use in the OD circuit for treble cut?

Thanks man! I only posted overdrive because I figured we all know what a SSS type clean sounds like by now.

The overdrive treble smoothing caps are about 280p , but there’s also the treble taper knob . I used a 1M pot with a 10N cap before the overdrive volume . I kept it at 11 o’clock for most of the clip , and I turn it up to 10 at the very end . Whereas in an ODS I do not like that feature , it’s an appropriate addition to this setup

Keep in mind , this is off the reservation when it comes to stock Dumble . I don’t even know what 121 circuit looks like , and the client isn’t a dumble fan , so this ended up not having any actual dumble circuit values that anyone is familiar with . Low plate high plate hybrids on clean and overdrive. Phase inverter tuned more like a twin . This has built in tube driven effects loop , but I wasn’t faithful to classic dumbleator either . It ain’t a clone , which is why I never really post anything here about it all .

The my favorite part is the crazy custom massive overkill iron I installed . There is no sag in this amp . And that high power twin OT gives you girth .

[WhopperPlate]

Fwiw I also have an impedance mismatch . That’s a 4 ohm output OT with a 8 ohm speaker . A little bit more compression and give from that arrangement .

And I outta also mention that all the cathode bypass caps are 22uf . FAT. Did I mention the client was a strat player ?

Skip to 2:35 and you can hear it really sing at volume

[beasleybodyshop]

So update to this - I was able to bring it up safely today - got the pair of KT120s biased up and so far, so good. The only odd thing I've encountered so far is when I turn the master volume up past 10'o clock on the knob i get a loud 10Khz squeal. This noise goes away when the master volume is turned all the way up though. When i put the output on a scope the noise presents itself as a 43Khz tone (well outside human hearing) as well.

Things I've done to investigate:

-Swapped Plate connections. This creates the typical loud screaming feedback noise when you accidentally inject POSITIVE feedback into the PI .
-Disconnected global feedback loop at the PI itself. No change in noise.
-Groundedvtop/input of master volume pot - makes no change, still squeals when the pot is turned up.
-Grounded wiper of master volume pot, noise goes away.
-Grounded PI input cap DOES make squeal go away.
-Reflowed all solder joints in PI and post PI driver circuit. No change
-Removed all preamp tubes except PI and Post PI driver - No change.
-Swapped PI tube and PI driver - no change.
-Swapped power tubes - No change.
-Added 220K resistor in between the master volume pot wiper and PI input cap. This actually makes the noise WORSE.
-Replaced the wire from the master volume pot wiper to the PI input with RG174 coax, with one end shielded to the ground buss. No change.

Power tube plate and screen nodes , bias circuit is grounded together and terminated at point near AC power inlet
PI and Output jacks are grounded together and terminated on the main ground buss.

I'm at a bit of a loss here as to what to try next. Seems based on the troubleshooting above the oscillation is injecting itself at the PI input cap. Though not sure why adding some series resistance here makes it worse?

Anyone have any thoughts?

[WhopperPlate]

If you take the effects loop send to a different poweramp does it still do this ?