Could We Do This?

Coda

Coda

Well-known member
In the following video, a guy that talks like a Convict explains how the Beatles got the Get back tone. TLDW; resistors off the cathodes of the power amp into a feedback arrangement. Supposedly implemented to tame the attack of a Twin (a low E through a cranked Twin hits like Ivan Drago) it resulted in too much compression, which is why Get Back sounds so good…


Could we do this as an OD pedal? Everyone’s take from the Get Back doc is that those Twins are strange. If possible, practical, I feel this would move product.

Potential names: Jojo Drive, Sweet Loretta OD, Everybody’s Got Something to (over)Drive Except Me and My PCB Supplier…
 
Coda said:
Potential names: Jojo Drive, Sweet Loretta OD, Everybody’s Got Something to (over)Drive Except Me and My PCB Supplier…
Click to expand...
I'd love to see that last one silkscreened on a Tayda enclosure! I'm having a hard time picturing the circuit, but I bet you could get somewhere with the old "slap a JFET where the tube should be" approach.
 
I am not an engineer. When I read your description and watched the video, the first thing that came to mind was madbean's Sparkplug. And while not a clone of any one thing, it's "of the lineage" of things like the LTD, Silver, etc. I love this thing. And to get back (ha) on topic, here's the redraw I did of it (slightly different power section, but otherwise drawn to the rev.1 spec.

sparkplug-redraw.png

While a bit more prominent than what I heard in the video, the SAT switch does something along the same lines, to my ear, if you use your imagination. I haven't tested it on a Twin, but I plan on sharing the last build with a friend who does.

I do like @Aleph Null 's suggestion of tinkering with something like a JFET or MOSFET and eliminate the op-amp entirely. That led me to something like the WIIO/RAH, but taming the overall drive push outside of the Townsend/May threshold.

WWIO.png

I am not an engineer. But nothing sticks (or not) to the wall before the first fistful of spaghetti is thrown.
 
So, they basically had a cathode-biased 6L6 twin? (Well, the fixed bias is still there). No wonder it felt different.

Aleph’s “slap a JFet/Mosfet” would be doable. Maybe branching off of ROG’s Thunderbird but adjust the “output” to be more ‘squishy’?
 
Now just what exactly the pedal equivalent is, that I’m not sure of. I think that would be the same as a cathode bypass cap on a stage like this (screenshot of the Windmill Drive).

The difference in my mind is still that cathode bypassing a single transistor gain stage has got to be different than this shared-cathode-bypass thing between two power tubes in parallel into an output transformer.

Could we set up three transistors, one as a phase inverter, and then the other two as two halves of a similar parallel pentode output section? (I have no idea, something tells me that if it were so easy and amazing sounding, greater minds than mine would have done it already)
 

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Another way of looking at it is trying to replicate the results, but not the exact circuit. I’m thinking a simple preamp into a Twin-tuned EQ section, into a boost/compression section that replicates what the “mod” is doing on the Beatles Twin…
 
Probably pointless to reference the Boss Fender pedals because 1)it's likely DSPs or 2) haven't seen a trace of one yet, but didn't look beyond the usual suspects.
 
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