# Demedash t120 mods



## seiche

As is well known, the early demedash t120s use a magnetron pcb. They received an additional tone pot (tape quality) at some point early on and even came with another daughterboard. 

Anyone know what is required to mod a magnetron pcb to t120 specs?


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## ZorakIsStained

Looking at the gutshot from another similar pedal not made by Demedash, it looks like one way to change the repeat tone is to replace R26 with a pot. I played around with the low-pass filter section using LTspice and I think a 50k pot would produce the biggest tone range. The only other obvious change they had made was to increase C17 from 330n to 470n. I think I'm going to get a Magnetron PCB and breadboard this out, though I won't have a T120 for comparison.


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## seiche

ZorakIsStained said:


> replace R26 with a pot.



This is what I did, albeit with a 25kB pot in line with the 10k (to get the regular tone on 0). The change is subtle. I'll try a 50k and report back.

I also used a 470nF.

Which "other similar pedal not made by Demedash" are you talking about?


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## ZorakIsStained

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Maybe this is you and we're just in a feedback loop? That'd be some irony.


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## ZorakIsStained

Well, regardless of all of that, Demedash is probably doing a little more than just adding a pot somewhere. There are a bunch of gutshots of normal T120s, 3 ICs are clearly visible; in one pic it's the PT2399, a LM358P, and LM324N. there's also a transistor-looking device that's probably the 5V regulator. The last two ICs are double and quad opamp parts, so Demedash has 2 more opamps in his design than in the Magnetron. Chances are those are used for some sort of active filter, maybe a multiple feedback filter like this: https://www.diystompboxes.com/smfforum/index.php?topic=76222.0
Something like that would loan itself pretty well to a daughterboard. I'm not sure where to insert it in the circuit, maybe before the last RC filter in the feedback path. Or maybe in place of that filter.


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## Cucurbitam0schata

Hey Folks - any luck with figuring out the Demedash? Most likely will build a Magnetron soon, interested in this discussion!


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## Boba7

seiche said:


> This is what I did, albeit with a 25kB pot in line with the 10k (to get the regular tone on 0). The change is subtle. I'll try a 50k and report back.
> 
> I also used a 470nF.
> 
> Which "other similar pedal not made by Demedash" are you talking about?



Hey

Yes, I think a 50k pot would work better than 25k. I'm not sure that's how Demedash implemented it though, it seems to be cutting lows, not cutting highs, on some demos I've seen.
Also the other ICs are probably for switching, not audio.

His pedal has evolved a lot, but to my ears it stills sounds pretty much like the Magnetic Echo from Keeley, just with a lot of extra features, which is quite cool I must say! But the base sound is definitely the Keeley circuit.


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## r.callison

I have a T120 from earlier this year, and can provide a gutshot if that helps


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## zoysiamo

r.callison said:


> I have a T120 from earlier this year, and can provide a gutshot if that helps


A gut shot would be great!


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## finebyfine

Buddy of mine just asked if I could do a T-120 for him, bumping in case anyone has more build recs for the mods on this


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## Harry Klippton

I posted this in the wish list since it came up again 





						Demedash T120 v2 Deluxe
					

Since that thread came up again, it reminded me of this pedal. Even getting to the bottom of what mods make a magnetron into a T120 would be interesting




					forum.pedalpcb.com


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