Demedash Effects - T120 Videotape Echo Pedal

Seiche · Post by **Seiche** » 06 Apr 2019, 11:31

Saw this on Insta. Apparently it's the deluxe version with two switches that hasn't even come out yet.

Almost all the part values and connections are good to see, so one should be able to do pretty good trace of this.

The only tricky part is that there are smd parts on both sides of the pcb

Seiche · Post by **Seiche** » 15 Apr 2019, 09:56

the most interesting part is probably the silent switching circuit without a microcontroller (using the cd4053 as a switch and the LM555 as a bistable flip flop to supply a control voltage to the cd4053 with a momentary spst)

http://www.geofex.com/article_folders/cd4053/cd4053.htm

https://todbot.com/blog/2010/01/02/mome ... using-555/

trampled_empire · Post by **trampled_empire** » 18 Apr 2019, 21:51

Hey, Steve from Demedash Effects here.
Let me know if you figure out how to overcome the issues inherent in the one design here. I ended up switching out a good chunk of it for something else.

Also, I tend to use different values than the silkscreen says lol so that might make it tricky.

Probably gonna just scrap this and start from scratch after finding this though.
I'm cool with sharing stuff in private and make a big effort to help anyone learn about this stuff... but I'm a single person operation running on a tight budget so this sort of thing isn't cool.

Seiche · Post by **Seiche** » 19 Apr 2019, 06:55

This is openly accessible on your instagram, why would you even post it?

PMowdes · Post by **PMowdes** » 19 Apr 2019, 08:30

Seiche wrote:This is openly accessible on your instagram, why would you even post it?

Why shouldn't be post it?? It's not an open invitation for people to copy his stuff.

I now this is a DIY forum and tracing circuits is what it's all about but at least let the guy release the thing first and make a few bucks before you rob him blind.

Seiche · Post by **Seiche** » 19 Apr 2019, 09:34

PMowdes, are you yourself not selling clone pcbs of currently in production pedals on your website? Or is spaceman authorizing you to trace and clone their circuits commercially?

I reposted one picture that the builder himself posted on insta to this forum, that's all I did. Furthermore, it's mostly SMD on both sides of the board, good luck tracing that. If this is crossing the line, then this community can pack it up.

Nobody is even showing interest in tracing this so far. It looks like it's a PT2399 delay with modulation and some clever (active?) filtering to make it sound more or less lofi, together with some interesting soft switching and a momentary switch to toggle oscillation. Never seen that before (at least since 20 1 4, maybe that's what makes it retro).

To be fair, the enclosure is awesome and hits all the right spots for nostalgia and the demos sound pretty good, so I wish nothing but the best to Steve, but talking about "robbing" anyone and "stealing" and the outrage is a bit much tbh. You know the main point of this forum is not to copy and make a quick buck and this has always been actively discouraged in the past. Hell, half the "pedal scandals" of well-known companies copying small builders were uncovered here (lovepedal amp11 for one).

Seiche · Post by **Seiche** » 19 Apr 2019, 09:48

trampled_empire wrote:Let me know if you figure out how to overcome the issues inherent in the one design here. I ended up switching out a good chunk of it for something else.

I can only guess what you are referring to, but I assume it's about the lm/ne555. R.G. himself posted the following advice here, maybe it helps:

R.G. wrote:There is a useful rule in designing effects - don't use the NE555. The NE555 has huge current spikes in its power and ground supplies right at the places where its output switches. Instead, use the LMC555 or one of the other CMOS versions that do not have the big current spikes.

trampled_empire · Post by **trampled_empire** » 19 Apr 2019, 18:23

Seiche wrote:This is openly accessible on your instagram, why would you even post it?

I posted this photo. You commented "I'm gonna trace this".
I thought to myself, 'damn, I thought better of the people who follow me', and took it down. It is NOT up for anyone to see. Further, you did not get permission to repost PCB artwork.

trampled_empire · Post by **trampled_empire** » 19 Apr 2019, 18:47

Seiche wrote:I can only guess what you are referring to, but I assume it's about the lm/ne555. R.G. himself posted the following advice here, maybe it helps:
R.G. wrote:There is a useful rule in designing effects - don't use the NE555. The NE555 has huge current spikes in its power and ground supplies right at the places where its output switches. Instead, use the LMC555 or one of the other CMOS versions that do not have the big current spikes.

Nope. Again, just because the footprint just says 555, that doesn't mean that's the exact part I'm using. The CMOS thing is fairly well-known.

Post by **modman** » 20 Apr 2019, 17:03

Hi Trampled Empire,

We have a thread devoted to these issues: https://www.freestompboxes.org/viewtopic.php?f=6&t=11263
It is a thread in which we collected all similar objections (you are taking food out of my mouth). Your arguments make no sense whatsoever, it's just sales talk. From a technical perspective, the history of guitar pedals is one of constant cloning, copying, emulating and improving.

You claim to be the owner of the brand, still I cannot see any prove of that in your profile or registered email. However, you have been a silent member since 2017...

There was the JHS VCR (€219), and even a pedalpcb version using the FV-1 chip,

bmxguitarsbmx · Post by **bmxguitarsbmx** » 22 Apr 2019, 00:13

If it is a unique design, I prefer we leave it slightly protected. If it's not, I prefer it be exposed. The constant cloning is bullshit. I buy pedals more than I build them. Or should I say, I USED to buy them. Mostly just end up feeling burned when I buy anything tho.

Seiche · Post by **Seiche** » 24 Apr 2019, 11:34

bmxguitarsbmx wrote:If it is a unique design, I prefer we leave it slightly protected. If it's not, I prefer it be exposed.

So it has come to my attention that it is not a 'unique' design, but may be based on the Keeley Magnetic Echo with a tone control and maybe some extra modulation. ILF talked about this matter-of-factly in february, and the early versions even used a PedalPCB Magnetron pcb. One can clearly see the PedalPCB logo in the gutshot. So I don't get the outrage about 'tracing and stealing designs' etc.

He makes his own PCBs now, so IF he didn't completely change the circuit from the early versions, and the 'Deluxe' is at least similar to the standard model, it's also just a Magnetic Echo tweaked even further. I haven't confirmed this though, as I haven't actually traced anything yet. NOW, I'll definitely look this over, though, as soon as I get the chance.

Seiche · Post by **Seiche** » 30 Apr 2019, 20:35

I did a quick comparison of some of the values around the PT2399 and the LFO section and highlighted the differences (and similarities). There are very few differences. All the coupling caps seem to be 4u7 though.

I've only spent half an hour on this and it's difficult to really see all the connections around the LM324, though two of the stages (pins 6-7 and 8-9) seem to be configured as buffers as they are directly connected.

I also haven't retraced all the connections around the 4053 switching circuit yet, as there are a few, but they should make the bypass and blend section clearer. I think the buffer circuitry is a bit more complicated than on the magnetron. There also has to be some kind of tone control for the repeats (tape quality) in there, maybe around the omitted C7 or in the feedback section around C3.

edit: I just realised the extra stages are probably for the "split stereo outputs" as mentioned in the features list. Also he included "buffered bypass with echo trails".

Seiche · Post by **Seiche** » 16 May 2019, 12:00

So I ordered a magnetron pcb and will try to build a clone with the above values subbed for the original values, and I'll also add a tone control similar either to the Hamlet Delay or Wampler Faux Echo

Another funny detail that I noticed is the design of the enclosure. I assumed this would be inspired by typical blank VHS tape designs from the 80ies and hence I thought it's quite clever. Now researching these designs for my clone I stumpled upon the Sony Dynamicron T-120 which the Demedash is almost a 1:1 copy of. That cracked me up. Sure it's not that bad, but instead of simply going for the a e s t h e t i c s of videotapes from back in the day, he cloned the design right down to the little dot logo in the corner and the name T-120.

~arph · Post by **~arph** » 20 May 2019, 10:32

Seiche wrote: So it has come to my attention that it is not a 'unique' design, but may be based on the Keeley Magnetic Echo with a tone control and maybe some extra modulation. ILF talked about this matter-of-factly in february, and the early versions even used a PedalPCB Magnetron pcb. One can clearly see the PedalPCB logo in the gutshot. So I don't get the outrage about 'tracing and stealing designs' etc.

Burned...

ppluis0 · Post by **ppluis0** » 20 May 2019, 11:38

Hi folks,

I discover some time ago (during a breadboard season) something about PT2399 that consider interesting to be mentioned here.
The value of the capacitor at pins 9 and 10 in this design and also in some Wampler delays is bigger than the usual 100nF seen in other implementations with this IC.
The resultant effect due increase the value of this particular capacitor brings more output level after the D to A conversion of this IC, but, in the other side, the dynamic range of the reconstructed delayed signal is sensibly reduced.
In some schematics appeared in the web the value of this cap and the other connected to pins 11 and 12 are of 47nF

Try use this lower values in your next designs and report what you hear.

Cheers,
Jose

captain_tango · Post by **captain_tango** » 21 May 2019, 20:10

It's always sad seeing when someone falls from grace within the strict open sourcedness of this forum, especially when they've been pretty helpful elsewhere. Steve seems like a good guy, but I wish he realised that trying to hide a circuit is only going to make people here try even harder at finding out what's under the hood.
More people, especially people trying their luck in the game of selling pedals, should take note of this.
Transparency does in fact not really kill your sales, quite the contrary. Sharing is caring and those who want to build your stuff, will find a way no matter what you do to avoid it. Best case scenario is you share something with such an inherent kindness and respect for the flow of future development of the guitar pedal universe that even some of these modders and tweakers who never buy anything may at the very least recommend your stuff to those who do!
That's just me, and I have to live with me.

Seiche · Post by **Seiche** » 23 May 2019, 04:45

In this gutshot of the standard version(?) there are a few things going on. This is also a magnetron pcb, but modified.

- there seem to be 3 wires going to the pot on the bottom left (level). Probably to relocate it to top center (echo)
- there seem to be 2 wires going to R13
- R12 looks like its missing
- there is something going on with the diodes (they are missing?) and C18
- maybe that pot varies R12 and R13 simultaneously to make the tone control with the wiper going to pin 14 of the pt2399
- the little "package" on the bottom right puzzled me at first, but then I saw reviews of the T120 in which the reviewer claimed it was a 1.5sec delay, which is only possible with a second pt2399. So my guess is this is the daughterboard for a second pt2399 incl surrounding components (I'll have to look into how that is accomplished). I assume this was dropped again for the deluxe version due to complexity and no real benefit.

Seiche · Post by **Seiche** » 23 May 2019, 14:30

Seiche wrote:maybe that pot varies R12 and R13 simultaneously to make the tone control with the wiper going to pin 14 of the pt2399

together with this related statement on reddit by trampled_empire this makes me think this is some kind of bandpass: "The ability to use the 'tape quality' knob to mix the lower mids out of the wet signal makes it possible to have the repeats turned up and busy without muddying up the dry signal."

trampled_empire · Post by **trampled_empire** » 27 May 2019, 02:00

I spent some time away from this, and sort of realized it wasn't the idea of this being traced that bothered me so much as the attitude of the individual who started this thread.

captain_tango wrote:It's always sad seeing when someone falls from grace within the strict open sourcedness of this forum, especially when they've been pretty helpful elsewhere. Steve seems like a good guy, but I wish he realised that trying to hide a circuit is only going to make people here try even harder at finding out what's under the hood.
More people, especially people trying their luck in the game of selling pedals, should take note of this.
Transparency does in fact not really kill your sales, quite the contrary. Sharing is caring and those who want to build your stuff, will find a way no matter what you do to avoid it. Best case scenario is you share something with such an inherent kindness and respect for the flow of future development of the guitar pedal universe that even some of these modders and tweakers who never buy anything may at the very least recommend your stuff to those who do!
That's just me, and I have to live with me.

While I have not frequented or contributed to this site in the past and really have no grace to fall from, I do my best to take the time to answer any questions anyone has about circuitry and share cool circuits that I think others might find useful elsewhere. I'm not going to stop doing that, but this experience has simply taught me to be more careful about what I share publicly.

If I'd been asked about the switching circuit in this to begin with rather than being flat out told that it was going to be traced, I would have been happy to share a schematic of it. The approach that Seiche has taken in this whole situation, however, has been aggressive and rather disrespectful. I apologize to anyone else if I was overly defensive and came across as demeaning towards this community at large. I have no bone to pick with anyone here besides the socially inept individual who has been nothing short of insufferable about this from the beginning.

I do not have an issue with circuit tracing as a rule. It's absolutely true that no makers these days would be doing what they do if it weren't for the people who figured out the circuitry that went into the pedals that came before.

I do have a problem with Seiche's complete lack of tact and I again maintain that he's a shit.

Also true that early units were adapted from the Mag Echo, using the Magnetron PCB from PedalPCB. I don't go out of my way to advertise that but don't try to lie about it either, just as Keeley won't advertise but won't lie that it's based on some other thing that was in turn based on the Rebote. There are plenty of small changes and a few bigger ones. But yes, the Mag Echo was sort of the platform I used to develop this back when I made the original one or two. It has and continues to evolve over time. But and the end of the day, this is just a nicely tuned delay unit, nothing mind-blowing or revolutionary. I've done here what many before me have done, made something new out of something old. Really not sure why Seiche is being driven into such a fervor over it.

Also, yes, of course I made it look like an existing VHS tape package. The point is that it looks like a VHS tape. If I invented some non-existent VHS tape package that noone recognized, you know what it would look like? It would look like some random pedal with vaguely 90s-ish artwork that says "VHS" on it, Seiche. Christ.

Demedash Effects - T120 Videotape Echo Pedal [traced]