Demeter Trembulator without ldr

[Danich_ivanov]

Hi everyone,

I'm looking for a way to use trembulator's oscillator in a schaller's tremolo manner which is pulling input signal to the ground by transistor without Ldr's and all that stuff. Would like to hear some suggestions on how it could be achieved.

[Kipper4]

If you get rid of the envelope detector (everything inc C9 to R17 R18)

Change the ldr Vact4-B to a 250k> pot wired as a variable resistance (eg lugs 2 and 1 tied)
Get rid of the R28 (to be determined)

and you have much the same idea but with a Jfet.
Credit to the designer of the EA Tremolo.

reply 10

http://www.diystompboxes.com/smfforum/index.php?topic=117570.msg1092064#msg1092064

[Danich_ivanov]

Thanks! I'll try that.

[duck_arse]

I'm not sure of kipper's numbers (you had that sleep yet?), so I'll say - on the demeter, keep R17 and all left of it (even tho I'm not sure what IC1 is doing) - on the schaller, keep C8, R7, P1 and to the right. connect the demeter to the schaller, see if it werks.

[Danich_ivanov]

A quick update. It is messy, it clicks, led doesn't blink quite as dramatic, and i'm a bit tired, but this problems were expected and the most important thing is that it works, it wasn't as staight forward as i though it would be, but it does what it suppose to. I need to spend a tad more time with it, so that i could give a more complete picture.

[duck_arse]

Danich_ivanov - how rude of me - welcome to the forum.

[Danich_ivanov]

Oh, thanks, i appreciate that! Although i'm not so much of a forum person, even though i visited this forum as a guest a number of times. As for the build, i'm nearly done with it, tweeking things mostly, i'm not super happy with the way depth pot works, also ticking, and the weird thing is that it works totally fine with bjt, but when i tried jfet it worked in reverse, so that without anything applied to it, it grounds the signal, tried various positions, tried other jfet, result is still the same.

[duck_arse]

Danich - search up R.G.'s page on the Trem Face over at geofex. it might give you some hints on jfetting the schaller.

[Kipper4]

Did you try a 47~100uf cap at the node of R5 R9?
It might help with the ticking.

Is it a ticking or a thump. Depending on the wave form on the output of the lfo
ref; (https://postimg.org/image/6hjxugerez/)

Is it ticking when you dont play too?

You can ammend the depth pot with a series resistance maybe.
Did you try some bigger value depth pots? 250k?

[Danich_ivanov]

I changed some things and jfet works properly now, although only when no ground is connected to it. Clicks are not an issue anymore either, although when they were an issue i tried caps, and they seem to help a little bit, but not entirely, they also messed with the range making the whole thing slower, and i wanted to leave lfo as intact as possible. All this problems were solved by using pin 7 instead of 1 on ic to grab lfo. Overall i'm mostly messing around with depth right now, while trying to keep part list as condensed and small as possible. Later i would like to frankenstein a few trem schematics using this lfo)

[Kipper4]

|Good work.
When your done please update the schematic.
Thanks

I hadn't notice you were new. oopps
Welcome aboard.

[Danich_ivanov]

Thanks man! Sure, since i found pretty much no info on how to apply lfo from ic's to transistor, and i was looking for it, and now i'm nearly there, i feel like it's important to share this kinda thing.

[Danich_ivanov]

Another quick update. I'm finally happy with a depth control and pretty much everything else, but i want to test this with an actual preamps from schaller and ea to see if there are any drawbacks, also wether or not it will daizy chain well since i was running it from the isolated psu the whole time, before i will frankenstein EA/Schaller.

Oh, and i just thought that i might also try it with Demeter's preamp.

[Danich_ivanov]

Conclusion time.

Here they are "Schaller tremulator" and "IYCBLDR" (or "if you can't buy ldr") tremolo.





Both sound amazing. I also wanted to include EA tremolo, but couldn't really make it work, for some reason this circut doesn't bond with jfets, and i tried bjt in conjunction with EA, but it sounded like crap, so i gave up on it, at least for now. Although, if you really want EA preamp, just disconnect lfo section from it, and apply the same method that's been used in a schaller and demeter. Might require some tweeking, but it should work.

Each pedal, when tested, was daizy chained with 5 other pedals, with no ticking or noise issues.

Hopefully schematics are easy to understand, and i thought about making it in a tiny cad, but it just didn't seem fun enough)

Overall i'm very pleased with the results, if you have any questions, please do, and it would be cool if someone could actually build this, and share ideas, thoughts and all that stuff. Cheers!

And thanks to duck_arse and Kipper4 for providing usefull info.

[duck_arse]

nice work, danich, when do we get to hear them? and what was the problem w/ the EA, we love fixing them.

one thing about your "I can't stand ldr's" version - on your circuit dia you have a line drawn from input to output, apparently shorting them together. is that a ground connection mis-drawn?

[Danich_ivanov]

Thanks! That's what i thought when i saw schematic for demeter, but apparently it is not, without this connection it simply doesn't work, not a usual design, but unless schematic that i used for reference is wrong, this is how it works, by mixing a clean signal driven by lfo with the signal that goes through op-amp which is not driven by lfo, and based on what i heard when i built it, comparing to what i heard in the demos, it sounds legit.

Also you can make it choppier at max depth if you want by increasing 22u cap.

I might record some stuff later, but the fastest way would be to build it yourself)

With EA, i'm not even sure where to begin, it barely trems, if you use jfet disconected from the ground, and it doesn't trem at all when it is connected to it, with bjt, it sounds like the affected and anaffected signals go in a separate ways, and that's all i can say about it at the time being, i spend i bunch of time with it, trying various combinations, and nothing, so for now i'm stepping back from ea, but might come back to it later.

But what i would like to ask, is how can i mark this topic as "(solved)", since i can't modify my first post?

[duck_arse]

^ like that, just type solved in the subject bar upstairs. however, I think this only sticks to the post you change the heading on, and any answers fall back to your original title. I think. we'll see.

about you input connecting to output - I'd have to look very closely and think very hard about it [but I'm not going to]. I have since noticed tho, that you have a 22uF in series w/ a 10uF at the lfo in. this works out as about 6u8. ditch one of those caps (losing the 10uF might give you more depth at low low lfo freqs).

[edit :] well, I tried, but the title change didn't show on the indexing page, so some of the impact has prolly bin lost.

[Danich_ivanov]

Sure, you can replace it with 6,8u cap if it will work for you, however, i found 10u to be too much, so that you can barely hear you'r signal, because the gap is too small, and 4,7u not enough, and i also found that using higher gain transistor makes things choppier and vice versa, so depending on a transistor you have you might want give it a bit of the edge, but because space between too extremes (4,7u and 10u) is relatively small, i found that using 2 caps gives a more precise result, where 6,8u might not do it necessarily.

I changed title, but it didn't make it to the main post (

[duck_arse]

you could "report to moderator", and ask s/he to modify it, I think, but why poke a sleeping dragon?

[Danich_ivanov]

That's what i thought)