DIY Optical Tremolo. How to design a tremolo guitar pedal.

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For my next lolly tin guitar stompbox build, I have designed an optical tremolo. The design has been derived from an old Elliot Sound Products circuit. Over the years, the ESP website has been one of my favourites. The circuit has the vactrol in a location that resembles an opto-compressor. Since the conductance in an LDR (light dependent resistor) rises and falls at different rates, this gives the audio pulses a slow attack and a fast cut-off. This is unusual for a tremolo effect pedal.
Here is the original ESP site page: sound-au.com/project29.htm

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Опубликовано:

5 ноя 2022

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Комментарии : 22

@neysonza Год назад

Can you elaborate on the c taper hack? Thanks! Also about the ticking, I've read that they usually use low power op amps. Like tl022 or maybe try using tl062.

@RobMods Год назад

Yes, I've read this also. In fact when I was filming I did talk about that as a possible 4th tweak if the others hadn't completely cured the ticking. (I cut it out in the edit though.) It makes sense, since a low current op amp also usually has a very modest slew rate, so it can't physically source the current in the first place, plus its output is slower to shift each time it flips. I did actually try an LT1475 (ultra low current device) that I found, but since it was a true rail to rail, the tremolo sound was significantly altered, since the LEDs were turning on a bit brighter. To make another op amp work would have meant breadboarding the circuit again, and the LM358 was just fine. It has a fairly modest current draw and slew rate anyway. FWIW, getting the LEDs to match also took some tinkering. I really wanted to use a 3mm as the status light, to match the other lolly tin pedals. I probably should have just started with a matching pair of 3mm LEDs and made the isolator with one of them. Thanks for watching my channel!

@RobMods Год назад

Oh, and the pot hack was simply that I needed a C50k (reverse audio taper), but only had a dual gang C100k. By wiring the two gangs in parallel, a C50k was achieved. IOW, the two left lugs were joined, the two wipers were joined and the two right hand lugs were joined. In this situation, the taper stays the same. FWIW, I have an old video with some other pot hacks... ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-iCUOVOOc5WY.html

@raymondbosse9713 Год назад

Great project, Rob. Many thanks!

@RobMods Год назад

Thanks Raymond. I'm glad you liked it. The pedal sounds really nice. I'm pleased with it for sure...

@J.C... 9 месяцев назад

My trem pedal had these out in the open. So I took electrical tape and covered them all and it actually made quite a difference in how the thing sounds.

@agentdouble-bylamomie Год назад

Well done, again ! Very nice ! Congratulations :)

@luissaints7082 Год назад

thanks

@thejoetandy Год назад

Not sure if you're intentionally following JHS content with how the mentioned circuits are sometimes made, but this is two in a row. Great build Rob

@RobMods Год назад

Well the clean boost was for sure a response to the JHS Solo Boost, although I'd always had a nice clean boost pedal on the list of projects for the channel. This one not at all, just a coincidence. I really love the tremolo effect, and was always going to have one on my lolly tin pedal board. Thanks for your kind words, Joe. Glad you like my content.

@jablonczyk Год назад

This is such high quality content! Love your videos! What would it take to make it commercial grade?

@RobMods Год назад

Thanks mate. I'm glad you like my stuff. I think you'd have to find a good consistent source of opto isolators. The LDRs i bought did vary quite a bit. Then batch test them and adjust the circuit from there or create a trimmer circuit and alignment procedure for consistency. Also I never tested or even simulated the circuit at 18v for example. I doubt the oscillator would work as intended with 18v. So a zener or reg or something would be need for the pedal to be idiot proof.

@joeswanderings Год назад

sweet

@poseidon8189 Год назад

I can suggest to use separate grounds for generator and audio path, especially if wave control has opto-coupler. This will reduce dramatically leaking of generator frequency into audio path. Also adding a high path filter on the end stage of U1 with frequency roll-off around 50-100Hz will greatly reduce that generator frequency sound at amplifier side.

@poykehmusic Год назад

16:10 Hello. Would a small *hot glue gun* be efficient there if I haven't any *CA Glue* ?

@bartekpodskarbi7817 8 месяцев назад

Hi, I've tried building this tremolo from ur schematic, and even though i created separate grounds etc. this ticking sound is still very present. I really don't know what should could I do about it. Is there anyone who could help?