Easyvibe: replacing LED's with light bulb?

[Lurco]

then again a DMM only measures so and so often over time, and doesn`t show linear rise or fall!

[solderman]

I got some crazy behaviour from a DOD compressor I made my own LDR/LED for. When I measured the LDR I discovered that it had a reverse logarithmic and fast (talking a five milliseconds) to rise and fall in resistance in no time. (from 2K at light to -2M dark in no time at all then from 2M to 10M ~2 sec) I was also amazed over that the LDR needed nearly no light at all to react. I just checked again from 2K to >1M is so fast that it's done at ones on my DMM. And I redid the dark room and light my amp control lamp from ½ m and the LDR reacts with 500K at ones. So if the LDR acts like a switch between 2K-500K for almost no light at all and in no time at all the origin or behaviour of the light source will be of little or no importance.

When I built my Easyvibe I first heatshrank the LDR facing and touching the LED's top. The sound was more like a phaser with a fast changing in the sweep. Like the on/off way you describe.

I then changed the way the LDR's are attached to the LED's. I still put the LDR facing but not touching (space of about 3mm) the LED's top in a simply tube (in fact a non heatshrunk tube) and the sound is smoother and closer to a Univibe than before.

I think the specific sound of the Univibe also comes from the way the LDR's react to the light reflections inside the shield (even the cheap Danelectro Cool Cat Vibe is built like this). Would another bulb/LDR's arrangement make the same sound ?

It  Shure wold be interesting to
1. try a LED in a  Neo or univibe
2. use a LED in the easy vibe and then change LDR:s to different specs.
3. Use bulb in the easy vibe and do the same thing.

//Solderman

[solderman]

Hi all
I have tamperd with the genes of two of the most loved DIY project.   
This thread http://www.diystompboxes.com/smfforum/index.php?topic=75101.0 concerning replacing the LED:s in a Easy Vibe by a light bulb inspired me to do a bit of GMO engineering. I have merged the best sounding easy built Vibe, The Easy Vibe, with the most versatile easy built LFO, the Tremulus Lune.

This is the result

This is the film crappy film where I try to show how the light from the LED affects the LDR and the sound. It is made with an old Cannon Ixus500 there by the quality of sound and pic.

http://www.youtube.com/watch?v=9UgC4elcEog

This is the test bench I used. I took R.G:s layout for the Easy Vibe and only populated the Vibe part. (about odd soldering to the PCB, I plan to reuse the components) and did some surgery to my Tremulous Lune Box. I had to add a 500K Lin pot in series with the speed put to get slow enough sweep for the vibe.I took out the LED and replaced it with hook-up wires to a separate board with 4xLDR and ONE led. Its actually two LED:s One bright blue and one dim read. I sanded the top of them and glued them together and added a switch between them to se if the brightness had any effect. As you can se in the end on the film the effect was non so I skipped one led in the new layout.

This is the 4 LDR 1+1 LED combo.

This is the test bench


This i a NOT verified project file for the project
http://solderman.fatabur.se/Future%20project/Luooney Vibe.pdf



//Solderman

[JKowalski]

I'm working on a trem/vibe pedal based around an ICL8038 I have, and debated the light bulb route. I do not have the audio portion of the circuit done, but in observing the effect of the lightbulb/ldr on the outputs of all three waveforms (square, sine, tri) I did not like how it looked on the scope (i scoped the output of a voltage divider made with the LDR)

All three were very distorted and very diminished in depth as speed rose, square wave practically became a curved tri again, and the triangle was very misshapen. But, hey, that could be the type of modulation you want. However, it looked like all three waveshapes through the lightbulb could be easily reproduced with a duty-cycle adjustment in your oscillator to give that same uneven pattern, and perhaps a filter to curve the wave a bit. Given that LED's rarely ever die out, are cheaper, smaller, and require less current, I see no reason why you would not use an LED, in any case, even if you are going for "that sound". It's not too hard to replicate it with much more reliable parts.

Keep in mind, the only purpose of an LFO is to make a waveform. How you get to that waveform will have absolutely no effect on how the modulation sounds.

[solderman]

Keep in mind, the only purpose of an LFO is to make a waveform. How you get to that waveform will have absolutely no effect on how the modulation sounds.

So true. This is why I think the "correct filament in the bulb and galas over the LDR" is Marketing BS. Ofcause as part of the mecahanism they have some effect but so littel that it can be ignored. But hey,   I'm buying stuff just because they are made by  "X-brand" so as long as everybody is happy....

It wold be very interesting if some one could do what JKowalski did and scope the output of the divider made by the with the LDR at x-Hz  y-Hz and z-Hz speed and MAX-MID-MIN depth for;

• The Uni Vibe (if someone have the original)
• The Neo Vibe
• The Deja Vibe
• The Easy Vibe

Just to compare the sine wave result for those.
//Solderman

[orangetones]

I have a feeling that Solderman might just box this up as a 1590A Vibe pedal!

[solderman]

I have a feeling that Solderman might just box this up as a 1590A Vibe pedal!

Well you might be right there.
Haven't given the Easy Vibe any 1590A thought since i made the phase 45 and with a Chorus coming up but Why not .......
But probably then with the   one LED/4 LDR combo the and original LFO since the Temolus Lune has to may knobs.

Anybody out there who's intrested in A 1590A Easy Vibe?

//Solderman

[danielzink]

I have a feeling that Solderman might just box this up as a 1590A Vibe pedal!

Anybody out there who's intrested in A 1590A Easy Vibe?

//Solderman

ummm....hello ? 

Dan

[nico13]

Just tried this and it works OK. Needs some fine tuning with biasing. I strapped a 1Meg resistor from Drain to Gate and this improved the action of the circuit. I used a 12v bulb rated at 0.183A.

Mick,

I understand that you put a 1M resistor between Drain and Gate of the IRF740 but did you keep the same value (1M) for the pot connected to Gate?

[Mick Bailey]

Yes, I did keep the same 1M pot though I noticed it has a narrow 'sweet spot' to get the bulb to modulate nicely. The circuit is very simplistic and I just knocked it together to see if it would work. Could do with a little bit of experimentation to get it 100%.