Passive tremolo video. Let me know what you think?

[darron]

hey guys. i think i've finished breadboarding my tremolo. it's basically a flashing LED / LDR combo sending the signal to ground.

i started working from this schematic, but with changes of course:
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#eyes.gif

the ldr ranges about 2K (light) to greater than 2M (dark). i suppose i could use two together in series to get even more depth, but this seems okay for to me.

as you can see/hear the ldr can range to REALLY fast, or long sweeps. there's a depth control which just puts resistance before the LED. there's also one more trimpot which i didn't touch in the video which controls the LED pulse. one way it is mostly dark and pulses bright a little bit, with a gap in between. the other way it is mostly light and dulls down a bit. in the middle is almost where i have it, but not quite.

the audio signal never touches any active components at all, so i doubt this unit will make ANY noise at all. if i connect the ground to the circuit's negative i do get the popping noise as the linear ramp changes direction unless i ground the breadboard base as well, so there might be an issue if you want to share a common power supply. we'll see.

i've never seen a schematic for a passive tremolo... what's up with that? i'm yet to see how it responses with buffers infront or behind it though....

OHH... for additional mojo i used a jrc4558d as the osillator!

please comment and tell me what you think?
http://www.dazatronyx.com/temp/passive-optical-tremolo.mov

[darron]

btw... excuse the crappy recording and playing.. i realised later i could have played something nice and in time with the pulse. it's going through a small 30watt laney amp and just getting picked up by my mac book pro mic. i didn't care too much about the farty recording noise.

[darron]

i made an enclosure for it...


it's my first sort-of success using photoresist etching. i'll do a better job next time. i like it better than pnp already.

[soulsonic]

I think that sounds pretty good. I love simple things like that. I like the idea that it's basically like you're turning the volume control on your guitar. I think "pure" effects like that are in most cases the best way to go. I wonder if it even needs a full bypass? I bet you could probably just use a SPST to disconnect the LDR from the signal an use that as a bypass. I have a mute box that works like that with a momentary switch.

[darron]

I think that sounds pretty good. I love simple things like that. I like the idea that it's basically like you're turning the volume control on your guitar. I think "pure" effects like that are in most cases the best way to go. I wonder if it even needs a full bypass? I bet you could probably just use a SPST to disconnect the LDR from the signal an use that as a bypass. I have a mute box that works like that with a momentary switch.

hey soulsonic. thanks for your feedback (:

yeah, it doesn't need bypassing. it just needs a spst to hook it up. but i'm also having one pole dedicated to powering the unit so that it doesn't take up power when in standby. since the power is totally isolated that shouldn't be a problem.

you could even just have the power switch on with a spst since when the unit it off it would only have a >2M resistance to ground, which won't effect the signal. still, i'll disconnect the signal since i'm probably going to use a blue 3pdt to mount the pcb.

i tried putting a resistor before the output to get more depth but it didn't make any difference... i don't know why.


would anybody to be interested in building this? i'm designing the pcb now. maybe i'll do a schematic first to help me out.

[jlullo]

dude, good job with this!  thanks so much for making a movie.  it's kind of nice seeing one for a change!

i definitely would be interested in checking out the schematic if you wanted to share!

[darron]

dude, good job with this!  thanks so much for making a movie.  it's kind of nice seeing one for a change!

i definitely would be interested in checking out the schematic if you wanted to share!

cool! i'm making it right now. it was made from parts i had lying around, and i don't have much lying around, so it should be pretty easy.

[soulsonic]

I wouldn't mind making one, but I wonder how well it would work with the "Two Transistor LED Flasher" circuit from that same page you put up a link to. You used the "Fading Red Eyes" one right? I just like the idea of going totally as simple as possible and using that little 2 transistor circuit.

[darron]

dude, good job with this!  thanks so much for making a movie.  it's kind of nice seeing one for a change!

i definitely would be interested in checking out the schematic if you wanted to share!

schematic up:
http://www.dazatronyx.com/support/optical-tremolo.pdf


if anyone has any tips for my schematic drawing skills that would be good too! lol. it's a bit messy. i drew the opamp as one component to save you working out what goes where.

hopefully i didn't make any errors because it's pretty simple, but let me know if it doesn't work.

[darron]

I wouldn't mind making one, but I wonder how well it would work with the "Two Transistor LED Flasher" circuit from that same page you put up a link to. You used the "Fading Red Eyes" one right? I just like the idea of going totally as simple as possible and using that little 2 transistor circuit.

i think the led flashing circuit on that page only flashes ON/OFF... that's why i chose this one.

interestingly though, there IS another circuit (next i think?) which fades one led in while the other one fades out. this could be a much better volume control as you could make a better voltage divider. i don't see a need for that at this stage though.

[the_random_hero]

I think I may just have to try this one out. The only thing I can see with the schematic is that you've missed an output - it might become a tad of a problem for some people :p:

[darron]

I think I may just have to try this one out. The only thing I can see with the schematic is that you've missed an output - it might become a tad of a problem for some people :p:

good call. i'll make an update. i also forgot to specify the power is 9v dc.

thanks (:

[darron]

for those of you in australia, this is the LDR i used:
http://www.altronics.com.au/index.asp?area=item&id=Z1621

pick up a really bright red led from jaycar. you could also us an LM1458 for the opamp, but you don't get the false vintage mojo

here's a picture of the optocoupler i made using a 14pin IC socket, heat shrink and cut foam:

note that one side has 3 legs which i didn't cut to remind me which end is the negative side of the LED.

if you want to be perfect, use red heatshrink to reflect the light inside

[darron]

i think using the two leds (fading while glowing) style of schematic on the list with two LED/LDRs would make a better volume control in terms of having something more compatible with everyone's setup. how come putting in series before the signal output doesn't help to increase the depth a little bit?

any ideas why he uses a quad opamp? do you suppose i could use the existing layout that i already have on my breadboard?

thanks in advance for your thoughts guys (:

[darron]

ohh guys, if you take the LEDs coming off pin 1 and connect them to pin 7, it's a square wave instead. it gives a very deep (almost mute) on/off. much more versatile.

just use a SPST or DPDT switch to tap off the wave type that you want.

i'm loving it (:

edit: i've just put this on the schematic...

[foxfire]

just bumping it so i don't forget to build it.

[darron]

just bumping it so i don't forget to build it.

thanks foxfire. don't for get to let me know how you go! use a really low resistance ldr. if you can't get low K's, then maybe two in parallel. i'm interested to know how it responds to different pickups and with buffers infront/behind also.

looking forward to it

[Jim Jones]

Hey Darron,

I think your trem sounds great!  I might just give this one a try.

Thanks!

Jim

[JasonG]

I just finished bread bording it. Subed in a 10 uf cap and had to use 2 LRD's to get the depth I wanted. I used to have a Boss tremolo. This trem puts that to shame. Now to put it in a box. :-)

[newfish]

That's excellent!

Thanks for posting your work - feel inclined to build one, as I've never worked with optical circuits before - and I'd like to replace my trusty Danelectro Tuna Melt (had it for 10 years and it's never failed) with a true-bypass effect.

Outstanding!