555 Ping-Pong Tremolo Idea?

[trad3mark]

Hello all!
I'm working on something that has a lot of potential, it's a sort of ping-pong tremolo. I don't really know how to explain it, but it's basically just a tremolo where the LFO can be messed about with a bit. Anyway, I'm doing it with a 555, cos i need something mega choppy.
I came across a nice 555 astable schematic that i'm planning on using. Right now, to indicate the + and - of the LFO waves, i have two LED's that light up nicely. All my controls are just how I want them, and I'm delighted with them. Now, here's my problem.

I don't really know how to "adapt" this into a tremolo? I know it could be done with an optocoupler very simply, but is there a way to do it where i dont have to go buy new parts? Is there some way to basically connect this to a simple buffer type circuit to basically make it a tremolo?
Cheers,
n

[Hides-His-Eyes]

You could try putting the ouutput of the tremolo at the 9v in of a buffer. I bet it pops like hell though.

[trad3mark]

ah. This might just do the trick...

[vendettav]

i guess putting a transistor as a switch there would do the job.. i dont know how though
skipped that class 

[Gurner]

If you've a fet in your collection, that'd work.

For a N channel FET, the more you make the gate negative vs the source the higher its drain/source resistance - when the gate voltage = source, the drain/source is at its lowest resistance.

For a P channel FET, the more you make the gate positive vs the source the higher its resistance - when the gate voltage = source, the drain/source is at its lowest resistance.

There are some quirks  eg FET non linearity, biasing, & even choosing the right FET itself, but it's a pointer to get you rummaging.

[vendettav]

btw is it possible to make the 555 give a sine instead of square wave?? i know the trick with optoisolators and LED=LDR trick as well but i couldn't get any in my country and dont want to order online for one part only

[trad3mark]

Right, so 555 > Vcc of the opamp is DEFINITELY out. That's just to make fart noises.

If you've a fet in your collection, that'd work.

For a N channel FET, the more you make the gate negative vs the source the higher its drain/source resistance - when the gate voltage = source, the drain/source is at its lowest resistance.

For a P channel FET, the more you make the gate positive vs the source the higher its resistance - when the gate voltage = source, the drain/source is at its lowest resistance.

There are some quirks  eg FET non linearity, biasing, & even choosing the right FET itself, but it's a pointer to get you rummaging.

I have a few fets, but i don't get what way to connect it up... It's that connection between buffer and LFO that i'm stuck with.

POWEREDIT!!:
Could this be done like the EH Pulsar somehow? See the way it's connected to R4? What happens there and could i use that?
http://www.tonepad.com/getFile.asp?id=29

[Hides-His-Eyes]

btw is it possible to make the 555 give a sine instead of square wave?? i know the trick with optoisolators and LED=LDR trick as well but i couldn't get any in my country and dont want to order online for one part only

Not a snowman's chance in hell. Look for the EA tremolo project or the tremulus lune.

[petemoore]

  Yupp, a couple of tremulous lunes aughtta do it.
  Let us know how it goes, I forewent the 555 blinkers because I feared clickings.
  I'd say 1 trimmed down lune [or similar what uses photocell to alter gain] to see how it works first.

[trad3mark]

looking into it, i think optocouplers are going to be the way to do it. Fortunately, it doesn't look to difficult to setup.

Damn.

[trad3mark]

Bonus question, could this be done with a relay? something like when relay fires it mutes the signal, and when it resets the signal is not muted? I'm unfamiliar with relays, but looking at them, would they work?

[Taylor]

IMO, 555 is no good for trem. You can twiddle with it forever to try to remove the tick, or you can use something less current hungry. 7555, but there are better options still.

Could you make this with a couple of trem lunes? Yes, and Dann Green already did that for you.   Could a relay be used? Perhaps, but why? And whatever problem you're trying to solve, I suspect the relay would introduce far more.

Optos are ok for chop, FETs are better but require deeper understanding to get them to work with decent s/n and distortion specs. OTA might be better but also tricky. Optos aren't great, they are common just because they're pretty easy to get working.

This is a situation where you could probably get better responses if you let us in on what you're trying to achieve exactly and why the normal solutions are not usable for you. I too like doing things the "wrong" way, but this path is paved with frustration.

[smallbearelec]

The Tremulus Lune is one solution. My Tremulous Bear is another:

http://www.smallbearelec.com/Projects/TremBear/TremBear.html

If you go the 555 route, you want the CMOS version as it is easier to quiet down.

What country are you in? Can you not find a photocell with a fairly high (> 10 Meg) dark resistance, light resistance maybe 10K and reasonably fast switching? If you have that, the rest of the job is careful isolation (both physical and electrical) and the articles on both pedal builds have useful ideas about that.

[deadastronaut]

555 no good for trem?.

ive done some pretty intensive trials, on the notorious 555 ticking problem. with tremolo's.

cmos is definately the way to go if your going down the 555 route, no ticking here!....using led/ldr's...

fading led circuit...

http://dl.dropbox.com/u/7464107/fadertest1.wav

stereo panner/ dual tremolo...is this what you meant by ping-pong?...

http://dl.dropbox.com/u/7464107/tinystereopan1.mp3

straight trem...

http://dl.dropbox.com/u/7464107/trem1wav.wav

all 555's.... doesn't sound bad to me!....

[trad3mark]

see, I'm trying to get a tremolo that's fairly simple, fairly choppy, but has really good rate and depth control, and PREFERABLY without the use of optos. I've tried the ea and pulsar circuits, but at higher rates, depth gets all @#$%ed. I'm guessing you don't get that same problem with optos, but they're expensive as hell over here (Ireland).

I dunno. My brain is totally melted with this problem.

[deadastronaut]

 i always roll my own opto's....led/ldr...

i bought 6 ldrs off ebay cheap.....

why dont you want to use opto's...just the price?..

[Hides-His-Eyes]

If you want one opto to ireland I bought a big bag of NSL-32s and could send you one for £1.50 + p&p. Beats spending €6 on a VTL5C9 at least.

[trad3mark]

ok, maybe optos are the way to go. BUT, before I do go buy them (turns out they're actually not too bad), I wanna get a few things straight. Firstly, I have a video showing the circuit I have so far, or at least, the effect of the controls. It gets a bit difficult to see the difference at high rates, but trust me, in real-life, you can see the change:
http://vimeo.com/20217252

Next up, if i want to maintain that choppyness/squarewave effect, can it be done with an optocouple? and if so, am i better off going for a specific optocouple component, or just buying an LDR and taping it up to bits?

[deadastronaut]

ive probably built the same circuit... with led/ldr's just heat shrinked...works ok for me..might not be as choppy as you want...i'm guessing you want a stutter type chop in stereo...

http://www.youtube.com/user/100roberthenry?feature=mhum#p/u/6/Hb0heYolcTc

ive tried various forms of lfo's and a lot of them tick like f....

[trad3mark]

http://www.youtube.com/watch?v=uLF8auCSX8k

at about 1:00, Jack White kicks in a bit of rotovibe. It's not quite 90 degree square wave chop, but it's not a million miles off. I'm guessing it'll be somewhere like that? It just seems to me that whenever I make a tremolo, once the rate gets up pretty high, depth is lost completely, and it's really hard to chop. from looking about, it seems to be a bit more reliable with optos, am i right? do you still get the ticking with optos?