Envelope controlled tremolo DEPTH

[aaronkessman]

I may be missing something, but in all my searches for envelope controlled tremolo, people want to use it to control the rate. What about depth? I'm much more interested in using pick attack to control the depth so that harder notes get more trem.

i imagine it's not too hard - any advice on getting this to work with a simple circuit like the EA trem? maybe using tim's uglyface control to act as the depth pot? (1M seems managable for an LDR...)

thanks guys.

aaron

[R.G.]

No biggie.

First, get an envelope signal. I did an article about note processing at GEO, there are many envelop detector circuits.

Then drive the LED of an LED/LDR with a current proportional to the envelope. It is possible that you could simply full wave rectify the signal and feed it to the LED, since the time lag of the LDR would smooth out the envelope signal for you.

The LDR becomes the depth control. Pick a tremolo circuit where the signal is being shunted to ground (EA trem works) and put the LDR in series. You may want to put a resistor in parallel with the LDR to keep the dark resistance of the LDR in bounds, as these commonly go to megohms when there is a period of dark. The parallel resistor would have to be chosen by listening in the particular circuit.

[aaronkessman]

thanks RG. figured it was that simple. yes, in this case I'd use a trimpot to adjust the range correctly, i'm thinking one in series may be helpful too.

[Mark Hammer]

Anderton's tremolo actually lends itself to that application nicely...I think.  http://www.generalguitargadgets.com/diagrams/catrmsc.gif

You cansee that the amount of gain reduction varies as a function of the combined parallel resistance of an LDR, and a 25k pot + 4k7 resistor.  The pot determines how much impact the resistance fluctuation in the LDR have on the gain of U1b.  There is nothing to provent one from taking a feed off U1a and sending it to an envelope follower like the one here:  http://www.generalguitargadgets.com/diagrams/cabff_sc.gif   and using that to parallel the pot.

The only proviso is that such envelope controlled variations often have to be "slowed down" a bit so that hey map onto passages, rather than simply individual notes.

[bigjonny]

I'm much more interested in using pick attack to control the depth so that harder notes get more trem.

What about LESS trem when one picks harder?  That way you can set the depth fairly agressive and "choppy", but when you want a note/passage to pop out, you can "dig in" and let it shine...  Anyhow, my 2¢...

[aaronkessman]

both good ideas.

[SonicVI]

You could build the Envelope Follower from Electronic Projects For Musicians and hook it up to just about any tremolo you want.

[StephenGiles]

Talking of envelope followers :lol:  :lol:


down arrows are 0v and up arrows are +9v. The unmarked 100k pot is obviously sweep rate!

Have fun!!!
Stephen

[soggybag]

That's a very interesting idea. I would recommend the John Hollis Ring Frobnicator since it is very low parts count. It uses a 3080 which may be hard to get. It also has a problem where it doesn't work if the battery is too new. I think the list came up with a solution to this.

[StephenGiles]

Something that I forgot to mention about the envelope follower I posted above is that it provides a similar start frequency/stop freqency type of sweep to that of the EH Microsynth, so that you get a normal or reverse sweep with a VCF dependant upon the settings of the pots. Remember that on the Microsynth, this is achieved by making the start frequency slider lower than the stop frequency slider (I think, or is it the other way round?), BUT......the sweep is the same however hard a note is played.

Now, the LM 13600 envelope follower is different in that it's peak is proportional to the strength of note played, but it's decay time is set by the sweep time pot, so there is little or no ripple. I have tried this with the Bi Filter Follower twin filters and it works very well.

The grounding looks a little odd, but I gather that the 324 can handle it, and I suspect this is why Joe Truchess at EH UK chose that amp - he also tried a 339 in the design stage of the Space Filter, but it was too heavy on power in the battery unit. If someone could come up with a decent opto contolled filter using the other half of the LM 13600 and unused amp in the 324, we would have a superb triggered filter with just 2 chips, and great for the little boxes you all like!!

One other point is that it could be worth using a separate pot and fixed resistor instead of the series resistor from the EG to the opto - I used  VTL5C4/2 which worked fine in the Bi Filter.
Stephen