Variable resistor to ground....

[lightningfingers]

What about me - I do prefer using CA3080 or LM13700 for modulators/controllable gain and filter stages, etc.  They are highly effective, linear, low consumption relatively to LED-LDR pairs, handle "high'-voltage signal and can not only control signal but amplify it at the same time. They are also very reliable and "undemanding".

All of the above is true, but on the other hand they are more expensive than LEDs, BJTs, FETs, Vactrols etc. and are more difficult to get hold of

[bioroids]

DDD, you're right about that, it's kinda dirty sounding and I think the modulation gets square in spite of the lfo waveform (taken from the EA tremolo, roughly sine I think)

I posted a few samples on my site http://ar.geocities.com/bioroids
if you want to hear a cheap designed tremolo

lightningfingers, i think the CA3080 is available from Small Bear, and not too expensive, though is easier to get hold of fets or bjts

regards

Miguel

[DDD]

bioroids,
since every modulator is actually a signals' multiplier, you have a lot of frequency products on its output, so every harmonic of your distorted pseudo-sine LFO generates numerous audible products.
In my opinion it's possible to build good distortion box using cheap BJTs and diodes but it's virtually impossible to build decent time effects or modulators without more expensive parts.

[bioroids]

Do you mean, DDD, the difference and sum of the signal frequencies and the LFO harmonics appear at the output? interesting

This does not happen with fet or ota based tremolos? or does it depend on the modulation waveform?

A few months ago I used this (with 4066 switches) for an 'aliasing simulator', it worked nice (I'm not sure what were the frequencies comming out of the circuit) but I was using a high freq oscillator (HFO?)

Regards

Miguel

[gez]

All of the above is true, but on the other hand they are more expensive than LEDs, BJTs, FETs, Vactrols etc. and are more difficult to get hold of

Just about every electronic component supplier in the UK sells the CA3080 & LM13700.  When you tot up the additonal cost of LEDs & LDRs/JFETs/ CMOS chips for matched MOSFETs, plus the extra board space for these components and extra current consumption if you go down the LED/LDR route, or the extra work of matching JFETs, then OTAs look pretty cheap to me (not that they're expensive).  Plus you'll get a more linear reproduction of your LFO waveform. :wink:

[bioroids]

Is someone using the NJM13600D otas? they are a little cheaper

I've never messed with this things before, but they seem to be nice little ICs. Luckily I have a few (for a Small Stone) so I'm gonna try a few things these days (when I finish moving!)

Regards

Miguel