Biasing issue with the Demeter Tremulator

[dpaul_gtr]

So I've just finished breadboarding a Demeter Trem clone. The thing is that, with the 5k bias trimmer, it sound very stuttery (I think that's the word, english is not my first language ). After trying it with a larger trim pot set to around 50k it sounds better, but still not as smooth as I expected. On the "volume rise" it sounds smooth and sine-wave-y, but the volume drop is a little too sudden, and with the 5k trimpot it was down right an instant cut-off.

I have to mention that the vactrol used is a hand-rolled ldr with around 200 ohms on resistance and over 20M off resistance, and the ICs used are one TL072 and one TL071.

Has anyone else run into this problem?

[fuzzo]

I've the same kind of issues with mine, a baja trem made few years ago now. It's more a square type tremolo . Not bad  you can tame the "hardness" of the sound with the mix control . It's tricky to get a perfect sinewave coming out of a LED/LRD.

Did you use this schematic ?



maybe change R2 for a smaller value to reduce the gain , x2 should be enough. If you increase the gain really high the sine wave becomes a ramp or square (cf. boss TR2 schematic)

[dpaul_gtr]

I've the same kind of issues with mine, a baja trem made few years ago now. It's more a square type tremolo . Not bad  you can tame the "hardness" of the sound with the mix control . It's tricky to get a perfect sinewave coming out of a LED/LRD.

Did you use this schematic ?



maybe change R2 for a smaller value to reduce the gain , x2 should be enough. If you increase the gain really high the sine wave becomes a ramp or square (cf. boss TR2 schematic)

Yup, that's the schematic I used (although I think there's a small mistake with the speed pot, it should have been 500k instead of 1k).
Thank you for the idea with the R2