Taplfo project

[samsam]

Hi everyone,

I'm new to this forum and i have struggling for a while getting my taplfo to work properly.
(sorry if my english is not perfect i am from france).

Here is my problem:

I have build this circuit to have my lfo acting as a tremolo. I have two oscillators connected to my taplfo and everything seems to work well. Problem is, the tremolo only works when the square wave is selected. On every other waveshape the sound stay on and doesn t modulate.


The weird thing is that my led behave normaly on every waveshape. My ldr (in the vactrol) seems to work. When i test the resistance with my multimeter the vactrol looks ok.

If you have any clue to solve my problem please let me know.

Thank you.

[PHOBoS]

That is a rather odd problem, but if the vactrol seems to be working it must have something to do with the opamp section.
I suggest measuring the voltage on the non-inverting inputs of the opamps to see if they are indeed Vref (1/2 the supply voltage).
If you have scope look at the output of the first opamp to see what that is doing, with and without the vactrol attached to it.
Also, what is the voltage level/amplitude of the audio signal you are using ?

[samsam]

Hi PHobos,

Thanks for helping me.

I have 3.36 volts on pin 3 of both opamp (tl071).
I don t have any scope to see the output of the first opamp.

I'am using two batteries for those circuits.

One 9 volt battery regulated to 5 volt to supply the oscillators and the taplfo
A second 9 volt battery (with vref) to supply the opamps section.

Do you think i should only use one 9 volt battery, and create the 5 volt and vref for the 9 volt ou of it ?

[PHOBoS]

3.36V seems a little bit low, although it could be correct if you happen to be using a rechargeable battery.
But it doesn't matter much for this circuit as long as it is around 1/2 the supply voltage.

using 2 batteries is ok as long as you connect both GND/0V connections together and it might even give you less noise.
Actually looking at the circuit again that doesn't even seem to be necessary since you only have an optical connection
between the circuits.

the weird thing is, as you already mentioned:

[samsam]

Thanks for your reply.

I have ordered a new taplfo and some vactrol (xvive) to see how my circuit behave with new parts.
The taplfo chips that i have behave strangely sometimes.

I'll let you know if a new vactrol and pic solves my problem.

Thanks for your help.

[samsam]

Problem solved! In the schematics the second opamp is not connected to +9 and 0. I just tried this connection and it works now.

[PHOBoS]

yeah that will help a lot
In the schematic a dual opamp is used which only has 2 pins for power so that makes sense.
Sometimes power pins aren't drawn at all so keep that in mind.

[samsam]

Hi everyone,

I ll keep posting under the same thread because i'm still having issues with my taplfo project.

I have made two circuits of this tremolo and both of them are in sync with each other, wich is what i wanted.

both of them are controlling some oscillators.

My problem is that they dont deliver the exact same voltage to the vactrols wich results in one oscillator being louder than the other one.

I mesure 4,11 volt on the output led of one circuit and 4,20 on the other circuit.
The weird thing is that the led showing the higher voltage is the one that shine the less. I thought it would be the opposite.

Also i have measured different voltage on pin 5 of the chip.
1,67 volt on one chip and 1,40 on the other.

Both circuits are the same so i don't understand how i can solve this.

If you have any ideas let me know.

Thanks

[blue hell]

[samsam]

Thanks Blue Hell for the reply.

I have tried a new circuit (with another vactrol) on the breadboard and it seems to work better. So yeah probably that vactrol behave differently.

So i will try to desolder and swap the vactrol for another one or redo the all circuit.

About voltage i have :

5 volt on pin 4
2,53 on pin 5

Yes the supply for the circuit is 5 volt.

I have started electronic 3 month ago and it's really confusing!

[samsam]

Ok so i have desolder and swaped vactrols and it works fine now.
Also i didn't notice at first but the two vactrols i used at first were not even the same brand...

Thanks for your help.