building a chorus, having a weird lfo signal at the lfo output

Hoping someone can impart some wisdom.

Building a chorus which has an lfo circuit. I'm getting a weird signal at the lfo output, which has a weird shape and seems to be way too low a frequency. My trusty little oscilloscope shows this is the output:

https://imgur.com/a/yB0Jpmo

The lfo circuit is also at the bottom. Does anyone have any clue ? I used a tl072 instead of a tl022, but that shouldn't be the cause right?

Posting the entire circuit might be a step in the right direction (imho)...

Also, perhaps simulating that chunk of circuit could help with showing what sort of signals you should see and where.

brndvnrdn said:

Hoping someone can impart some wisdom.

Building a chorus which has an lfo circuit. I'm getting a weird signal at the lfo output, which has a weird shape and seems to be way too low a frequency. My trusty little oscilloscope shows this is the output:

https://imgur.com/a/yB0Jpmo

The lfo circuit is also at the bottom. Does anyone have any clue ? I used a tl072 instead of a tl022, but that shouldn't be the cause right?

Click to expand...

I can't make much sense of the image, but when you say chorus (a time delay based effect) are we to ASSume you are using a BBD or similar charge coupled device, or writing digital samples to memory and reading them out at a different rate?

I haven't designed using BBD devices since the early 80s but probably remember a little about it. I have seen DC shift with extreme clock frequency so if you are using BBD check the HF clock..

JR

What is the impedance of your trusty oscilloscope probe? If it's not at least 1M like probes usually are, you could just be draining something inadvertently. Impedances of that circuit are pretty high so even 1M might have a significant effect on the output. It looks like something is getting drained too quickly. Yes, TL072 should work just fine.

The TL022 looks to be some low-power, bipolar-input opamp, so TL072 should be arguably "better".

For what it's worth, simming the circuit with LT1057 (with starting the voltages at 0v) seems to work just fine, so...

As squarewave said, either a too-low impedance probe, or some cold solder joints, or something mis-wired / mis-connected.