Pulsating noise from analogue chorus pedal

eru

I recently bought a cheap analogue chorus pedal from China that has an issue with outputting a continuous pulsating blip noise. The noise (which is not very loud, but enough for me to be annoying) occurs regardless of whether the pedal switch is in the on or off position, but only when a cable is plugged into the input socket. The pulsating goes faster or slower when adjusting the chorus speed knob.

Does anyone know what might be the cause of this and if it can be fixed? It's definitely not an issue with the power adapter as I've also tried powering the pedal with a battery and it does the same thing.

I've attached a photo of the inside of the pedal. The speed pot is the centre one with the black knob. I noticed there's a bias adjustment on the board but not sure if I should start fiddling with this.

Thanks for any help.

ICBM

It's clock noise from the oscillator circuit leaking into the audio path.

If it does it on a battery as well it's not a power supply filtering issue, so that leaves either an onboard filtering issue (in which case replacing it with a different example might fix it) or just an inherent issue with the design.

It's unlikely to be affected by the bias setting, and adjusting that will invalidate the warranty, so don't.

pedalo

Try putting a buffer before it

EricTheWeary

pedalo said:

Try putting a buffer before it

Worth trying a) guitar straight in and b) after a buffer as these would be easy fixes. Obviously if they work you are then stuck with where it will work in an effects chain without doing an electrical fix. 
I've had a couple of pedals in the past that have had clock noise but could be sorted in these ways. 

pedalo

Yeah my Caroline Somersault does this and I emailed Philippe about it and he said it was the LFO and working as intended.

They benchmarked it against vintage Boss pedals which have some noise too and the noise level is affected by the rig, power and proximity to other pedals. Putting a buffer in front sorted it for me.