Ibanez WH10 calibration issue

Souleyman · Post by **Souleyman** » 30 Sep 2020, 11:51

I'm with a theoretical question probably.
Here is the service manual for WH10

Ibanez_WH10_ServiceManual.pdf: (560.39 KiB) Downloaded 75 times

which says about calibration of the wah pot rode angle.

They says the 0db is 775mV RMS right?

I should put on input 775mV RMS
And then I should get about +20db on output with some frequencies and positions of the pedal with full up Depth knob.

+20db that is 7.750V RMS isn't it?

I can't get that voltage and got only about 3.16V on output.

What am I doing wrong?

This is what I got on my scope

Souleyman · Post by **Souleyman** » 30 Sep 2020, 12:31

alexradium · Post by **alexradium** » 30 Sep 2020, 15:48

you can't get 7,7 Vrms out of a 9V pedal,that's why you see a clipped signal.
Your guitar can be anything up to 1V peak on the attack of the note,the average signal is obviuosly less than that.
Opamp circuits output 6/7 volts peak to peak,unless you use special high quality chips
Transistor buffers limit the dynamic range even more.

Souleyman · Post by **Souleyman** » 30 Sep 2020, 16:03

alexradium wrote: ↑30 Sep 2020, 15:48 you can't get 7,7 Vrms out of a 9V pedal,that's why you see a clipped signal.

That's exactly as I supposed.
But that's very strange for me is seeing on that manual 0dbv = 775mVrms and their instructions put 0dbv sine and waiting for +20dbv on the output.

alexradium · Post by **alexradium** » 30 Sep 2020, 17:44

Dbs are just a relationship between values, when measuring guitar circuits you use 100mV in input,in this case you should get 1V at output

Souleyman · Post by **Souleyman** » 30 Sep 2020, 17:55

Of course but they noticed on the Specs block that the 0dbv=775mV and that is confused me.

Anyway the max output points on these frequencies (350Hz and 2.2kHz) helped me to check a properly position of the pot shaft.