Guitar Input Too Loud?

9 years 5 months ago #168 by jasolag
I have recently assembled a pedalSHIELD guitar pedal and it is pretty interesting. I have found one issue however.

When I first started to play with it everything was distorted so I used the adjust_trimmer program to set my guitar volume. Strangely, I have to turn my guitar volume all the way down to 2 (out of 10) for it to be within the volume parameters. This makes it extremely difficult for me to use it as I have to adjust the volume of my guitar when I use the pedal.

The purpose of a pedal is to change the effect in the middle of the song instantly and I can't do that currently with this pedal. Is there a way I can fix this by programming the pedal so that it reduces the input volume first before applying the effects?

I'm using a Squier Bullet Stratocaster with a Powered by Lace Humbucker.

P.S. Is it possible that I need to adjust the trimmer resistor RV1?

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9 years 5 months ago - 9 years 5 months ago #169 by JR
Replied by JR on topic Guitar Input Too Loud?
The input range of the Arduino ADCs is from 0 to 3.3V.
When the guitar is connected to pedalSHIELD, the input stage can adjust (with VR1) the voltage coming from the guitar to the optimum range for the Arduino DUE ADC.
  • With VR1 to the minimum: Voltage gain is 1 time. (no gain)
  • With VR1 maxed out: Voltage gain is 26 times.

The situation you are mentioning is odd because with minimum gain (gain=1), you should have a guitar pickups with an output voltage of 3.3V to saturate the ADC (which is not very probable).

The most probable situation is that one of the resistors of the input stage are swapped, giving too much gain.

Could you double check this resistors or update a picture of your PCB for us to check it?

keep it simple

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9 years 5 months ago #172 by jasolag
Replied by jasolag on topic Guitar Input Too Loud?
Thanks JR for your help.

It is a little embarrassing but it turns out that I got RV1 all the way down so it is clipping every sound I play through my guitar :oops: . It is working perfect now after I adjusted it.

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9 years 5 months ago #175 by Ray
Replied by Ray on topic Guitar Input Too Loud?
Its nice to see that your issue is solved :) , the input stage was designed to be driven by any guitar or bass guitar.

In the software utilities topic there is a code (adjust_trimmer.ino) which can help you to adjust the trimmer to your guitar signal level:

The idea is to adjust the trimmer while playing guitar (open E2 for instance), if the LED is ON means that the gain is too high (in that case just turn the trimmer down a little until the LED goes off)

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