Just put it all together and when I turn on an effect, it's super noisy. Even with the signal generator from www.electrosmash.com/forum/pedalshield-m...rduino-mega-2560-adk

I made a mistake initially and put the op-amp cover upside down (don't think the instructions actually specify which side is up). Not sure if it is related.

I still get a lot of noise even when I unplug the input cable.

It's a loud hiss that is very very audible. Like something is obviously wrong.

Ok it appears that my op-amp cover was put on in correctly. I took it off and it worked. And I put it back on and it's all good now. Is the cover merely for protection? Doesn't seem like it's needed and the instructions don't even say to put it on.

How much noise is expected?

I get an audible hum and I'm pulling power from a USB wall socket adapter (for my iPhone).

When the effect is bypassed, it sounds super clean. When I turn on an effect, my guitar signal is fairly quiet and I hear an audible hum/buzz. Even the clean effect has this problem.

for oop-amp cover you mean the op amp socket? something like this: www.atomsindustries.com/assets/images/items/1055/1055.jpg
The op-amp socket is just there in case you want to try or change the op-amp, is not 100% needed, it is just a cool feature.

I saw that you are using an external power supply, have a look at this if you didn't read it yet, just in case...:
www.electrosmash.com/forum/pedalshield-m...ing-pedalshield-mega

Also adjusting the VR1 resistor helps to improve the Signal/Noise ratio. It can make the signal much bigger than the background noise. Make sure that the input signal gets as loud as possible without clipping.
A low-level background hiss could be heard but should be very small compared with the guitar signal.

Make sure that you dont have ground loops, sometimes pluging the pedal close to the amp plug helps.

Howdy,
First post here, greetings from Ireland.
And yes, it is raining.

I have built the pedalSHIELD mega.
I think the project is super cool

Output on my pedal is perfect (tested with sinewave).
Pedal off - Sound is perfect.
There is a lot of hiss as soon as I turn on the pedal with or without instrument connected.
I have followed all the troubleshooting.
Wondering how do I pinpoint an issue on the input side?

Thanks!

So, seems that your output stage is working properly but something is happening in the input area:

• Have you check this?: www.electrosmash.com/forum/pedalshield-m...lshield-mega?lang=en
• The power supply makes a big impact on the sound quality(this is for the DUE but is all applicable to the MEGA): www.electrosmash.com/forum/hardware-peda...powering-arduino-due
• Check that you have the op-amp with 5V at the pin8 and 2.5V (approx) on pin 5.

Please check the dc adapter，I have this problem just one minute. Use usb supply noise is so big，but use 9v adapter all noise disappear. If power supply voltage down to 7v，op will not work correctly. So， you can try the 9v outside power supply.

Thanks for the inputs.
I am using a clone Mega with a 12v 2A power supply.
I'm not quite getting 5V at pin8 and 2.5V on pin 5.
I have a wemos d1 - to rule out power step down on the main board I will test the d1.
I suspect I have cooked a capacitor with over zealous soldering.

I heared something about cloneMega,the power supply design maybe use some awful piece or more less components. Some cloneMega made in Shenzhen China. I bought one!But not the cheapest.