Some things I've learned about the FV-1

[alassg]

So, here is my feedback on FV1 and noise:
- I have used juste one 3.3v supply on my PCB (REG113NA)
- No noise at all when using a 5V power supply adapter to supply my op amps (OPA1642)
- Noisy when using a 9V power supply adapter to supply my op amps (OPA1642)

I have other issues but not related to the power supply. For example, i tied the audio right and left output with two 10kohm resistors and it seems that my signal is too much attenuated.

this seems odd to me. the opa1642 should be fine with either of those voltages, so maybe you had a noisy 9v adapter? and was the same supply used to power the reg113na as well?

Actually the noise almost completely disappear when i touch my guitar strings. The 9v adapter might be noisy indeed and yes, it supplies the reg113na and the opa1642 but my issue might also be a bad layout but i really have troubles with that FV1 chip. On this kind of mixed signal IC, the digital and analog grounds should be separated in the chip but it's not the case with the FV1. I don't want to take the risk of ordering new PCBs and getting noise again. I think i'm done with that chip.

[frank]

From your description all the noise sources are external to the FV-1 (9V supply, guitar strings, etc.) so it seems to me to be sources and/or PCB layout. Have you looked at the noise on a scope?

There is no need for split grounds in the FV-1, it has split power. Use good bypassing on the power.

[ice-nine]

Hi alsag, You have described that you have noise until you touch your guitar strings, this would suggest that you might have a grounding/wiring problem with your guitar. This type of grounding problem may be apparent as buzz. Of course you may also have other issues but ditching development of the FV-1 and moving on to other platforms won't fix the underlying noise problems you have. I would first suggest looking into your guitar wiring and make sure the ground wire inside is actually connected to the bridge of your guitar so that the strings and other metal contact parts are correctly connected.

[amz-fx]

Here is an interesting (but amusing) look at one player's problem with noise in a guitar amp: https://youtu.be/t6E0O8UtObU

With few exceptions, a buzz will be related to poor grounding, bad cables or defective jacks.

Identify types of noise: http://www.muzique.com/news/hum-whine-and-noise/

Best regards,

[smear]

speaking of making separate DVdd and AVdd supplies, has anyone tried adding an inductor (or even just a ferrite bead) in series between the +3.3V supply and the AVdd and REFP pins? or any ideas on values that might be suitable to give cleaner power to AVdd and REFP?

i've seen this done with other codecs with significant de-noising results, and it's a lot easier than adding a second regulator.