About time.

[SpaceCowboy]

After a few hundred dollars and a few months of beating round the bush, I've finally gotten around to building by damn stompbox.
It's a simple FV-1 based effects pedal with active low pass filters for input and output.

Anyways, here's the picture,



and although it looks kinda nice, there's are a few issues with it.

First of all, there's this annoying noise/hum noticeable especially when the volume on my amp is turned up.
Here's a clip of the audio, when amp volume to max and guitar connected, as well as bypass.
http://www.mediafire.com/listen/22bjjfv28ndi7qv/VID_20130729_201615.mp3.
With Audacity's spectrum plot, the peaks of the noise are revealed to be ~144, 310 and 1212 Hz.

Also there's seems to be some noise on the delay program when adjusting the delay time, though that may very well be the program's fault.
But my biggest gripe is the noise issue.

Here's the schematic:



and the board layout



I'm using an MCP6022 opamp at 3.3V for the amplifier.

I know the noise is coming somewhere from or after the input filter stage. In fact, I've spent a whole after noon trying to get rid of the high pitch hissing noise from the circuit and ended up replacing the 1n film capacitor to ground before the RIN/LIN pins of the FV-1 chip with a 10M resistor to ground and this ended up bringing the pitch of the noise down to its current level, as in the sound clip. Its slightly less annoying but bleh.

Well, it's been quite a ride, and I would appreciate any kind feedback to help me mend my stompbox. Thanks lol.

[PRR]

Sounds like general room-noise from power wiring, fluorescent lamps, or computer.

Looks like the in/out jacks are insulated from case??

[SpaceCowboy]

Thanks for the reply.
Um i'm using Cliff Jacks not those regular ol' conductive sleeve type ones, but I've made sure to ground the enclosure through my 2.1mm DC jack.
If it were electrical interference, the noise would peak at ~60Hz right? I'm seeing noise peaks all over the place.

[octfrank]

Nothing in the chip runs at those frequencies so no idea where they are being generated. Does sound like room noise in the recording as PRR said. Try a battery in place of the adapter and see if that makes any difference.

Noise when changing delay is most likely zipper noise, there will always be some noise when changing a delay length but if it sounds like a buzz then that is probably zipper noise. If you wrote the program then just filter the control pot with a low pass filter before using it to change the delay length.

[SpaceCowboy]

Thanks. Yeah I tried to run the stompbox on battery, and damn LOL it sounds better. Stupid AC adapter. Man before I thought the crystal was the problem... I  desoldering the damn thing and resoldering a new crystal... what a waste.

But yeah   thanks for the help. And oh I guess the post i made on Spin forums is redundant lol.

EDIT: Lol. perhaps its not time yet to bring out the cigars. The noise is still evident when I remove my headphones.

EDIT II: Upon poking around, the source of the noise seems to be the output filter. Will explore some more and report.

[PRR]

> noise would peak at ~60Hz right?

Generally 120Hz picks-up much better.

You said 144Hz, my scan suggested 122Hz. Which is not 120Hz, and my technique should know the difference. Can't account for that. However a quiet listen (man that upload site craps-up a browser!) soundled like stray wire on an average workbench with lots of power wire and lights. As Frank says.

[SpaceCowboy]

Well, so to cut down drastically on the noise, which gets out of control when distortion is turned on, I've bypassed the output active filter and that seems to have brought the overall noise and sound down by a lotta dB. Now off to play some Soundgarden.

[Ice-9]

Wow, it sounds like you have a dyson hoover cleaning the carpet in the background.

[Seljer]

> noise would peak at ~60Hz right?

Generally 120Hz picks-up much better.

You said 144Hz, my scan suggested 122Hz. Which is not 120Hz, and my technique should know the difference. Can't account for that. However a quiet listen (man that upload site craps-up a browser!) soundled like stray wire on an average workbench with lots of power wire and lights. As Frank says.

To add to the numbers, I downloaded it an opened it in audacity and got a peak at 125Hz, a slightly smaller one at 146Hz a then a load of junk around , along with the expected mains frequency at 60Hz (25dB lower so it's not that bad) so I don't think its mains related.