Pedal PCB "Octagon" FV-1 Multi FX noise problem

[claytushaywood]

I built the Pedal Pcb Octagon a while back- and I'm having a strange noise issue.  I get a lot of white noise when using this circuit.  I've tried increasing filtering with little success.  But one weird thing about it- when I put my  super low impedance "jerry garcia tiger buffer" (just an opamp buffer) right in front of it I get drastically less noise.  Also the tone of the pedal completely changes- with the buffer on in front of the circuit it sounds MUCH brighter (like its supposed to sound brighter not unnaturally bright) I didnt notice how muffled it was until I tried the buffer in front of it- and I'm not talking about like yeh a buffer will make your signal brighter with long cable runs- without the buffer it sounds like there's 200ft of cable.

The noise isnt constant- when I turn down the mix I get less noise- when I turn down the volume I get less noise. 

I emailed the dude at pedal pcb a few times- and he said he had never had anyone having any issues with noise.  Wondering if anyone out there has had the same issue?

here's a link to schematic and pcb layout.
https://www.pedalpcb.com/docs/Octagon.pdf

I'm positive I have every part 100% correct as I built this about a year ago initially and have revisited it about 20 times and checked the layout at least 40x over.  This is the most thoroughly checked build I've ever done- if it didnt have an fv1 and a purchased pcb this would have been in the trash 10 months ago

so any input or ideas on the fv-1 and noise would be greatly appreciated!

[gordo]

FV-1's have an inherent bit of noise but not that drastic.  Can you get a clip to give us an idea what you're hearing?  I don't know how it would happen but I wonder if your chip is buggered up?  What crystal did you use?

[madbean]

The input to the Octagon is a buffer itself so obviously something is quite wrong. Have you taken any voltage measurements? I'd check the 9v rail and Vref rail first to make sure they are reading about 9v and 4.5v resp. Also, audio probing some key points to see where the noise is introduced:

Pins1 and 7 of IC1, pins 1, 2 and 28 of IC3, pins 7 and 1 of IC5. That would narrow it down.

[Willybomb]

I don't want to be a dick about it, but I've got 3x Octagons in my Megatron TMK2601 with no real noticeable noise issue, even with them all on at the same time.  What your problem is though, I have no idea!

[Boba7]

I built a double tracker from pedalpcb and never boxed it because of how noisy it is. Too much white noise, even with mix at minimum. Tried everything, couldn't resolve the issue. Went to my pile of unboxed pcbs.

[ahiddentableau]

My Octagon has some noticable noise when the mix knob is pushed towards the maximum settings.  Bugg told me this was normal--a limitation that is part of the FV-1 chip.  But provided the mix knob is below 2 or 3 o'clock it's fine...comparable to any of my other pedals.  So I agree with the other comments.  It sounds like there's something wrong with your build.

[claytushaywood]

The input to the Octagon is a buffer itself so obviously something is quite wrong. Have you taken any voltage measurements? I'd check the 9v rail and Vref rail first to make sure they are reading about 9v and 4.5v resp. Also, audio probing some key points to see where the noise is introduced:

Pins1 and 7 of IC1, pins 1, 2 and 28 of IC3, pins 7 and 1 of IC5. That would narrow it down.

i checked all the voltages I knew how to check a couple times (everything besides the fv1)  But I'll go back and double check as it was so long ago. 

One time I remember I powered it up and didnt experience the noise- then something shorted (it was just like a sleeve tab on my jack- on my ghetto test rig) and it came back! 

Ill get back to you with voltages- thanks for the replies and experience shared so far!

[p_wats]

I built one of these a while back and have used it extensively in recording and live performance without noticing anything (beyond what sounds normal for FV-1 noise). I'll triple check my mix levels to confirm, but no issues that I recall.

[p_wats]

I checked my Octagon last night and it is very quiet (some minor noise when the mix and volume are maxed out, but not louder than expected).

Coincidentally, I was working on a ThreeVerb last night too and had a lot of noise...until I realized I totally missed populating the 10uf capacitor. Now it's very quiet too.

Could yours be something to do with filtering caps as well?

[claytushaywood]

I checked my Octagon last night and it is very quiet (some minor noise when the mix and volume are maxed out, but not louder than expected).

Coincidentally, I was working on a ThreeVerb last night too and had a lot of noise...until I realized I totally missed populating the 10uf capacitor. Now it's very quiet too.

Could yours be something to do with filtering caps as well?

Thanks for the reply!  i def didnt miss a cap but Ill look over the power filtering again! Thanks!

[Betty Wont]

I've built a few of the pedalpcb fv-1 projects and i notice a fair amount of white noise on all of them with the volume and or/mix knobs past noon. Which is required for unity gain. I feel the low headroom on fv-1 circuits tends us to crank them to hear noticeable effects. 

[Willybomb]

I've built a few of the pedalpcb fv-1 projects and i notice a fair amount of white noise on all of them with the volume and or/mix knobs past noon.

Yeah, I dunno.  If you look at my video for my BOTY entry you'll see the volumes on all 3 up past noon, with all effects running, and it's not noisier than any of the other settings.  What I have found with them though, is that you can't hit them with a particularly hard signal as you will get a bit of digital clipping or something...

[madbean]

I've built a few of the pedalpcb fv-1 projects and i notice a fair amount of white noise on all of them with the volume and or/mix knobs past noon. Which is required for unity gain. I feel the low headroom on fv-1 circuits tends us to crank them to hear noticeable effects.

The circuit input actually has a pretty low input impedance as well. Making R2 470k or 1M might help a little.