Deflector Reverb - noise

[owlexifry]

first dabble at FV-1. first time using the 'basic relay bypass' board.
finished this a few weeks ago (pcb came with FV-1 presoldered)
was super excited.
sounds really cool.
just wish i could get rid of this noise

https://soundcloud.com/alexshriffs%2Fdeflectornoise

in this demo everything is at noon, except mix, which i turn up to noon to bring in the effect (and the noise) at the start.

- noise disappears when mix is turned all the way down.
- noise repeats with the echo repeats.
- noise isn’t really affected by altering positions of any controls (except mix)



i thought it might be coming from the relay switch circuit, so i snuck in a 1N5817 between the relay circuit +9v supply, and that did nothing.

volts:
supply - 8.98v
after 1N5817 - 8.68v

tl072 pin8 - 8.68v

ic3
pin 8 - 3.34v
pin 6 - 3.33v

FV-1
pin6 - 3.33v
pin13 - 3.33v
pin14 - 3.33v
pin26 - 3.33v

https://docs.pedalpcb.com/project/Deflector.pdf

is there something i’ve done wrong?
where do i start looking?

 

[owlexifry]

We've also eliminated the EEPROM as the problem.

Does the noise happen when you aren't playing?

not that i can hear.
noise only happens when there’s signal going through it.
just testing it now with the guitar sitting on the stand, i can just reach over and tap one string and let that ring and it will make noise (as you can hear in the clips, as the chord rings out, the noise continues proportionally).
but with no guitar signal, it doesn’t make noise.

 

[Cybercow]

not that i can hear.
noise only happens when there’s signal going through it.
just testing it now with the guitar sitting on the stand, i can just reach over and tap one string and let that ring and it will make noise (as you can hear in the clips, as the chord rings out, the noise continues proportionally).
but with no guitar signal, it doesn’t make noise.

Perhaps it's time for a signal trace along the signal path(s) to learn if the scope can see it.

 

[chris.knudson]

The noise is clearly a digital artifact. If the EEPROM has been eliminated and the CD4049UBE has been eliminated, I hate to suggest this, but it could be a bad FV1.

 

[Bio77]

I've had weird things like this from a bad cap. I think tracing the signal through would be a good bet. You can use an audio probe or your scope with a signal generator. There's a few signal generator apps for the phone, you just need to make a headphone to 1/4'' adaptor.

 

[Gordo]

Geebuz this is exciting. I'd send you mine just to solve the problem but it's been a mainstay on my board since I built it. It's a terrific effect.

 

[owlexifry]

I've had weird things like this from a bad cap.

given that the dry/direct signal is 100% all good, that would narrow it down to x3 possible coupling caps (assuming).

i’m not sure how i would identify a bad filter cap, my assumption is that C3, C4, C5, C7, C10, C11 are all filter caps, or part of RC filters.

so i’m guessing that only leaves C6 + C8 (feedback loop), and C9 (wet signal output coupling cap) as the only real possible culprits.

C6+C8 are mlcc caps. i’ve never used these type of caps before. i wonder what the fail rate is like with them?
C9 is electrolytic, could be fucked maybe?

but given the cyclical/repeating nature of the noise/digital artefact demonstrated in the clips, it really doesn’t seem to be caused by a cap (unless there is a filter cap somewhere that is failing to filter a noise that a correctly operating circuit would normally eliminate)

You can use an audio probe or your scope with a signal generator. There's a few signal generator apps for the phone, you just need to make a headphone to 1/4'' adaptor.

yep, i have an established audio probe setup that’s helped me many times previously.
i just use a signal from my iphone into the pedal input, an audio probe (100nF cap, open frame jack etc.) and the signal from the probe goes to a marshall MS-2 that sits on my desk lol
i’ll also try something similar with the oscilloscope.

 

[owlexifry]

Geebuz this is exciting. I'd send you mine just to solve the problem but it's been a mainstay on my board since I built it. It's a terrific effect.

that’s a generous thought.
christ on a bike i wish i could get rid of this noise so i could actually enjoy it

 

[Cybercow]

At the risk of redundancy on my part, perhaps doing a signal-path trace with your scope can help identify from where the problems actually starts.

 

[Cvoxdog]

You might just have to face the facts and accept that you'll never be able to build a fully working pedal ever again.

 

[Giorfida]

You might just have to face the facts and accept that you'll never be able to build a fully working pedal ever again.

Ouch! Feel the love!!!

 

[Cvoxdog]

Just kidding!

 

[owlexifry]

use an audio probe

try a signal trace thru the wet signal path

i don't have a signal generator, yes i could just use a 200Hz sine sample or whatever off youtube and send it with my iphone to the pedal, but i'm too dumb to gather anything useful from that process anyway.
so audio probe it is.

- guitar direct into pedal
- audio probe into audio interface:

Pin 2 (INPUT) - clean as a whistle

https://soundcloud.com/alexshriffs%2Fdeflectornoise-pin2-audio

Pin 27 (FEEDBACK) - obvious cyclical repeating artefact noise. (pin 1 is very similar)

https://soundcloud.com/alexshriffs%2Fdeflectornoise-pin27

Pin 28 (WET OUTPUT) - same noise as in previously posted clips

https://soundcloud.com/alexshriffs%2Fdeflectornoise-pin28-audioprobe

so the input signal into the FV-1 (pin 2) is clean and crisp.
the feedback loop output (straight from the FV-1 pin 27) indicates a distinct cyclical repeating clicking noise, also ending up in the wet signal.
and yep the wet signal straight from pin 28 is fucked, despite a perfectly clean input signal.

how does this make any sense.

 

[jwin615]

Sounds like a bad fv-1....
Have you tried reflowing all your solder joints (on the fv-1)?

 

[jwin615]

Or sale it to EQD as a prototype.
But it seems the fv-1 isn't staying in time with the clock(jitter). As I said early on, this is exactly what jitter sound like. If you've ever tried to use an audio interface and had the DAW and interface following different word clocks, this is the resulting sound.
The only other thing I could think to try is the cap to ground on the clock pin. Could probably hold it on there temporarily with a loop playing. (See post 20). I know a bunch of pedals have been built without this, including EQD pedals, but maybe it will clean up your clock enough? That's kinda the hail mary before calling the fv-1 bad.

 

[Cybercow]

i don't have a signal generator, yes i could just use a 200Hz sine sample or whatever off youtube and send it with my iphone to the pedal, but i'm too dumb to gather anything useful from that process anyway.
so audio probe it is.

- guitar direct into pedal
- audio probe into audio interface:

Pin 2 (INPUT) - clean as a whistle

Pin 2 of the FV-1 should be clean as it is the raw signal input.

Pin 27 (FEEDBACK) - obvious cyclical repeating artefact noise. (pin 1 is very similar)

Pin 28 (WET OUTPUT) - same noise as in previously posted clips

so the input signal into the FV-1 (pin 2) is clean and crisp.
the feedback loop output (straight from the FV-1 pin 27) indicates a distinct cyclical repeating clicking noise, also ending up in the wet signal.
and yep the wet signal straight from pin 28 is fucked, despite a perfectly clean input signal.

how does this make any sense.

Try it again with the "Deflect" pot turned all the way down - fully counter-clockwise so the feedback signal into pin 1 of the FV-1 is nil.

 

[owlexifry]

Sounds like a bad fv-1....
Have you tried reflowing all your solder joints (on the fv-1)?

the FV-1 came pre-soldered on the board, and on initial inspection it looked like it had been done pretty well and clean.
re-flowing everything will be my last ditch effort.

The only other thing I could think to try is the cap to ground on the clock pin. Could probably hold it on there temporarily with a loop playing. (See post 20).

just clarifying: you're suggesting inserting a 15-27pF cap from X1 (pin 10) to ground?

I guess that would be as easy as just holding one on pin 10+11 and see if it does anything.

I know a bunch of pedals have been built without this, including EQD pedals, but maybe it will clean up your clock enough? That's kinda the hail mary before calling the fv-1 bad.

is the clock really a culprit though? as far as i can tell, the oscilloscope probe on pin 10 indicated a fairly clean signal across the full sweep of the density control (post #34)

Try it again with the "Deflect" pot turned all the way down - fully counter-clockwise so the feedback signal into pin 1 of the FV-1 is nil.

this has been checked and confirmed already (post #11, post #15)
the noise is present regardless of the position of any control (except the mix control)

 

[jwin615]

the FV-1 came pre-soldered on the board, and on initial inspection it looked like it had been done pretty well and clean.
re-flowing everything will be my last ditch effort.

More of a joke than anything

just clarifying: you're suggesting inserting a 15-27pF cap from X1 (pin 10) to ground?

I guess that would be as easy as just holding one on pin 10+11 and see if it does anything.

Yeah, that's what I was thinking.

is the clock really a culprit though? as far as i can tell, the oscilloscope probe on pin 10 indicated a fairly clean signal across the full sweep of the density control (post #34)

It may not be the clock but the ability of the fv-1 to follow the clock.
Maybe there's enough ramp in the clock signal that the fv-1 is triggering 2x on some pulses?

this has been checked and confirmed already (post #11, post #15)
the noise is present regardless of the position of any control (except the mix control)

 

[music6000]

I thought it was 15-27pF from Pin 9 (X2) to Pin 11 [GND) ???

 

[owlexifry]

I thought it was 15-27pF from Pin 9 (X2) to Pin 11 [GND) ???

it could be, ill try both (pin 9 to 11) + (pin 10 to 11)

 

[owlexifry]

The only other thing I could think to try is the cap to ground on the clock pin. Could probably hold it on there temporarily with a loop playing. (See post 20). I know a bunch of pedals have been built without this, including EQD pedals, but maybe it will clean up your clock enough? That's kinda the hail mary before calling the fv-1 bad.

I thought it was 15-27pF from Pin 9 (X2) to Pin 11 [GND) ???

well, just tried both with a 20pF ceramic cap.

no bueno.

in fact both of these just introduced a slight buzz (probably caused by me holding the cap)