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?

 

[Digital Larry]

Is the clipping LED installed? Is it clipping?

I don't know anything about what the FV-1 hardware wants.

 

[Cybercow]

@Robert why was the 15-27pf differentiator cap was omitted on this build? Does it interfere with the density control at the extremes?

No. I've successfully built the Deflector Reverb with zero issues at the extremes of the Density control.

Wonder if the TI 4049s have some unwanted spikes that may be smoothed/filtered out with it.

I've used both a TI CD4049UBE and the NS CD4049UBE with zero issues.

IDK if the fv-1 prefers pulses over square wave clock but that seems it could cause a difference. Maybe @Digital Larry could give input on that.
@owlexifry do you have an o-scope? Would be nice to see if you are getting a clean clock cycle.
Also, if you haven't, double check your values around the clock circuit.

When an external, controllable clock circuit is used in place of the crystal, X1 or X2 can be used. I've seen this done in different FV-1 builds. (See the EQD Transmisser - it uses X2 as the input where it uses the CD4049. And FV-1 based PedalPCB boards that use the CD4049 for the clock use X1. As long as one of the 𝕏 inputs have a solid clock, it will still work that way.)

I suspect the noise is coming from a bad 4049.

 

[Robert]

@Robert why was the 15-27pf differentiator cap was omitted on this build?

It wasn't omitted, it wasn't part of the original.

 

[Robert]

I don't suppose by any chance you have an EEPROM programmer?

 

[owlexifry]

I don't suppose by any chance you have an EEPROM programmer?

i don’t.

 

[owlexifry]

do you have an o-scope? Would be nice to see if you are getting a clean clock cycle.

i have one of these. probably should've pulled it out last night for a look when i was checking with the meter..

double check your values around the clock circuit.

haven't found any obvious errors yet.

 

[owlexifry]

..just noticed the updated PCB layout

old layout


C6 is now polarized? something i should consider?
(assuming probably not, since my noise issue is unchanged by the deflect control position)

 

[Robert]

You have the most recent layout.

The first revision used a polarized cap, which worked fine, but could potentially be subject to reverse polarity depending on the position of the Deflect pot. It was changed to non-polar as a preventive measure.

 

[owlexifry]

You have the most recent layout.

The first revision used a polarized cap, which worked fine, but could potentially be subject to reverse polarity depending on the position of the Deflect pot. It was changed to non-polar as a preventive measure.

ahhh, so it's the other way around. thanks for clearing that up.

I suspect the noise is coming from a bad 4049.

well, holy crap. pulling out that 4049 absolutely sucked. i've never had to do it with that many pins before. even finally replaced the tip on my solder sucker that i'd been putting off for the longest time.

- put in a socket.
- installed a new CD4049 (of a different batch code)
- same shit - noise is still there

then i ran out of time.
so next i guess ill try some more CD4049s and get the digital scope out and see what it's putting out.

 

[Robert]

Connect the lower end of R4 (22K) to ground to enable the internal program and see if the noise is still there.

Make sure you turn the Deflect pot all the way down first, otherwise it might self-oscillate and lock up (if that happens just disconnect/reconnect power).

 

[owlexifry]

Connect the lower end of R4 (22K) to ground to enable the internal program and see if the noise is still there.

Make sure you turn the Deflect pot all the way down first, otherwise it might self-oscillate and lock up (if that happens just disconnect/reconnect power).

this point?


will give this a try tonight - thanks for the tip.

 

[Robert]

Yep, that's the one.

 

[owlexifry]

Connect the lower end of R4 (22K) to ground to enable the internal program and see if the noise is still there.

Make sure you turn the Deflect pot all the way down first, otherwise it might self-oscillate and lock up (if that happens just disconnect/reconnect power).

R4-grounded:

https://soundcloud.com/alexshriffs%2Fdeflectornoise_r4-grounded

much less noise with that lead in place. it does sound different.. more like a chorus?
still, if you listen closely all the way through, there's still some weird repeating artefact - should that be there? (it is definitely not me or my guitar making any noise that's causing that)

and back again with the ground lead removed (R4 not grounded):

https://soundcloud.com/alexshriffs%2Fdeflectornoise_r4-notgrounded

obviously a lot more noise.

exact same settings in both clips. everything at noon, except deflect at minimum.
(mix at zero at the start of both clips, then dialed up to noon, then 1400/1500 for more emphasis on the noise)

 

[owlexifry]

@owlexifry do you have an o-scope? Would be nice to see if you are getting a clean clock cycle.

how’s this?

 

[jwin615]

how’s this?

Looks clean. Is it a steady freq? I assume you are moving the density pot.

 

[owlexifry]

I assume you are moving the density pot.

yep, the change is me moving the density pot

 

[Cybercow]

how’s this?

IMO, that appears correct and clean. Do you have another CD4049 (and socket) to swap out the one on the PCB?

Can you swap out that TL072?
I've run into whole batch numbers of TL072CP opamps that had a very staticky component at low levels. From where did you get that TL072CP?

I know that being soldered in place, instead of being socketed, changing the chips will be a PITA.

Alternatively, you could inject a clean signal into the circuit and follow it with your scope probe to see if you can sort out precisely where the static starts showing up in the signal path. That might help pinpoint the problematic element(s).

(Troubleshooting is a process of elimination.)

 

[owlexifry]

IMO, that appears correct and clean. Do you have another CD4049 (and socket) to swap out the one on the PCB?

Can you swap out that TL072?
I've run into whole batch numbers of TL072CP opamps that had a very staticky component at low levels. From where did you get that TL072CP?

I know that being soldered in place, instead of being socketed, changing the chips will be a PITA.

Alternatively, you could inject a clean signal into the circuit and follow it with your scope probe to see if you can sort out precisely where the static starts showing up in the signal path. That might help pinpoint the problematic element(s).

(Troubleshooting is a process of elimination.)

yep, last night i pulled the original cd4049 and put in a socket, i put in another cd4049 and that did nothing.
i have x3 more cd4049 that i can try. they are all of the same brand, doubtful this will make a difference. especially when the scope appears to be showing a clean signal. i could try and get another brand (that looks like it might be NS) from a local electronics shop..

there’s zero issue with the direct/dry signal.
you will hear this if you listen to the clips - they all start with the effect engaged, mix control all the way down, and there’s no noise. then the mix dials up to bring in the effect, and you can clearly hear the noise is coming from the wet/effect signal from the FV-1.
so at least we know there is nothing wrong with the TL072

 

[Robert]

We've also eliminated the EEPROM as the problem.

Does the noise happen when you aren't playing?

 

[Cybercow]

yep, last night i pulled the original cd4049 and put in a socket, i put in another cd4049 and that did nothing.
i have x3 more cd4049 that i can try. they are all of the same brand, doubtful this will make a difference. especially when the scope appears to be showing a clean signal. i could try and get another brand (that looks like it might be NS) from a local electronics shop..

there’s zero issue with the direct/dry signal.
you will hear this if you listen to the clips - they all start with the effect engaged, mix control all the way down, and there’s no noise. then the mix dials up to bring in the effect, and you can clearly hear the noise is coming from the wet/effect signal from the FV-1.
so at least we know there is nothing wrong with the TL072

Agreed - doubtful that changing the CD4049 will have any further effect.
Also dbl-check the VRef voltage at the junction of R100 & R101 or lug #1 of the MIX pot.
I would next try a signal trace thru the wet signal path and see if your scope can show you from where the noise is coming.