# Backfeeder rhythmic noise



## quazimoto (Mar 26, 2020)

Greetings all! I am trying to track down an issue I have with the Backfeeder. I am not sure if it is grounding issues or IC issue. I have gone back and re-soldered eventhough I did not find any glaring issues. I was pretty thorough on making sure values matched up for components. The pedal works as it should except for this noise that is always in the background. I attached a video of the noise. 



   Any thoughts would be greatly appreciated!


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## K Pedals (Mar 26, 2020)

quazimoto said:


> Greetings all! I am trying to track down an issue I have with the Backfeeder. I am not sure if it is grounding issues or IC issue. I have gone back and re-soldered eventhough I did not find any glaring issues. I was pretty thorough on making sure values matched up for components. The pedal works as it should except for this noise that is always in the background. I attached a video of the noise.
> 
> 
> 
> Any thoughts would be greatly appreciated!


I made two of them and both of mine did the same thing...
I never went back and tried to figure out what it was


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## museums (Mar 26, 2020)

K Pedals said:


> I made two of them and both of mine did the same thing...
> I never went back and tried to figure out what it was



Oooof probably not going to bother finishing the one I've been working on in that case.


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## Robert (Mar 26, 2020)

I'm not sure if we've discussed this or not (I know at some point in the past someone had this issue) but you have to ensure the momentary footswitch is oriented properly (see the build docs, the normally open contacts have to be on top).      If the footswitch is oriented backwards the PLL will constantly try to relock while you're playing and give weird glitches similar to your clip.

There have been quite a few successful builds.   I have one, as well as a prototype of the standalone feedback function.

They can be glitchy at times but what's happening in your clip is not normal behavior.


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## quazimoto (Mar 27, 2020)

Robert said:


> I'm not sure if we've discussed this or not (I know at some point in the past someone had this issue) but you have to ensure the momentary footswitch is oriented properly (see the build docs, the normally open contacts have to be on top).      If the footswitch is oriented backwards the PLL will constantly try to relock while you're playing and give weird glitches similar to your clip.
> 
> There have been quite a few successful builds.   I have one, as well as a prototype of the standalone feedback function.
> 
> They can be glitchy at times but what's happening in your clip is not normal behavior.


When I originally built it I did have the switch backwards. I posted here in the forum and you helped me correct that issue as when I hit the momentary switch the feedback would never stop. I now have the momentary switch oriented correctly. The sound clip I posted is me engaging the effect and not even plucking the strings or hitting the momentary switch. Could this be a back IC/chip possibly?


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## quazimoto (Mar 27, 2020)

I did just realize that the CD4069 and CD4013 both have the suffix “BE” and not “N” like the part list calls for. I don’t know enough to understand if this would be causing my issue. I know the “BE” is buffered but unsure if this causes a problem for this circuit.


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## Robert (Mar 28, 2020)

quazimoto said:


> When I originally built it I did have the switch backwards. I posted here in the forum and you helped me correct that issue as when I hit the momentary switch the feedback would never stop.



Got it, I knew that I had that conversation with _someone _here...  Normally the orientation of a 3PDT doesn't matter so it's an easy mistake to make.



quazimoto said:


> I did just realize that the CD4069 and CD4013 both have the suffix “BE” and not “N” like the part list calls for.



I'll look in mine today and see for sure which ones I used.


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## quazimoto (Apr 3, 2020)

Robert said:


> I'll look in mine today and see for sure which ones I used.


Any update on this? I have tried looking for a CD4013N and the CD4046N but I can’t seem to find any with that suffix.


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## bengarland (Apr 13, 2020)

Wow I thought it was just me -- my Backfeeder has the same issue. Sounds like a yappy dog, sometimes also with a faint "weeee uuuu weeee uuuu" oscillation in the background. But the yapping goes away when I do any of this:

1) Depress the Feedback switch, no yap.
or
2) Turn the Distortion pot to zero, no yap.
or
3) Mute my strings with my hand, no yap. As soon as I make any string noise, even just slightly sliding a finger, the yapping returns. This is with the pedal on and Distortion turned up higher than zero, but not pressing the Feedback switch.

It seems like it might be related to EMI and impedance / grounding + the Distortion part of the circuit? The yapping definitely gets more intense when I'm holding my guitar but not touching the strings. As soon as I touch the strings, the yapping calms down and sometimes it will disappear completely for a moment.

Maybe Backfeeder needs some "hack" to the circuitry to fix this issue?

I will note that I've never seen this type unexpected noise issue with any other pedal and it doesn't seem to matter which power supply I use or what other equipment in the room is or is not turned on. Everything points to something being odd with the Backfeeder itself.


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## bengarland (Apr 13, 2020)

quazimoto said:


> Any update on this? I have tried looking for a CD4013N and the CD4046N but I can’t seem to find any with that suffix.



The ending letters don't matter most of the time -- it just designates the chip size and/or material. The "BE" type are the current label for DIP size in this case.


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## Barry (Apr 14, 2020)

I think the CD40XX chips may be ones the suffix does matter


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## music6000 (Apr 14, 2020)

This is from Member cooder build.
Maybe he can chime in if he has had your issues!


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## museums (Apr 14, 2020)

Those TL072s look weird


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## analog_memories (Apr 24, 2020)

Not sure if you have resolved this yet.  Try replacing the cap at C22.  If that does not resolve, change out the IC7.  It is possible you have either a leaky cap, or, you have a bad TL072.  But, I would say the cap is more suspect.  IC7 also spans from the distortion into the signal gain for the feedback frequency circuit.


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## HegeMoney (Nov 8, 2020)

Sorry to revive an older thread, but has anyone resolved this issue yet?
Just finished this build recently and am also experiencing rhythmic noise.
The distortion works fine, but with no signal coming through pulsing noise can be heard that increases with the level and distortion controls.
Instead of feedbacking hitting the momentary switch just creates a humming sound. 
Attached a zip with a recording as an example.


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## music6000 (Nov 8, 2020)

Did you use correct Footswitch in both positions.
Momentary 3PDT with Normally Open on top. on the Left Footswitch.
Standard 3PDT latched on the Right Footswitch


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## HegeMoney (Nov 8, 2020)

I believe so, unless I am misunderstanding in this context the difference between open and closed.
I double checked with a multimeter, when the momentary switch is in it's normal/resting state (not being pushed/clicked down) there is continuity between the bottom two rows. When the switch is pushed/clicked down there is continuity between the terminals in the top two rows.
I don't believe there is any issue with the standard latched footswitch. No issues when the effect is bypassed and the distortion itself is sounding like a DS-1.


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