DIY True Bypass/Feedback Loop (aka KROK)

[wideyed]

so then how does that effect the diagram he had previously drawn up recently?
sorry to be a bother. just very eager to build this.

[teamastra]

this is a simple diagram of how the circuit shout be wired up.

[fNNR]

Hi everybody

I made myself a feedback looper last night, it *almost* works. The schematic can be found here: http://rafnem.hi.is/~fkp1/gogn/fb_looper.pdf

What happens is that it seems to work completely, except that when I switch the pedal off, while in feedback mode with the potentiometer set all the way clockwise (that is zero resistance = 100 % feedback), I get a low sounding feedback underneath. I'm not quite sure why this happens, I was hoping someone here could enlighten me and point out the error in the schematic or something.

I connected the grounds together just via the metal box (so no wires were needed for that), is that usually considered allright or? The ground lug on the mono jack seems to be connected directly to box when it has been fitted...

I've also got a question on the schematic on page 1 (the first schematic/drawing by colin) on this forum thread. When the pedal is bypassed, in feedback mode, with the pot set at zero resistance, isn't the input signal shorted to ground, because the send tip is connected to ground? I'm not saying that it doesn't work, I'm sure it does =). I'm just wondering...

Thanks alot!

[expanoncolin]

Hi everybody

I made myself a feedback looper last night, it *almost* works. The schematic can be found here: http://rafnem.hi.is/~fkp1/gogn/fb_looper.pdf

What happens is that it seems to work completely, except that when I switch the pedal off, while in feedback mode with the potentiometer set all the way clockwise (that is zero resistance = 100 % feedback), I get a low sounding feedback underneath. I'm not quite sure why this happens, I was hoping someone here could enlighten me and point out the error in the schematic or something.

I connected the grounds together just via the metal box (so no wires were needed for that), is that usually considered allright or? The ground lug on the mono jack seems to be connected directly to box when it has been fitted...

I've also got a question on the schematic on page 1 (the first schematic/drawing by colin) on this forum thread. When the pedal is bypassed, in feedback mode, with the pot set at zero resistance, isn't the input signal shorted to ground, because the send tip is connected to ground? I'm not saying that it doesn't work, I'm sure it does =). I'm just wondering...

Thanks alot!

Try a grounded input true bypass instead:

http://www.singlecoil.com/tb-strip/images/dia1.gif

The pedals in the loop are still feeding back when it's bypassed, so what you're getting is some signal leakage.

-Colin

[fNNR]

Try a grounded input true bypass instead:

http://www.singlecoil.com/tb-strip/images/dia1.gif

The pedals in the loop are still feeding back when it's bypassed, so what you're getting is some signal leakage.

-Colin

Yeah, I was going to do the grounded input true bypass but it seemed to be unnecessarily complicated. I guess you can't get away any cheaper =)

What about connecting the grounds together just through the metal box, isn't that allright?

Thanks again
Finnur

[expanoncolin]

Try a grounded input true bypass instead:

http://www.singlecoil.com/tb-strip/images/dia1.gif

The pedals in the loop are still feeding back when it's bypassed, so what you're getting is some signal leakage.

-Colin

Yeah, I was going to do the grounded input true bypass but it seemed to be unnecessarily complicated. I guess you can't get away any cheaper =)

What about connecting the grounds together just through the metal box, isn't that allright?

Thanks again
Finnur

That can be an OK way to go, use a multimeter to check.

-Colin

[pstretz]

hey all, I'm new to this thread, having stumbled across it while looking for something completely unrelated.  can someone explain to me why you don't need a mixer for the input and return?  when I made my own feedback circuit I thought I had to mix them.
My design here:
http://www.instructables.com/id/Apocata ... digital_d/  

I'll try yours this weekend as it looks easier and has a bypass.

[expanoncolin]

hey all, I'm new to this thread, having stumbled across it while looking for something completely unrelated.  can someone explain to me why you don't need a mixer for the input and return?  when I made my own feedback circuit I thought I had to mix them.
My design here:
http://www.instructables.com/id/Apocata ... digital_d/  

I'll try yours this weekend as it looks easier and has a bypass.

I'm not sure what you mean by a "mixer" - you mean to adjust the level of input signal vs feedback signal?  There is indeed a feedback pot in there already, which might be what you're talking about.

-Colin

[pstretz]

as per this site, http://www.epanorama.net/circuits/linesum.html, and many others, you can't just tie two outputs together.  The way I understand your circuit working is this:

Code:

    --Send
In--|
     ------
          |
          V          --Rtn
      --/\/\/\-- \--|
                     --Out

doesn't there have to be a resistor at the input also so that the send is the mix of the Rtn/Out and the In? Like this:

Code:

            --Send
In--/\/\/\--|
             -----
                |
                V          --Rtn
            --/\/\/\-- \--|
                           --Out

I think this might provide a more even blend of the two signals and whatever you are plugging into this pedal won't have to fight so hard to deliver it's signal.

Or is that really only a problem with line level stuff and since we're not working with line level it doesn't matter?  Just trying to understand this stuff better.
-Peter

hey all, I'm new to this thread, having stumbled across it while looking for something completely unrelated.  can someone explain to me why you don't need a mixer for the input and return?  when I made my own feedback circuit I thought I had to mix them.
My design here:
http://www.instructables.com/id/Apocata ... digital_d/  

I'll try yours this weekend as it looks easier and has a bypass.

I'm not sure what you mean by a "mixer" - you mean to adjust the level of input signal vs feedback signal?  There is indeed a feedback pot in there already, which might be what you're talking about.

-Colin

[expanoncolin]

Nice diagrams! Thereis in fact a resistor in the diagram - it's just 0 ohms. If you put a resistor between in and the send, then you probably wouldn't hear the input.  The feedback loop'd signal is MUCH louder.

-Colin

[eikipi]

sorry if this has been posted before,
but everything's wired in the right places n such as far as i can tell
but
it doesn't work when bypassed, or only when its not bypassed,
hard to tell cuz the send and return aren't working at all,
and
when the clean signal is going through,
the pot works like a volume knob,
and if i flick the toggle switch,
the sound also stops

can anyone help please?

[expanoncolin]

sorry if this has been posted before,
but everything's wired in the right places n such as far as i can tell
but
it doesn't work when bypassed, or only when its not bypassed,
hard to tell cuz the send and return aren't working at all,
and
when the clean signal is going through,
the pot works like a volume knob,
and if i flick the toggle switch,
the sound also stops

can anyone help please?

Recheck your wiring.  Use a multimeter to make sure nothing is shorting out to the case.

-Colin

[eikipi]

sorry if this has been posted before,
but everything's wired in the right places n such as far as i can tell
but
it doesn't work when bypassed, or only when its not bypassed,
hard to tell cuz the send and return aren't working at all,
and
when the clean signal is going through,
the pot works like a volume knob,
and if i flick the toggle switch,
the sound also stops

can anyone help please?

Recheck your wiring.  Use a multimeter to make sure nothing is shorting out to the case.

-Colin

i dont have a multimeter, but would if somethings shortin out the case would that explain such things as, the return and send working backwards though wired correctly?

[eikipi]

alright, alright,
i'm sorry for all the newb questions,
but i've almost got this thing done but i need a lil more help,
you see,
it bypasses fine
and it works as a feedback pedal fine,
but the pedals have to be plugged in backwards to the fx loop (i'm assuming the "send" line should go to the "input", and the "return" should come from the "out"... just makin sure, this problem seems veddddy veddddy odd)
and the toggle switch does nothing but make the feedback loop louder or softer... which i imagine it due to a poor solder in the toggle tough it doesn't appear to be so, but is the least of my confusions,
and zee pot
it does NOTHING

i've checked, n rechecked my wiring but i can not for the life of me see any problem with that
so..
i dunno if i just have a messed up switch,
or what,
if some could tell me,
or even post a schematic of what i'd need to do to be able to toggle the feedback loop with such a set up (using the original krok set up, but the 6 being the input, and the 3/8 being the output) that'd be great,

thank you for your time
i love this board

[expanoncolin]

It sounds to me like there's a wiring issue.  It's very hard to test for that sort of stuff over the internet.  Try taking it out of the case it's in.  Failing that, unwire it all, clean it, and re-wire it, then try again.  I promise the diagram works!  The send should go to the effect-to-be-feeding-back's input, and the return should come from the output.

-Colin