Feedback pedal similar to Line6 Dr. Distorto

[Satan Of Saturn]

I love feedback sound at some point. But I cant find such nice pedal for DIY. something similar to Fender Runaway or Line6 Dr. Distorto. Does anyone have any kinda information regarding these two pedals or something similar to them. I've heard Line6 Dr. Distorto is a digital pedal so it would need some coding. But is there any alternative? BTW i love Line6 Dr. Distorto... perfect for sustain as well as feedback

[Mark Hammer]

Both the pedals you mention are essentially digital extensions of the concept explored in the analog Boss DF-2, which Behringer has a low-cost clone of.  I have both a DF-2 and a Dr. Distorto, and the Distorto both tracks pitch better and also offers more flexibility.  The dual-switch system in the Tone Core series also addresses some of the cumbersome aspects of the DF-2, which required one to hold down the foot treadle for a while to engage the feedback function.

In some respects, the DF-2 could have been a much better, and more usable, pedal if it had been built into a chassis that permitted two footswitches, like the dual-treadle units Boss uses for some of their delays, chorus, rotary, slicer, looper, and other effects.

You can find the schematic of the DF-2 posted around.  Many find the distortion section itself nothing special, and I'm inclined to agree with them.  And a big chunk of the feedback engaging circuitry is actually dedicated to the task of differentiating a short from a held switch closure in the single-switch form-factor.  Convert to two switches (TB + momentary), and the circuitry may simplify considerably.

[Satan Of Saturn]

Thanx Mark... 

[gasmask]

Boss df2 schematic.
I tried to modify it to create pure feedbacker but without results.
I hope you will be able to do it 
Good luck 
Gasmask

[Satan Of Saturn]

Thanx  I've this schematic
Actually this is a nice pedal to but I dont want the distortion unit of this. I'd prefer using it with Wampler Triple Wreck or Toneczar Openhaus. Anyone tried to rip of the distortion part from the schematic?

[Mark Hammer]

The distortion part is largely separable from the feedback emulation.  That is, the feedback emulation goes through the distortion circuit, but doesn't have to go through that exact circuit in order to work as a feedback emulator.  You could easily change a number of aspects of the distortion subcircuit and it would still function the same way.

[gasmask]

Ive read on this forum that the easiest way is to buy original pedal and bypass clipping diodes. I tried to understand the feedback part, but its too hard for me now.

[aron]

Uh oh... I forgot about my Dr. Distorto..... will have to use it tomorrow night!

[Mark Hammer]

Actual DF-2 pedals may be a little pricey.  You can probably find a Behringer FD300 (a DF-2 clone) for under $40, new.  Whether you can identify the relevant components on what is likely a double-sided surface-mounted board is a whole other thing.

[tca]

Fender Runaway is digital, isn't it?
- http://www.softube.com/index.php?id=runaway

There is a patent somewhere that you can read.

P.S. (edit)

- https://www.google.com/?tbm=pts&gws_rd=ssl#q=inassignee:%22Softube+Ab%22&tbm=pts

[roseblood11]

What about using a FV-1? I had a Z.Cat "Hold/Delay/Chorus" with that kind of sound. In fact, it sounded like shit, worse than the hold effect in my old Boss ME-8, but maybe it could be done better?
Instead of a switch, I'd use a pedal to fade in the feedback sound. That's how it was done in the ME-8, and I really liked that feature when I was a beginner.

[Mark Hammer]

The other approach to take is to not aim for a perfect emulation of feedback, per se, but to simply provide a means for gradually introducing an octave up.

Most of us are accustomed to octave fuzzes producing an audible octave all the time (well, at least if you're picking above the 7th fret, on the neck pickup, with the tone rolled back  ).  In these instances, the entire signal is fed through the rectifier circuit, with ersatz doubling produced, and that is the audio output signal of the pedal.  There aren't too many instances where the octave-up is produced separately, and blended in.  The Visual Sound Angry Fuzz is the only commercial fuzz pedal I'm aware of that adopts this approach, though it's a big woprld and I imagine there must be other pedals that do this as well.

If a person had a pedal that split the signal, and "went the distance" to produce a good octave-up, and the octave-up could be gradually blended in via a footpedal (wah shell), that would cover some, though clearly not all, of what feedback pedal users want.

In the case of the DF-2, since the 4046 locks onto the pitch of the sustained note, you can actually use that note as a drone and play over it, while the original "feedback" note is held.  Obviously my suggestion of a foot-blendable octave up would NOT do this.

[gasmask]

Well, I have crazy idea. Signal goes into lm386/tl072, then output goes to output jack and another opamp/amp with octave option which will be connected to input of pedal.
The octaveup delay can be set up with a photoresistor. Sounds crazy and silly but maybe it can be a little step in diy feedbacker.

[thehallofshields]

By god that's complicated. If only I had the skill to chop this like (Sweetalk?) did with the OC-2.

To me it looks like a Comparator driving the clock of an LFO but I could be way off. I also don't have a clue as to how it locks the Frequency and if the "Overtone" control is a Bandpass Sweep or what.

[wordstep]

About the DF-2
Before R58, it is just like a OC-2, get the note frequency into square wave.

The square wave signal goes in PLL (phase lock loop) IC 4046.

4046 works all the time (output).
When 4066(8a) pin 13 gets LOW, Pin9 and Pin13 of 4046 disconnect.
4046 begins to ignore the input from PIN14, and " LOCK" in the frequency a moment ago.

At the same time, Q10 turn on, then turn on Q11, Q12, the output of PLL 4046 and 4013(5b)  can go out VIA Q11,Q12.
At the same time, Q8 turn on, output from C47 can go through to C38. (I think Q8,C38,R65,C47,R66 are just for mute switch function.)

To simplify the circuit, get rid off Q8,C38,R65,C47,R66 , get rid off R73 Q11,R72,Q12,Q10,C54,D14,R90
just use a physical switch to replace the 8a of 4066, it will work.

But there will be some noises output when the 4046 is not "lock".

[thehallofshields]

Wow. Great analysis.

Does anyone know of any other analog pedals out there that use these PLL Chips?

4046 works all the time (output).
When 4066(8a) pin 13 gets LOW, Pin9 and Pin13 of 4046 disconnect.
4046 begins to ignore the input from PIN14, and " LOCK" in the frequency a moment ago.

This tech is way above my current knowledge level, but is just really interesting to me.

Please ignore the following observations and confusions:

So a datasheet I found says Pin 2 is Comparator Output 1 and Pin 13 is Comparator Output 2. Are these just in reverse Phase?

It also appears that you feed it Signal at Pin 14. Kind of confused why you would need to feed it from a 4013 Flip-Flop Chip after the Comparator.

Is the 'Envelope Generator' portion what gives the circuit the gradual Swelling affect?

[wordstep]

Example:
1k HZ sin wave input to R2, Pin1/Pin2 of 4013(5a) is 1k Square wave.
Pin3 of 4046  is 1k Square wave. Pin4 of 4046 is 2k Square wave.  

1k Square wave --------filter------\
                                                mix together--------filters--------go to R4
2k Square wave --------filter------/

I believe this is the 'Envelope Generator'.
--------------------------------------------------------------------------------------------
PLL(4046) is not straight forward to me. Let me try. 4013(5b) here in PLL term is a divider.
Example:
1k Square wave input in Pin14 of 4046.
If Pin3 direct connect to Pin4 ( divider=1), Pin3 and Pin4 are 1k Square wave.
If Pin3 connect to Pin4 by divider=2  (like 4013(5b))  , Pin3 is 1k Square wave. Pin4 is 2k Square wave.
If Pin3 connect to Pin4 by divider=4  , Pin3 is 1k Square wave. Pin4 is 4k Square wave.
.... ( in 4046 frequency range)

--------------------------------------------------------------------------------------------
Please check different manufacture's 4046 datasheets. Good luck.

[thehallofshields]

I just realized the DF-2 uses Vibrato as an attempt to get a more natural sounding feedback. I'm guessing that's what the entire LFO section drives.