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Make sure you have an always easily reachable master gain control of some kind.
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Don’t really think you need a compressor if you have 1) above.
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Limiter might be helpful in protecting speakers, set threshold just below digital zero.
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Try a frequency shifter (not pitch shifter) in the feedback path somewhere. For example, a frequency shifter in the feedback path of a delay, with very low shift amounts, will allow you to crank the feedback/regeneration/resonance up way higher before runaway oscillation, and can sound very, very cool too!
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In my experience/advice: Feedback anything and everything you can, don’t worry about damaging anything except the PA so don’t make the amp itself clip
Try a frequency shifter (not pitch shifter)
try ‘and’ pitch shifter too tho 
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It’s pretty simple:
FB Keeper.unit (7.1 KB)
The HPF is just to block any DC bias (though the ER-301 has AC coupled outputs, one can also use this in an internal feedback loop; having another unit in front of the VCA also helps make routing easier inside the custom unit). The VCA has a positive bias but the gain on the envelope follower is set negative. The output limite r isn’t really necessary if patching this in hardware, but in the ER-301 I figured why not have a little extra control over saturation and the output level.
The main idea is, the VCA increases the level when it’s low but the envelope follower suppresses it when it’s high. Works best with a delay, reverb, resonator etc. in the feedback loop so there’s more than just a noise floor to amplify.
I like my tanh[3], but I tend to use it for saturation or to change CV shapes instead of in feedback paths. It’ll eventually turn everything into squarewaves if something else isn’t managing gain anyway.
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cheers. thanks for this. I tried to use my tanh in the feedback path of my 4ms DLD after sending through a filter, but couldnt really find the sweet spot between little effect on the signal, versus runaway oscillations.
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Ahh yes, this is exactly what I do with my no-input mixer setup. I have the mixer running into a cheapo Boss DS-1 Distortion so I can tame the levels before it hits the audio interface and/or main mixer. I also have a couple delay pedals set up on the fx send/return. Pure noise.
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Anyone have info on how Radigue used feedback in her pieces?
I highly recommend Kassel Jaegers Retroactions for anyone interested in feedback based recordings… it’s also inspired by Radigues feedback works and was released on Eliane tapes 
(looking forward what they will release next!).
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FYI I did programming and live sound engineering for Alvin for a while some years ago, and at that time (of course, decades after some of his classic, now canonical, works), he was opposed to the employment of a limiter within live feedback loops. This demanded mores significant involvement on my part, i.e., “playing” the feedback loops in real-time to keep everything under some control.
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check out Julia Eckhardt’s book on Radigue, Intermediary Spaces. Its mostly one long interview with Radigue and some other additional writing, and she goes into a bit more detail about working with larsen/feedback and tape loops than other talks/interviews I’ve seen. Not in an overly technical “here is how you do this” way but if you just want more info on her processes and development/personal history you can’t do better than that book
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Has anyone ever used guitar EQ pedals in feedback loops?
I was thinking about something like a FXDf (if only I could find one!), or an EMW Fixed Filter Bank or Bastl Propust, when it occurred to me maybe a pedal would do the job. I’ve been using software EQs, but I can see benefits in having analog EQ for feedback loops and/or overdriving…
EQ is one of the things that can affect a feedback loop the absolute most. I do have a graphic EQ pedal but I have to admit I rarely use it compared to the EQ on my mixer. I can try to make a demo of it though.
I think the ideal, which is what I’m looking for right now, would be a rackmount graphic EQ as they can go for very cheap used. It depends on if you have the space for one though.
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I could squeeze a 1U EQ into my rack box, but it’s a risk – the audio interface I have in there tends to run on the warm side and it kinda needs ventilation space.
I’m thinking about the Caline CP-24, which has 10 bands… I could patch it through the matrix mixer in my modular pretty conveniently. Of course the difference from some modular filterbanks/EQs is no individual outputs per band, which could get into some interesting territory.
I do feedback loops using pedals/norns/fx through a mackie mixer and the channel strip EQ’s can really transform the sound (feedback can amplify even subtle EQ stages into a much more drastic effect). Some loops would be unusably bass heavy otherwise and boosting while sweeping through the mid frequencies can find resonant saturated tones that are quite beautiful and sound not unlike guitar feedback.
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I use an old electrix filter queen in my feedback loops, a low pass with an lfo creates wonderful oscillating textures. I don’t know of any pedals that offer the same feature set but there are a few pedals that do other interesting things, like the Klein Bottle.
As for EQ, I find parametric much more useful in a feedback context: I’m planning on grabbing an empress paraeq which seems perfect for it.
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I picked up a FXDf for this exact purpose. I’ve been using it with a crossfader - fading between different bands - along with switches, mixers etc. I find that certain bands in the 12db slope can cause feedback get out of control, which is why the crossfader comes in handy; fading into another band will dampen the feedback oscillation.
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I use the MXR ‘six band eq’ pedal for feedback loops with my matrix mixer, and a MixPre as the limiter for ear protection.
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I went ahead and ordered the EMW Fixed Filter Bank. Seems like a good combination of features and a relatively reasonable price.
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Another feedback instrument:
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Bumping an oldish thread to share my latest eurorack experiment, sequenced feedback. I used one channel of the matrix mixer to create a feedback loop via a handful of distortion/fuzz/waveshapers, then a VCA, back into the matrix. Promising stuff, tho like a lot of feedback-centric setups it’s wildly variable depending on different settings at every stage of the chain, and easily drops off into silence or clicks if you are not careful with what knobs you twiddle
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I have one and love trying to figure out what to set it on. It has a tiny bit of learning curve in terms of keeping the squeal-y feedback under control and how to touch it to guide the vibrations along, but it’s intuitive enough, I think. I sort of wish I had bought two of them so they could play off of each other, but maybe at some point…
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