I donāt think the Lyra 8 FX will ever leave my rack now that I know itās a feedback machine.
The following is a four-section subset of sounds from a 40-minuteish recording. Thereās no input signal at all, it all starts with the Lyra 8 in full feedback which is then sent to a Twinpeak and then a Mimeophon, which is also feeding back at times. Modulation from a Benjolin and Sloths:
How are you liking it? Iāve been wanting an FFB for ages, but have choice paralysis (and budget concerns when I look at something like a Fumana).
I didnāt really get along with the EMW FFB at all, Iām afraid, and it didnāt take me long to sell it. I liked Make Noise FXDf better, but then I went for a Mutable Shelves instead.
I find Shelves more flexible, but I think I might just be too spoiled by software EQs. Since getting Blades recently, I have an abundance of filters (I have VCFQ and Angle Grinder too), so I might not keep Shades in the long run. Iām going to wait a few months to let things settle before changing anything else at all in my modular, though.
I suppose I should investigate my software EQ more ā I always think of it as a static set and forget type of thing. I can easily automate it and use it like an FFB, hadnāt really even considered that. I have thought a lot about the MN FXDf, but it appears to be sold out completely. I wish theyād offer up a DIY version.
Maybe take a look at Bastl Propust for a compact (and diy) ffb. Itās more basic than the make noise but might get you places (not sure how they implement the different slopes on the inputs of the fxdf). You could experiment with different cap values too if youāre wanna get your hands dirty.
There are some old moog schematics around of low and high pass ffbs (passive, so non-resonant) and they are surprisingly simple.
I just started exploring this with my serge reseq but itās fun to set the upper and lower settings (which are different bands) and treat them like left/right outs for various feedback stuff (or mid/side wackiness though this is still a bit of a black box to me in practice). I imagine it might be fun to make two side by side passive ffbs with slightly different component values for a somewhat similar effect (though the resonance in the reseq seems to do a lot of the heavy lifting regarding that feedback magic)
Also if youāre handy with a soldering iron consider L-1ās quad resonant EQ. Itās not a cheap build (but MUCH cheaper to diy than buy the āfactoryā version) but also a pretty easy one (most components are presoldered if I remember). Itās also an hp hog- I kinda wish it was only dual.
Also wanna give a shout of to the humble music thing simple eq. I was having some fun the other night putting the tilt half in a runway feedback patch and using that to tame it, let it run wild, tame it again, and so onā¦ 
If you want to step into a truck sized rabbit hole on diy ffbs/eqs click over here 
The big slider CGS version of the serge reseq is a rewarding diy project and combined with a line in to modular level amp module Iād say thatās worthy of its own box as a standalone unit! I must say I donāt find myself using the individual outs as much as Iād hoped, though. They are fun to run into an FM input of a filter in a feedback path though.
As for other uses of outboard eqs Iām afraid Iām not the person to ask - maybe @Starthief can weigh in? 
Iām partial to my doepfer 106-5 on everything including feedback patches but I also donāt have a very discerning ear. I have an old two channel Rane rackmount eq Iāve been wanting to try but it has a broken bypass button so itās sadly just been sitting there until that day I open it up. Maybe this will give me the kick to get it running!
I canāt speak to outboard hardware EQ really. I have some favorites in software though.
CraveEQ: great for cleanup/surgery/minor tweaks, but also for peaking bands that can be automated.
SurferEQ: can track the pitch of the input and have bands follow along, which is great. Also one of the bands has some harmonic series shapes, including highly resonant ones ā I really need to work with feedback with this one more than I have so far 
Peel: it has a different method of visualization, showing harmonic content in the stereo field quite clearly. You can draw a box around an area to mute, isolate, or feed it to a separate output to process separately from the rest.
Uhbik-Q: the one I use when I donāt want a graphical EQ or precise numbers, just going by ear and feel.
That fxdx shows up used pretty often. Highly recommend trying one out. If you already have a bunch of vcas itās a really inexpensive way of checking out ffbās.
@namon Iāll definitely keep an eye out for it, thank you!
@starthief Iāll look into those EQs. Iāve got Fabfilter Q3, but am not terribly adept at it, I kind of just use it at a very base level. I also found an FFB M4L last night, so Iāll try that out soon.
@addam Thatās actually the thread that created the desire to get an FFB. Thank you for reminding me of that, I need to re-read the whole thread.
how have i missed this thread for so long?
Glad I tagged you. I very recently gave in and decided to start using ableton as more than a multitrack recorder and started using plugins a bit. Been enjoying the visualizations in the cheapie version of izotope ozone but that Peel plugin looks like a lot of fun!
@Whinger if you do end up DIYing or acquiring something please update us (me )
Great thread! Just read it all tonight. I recently got a Fairfield Hors dāOuevre feedback loop pedal which Iāve been using just in my modular effects send/return. It generates some great feedback based on what pedals are in front of it, and has separate wet and dry controls on the return so you can ātameā the feedback to some degree, or just let it oscillate and put that lower in the mix than the dry signal. This thread got me thinking an eq after it would provide even better control over sculpting the feedback. Looking up some of the modular and pedal options for eq suggested in this thread. Thanks!
One area of feedback I use a lot is having a delay just reach self oscillation in its feedback settings and then running stuff through it, extra helpful if the delay time can be voltage controlled. I use the Bugbrand PT Delay a lot for this, has two simple but very useful Low/Hi EQ parameters also which are handy for control of the feedback.
Can really add a bit of edge to something you might want to sound edgy.
Iāve had the PT delay for a couple of months and have found it amazing. The features are just perfect for sculpting feedback
Indeed, think Tom definitely designed it with that sort of usage in mind!
Does anyone know the basic high level circuit design of something like the BOSS FB-2 Feedbacker/Booster of the other boss feedbackers? Is the basic idea to add gain via a boost circuit and then feed a certain amount of the boosted output back to the input of the boost stage? Do you think thereās any compression going on to control levels? Or maybe they start to clip/saturate naturally once they reach a certain level?
I donāt know too much about electronics (built a few pedal and eurorack kits) but I had a sudden urge to heavily modify a squire jaguar and was thinking about some creative controls. One idea, the only one that would require active electronics, is a feedbacker circuit built into the guitar. I know boosts are pretty simple to build and it seems like one of those plus a switch and a dual pot to control boost gain and feedback would be in the realm of my DIY skills if it is as straightforward as it seems Any ideas or input or things I should consider?
Sounds like a fun project. I donāt have much to add to the technical side but perhaps putting a tone control like this in the feedback path might be helpful. I imagine you could get more sophisticated with something thatās not passive. The doepfer DIY page has some simple passive filter designs, too.
I recently picked up a SSF Vortices which turns out to be incredible for feedback and saturation exploration.
I created this very orchestral piece inspired by the Vortices manual. Really excited about using Vortices in this way!
Itās marketed as something for heavy saturation, but it can be used to create some really lovely textures for ambient music. The Vortices is at the centre of this patch, but also getting a lot out of feedback patching Verbos Multi-Delay, SSF Stereo Dipole, Intellijel Springray, Instruo Arbhar and Lubadh.
Beautiful !
I also have a Vortices and itās indeed a great module for feedback patching:the saturation and limiters help keeping everything under control. I have some videos of a patch I did that Iāll post when Iāll have a bit more time.
About feedback patching in the box: I like to use Pitchmap in the feedback loop to create a constant fight between it trying to correct the pitch and the feedback that wants to run wild.
i love this thread.
and the title includes āsafelyāā¦ for some reason, this got me thinking of all the greatest feedback-related dangers possible in the universe:
if you create one wormhole, as the destination for another wormhole, light-years away from each other in space, so that at this point, light can travel across distances of ālight-yearsā faster than the speed-of-light, how can any amount of energy transfer be measured accurately, if distance is no longer a point-of-reference by which to uphold the constant C(speed-of-light) in the equation, āEnergy = Mass * C^2ā?
Think about it! 
also, i recently discovered, in the digital-audio realm, instead of compression/limiting to contain feedback, you can also saturate right before limiting with ātanhā: you multiply the signal by half before tanh, that way anything that normally wouldāve gone into clipping territory now gets pulled back down within saturation territory(focused around the curvature of the knee near the top of the tanh s-shaped response curve), then put through tanh for the saturation/limiting, and then multiplied by 2. to normalize back out to full volume.