Importance of compressor/limiter in feedback path, and options

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B0bcat
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Importance of compressor/limiter in feedback path, and options

Post by B0bcat » Thu Oct 15, 2020 5:12 pm

I've started to explore feedback patching in a small, dedicated standalone system, and I'm wondering how important folks would think having available a dedicated compressor in the feedback path(s) would be, rather than just riding the attenuators. MSCL is small and seems like a well-regarded compressor, and I do have one in my main case, but it's stereo with only one set of controls, so it doesn't seem ideal for the task
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Re: Importance of compressor/limiter in feedback path, and options

Post by Buttons ARE toys » Thu Oct 15, 2020 5:52 pm

I think that depends on what it is you're trying to do with the feedback and how well riding attenuators is working for you. What sort of stuff are you doing with it? And, if you've already got the MSCL you might as well just throw it into the small case for a session and see what it does for you, and what you wish it did.
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Re: Importance of compressor/limiter in feedback path, and options

Post by Joey P. » Thu Oct 15, 2020 6:10 pm

Make Noise Dynamix can work for auto leveling. But it's also an LPG, so that may or may not work for you.

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Re: Importance of compressor/limiter in feedback path, and options

Post by starthief » Thu Oct 15, 2020 7:01 pm

Every feedback loop is different. Some are extremely twitchy and hard to ride manually without going places you may not want (dying out or clipping), others just maintain themselves with no effort. It depends on the modules/gear in the loop, and what you've got circulating through it, and your goals/tastes.

I personally think MSCL is really handy if you play with feedback a lot. I used to use Maths plus a VCA, or Bastl Dynamo plus a VCA, and that took a bit more fiddling to get the levels right and keep them steady instead of oscillating.

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Re: Importance of compressor/limiter in feedback path, and options

Post by rew_ » Thu Oct 15, 2020 7:06 pm

Instruo Tanh is specifically made for this

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Re: Importance of compressor/limiter in feedback path, and options

Post by starthief » Thu Oct 15, 2020 7:28 pm

I didn't really like tanh for feedback. It doesn't cleanly lower the level, it just saturates. It was good if you wanted some waveshaping/distortion (or to mess with envelope shapes!) but is fundamentally different than a compressor/limiter.

A compressor will measure the overall amplitude of a signal and lower the level without changing its shape. There's also makeup gain which can help keep a feedback loop going.

Tanh smoothly "bends" the upper and lower parts of a wave toward zero if it's above/below some threshold, to keep the maximum amplitude within a particular level. It can be used to prevent clipping, but if you have more than 1.0 gain in the feedback loop, it's going to grow increasingly distorted; if you have less than 1.0 it will eventually die out.

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Re: Importance of compressor/limiter in feedback path, and options

Post by Funky40 » Thu Oct 15, 2020 9:09 pm

an envelope follower could be your solution, plus VCA.
Plankton electronics (spain) has a 2hp wide ENVFollow ( which i dig)

also has 2hp a 2hp wide compressor.
not used mine so far exept some first testing


the other thing to tame feedbacks is shifting frequenzies around with modulations.
compression is not your only possibility.
working with an envelope follower would open here up some more doors than a comp alone can do.


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Re: Importance of compressor/limiter in feedback path, and options

Post by adaris » Thu Oct 15, 2020 9:23 pm

I like the DPW Triple Limiter for controlling feedback.


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Re: Importance of compressor/limiter in feedback path, and options

Post by autopoiesis » Fri Oct 16, 2020 2:12 am

the MSCL you have is perfectly good for this, and I use mine mostly for massaging feedback loops. the left and right signal paths are completely isolated from each other, so you can use it like two limiters or two compressors for separate feedback paths that have similar amplitude characteristics.

tanh3 is also very nice but I agree with Starthief's thoughts on it, and if I had to keep one it would definitely be MSCL for greater flexibility (being primarily a nice gluing or sidechaining stereo comp).

also agree with funky40 that frequency shifting is worth exploring in feedback loops, but the challenge there is that you might involuntarily overdrive the shifter with high levels of feedback (or, end up effectively suppressing the feedback at certain frequency shifting settings) and so a limiter/comp is also useful in such a patch.

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Re: Importance of compressor/limiter in feedback path, and options

Post by Joey P. » Fri Oct 16, 2020 9:28 am

Funky40 wrote:
Thu Oct 15, 2020 9:09 pm
an envelope follower could be your solution, plus VCA.
Plankton electronics (spain) has a 2hp wide ENVFollow ( which i dig)

Right...this ^^^^

That's what the Dynamix is. A VCA/LPG w/ Level input controlling CV and the second Dynamic input accepting audio and applying it to an envelope follower and an attenuverter. Audio input is normalled to the dynamic input.

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Re: Importance of compressor/limiter in feedback path, and options

Post by Pyrrhix » Fri Oct 16, 2020 11:03 am

There were some interesting suggestions in this thread, some of which I'll have to try out. I just wanted to mention, if you're not already, stick an equalizer in the feedback path. It opens up so many options when your feedback doesn't have to be dominated by the strongest frequency in your input sound. EQ allows for more subtlety than filtering for this purpose. Inverters, or anything that alters phase, are also great to experiment with in a feedback path.

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Re: Importance of compressor/limiter in feedback path, and options

Post by Funky40 » Fri Oct 16, 2020 12:16 pm

a super simple trick is to patch your feedback just over a VCA and modulate the VCA a tiny bit,
or same with filters,........just run permanently some slight modulations. often thats allready doing it

autopoiesis wrote:
Fri Oct 16, 2020 2:12 am
also agree with funky40 that frequency shifting is worth exploring in feedback loops, .......
oh, you took my ("funky") wording wrong:
i meant with ---->"shifting frequenzys around"........, not "frequenzy shifters" but things like filters that you slightly modulate or even better filterbanks, ...........ideally a CV-able FFB which most of us don´t have.

But: most of my feedback patches back then when i was much into patching with feedbacks were indeed based on working with FS ;)
or then based on working with pitchshifting within the feedback.
my personal pleasure with FB patching lies definitly there. ;)


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Re: Importance of compressor/limiter in feedback path, and options

Post by B0bcat » Fri Oct 16, 2020 12:23 pm

Thanks all for the interesting suggestions so far, please keep them coming! Some modules came up that I was not familiar with and that I will look into more closely. I can say that I do have a ResEQ in my setup, but I might look into a smaller and more vanilla EQ option on top of that.
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Re: Importance of compressor/limiter in feedback path, and options

Post by Addam » Fri Oct 16, 2020 12:49 pm

Feedback patching is the best reason to have eq in the rack I think. Music Thing has the small Simple EQ which I dig, there's also a 2hp Mineq by Zlob - both are cheap.

I've had similar experiences with the tanh3.. fun as an effect but tricky to dial in to cool-out feedback loops. I don't mind no cv control but I wish it was 2 channels with an input attenuator on each... which I think is part of my problem (not bothering to properly attenuate incoming signals).

Also, as mentioned above, throw an attenuverter in the path - sometimes flipping the phase can have a dramatic effect.

I recently got my hands on an SSF autodyne and haven't used it much for this purpose yet but suspect it will work nicely.

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Re: Importance of compressor/limiter in feedback path, and options

Post by B0bcat » Fri Oct 16, 2020 12:52 pm

Good point on the attenuversion- the setup is centered around the Doepfer matrix mixer, and I do have separate attenuverters on board.
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Re: Importance of compressor/limiter in feedback path, and options

Post by Pyrrhix » Fri Oct 16, 2020 1:03 pm

I have a related question. Does anyone here know of a euro reverb that plays well in feedback patches? I got an FX Aid XL, which is a great module otherwise, but it doesn't have sufficient headroom for use in feedback patches at all. I get nasty digital clipping/crackling even at pretty low levels of feedback with it.

Also wanted to mention, the ALM PE-1 is another EQ that works well in a feedback path.

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Re: Importance of compressor/limiter in feedback path, and options

Post by Funky40 » Fri Oct 16, 2020 3:36 pm

Addam wrote:
Fri Oct 16, 2020 12:49 pm
Also, as mentioned above, throw an attenuverter in the path - sometimes flipping the phase can have a dramatic effect.
thats an interesting idea,
should work with an RM/4quadrant multipler and throwing in a +-V squarewave LFO......?


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Re: Importance of compressor/limiter in feedback path, and options

Post by Addam » Sat Oct 17, 2020 7:43 pm

Funky40 wrote:
Fri Oct 16, 2020 3:36 pm
Addam wrote:
Fri Oct 16, 2020 12:49 pm
Also, as mentioned above, throw an attenuverter in the path - sometimes flipping the phase can have a dramatic effect.
thats an interesting idea,
should work with an RM/4quadrant multipler and throwing in a +-V squarewave LFO......?
I had some time with the modular tonight and tried a couple things - Rings output mixed with some noise and a filter in there somewhere (not doing a lot) back into Rings input and inserting a ring mod in there in a couple places definitely yielded nice results. Tried the 2nd Rings output into X input on my ring mod with slow square wave lfo into Y and tried the ring mod more directly in the feedback path and had different but also fun results. Maybe not the best test as rings always sounds good in feedback patches in my opinion. :hihi:

It would take a beat for the timbre to change with the lfo (as the feedback died down) so it sounded a bit like a triangle wave, very nice though no easy control over the rise/fall time. A triangle wave into Y on the ring mod sounded a little smoother.

I did something (bad?) to my scope so I didn't monitor exactly what was going on but this is worth playing with some more for sure. I tried doing the same thing through a vca instead of a ring mod and the results were more boring as I would hope ;) Had a nice sound running a unipolar envelope into the ring mod y input too, in which I guess it acts like a vca more or less. Using the old Pittsburgh "Mod" so that was definitely imparting some character though as I had the X input at max. I'm not well versed in ring mods but this has me wanting to dig in more!

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Re: Importance of compressor/limiter in feedback path, and options

Post by batch » Sat Oct 17, 2020 7:50 pm

rew_ wrote:
Thu Oct 15, 2020 7:06 pm
Instruo Tanh is specifically made for this
Agree, have one for this and it’s great. Also excellent as a bit of a waveshaper, distortion, etc.
FS: Motomouth Filter $200 and lots more

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