Sustain effect sans ldr? Recommended schems and tips welcome!

[Clips]

I'm fairly new to the whole diy pedal scene and still trying to learn the ins and outs, so please excuse my ignorance 

That being said, I have a general question: is it possible to create a sustain effect with a positive feedback loop alone (and a summing circuit if need be) and no ldr/heatshrink/led combination, or is is more of a secondary effect caused by high-gain circuits? Can it be done with something clean and with no or little distortion? say, a booster?

I played with feedback loops a little last night and feel as though I achieved something fairly satisfactory, but after fiddling with the circuit a little more I wasn't able to go back and recreate it. 

I googled for a while about this, but can't really find any info aside from the pages and pages of "keyboard sustain foot pedals". Any info or explanations is appreciated. 

[merlinb]

You mean an acoustic feedback effect ("sustain" is normally a synonym for a compression effect). One way to do it would be to have a footswitch that engaged a positive feedback loop, causing a gain stage to start oscillating. The tricky part would be to make the oscillation build up in a gradual, musical way when you hit the switch, rather than just slamming on like a Morse code key!

[Mark Hammer]

I'm getting the sense that Clips uses "sustain" in the manner that many compressors are either peddled ( ), or perceived by users: i.e., as a source of "sustain".

If I'm correct there, then the answer is "yes", an LDR is not required to achieve the illusion of sustain via compression of the signal.  The question to consider is why are LDRs often used.  The answer is "Because they yield a cleaner version of that fake sustain, with a relatively simple circuit".  So, you can certainly produce enough compression to mimic a sustained signal without involving an LDR, but you may need a few more parts to do it.

[Clips]

Off, sorry for such a late reply!

You mean an acoustic feedback effect ("sustain" is normally a synonym for a compression effect). One way to do it would be to have a footswitch that engaged a positive feedback loop, causing a gain stage to start oscillating. The tricky part would be to make the oscillation build up in a gradual, musical way when you hit the switch, rather than just slamming on like a Morse code key!

Yeah, getting feedback to not run out of control has  proven to be quite tricky. I've gotten my share of gurgling and toilet noises trying to get this idea to work, haha.

I'm getting the sense that Clips uses "sustain" in the manner that many compressors are either peddled ( ), or perceived by users: i.e., as a source of "sustain".

If I'm correct there, then the answer is "yes", an LDR is not required to achieve the illusion of sustain via compression of the signal.  The question to consider is why are LDRs often used.  The answer is "Because they yield a cleaner version of that fake sustain, with a relatively simple circuit".  So, you can certainly produce enough compression to mimic a sustained signal without involving an LDR, but you may need a few more parts to do it.

So what you're saying is it's not so much a question of "can I do it?, but "is it conventional?".

I originally thought that the ldr/led route would be very haphazard and rougher sounding, but I'm willing to give it a shot with something such as the "Supa Sustain" if it is in fact cleaner (and less parts to boot) rather than building half a compressor for "fake sustain". By the way, I've heard others refer to compressor sustain as mislabeled and 'fake' and I have to ask, for the sake of understanding what I'm doing here, what sets it apart from 'true' sustain and how does it affect clarity? Sorry if this is a big question, I've looked into it before but to no avail.   

[Beo]

Well, how good are you at holding your fingers and body steady to keep the strings vibrating. How loud are you playing through your amp and can you turn just the right amount towards it to feedback just enough energy back into your guitar. Do you play solid body, semi or full hollow. There's a lot that can be done to give you sustain, before you look to electronics to "fake" it. I don't think using an LDR/LED in the circuit is the issue. Compressors are fun to build and each has its own character. Try some, and remember to feed it lots of power supply to give it lots of headroom (I use 11-12v).

[samhay]

By the way, I've heard others refer to compressor sustain as mislabeled and 'fake' and I have to ask, for the sake of understanding what I'm doing here, what sets it apart from 'true' sustain and how does it affect clarity? Sorry if this is a big question, I've looked into it before but to no avail.    

That sounds like marketing nonsense.

If your definition of sustain is essentially that notes stay louder for longer, the you have two obvious options.
If you want clean sustain, build a compressor.
If it doesn't have to stay clean, build a fuzz.

Edit - just re-read the opening post. If you want a true feedback effect, then there are other options.

[deadastronaut]

If you want a true feedback effect, then there are other options.

i'm all ears..

[samhay]

If you want a true feedback effect, then there are other options.

i'm all ears..

How about a PT2399 with a short delay time and the feedback turned up. Not a terribly clean effect, so perhaps add some pre-distortion and include some high pass filtering and more clipping in the feedback loop.

I have had something like this on-and-off the breadboard. It has some merit, but is a slow work in progress - there are a lot of control options, which need some thought.

[deadastronaut]

cool, sounds interesting...

been meaning to get back to this old chestnut...could never get it 'clean' though, as i suspect nobody ever did ...always a bit of fizz on it...one day.....hmmmm

https://www.youtube.com/watch?v=WPso1EYrD3Y

[Mark Hammer]

ALL compressors will introduce gain-recovery at some rate.  If the gain is pulled down for a brief instant and reinstated quickly, we find that helpful for fast picking that can be heard as fast picking.  If the gain is pulled back, and reintroduced more slowly, in a manner similar to having a soundman gradually turn up the fader on the mixer, then it becomes more supportive of what we mean by "sustain".

So, what Clips likely wants is a compressor with a pretty slow gain recovery, and enough output juice to keep them speakers moving.  Basically, make yourself a Dynacomp/Ross and make the 150k resistor that goes between V+ and the 10uf cap to ground and collectors of the two transistors a larger value, like 200k.

[midwayfair]

This isn't really what you're looking to hear, but the term "sustainer" or "sustain effect" bugs me.

A pedal will not make an instrument sustain longer than the instrument is physically capable of. All a compressor pedal does is compress your instrument's dynamic range to make things sound smoother, making quiet sounds less quiet and loud sounds less loud. Distortion creates dynamic range compression, because the loudest sounds can't get louder than much quieter sounds (they're clipped). Compressors work by sensing the input signal and adjusting the gain or output down when things get loud. A positive feedback loop will create positive feedback, but it won't make a note sustain longer ... it'll definitely create a bunch of noise and howling, though ...

A guitar is a closed system by itself. A string is attached to a couple pieces of wood between two nodes, the nut and the bridge. Pluck the string, and its energy is diffused into the guitar wood (and your hands, and friction). You can use the world's greatest compressor and it will never change that. The only way to do so is to add energy to the system or reduce loss. You can do this a few ways:

1. Volume. This is one reason why a lot of your favorite records and bands seem to have a lot of sustain without any help from pedals --- they're playing really loud. The sound feeds back into the guitar, even a solid body, and you get lots of sustain without a compressor or more distortion.

2. Ensure that your instrument is set up well. You should do this before you ever look at adding an effect. Your bridge should not create dead spots. Your neck should have its frets well-dressed and not create dead spots. Your nut should be filed properly.

3. Work on your technique. Vibrato is important.

4. Use a sustainer pickup or an Ebow. These are completely different from pedals. They actually cause the string to vibrate, adding energy to the system and creating more actual sustain. A sustainer pickup is what's going on in "With or Without You" by U2. There's a thread around here about creating your own, like the one in the video Rob linked to. It USES positive feedback, in a way, but it's not just a positive feedback loop.

---

As far as the use of photocells, a photocell is just a variable resistance element with a fixed minimum on/off time (both of which can be adjusted upward by other elements). You can also use a transistor (usually a FET, but not always) as a variable resistance element in a compressor, and many do, including the most ubiquitous (but not best) compressor ever, those in the Dynacomp/Ross family, the Orange Squeezer, and one of the best rack compressors ever created, the 1176. Typically, in a guitar compressor, your guitar signal is rectified (turned into DC instead of AC), and then the DC signal is used to either light an LED (in a photocell) or vary the resistance between two pins of a transistor, which usually does something to an amplifier in the circuit, like adjust the bias of a chip or lower the gain of a transistor -- or, say, simply lower the resistance to ground on the signal itself, like in the Orange Squeezer.

[karbomusic]

How about a PT2399 with a short delay time and the feedback turned up. Not a terribly clean effect, so perhaps add some pre-distortion and include some high pass filtering and more clipping in the feedback loop.

Actually a longer delay works very well, I use it that way all the time because the fact that the note that is ringing out is also being delayed (you just can't hear it because you're just holding it) raises the amount of total energy and sustains longer as well is much easier to get into controlled feedback. Keep in mind I'm leaning towards controlled feedback but they become very close to becoming the same thing when that controlled feedback is the actual note rather than just one of the overtones.

Anyway, I used a 250-400ms delay last night for this very thing and when I didn't want the tendency to sustain to be as much, I turned off the delay but the other band members had no idea I had a delay running if that makes sense.  

[karbomusic]

If you want a true feedback effect, then there are other options.

i'm all ears..

Your XFUZZ does an incredible job of this btw. Of the 5 (count 'em 5) fuzzes on my pedal board, yours is the one I use when I want really nice feedback sustain.