Understanding delay feedback and master feedback for oscillation

Jonathan Thomas

Jonathan Thomas

Inspired
Can someone explain the way the master feedback works on the delay block, please?

From the wiki:
This goes up to 200% to create oscillating delay effects.
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From the blocks guide:
Scales any and all feedback parameters. Note that the range of this control is 0–200%, making it possible (easy, in fact) to overload the feedback loop.
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Reason I'm asking is because with each algorithm, self-oscillation happens at different points of the balance between the feedback and master feedback controls.

I'm wondering, with the analogue style delays, DMM included, if anyone has found a sweet spot for edge of oscillation. That creates an almost infinite delay spread behind their playing, but never self-oscillates to the point of raising in volume and getting out of control, as is so easily done when trying to do this stuff.

I've got there, in a way, but I'm not quite content and would like to understand the relationship between the two controls more and how I can utilise them both to my advantage to create this stuff. Many thanks.
 
Heya Jon. Hope you're doing well mate.

I believe it is a simple scalar. So if your main feeback is at 20%, and you set the master feedback to 200%, then the actual feedback you're hearing is 40%. I could be wrong there, but it seems to be the case. So 103% of 20, is 20.6... meaning depending on your values of each knob, you might not get the same ultimate value as when turning just the feedback knob, due to the weighting of the feedback knob itself.

It can be tricky to dial in any delay to remain in that sweet spot, particularly since analog delays tend to change their oscillation character depending on the amount of stuff you play into them and where on the fretboard you're playing. You'll notice sometimes certain pitches cause the delay to get more chaotic than others. The best thing I find is to attach one of the feedback parameters to an expression pedal, so you can kinda ride the wave with it.
 
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Brilliant, mate, I hoped you'd chime in! Great to hear from you! :)

You make a cracking point about where you are on the fretboard being an important factor. Certain resonant frequencies cause that bloom and nice clipping in the oscillation that we love/hate, depending on ones persuasion. I love it.

I guess that the master feedback shouldn't even come into play with what I'm trying to achieve and is likely more useful to those delay algorithms that have dual feedback controls. Because in this context, I just can't see any scenario in which I'd set the feedback and think "another 2%/12%/24% on that and I'll be in self-oscillation territory", seems quite arbitrary. But I expect that once I learn it more, I'll get more out of it - your explanation is helpful, thank you.

Thank you for the advice re:expression pedals, I need one for loads of different reasons, that included.

One thing I'll say is that I spent the entire evening last night messing with the many delay algorithms and I could genuinely find a use for most of them, they sound fantastic.
 
Jonathan Thomas said:
I guess that the master feedback shouldn't even come into play with what I'm trying to achieve and is likely more useful to those delay algorithms that have dual feedback controls. Because in this context, I just can't see any scenario in which I'd set the feedback and think "another 2%/12%/24% on that and I'll be in self-oscillation territory", seems quite arbitrary. But I expect that once I learn it more, I'll get more out of it - your explanation is helpful, thank you.
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Master feedback really comes into its own when you've assigned the main feedback to a controller source. So imagine this.... you've got an LFO assigned to the feedback of your delay, to make it just kinda wiggle around a central point, making sure it stays in the sweet spot.

But now you can't change the underlying central value without messing around with the modifier settings, the min and the max and what not. Sod that. Just use the master feedback instead, and you'll be able to move the centre point of the delay feedback around, without having to mess up any of your assignments. It really is quite powerful!

Jonathan Thomas said:
One thing I'll say is that I spent the entire evening last night messing with the many delay algorithms and I could genuinely find a use for most of them, they sound fantastic.
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They're seriously good! As you know I've been primarily a Helix user since 2016, but I guess I just got tired of the delays and how inflexible they really are. On the Axe3 you can do soooooo much just with the digital delay and the built in EQ. It's pretty amazing to be honest. Reverbs too!
 
That’s very clever, I don’t think of doing stuff like that, but it would be very useful for my needs. Thanks for the idea!

Yep, the reverbs are awesome too. I’ve been on a bit of an analogue pedal hunt in recent weeks. Got myself a spaceman aurora which is immense. Following that trend I had a few things to try regards to chorus, delay and phaser etc, but blasting through a few algorithms over the last couple of days, I just can’t justify the spend. I’ve managed to achieve everything I’ve had in my head. It’s an awesome unit.
 
Jonathan Thomas said:
That’s very clever, I don’t think of doing stuff like that, but it would be very useful for my needs. Thanks for the idea!

Yep, the reverbs are awesome too. I’ve been on a bit of an analogue pedal hunt in recent weeks. Got myself a spaceman aurora which is immense. Following that trend I had a few things to try regards to chorus, delay and phaser etc, but blasting through a few algorithms over the last couple of days, I just can’t justify the spend. I’ve managed to achieve everything I’ve had in my head. It’s an awesome unit.
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I've sold nearly £2000 worth of pedals in the last 90 days ! :eek: :eek: :eek:

I'm all in on Axe3 at the moment. I was thinking about getting an 8U rack, whacking Axe3 and Helix Rack in it, SPDIFing and MIDI'ing them together, adding a poweramp, and calling it done!
 
Just on this again - if it isn't clear, you can use the EQ on the delay block to completely change the nature of the oscillations on the delay. You can set drive to a very small value to clip the oscillation so it doesn't get too crazy loud, and you can also use the compander to add some character as well.

A lot of people jump to modulation options to add character to their delays, but I much prefer doing it with the other options. Less pitch warbly nonsense creeps in that way.
 
Orvillain said:
Just on this again - if it isn't clear, you can use the EQ on the delay block to completely change the nature of the oscillations on the delay. You can set drive to a very small value to clip the oscillation so it doesn't get too crazy loud, and you can also use the compander to add some character as well.

A lot of people jump to modulation options to add character to their delays, but I much prefer doing it with the other options. Less pitch warbly nonsense creeps in that way.
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Got an example by chance?

I may be using my axe3 for a new group and have interest in various “fun buttons” to go along with other guys whammy.
 
Okay, so here goes....

We all know the standard digital delay sound:


1689504626996.png
1689504639462.png

This is basic as it gets. No real frequency manipulation to speak of, bog standard digital delay like you'd get in pretty much any delay pedal.

But what happens if we roll off a ton of low frequencies and high frequencies, and use the two parametric bands to create little bumps in the EQ part of this delay:



1689505021218.png

You can hear almost immediately, we have a pseudo-analog delay, because of the severe roll off of frequencies in the low and high regions.

Now what happens if we raise the High+Low Q factor half way through the recording:

1689505069213.png

You can hear as the clip progresses, we get more oscillation characteristics, and this is because of the small boosts we are giving the signal using the Q control and band 1+2.

So... let's try another thing. Reset the EQ completely and set band 2 to have a frequency around 1500hz, and part way through the clip let's raise the gain for band 2:

1689505389678.png

You can hear we have a completely different oscillation characteristic now. The overall tone is much clearer and more broadband, but the oscillation kicks in around the frequency we've specified using band 2. We've told the delay to amplify 1500hz each time it loops around. The click at the end of the clip is me double-clicking the gain 2 control, to reset it to zero. You can hear it is about to go into runaway oscillation just before.

Now let's switch to an analog delay. I'll use the DM-Two. You can see the default EQ shape is setup like this:
1689505635605.png

In the audio clip I will play with the feedback control on the Time/FB page:


I'm ramping the feedback and master feedback to create various amounts of oscillation. But you can hear it is always dark and muddy - the end of the file is glitchy, pretty much what you would expect from a real DM-2 if you've got the time control at 106ish BPM; the chips cannot maintain the fidelity at this kind of tempo. (side note; the Adriatic Delay on Helix allows you to specify the number of chips, and thus increasing fidelity in these kinds of scenarios)

Now if we do the same thing, but we use an EQ curve like this:
1689505898793.png

We get marked different results:


You can hear there's very little delay initially. But as I raise the feedback and master feedback controls, you can hear a particular ringing tone start to come through. The oscillation characteristic is bright, crisp, fizzy, aggressive... all of those kinds of buzz words. If you want to create a proper wall of noise, this is the direction to go in - IMHO.

If you're curious about how I've used this kind of thing in the past (regardless of gear used) checkout this song at around 1:08:
https://bridgedisaster.co.uk/track/truth-escapes-2

And this song around 2:55:
https://bridgedisaster.co.uk/track/the-world-inside-2
 
I would note with this technique, a little goes a long way. You don't need to be doing anything like 5dB boosts usually. 1 or 2dB in key areas will normally suffice.
 
Orvillain said:
Okay, so here goes....
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Just spent a long time listening to your clips and soaking all this good information in, thank you for taking the time, mate. Really appreciate it!
If you're curious about how I've used this kind of thing in the past (regardless of gear used) checkout this song at around 1:08:
https://bridgedisaster.co.uk/track/truth-escapes-2

And this song around 2:55:
https://bridgedisaster.co.uk/track/the-world-inside-2
Click to expand...
I f***ing love that album by the way!
 
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