General ideas on increasing regeneration on delay pedal....!

[Gabsonjackellis]

Hello, OK so ive got an idea for modifying a delay pedal - specifically a Marshall EH-1 Echohead.

What i want to do is increase the internal regeneration so I can get the regen to raise in volume in a dub stylee. at the moment its set to tail off over the course of 5 seconds at maximum.

those familiar with the pedal - I only use the "tape" setting.

Ok so what I was thinking is cant i just mess with the resistance of the feedback pot? try a different value pot?

I'm struggling to find much info on it on the web as it's not the world most popular delay effect.

Has anyone tried a similar idea on another pedal that they could share?


Any help appreciated - cheers again

Jack

[Mark Hammer]

The obstacle you would need to address is that both analog and digital delay pedals use a basic core which results in audio artifacts. To make them a tiny part of what you eventually hear, the circuit includes some lowpass filtering, to get rid of the clock signal and the aliasing created by fairly modest sampling rates. Every time the signal is fed back to the input it passes through that lowpass filtering, introducing some amplitude loss. You can remove the filtering so that you don't experiencing progressive attenuation of the repeats, but you have to accept the degradation of signal quality that accompanies it.

Looking at the manual for the EH-1, it would seem that this pedal goes well beyond the simple BBD or Princeton-chip delay, and likely includes a DSP chip of some sort. And THAT screams "surface mount", which is going to be a bugger to mod without screwing things up. I've been modding pedals for over 30 years, and I wouldn't touch it. If it uses a surface-mount DSP chip and through-hole components too, then maybe, but a complete SMT board is probably best left alone. Get yourself another cheap pedal to experiment with.

All of that being said, yes, such a mod is possible and I've done it a few times on analog delays.

[Steve Conner]

I have a Line 6 Echo Park, and it will repeat forever with the "Repeat" knob turned up full. It has a 3-position switch- "Digital, Tape, Analog"- to select the amount of simulated degradation. On "Digital" it doesn't seem to degrade at all, and will happily repeat for minutes at a time. But the other two positions make the sound progressively crummier.

So the easiest mod to the Marshall would be to swap it for one of those. If the pedal is digital, the maximum regen gain is probably set in firmware.

[Gabsonjackellis]

Ok sweet,

Thanks for the advice mark! Could you suggest a delay pedal you found easier to modify? This marshall one is all surface mount and I expect DSP which doesnt help with the whole friendliness of the internal guts of it...

I like the degradation! I'm a big fan of real tape machines

-Steve with the echo park - I'm after an actual gradual INCREASE with the regeneration if that makes sense....




The plan is to link up the new regen pot to a foot treadle and swoosh it in and out for prechorus build ups etc.


cheers for the help so far guys
Jack

[Steve Conner]

Oh, you're looking for more than 100% feedback? I haven't seen that before. If you don't have programming skills, I guess you might have to get a real tape echo unit.

Or, make an adaptor that actually takes the signal coming out of the delay pedal's output jack and stuffs it back into the input jack, mixed with the guitar signal. An analog solution to a digital problem. I've done this with a mixer and a rackmount delay, by turning up the delay's effect send on its own output, and it seems to work. Maybe you could build it into the case of an old wah-wah.

(If you do have programming skills, you could knock together a quick VST plugin or Apple Audio Unit for your laptop. Or maybe there is a plugin already that does what you want, or you can bodge it up in Max/Msp, Puredata, etc, and control it with a MIDI foot pedal.)

[Mark Hammer]

There are degrees of "increase", Steve. If my understanding of dub style is correct (and all I have is one King Tubby single I haven't played in years, and a smidgen of radio to go by), what the OP is describing or alluding to is a characteristic sound where the repeats get progressively more strident and harsh and don't really die out easily. As near as I can tell, from my own experiments, this comes out of having a progressive attenuation of bass on repeats, and juuuuuuusssstt a bit of gain in the feedback loop. Typically, whether BBD or tape-based repeat, the sound also progressively deteriorates as the repeats continue and get harsher.

Traditionally, many effects that use regeneration/feedback would include an internal trimmer adjustment. The circuit may be designed under the assumptin that there is unity-gain in the feedback path, but there can be many stages between the start and end of the wet path, and if this one has a gain of 1.02x and that one has an unintended gain of 1.05 (due to 5% component tolerances), pretty soon the entire path adds a bit mroe amplitude at the output, and once you feed that back and re-amplify, it starts to add up. During setup, the folks at the factory would adjust the aforementioned trimmer by setting feedback for max, and then turning the trimmer until any oscillations introduced at max feedback would stop. The oscillations come out of greater-than-unity gain between the input and outputs of the wet path. Obviously, in any SMT/DSP-based pedal, those insertion points may well not exist, or at the very least be hard to identify.

Virtually any BBD-based delay pedal can be modded to do this. The critical thing is that the EH-1 has far more delay-time on tap than 99% of analog delay pedals, so while the effect may be easy enough to implement if the OP is up for it, he may well be confined to implementing it with no more than 350 or so msec delay time.

[Steve Conner]

The best example of the effect in my record collection is on the Massive Attack "No Protection" remix album. The repeats actually get louder until they turn into feedback.

I have achieved the same effect myself using extra analog feedback around the outside of a digital delay box, and I believe that is how newer dub producers do it (the original ones of course used tape delays)

I recommend this method because it involves no mods to the pedal at all. Of course it is less technically satisfying than hacking the firmware to boost the loop gain, but the guy mentioned that he liked degradation, and with the analog feedback he will certainly get more of that.

If the pedal has a DSP, the entire feedback loop will almost certainly be digital, with no way of increasing the gain by the ordinary kinds of mods.