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Delay Pedals: it's a Matter Of Time...

More pedal musings! This time my experiences of making the first SEFX delay pedal .. pedal... pedal..... pedal.......... pedal.............. etc

Right - my trusty DD-3, taking care of all my delay needs! Having been at this for a couple years now (on a very 'side hustle' basis) I've yet to stray beyond the realms of 'clipping' circuits, effects that distort the guitar signal. The thing about 'Overdrive' effects, is that the quality of the outcome is entirely subjective. There is no good or bad overdrive sound until you give it a context. For example the gnarly, velcro-rippy OD of a ProCo Rat pedal is nothing like the ballsy crunch of a Fulltone OCD. However if an OD pedal claims to sound like a cranked Marshall JCM 800, and it doesn't, then it could be described as bad as it doesn't meet the promise, but there's every chance it could still be a 'good' overdrive for other jobs. I'm sure you take my meaning.

The way I see it, this is not the case with other effect types - in particular time based effects like chorus/delay/reverb operate in a much more defined criteria. Unless you're designing a full Digital Processor based effect with serious amounts of programming that can cover many bases (eg. Strymon Timeline - the most comprehensive delay I've ever used) then your Delay pedal needs to be more narrowly characterised. Eg tape delay, slap-back, doubling, modulating...

I'm not a huge user of delays, my trusty Boss DD-3 has taken care of most of my spacey needs for the last 8 years, but I definitely have a preference when it comes to the effect, and I had to follow this preference when starting to create my own.

What I normally do when making an effect is take one I know I like and ask how I'd like it to be better FOR ME (crucial!) and mess with it until it, to my ears at least, sound more inspiring and/or is more useful. The House Of Noise Treble Booster is simply (like most TB's) a Dallas Rangemaster with less gain and variable High Pass Filter. For this delay pedal however, I started with a datasheet and a bunch of components, from scratch so to speak. So for the first time, I needed objectives to achieve in advance or else I'd be chasing my tail. That's not to say I don't have these for OD designs, but my earlier point of them being subjective to taste affords more wiggle room in the results, if that makes sense. Probably not.

Firstly I need to know what I'd like to control on the effect. There are three basic controls almost every delay effect contains - Time/Feedback/Level. There are of course many other options but these can be 'set' within the circuit, but these three parameters have to be user configurable!

Left - The oft used PT2399 IC!

My patience for programming is limited, to say the least, so that ruled out a DSP based circuit - where a processor chip digitally through programmable code controls all parameters. And rather than go all analogue for my first delay I'm using the fabled PT2399 IC chip as the basis for my repeats. Though this chip does 'digitize' the signal, it's only purpose is to create the delay then pass it out after a given time. All other parts of the circuit are analogue, so it's a kind of in-between worlds method. I got to work with the objectives below.

Time - I don't need huge delay times, 1000ms is more than enough for your average legs-astride wind-blown guitar solo but I do need the delays to be quick enough for the rockabilly slap-back style, a range of 10ms to 800ms would suffice my needs. By increasing the range (without adding more controls) you reduce resolution in your pot control, making it harder to get the time you want. A huge advantage of digital delays is you can set the delay with with ms accuracy.

Feedback - The number of repeats is a fairly easier parameter to control, so I didn't stress too much on this, though I did encounter an issue in early designs where at around 3/4 to full the delay hit oscillation, an unpleasant state of infinite feedback so had to work around this so at maximum feedback you get about 10 -12 repeats - more than enough!

Level - The wet/dry level of the delays. Depending on where the pedal is in your FX chain this will be set differently.

I pulled up the ancient looking datasheet and just built the example circuit within, with basic input and output sections. Voila, I had delay! Though it was very boring, and thoroughly uninspiring. The delays were too static, and very clean so I set about messing them up a bit. I ended up with the following controls.

Wobble - By adding a Low Frequency Oscillator into the pin that controls the pitch and tempo of the repeats you can get a nice 'vibe' style effect of the delays, making it much more characterful.

Rate - Changes the frequency of the LFO sine wave, resulting in faster or slower 'wobbles'.

Left - Looking like the larger 1590BB enclosure for this one!

Finally, I really like 'tape delay' - an effect where each delay gets darker with every repeat. Darker basically meaning less treble and I also thought this would be a nice option to offer so tinkered with the 'character' of the delays being a switchable option. I landed on two feedback modes, one standard 'static' repeats (to my tastes, so still quite dark) or 'tape' style where each repeat is darker.

Darker repeats get less 'in the way' I find. Clean, bright delays are better for U2 style riffs, great for some but I had to pick a lane here and am going with what I like, not what The Edge likes! This is the main gripe for my DD-3, which is unashamedly digitally 'clean' sounding!

Right - Breadboarded and in the fine tuning stage...

So there is a brief run through of my progress on my first big-boy grown up delay pedal! I may not be breaking any moulds here but I don't profess to. I'm just trying to have fun and make some noises I like 😀

I'll be finalising the design, getting some proto's done and recording some demo's in good time. Cheers for reading my ramblings.

P.S. - I have a crazy sale on the remaining 'Nails Overdrive' stock, only 4 left and I'm clearing some space! Grab an absolute bargain! SHOP HERE

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