Delay build

[Papa_lazerous]

Ok I am gona be a thread whore tonight I think  (will make up for too much time away)

Anyway Its time for me to make a delay pedal......

All I ever hear about is the rebote 2.5

are there any other delays I should consider or even any analogue delays about?

Just thought I would cover all bases before building the rebote

Cheers John

[Mark Hammer]

Once upon a time, there was just "delay".  A bandwidth of around 4khz and a delay time between 300-400msec was squeezable from a single MN3005 or SAD4096, people predicated their use of delay on that delay range and sound, and that was that.

At this point in technological history, the inevitable question that must be asked at this juncture is "What do you want to use it for?".  That's a pretty important fork in the road because it determnes whether you turn left (analog) or right (digital), as well as where you go after that.

So...what do you need it to do?

[jonathan perez]

very good question, Mark.

arent all of our delay builds (besides the tape echo) digital?

[Papa_lazerous]

Well I have a beautiful Delay already at home.  A totally mint DM-2 and has a great analogue sound.

I would like a few second delay if possible.  which limits me analogue I know.

[jonathan perez]

EH #1 delay?

[Mark Hammer]

A long time ago, I asked a question here about the dividing lines between delay times that permit/encourage different uses.  I guess I asked it too soon.  The traditional analog delay with 400msec or less is great for having overlapping lines and a sense of ambience, butpoor at having anything that circulates for a long period of time and is meant to capture an entire phrase.  There, you move up into the 500msec+ zone and you are obliged to go digital.  Not just because of the delay times feasible, but because signal quality degrades pretty dang fast in the analog domain, so you need to filter the crap out just to keep up with what happens to the signal every time it passes through those same 4096 stage...again.  I'm sure there is also alteration to signal quality when you take the D/A output of a 10-bit delta-modulation chip like the PT2399/95/96, filter it, level shift it a bit, and feed it back to be A/D reconverted again....just not as much as with an analog BBD.  Consequently, the digital chips hold up better if one is attempting to keep a riff going for more than a couple of repeats at 800msec.

I made one of the delays with the old Holtek chip, following Dean Hazelwanter's PCB layout.  Works great, and the 800msec delay time is plenty for a variety of tricks.  Not Frippertronics or a looper's delight, but it allows a much bigger palette than 330msec does.  The PT2395 provides the same delay time in the same general manner as the Holtek chip (using a 256k DRAM), but with higher sound quality than the Holtek, because of the type of A/D conversion process used.  Unfortunately, no one has generated a layout for a 2395-based delay yet.