Saturday, 25 February 2012

Crap-Fi Delay

I thought the delay freaks may like this interesting alternative to the pristine digital delays that you see all the time.  This was put together by allesz at freestompboxes, and below is his description of the circuit:

"It is the results of my experiments with the ultra famous pt2399 chip.

It is a simple circuit and it works good but: the mix and repeats pot are a little interactive in quite a strange way (anyway they work different from a standard echo: to turn off the delay you don'use the mix pot, but you turn to zero the feedback pot) and the on off is a little bit noisy (the clip is recorded at low volume and you will hear kids (always noisy) and clicks so, mostly, the clicks are from the mechanical sound of the switch, but a little noise makes it to the amp too) in order to minimize the clicks the input is grounded on bypass.

The major differences between my schem and the others pt2399 projects I know are that I didn't use the opamp between pins 14 and 13 and I didn't put a cap between pin 2 and three (repeats sounded cleaner to me this way).

I put a small switch to select between long and short delay; the long delays are quite dirty

Anyway this is a dirty cheap crappy fi delay, so if you mind noise and fidelity look elsewhere; I know it can be perfected but for me it is good as it is."

Allesz clip can be heard here.  To wire the switch so the input is grounded during bypass, use the method shown in my offboard wiring post.


16 comments:

  1. You can call this one verified, if it wasn't already.

    It's really noisy and absolutely so lo-fi that i would say this one is a must have toy.

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    1. Excellent, thanks for that mirosol!

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  2. Thanks a lot for this layout, it is really a wonderful delay! I'm very glad i've builded this one.

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  3. Hello, can you please tell me what do i connect the repeat 2 lug to? thanks.

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    1. You should see 'Mix 1 & Repeat 2' at the bottom right of the board, so just take it to Mix 1, or take it to the next hole to the left on the bottom row of the vero if you prefer not to have 2 wires going to the same pot lug.

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  4. I have a very strange problem with this pedal. It only works in a chain with other pedal and if I use a daisy chain power supply. The effect doesn't work on his own. I've already tried different adaptors, but that really doesn't seem to be the problem... Any ideas on this?

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    1. You could check the regulator first. 78L05 is rated at 100mA, and there's nothing to protect that from higher amps. I've seen pretty strange behaviour from burned regulators.

      Does it work with a battery?
      +m

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    2. ...considering that PT2399 would somehow drag more that 100mA.

      Short is easy way to burn regulators.. I guess that it's even easier than burning them with higher voltages.
      +m

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    3. Yes a very strange problem. Measure the voltages at the IC and regulator pins with the daisy chain and then on it's own, to see what differences there are.

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    4. Very very strange... When the pedal is daisy chained, the output of the 78l05 gives me 4,98V; which is perfect. But when the pedal isn't daisy chained, the output of the 78l05 gives me 8,10V! I don't understand how a 5v regulater can emit 8,10V...

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    5. How have you got your offboard wiring? I'm just wondering whether you have a ground point isolated from the rest which is only being satisfied through another pedal via the daisy chain. Just check for continuity between every point of ground and reflow if any of the connections look suspect.

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    6. Yes thanks that was the problem. I had the neg power lug connected to a wrong lug on a jack.. Problem solved and another pedal working perfectly!

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    7. I was having the same crazy problem with the daisy chain working and the straight 9v adapter not working. I resoldered (is that a word?) all of my ground connections and now its working great. It sounds dirty, spacey, and awesome. With the feedback set to full it can make some very cool experimentalish drone/noise/doom sounds.You the man IvIark (and allesz!).

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  5. http://a6.sphotos.ak.fbcdn.net/hphotos-ak-snc7/s320x320/301778_324139410999111_100002091650466_719618_820566351_n.jpg

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