Mobius Trip Looper

Thanks to Dean Hazelwanter for this looper. The IC is obsolete, but may still be available from Small Bear.

Dean’s Notes on This project:

  • Inspired by VZex’s LoFi Loop Junkie and
  • Based on 20 second voice recorder chip, Winbond ISD1000A – Why, because I had one. Although they are obsolete, some RadioShack stores still have them (276-1325) in their discount bins.
  • Three pots: Record Level (to optimize the signal level going into the ISD1000A), as well as Playback Level and Dry Level.
  • Two footswitches : Record/Play (lights red ‘Record’ LED in record position), and On/Off (lights green ‘On’ LED in on position). ‘Record/Safe’ switch (toggle or slide) helps to prevent over-writing saved loop
  • There is a long vertical jumper near the middle of the board, which carries the signal into the ISD1000A. Notice that there is an extra, grounded, pad to the right of the bottom of this jumper. When I laid out the PCB, I put this ground pad in case the long jumper picked up noise, so the jumper could be shielded. It doesn’t seem to be a problem, so the jumper doesn’t need to be shielded.
  • All of the off-board wiring is laid out to use 3 pin 0.1″ center connecters that I’ve been using for a while. One connector for the 2 switches, one for the 2 LEDs, one for each of the 3 pots, one for each of input and output jacks, and one for 9v DC.
  • The corners of the PCB can be notched out to mount it in a 1590B, or just drill the corner pads for using standoffs.
  • I mounted the disc cap across the looper chip power supply pins directly to the back of the PCB. One end of a 0.1uF cap goes to pin 12&13, the other end goes to pin 28.
  • For the 5 volt voltage regulator, you can use either the 7805 (TO-220 case) or the 78L05 (TO-92 case). The PCB is laid out with the 7805 outline, with the front (the side with the writing) pointing to the right of the PCB. If the 78L05 is used, face the front of it (the side with the writing) to the left of the PCB.