Mobius trip looper at GGG No sound

[John Lyons]

I've just finished the Mobius trip looper. I didn't sub anything except the recorder chip which is a ISD1020AP from small bear.

I can't get it to record yet. I have a couple questions:

So both switches need to be closed (to ground) in order to enable recording correct? Record/enable switch enabled, red LED, and Play/ record swich enabled, green led on.

I have the post by dean hazelwanter which goes over all this...I just can't get anything to happen sound wise. I assume the 4001 chip is fine because it's switxhing the LEDS. I have checked over the Polarized caps and the voltages are correct on the Op amps and power to the recorder chip. I built it with the PCB and schematic to the T as far as I can tell.

I get a bit of white noise and some (DC sounding) scratch on the pots as well. The straight volume works but I don't have any sampled playback...

Also, there only is one cap that needs to be added to the PCB, the 0.1 from ground to pin 28. Correct?

Just looking for where to look now!!!! So close but yet no sound

Thanks folks

John

[idiot savant]

make sure you add the jumper from dean's suggestion in this thread:
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=32651&highlight=mobius+trip+looper

and here's a simple footswitch wiring scheme i whipped up(sorry it looks so crude) it work's great though it is not true bypass, but it allows a single stomp record, and a single stomp play, like the Zvex lofi loop junky..

[John Lyons]

Thanks for the Wiring diagram Idiot Savant. Right now I've got it hard wired for effect only, no bypass. (jacks wired to the board, in and out)

I made the jumper to ground the un-used pins on the recorder chip and reflowed solder and looked for solder briges on the board...

Currently I have two footswitches set up to switch to  ground on the Record/play switch and the Enable switch. Each switch is set up for SPDT only.
I get static as the recorded sample now. I can slightly hear guitar notes or at least modulated  blips from the guitar notes I try to record...WHen I'm in the record mode and recording I get a sort of cartoon lazer gun sound...Not sure whaere that comes in...Straight sound is clear and loud, with a slight bit of static that varies.

I have to keep looking for the problem. Hopefully it not the recorder chip that got zapped somehow... I used a socket for it, it should be fine but who knows.
All voltages are ok, not sure where to look.

John

[John Lyons]

It's alive!

I thought I had followed the switching scheme from the schematic...guess I didn't get it right. I tried the scheme above that Idiot Savant posted and it works now!!!
I've only played with it a bit but I does what I though it would. A bit noisy but to be expected.


I'm going to use a 3PDT switch instead of the DPDT (substitute for the "play" switch) so I can have true bypass and an indicator LED.

Thanks a bunch for the Project and the advise guys.

John

[idiot savant]

gald you got it to work, however, just subbing in a 3pdt wont work for true-bypass, because in order to record, the bypass would have to be wired to the REC switch as well as the PLAY switch, I wrote out the diagram with the intention of mimicing the switching style of mr. Zvex's lofi loop junky. So I'm sorry to say that true-bypass is not really viable using this switching arrangement. Perhaps some clever use of the RESET pin on the ISD chip would make swiching more smooth. I simply did this one so I could get a 1 stomp record, and from that, a 1 stomp play. using true bypass would mean that you would have to individually switch record on, then enable on to RECORD. then you would switch enable off, switch rec off, and then switch enable back on to PLAY. so 2 stomps for REC and 3 for PLAY. The lofi loop junky isn't true-bypass(anymore) and i dont think it's detrimental to the performance of the pedal(doesn't seem to bother Zvex users) anyways LED switching is not necessary for the mobius trip, all the LED switching is done on the PCB, so all you have to do for the indicators is wire both (-)negative sides to ground, and both (+) positive sides to their respective spots on the PCB.  they automatically switch on and off depending on the stompswitches. It would probably be a good idea to put a buffer on the input side as the input impedance is not that high as is. I havent thought it through, but i think in order to get true-bypass you would need a 4pdt, and a 3pdt for the switches, with ALOT of inter-switch jumpers. I just kept mine as simple as i could.

glad it worked for you though.

[idiot savant]

acutally, i take it back, true-bypass would be doable with two 3pdt's however it would mess with some of the features of the pedal itself, if you REALLY want it, i'll post a diagram later. It would involve my diagram as before, but using 3pdt's and switching ONLY the INPUT side of the effect on the REC footswitch, and the OUTPUT would ONLY be switched on the PLAY switch. this would technically be true-bypass, however your straight signal would ALWAYS be unity gain, and the Volume control for the straight signal on the pedal would be completely useless, since in REC mode, only the input would be connected, and the output would be bypassed, and when in PLAY mode the INPUT would be bypassed, and ONLY the OUTPUT would be connected.
thats why i opted for non-true-bypass....

remember KISS :lol:

[John Lyons]

Isn't it just a matter of using a 3PDT for the Play/Bypass switch in your diagram and wiring the first two poles (left most) as a standard true bypass...and the 3rd pole as a SPST same as in the diagram?
So when the switch is "up" the effect is bypassed and when "down" it's in play mode and the ins and outs to the effect are connected.
Maybe I'm missing something.

John

[idiot savant]

i get what you're saying, but for the record function to work, the input jack must be in contact with the circuit input, or else, how will it record? during record mode, both "enable" and "rec" have to be switched in. as i said before, true-bypass is doable, but a different switching scheme would be needed, since as drawn, my scheme switches "rec" and "enable" on one footswitch(for the REC function), so if it was (true-bypass)in bypass mode(with both the circuit input and output bypassed)you can't record, because the circuit input would be bypassed. So to answer your question, yes you can use true-bypass, no it will not work with the scheme posted, and you would need more stomps to switch between modes using true-bypass. *whew*

it stumped me at first too, i was so sure i could pull it off when i built mine, and i went through nearly every switching arrangement i could think of. for ease of use's sake this is the easiest, fastest way possible using the fewest stomps to switch between modes.

the way you describe *can* work though you would eliminate the "enable" section on the "REC" footswitch(as shown in my diagram). Then you would wire the "PLAY" footswitch as you described. this would mean to record you would switch "REC" on, then hit the "PLAY"(bypass) to begin recording. then to play you would have to switch "PLAY" off, then switch "REC" off, THEN switch "PLAY" back on to begin playing the sample.

i did mine this particular way to have a one stomp record, and a one stomp play. the way you describe would be a one (hitting both switches) stomp record, and a two (hitting both switches "off" and then one back "on") stomp play. i did try it this way, but it makes it hard to stay in time (for me at least)

best of luck to you.

[John Lyons]

Oh yeah...you're right! Once the sample was recorded and recording  switch turned off, the box would be bypassed with the switching as I decribed... Silly me!

If it hasn't been a problem so far with everyone...it's probably ok with non true bypass. If it seems to be a problem then I'll do something else.

Thanks for breaking this down for me.

John

[fpaul]

Does anyone have a diagram or can explain to me how to wire the Mobius for one stomp record/one stomp play as discussed in this thread? The diagram has been removed.   I just got mine working using jumpers and just need to add the switches.

[idiot savant]

Does anyone have a diagram or can explain to me how to wire the Mobius for one stomp record/one stomp play as discussed in this thread? The diagram has been removed.   I just got mine working using jumpers and just need to add the switches.

sorry, i moved it...

in all its 5 minute mspaint job glory:



now if i could just get my payback to work

[fpaul]

Looks Great, Thanks!