Payback Looper - Anyone Built It?

[mydementia]

Hi guys.
I'm about ready to build The Tone God's Payback looper circuit.  I've had all the parts for a while - but haven't had the time to go through the schematic and verify that I understand what's going on in Michael Allen's layout (http://www.diystompboxes.com/smfforum/index.php?topic=47038.0) - it's SO small!!!! 

I'm wondering if anyone (aside from Andrew and Michael) have successfully built this circuit?  Any build notes?  What about pictures of the guts?  Closeup of the completed board?  Wiring?  I've seen a couple threads talking about errors in the layout (specifically: http://www.diystompboxes.com/smfforum/index.php?topic=49509.0) - just wondering what pitfalls I'm about to experience... might be worth the $180 for the Boss RC-2 (http://www.zzounds.com/item--BOSRC2).

Thanks for looking.
Mike

[Morocotopo]

Mydementia, this one is in my ever growing list... but...
The PCB layout posted some time ago by someone (so much for precision, eh?) has traces going in between IC pins, components under IC sockets, and it´s in general not really suitable for the usual PnP etching method, I think. Too small and detailed. I think that might have prevented people from trying it. The reason for this is that the tone god originally wanted it to fit into a really small box. If we don´t mind about the size of the PCB, I think a layout could be made that´s easier to etch.
  I plan to eventually try to design one, but it´s also more complicated than an analog one (digital /analog grounds, decoupling, etc). don´t know if I´m up for the task.

morocotopo

[A.J.]

Hi Mike;

I built it using Michael Allen's layout -  I traced through the layout and it seemed correct - I couldn't get all the small parts so I ended up solding some of them on the back of the board - a real mess - it looped ok, but the vibrato didn't work and it was really noisy - I'm pretty sure it was my error and that I had a solding trace or two somewhere that I just couldn't find - ended up getting mad and scrapping it.  Was thinking of trying to make a larger layout at some point and rebuilding it - I wouldn't recommend doing it the way I did....hope that's some help to you - let me know if you get it working....oh - I used photopaper and the pcb came out really well....

A.J.

[mydementia]

I started making a layout using bancika's tool...it was really messy!  Maybe I'll have to revisit that effort - especially since it sounds like there's interest in the community for a larger (read as - more buildable?) layout.  I asked Andrew for a more legible schematic...hopefully I'll be able to figure it all out...

Thanks for the responses so far...
Mike

[hank reynolds 3rd]

me too,mydemetia
I've still got a few things to do,and i think I made the width of the ISD25xx chip on hole too small
it's on the list of 'things to get sorted' ...

[The Tone God]

I'm wondering if anyone (aside from Andrew and Michael) have successfully built this circuit?

I have received one build report that someone built the circuit as per the schematic and that it worked right away without any problems. They used their own layout.

The PCB layout posted some time ago by someone (so much for precision, eh?) has traces going in between IC pins, components under IC sockets, and it´s in general not really suitable for the usual PnP etching method, I think. Too small and detailed. I think that might have prevented people from trying it.

That sounds like the old layout. I belive I made some comments about the resolution issue on one of the first layouts that had traces between pins. Another updated layout was created that eliminated these traces although there were still some tight areas IMHO.

The reason for this is that the tone god originally wanted it to fit into a really small box. If we don´t mind about the size of the PCB, I think a layout could be made that´s easier to etch.

I originally designed the Payback to work and be as simple as possible. Size was never a design criteria. I tried to see if I could get it into 1590B just for a joke. I think that inspired Michael to try to do a board that fit into a 1590B. I would strongly encourage DIYers to goto a larger case and layout. It will make things ALOT easier. Personally I think the way to do it if you want it to fit into a 1590B is either a multi-layer board or a board with jumpers on it.

Andrew

[FcKw]

Hi,

I also built it on perf and it works great! For getting the best s/n-ratio imho you have to record with the record level as high as possible (just before overdriving the chips input).
I put it in a taiwan 125B enclosure with 3 2dpt footswitches for recording, bypassing and selecting between 2 30sec loops and it's just perfect for practicing solos.

P.S.: A big thanks to The Tone God for designing this great circuit!

FcKw

[mydementia]

Well - I layed out the op-amp section of the Payback circuit and placed the ISD25xx chip (7x14 holes) and started working on the logic section...  As I was looking at the ISD25xx data sheet, I read about logic circuit layout techniques and recommendations - this is where I stopped.  With my op-amp section, I would have a difficult time keeping the logic runs clear of the power runs... so I think I'm back to Michael Allen's layout... unless someone wants to pick up my .diy file and give it a go...

I'm going to run back through Michael's layout - as I recall, there's a 100uF power filter cap that looks like it's missing a pad - same with the 1uF output cap...

Mike

[mydementia]

Gave up on a new layout and made a PCB from Michael Allen's project file. 
I have one question - the 100uF power cap is shown straddling the ground rail... shouldn't this rotate 90degrees?
I put together a build album in my gallery - I just added the following image with my assumed solution to the power cap question - hopefully someone will verify that I'm right.
http://aronnelson.com/gallery/album112/Payback_LayoutTS1?full=1
I also read that the opamp is backwards in the layout... I'm going to step through the schematic again before I insert the chip...but I marked all the 'pin 1's' per the layout (green dots).  Hopefully the layout is right...

Thanks for looking... I'm getting close to having this thing built... I'll add more pictures as I go.  I'm going to start wiring now...
Mike

[The Tone God]

I also built it on perf and it works great!
...
P.S.: A big thanks to The Tone God for designing this great circuit!

Make that two positive build reports. Thanks for chipping in and the compliment.

I have one question - the 100uF power cap is shown straddling the ground rail... shouldn't this rotate 90degrees?
...
I also read that the opamp is backwards in the layout... I'm going to step through the schematic again before I insert the chip...but I marked all the 'pin 1's' per the layout (green dots).  Hopefully the layout is right...

Yes that sounds right. The cap's positive pin should be connected to the gate's output with the negative pin connected to ground. Right now the cap and gate output are being shorted. Most quad opamps have their V+ on pin 4 which is on the bottom row so in your picture it is incorrect. The ISD25xx looks right.

Andrew

[mydementia]

STATUS:
Not sure what's up with the layout - but when I went to put the ISD25xx socket in - the pins were too far apart (both dimensions)... strange, since the 2n5088 socket fit perfectly...
Maybe I honked something up with the scaling...but everything else seems to fit.

MAN - There's a TON of wiring on this beastie!!!!  I put the 6 pots on a strip of perfboard and wired away.  I hope it works!!  I'm thinking that I should be able to get a 28-pin 'pigtail' socket and shove the long legs into the offset socket... then I should be looping to my heart's content...

Thanks for the double-check Andrew - I spent ALL DAY on this thing and wanted to be sure I didn't honk up something mundane in the end...

Stay tuned...
Mike

[mydementia]

STATUS - 12/23/06

I got the right opamp (was using a Rat Shack quad opamp... went and got a TL074) and rigged the ISD chip in place (actually had to put a new socket on a daughter board and run WIRES to the sockets on the main board - ridiculous!!!).  Today's verdict...maybe I don't know what I'm trying to do with this circuit...

I engage the circuit (I know it's 'on' because the Output Level knob effects the signal) - I turn the Safe switch OFF - I click the Record switch - nothing happens... the Record LED does NOT light.  The Vibrato LED is solid (not vibing to the speed).  Interestingly enough, the Depth pot makes the Vibrato LED bright or dim to off - neat indication... but I expected pulsing to the Speed...maybe present when a recording is playing back?  When I click the Record switch again, engage the Safe switch, and click the Bypass/Playback nothing happens...

I also get a very large pop when clicking the Bypass/Playback switch on and off...  I've gone through and scraped out the 'goo' between traces and used my DMM to ensure continuity is where it's supposed to be.  The Opamp voltages look great - don't know about the 4093 or the ISD2560 (first time using these puppies).  The regulator is putting out 4.96V (so I got it in there in the right orientation).  I made another daughter board for +9V and Ground - so EVERYTHING is common...

Another note - it looks like my Output Level pot works backwards... I guess Michael Allen didn't use the 'looking at the back of the pot 321' convention... 

Any thoughts/recommendations?  Any other voltages I can check?  I'm going to have to pack in my workbench for the next week (family coming to town) but have a few hours tomorrow to work on it...

Thanks in advance.
Mike

[The Tone God]

So we are now at the debugging process. It is best to break the circuit into it's function blocks and get each piece working. I usually break it down to the audio portion, digital, vibrato, power supply, and the ISD. Lets deal with the audio portion for now.

First check to see if you get a bypassed signal when the effect is disengaged to see if the bypass switch is working. If good then pop the ISD and logic ICs out. Put a test signal at the input and put you probe at the ISD's ANA IN (pin 20). Tweak the record level the see if the signal level changes. If that works then put your probe on the effect output with the output level set at max. You should hear the input signal unaffected by the record and playback levels. If that is good move onto the audio output section.

Connect your test signal to the centre pole of the phase switch. Play with the playback level and tone controls to see if you hear anything changing.

While you are at it check your power supply readings. With the ICs removed connect the negative probe of your DMM to ground. You should read the following voltages (approx.)

V+: 9v
Voltage regulator out: 5v
Opamp pin 4: 9v
4093 pin 14: 5v
ISD pin 28: 5v
ISD pin 16: 5v

Report back.

Andrew

[scaesic]

are there any sound clips for this?

[mydementia]

My values in red

While you are at it check your power supply readings. With the ICs removed connect the negative probe of your DMM to ground. You should read the following voltages (approx.)
V+: 9v 9.12V
Voltage regulator out: 5v 4.95V
Opamp pin 4: 9v 9.12V
4093 pin 14: 5v 4.95V
ISD pin 28: 5v 4.06V
ISD pin 16: 5v 4.06V

Report back.

Andrew

I get output when the playback/bypass switch is in both positions... but I get a loud pop every time I click it...
I didn't have time today to get my circuit sniffer out and plugged in... have to wait a while to chase the audio path...

Is what I described in the post below the intended 'order of operation' for this circuit?  I just want to be sure I'm not doing something dumb...

Happy holidays all.
Mike

Oh yeah scaesic - I'll make some soundclips of this circuit when I get it figured out... but it's just a looper...  record a phrase, play the loop indefinitely, play over it - that's what it does (not considering the vibrato, phase, and tone additions).

[The Tone God]

Everything voltage wise looks good except the voltages on the ISD. It looks alittle low. There might be something going on with the vibrato. For now you can bypass the vibrato by jumpering the emitter and collector of the vibrato transistor that feeds the ISD. You should read the 4.95v then.

Is what I described in the post below the intended 'order of operation' for this circuit?  I just want to be sure I'm not doing something dumb...

There could be a number of reasons why the switch is popping. I think it is symptomatic of something going on with the circuit that shouldn't be so I was say for now put that problem on the back burner and go through debugging as normal. I would not be surprised that as the various operational problems are solved that the popping goes away.

Happy Holidays.

Andrew