hey, doesn't my lo-fi loop junky do everything on your list except go for longer than 20 seconds?
On that list yes. I will be hopefully including a few other features as mods like a phase switch for the recorded output so if you play along you can get a different chorus effect. The big feature I hope to get working is the multiple loops as that is one the big reasons why I went with the 25xx series. I have a few other minor features I want to play with.
The controls on my current looper are also more extreme. The vibrato can for example slow down the playback to the point of almost stopping, but not reseting the IC, without causing too much added time to the loop. It sounds like a record starting up. The loop input and output volume controls also have more so the IC's input can be overdriven or the output could overdrive other effects/amps. There is also a final output control so one could mix the loop and dry signal to their tastes.
i guess the way i got it to fit on that small board was by not needing a logic chip... the family i used has enough on-board logic to use simple discrete component tricks to make it do what i wanted.
I took a quick look through the other family datasheets and I can see why it would be alot easier to use one of those. Those families are really optimized for pushbutton operation where the 25xx series is trying to cater to both pushbutton and uC needs. To do that they removed some of the internal logic and exposed more of the internal controller's inputs and outputs. For this reason I have generate some of the logic externally to get back the functionality. In the end it has only taken three gates, three resistors, and two caps to do the logic.
While I'm probably losing space with the external logic I'm probably getting some back in other areas. For example I'm using the last gate as the clock to drive the vibrato. Besides using a unused gate to save space I can add the feature that the vibrato will be automatically disabled during recording and enabled during playback. I also can do a power down / true bypass trick using only a DPDT switch with the addition of only one part.
The other big problem is that if I'm going to do multiple loops I need access to the address pins which mean I can't use any of the internal operational modes. Hopefully I can get the loops to work so that as you are in the middle of one loop's playback you can select another loop and when the current loop reaches the end, or you cycle the bypass switch, it will jump to the selected loop allowing different phrases to be stored.
The logic took me a couple of days to get working right. I could have grabbed a uC and done it in minutes but that would be cheating.
If I had decided to go with a uC I would have grabbed one the other IC families and done some really cool stuff. The output portion ALOT easier too.
i always wanted a longer looper, though... good luck, tone god! 8^)
Thanks Mr. Vex.
I haven't done a small build awhile so this should be fun.
Anyways back to work.
Andrew
