Echo Base Stereo Dual Delay - comments please

[FunkyGibbon]

This is simply a slightly modified version of the existing Echo Base project by Slacker (Ian M.):
http://www.diystompboxes.com/smfforum/index.php?topic=60662.0

I have also been helped by many of the ideas from CPM's stereo ping-pong version of the Echo Base:
http://www.diystompboxes.com/smfforum/index.php?topic=71201.0

I have simply amalgamated the original project with the series delay ping-pong idea, added switching to allow parallel stereo delays, replaced all the original switching with 4053 chips (because I have a lot), allowed 'true' (not quite) bypass as well as 'tails' mode, added a Self Oscillation footswitch, plus included a lot of the other mods that have been mentioned in discussions about the Echo Base.

Here is the schematic:
http://www.aronnelson.com/DIYFiles/up/Echo_Base_-_Stereo_Dual_Echo_-_complete_schematic.pdf

I gave up on trying to find a way to have a switch that could multiply or divide the clock frequency by exact increments. I have simply used independent Time controls for each delay, with a Fine control for each. I haven't built this yet, but I anticipate one should be able to get 'dotted quaver' rhythms with Delay A, while Delay B plays the beat (parallel mode), as well as shuffle or swing rhythms (ping-pong mode) by offsetting the times of the two delays by a bit. Like in CPM's version of the project, you can get long delays by switching off the output from Delay A. In this version, this is done with the Echo A On/ Off footswitch (when in ping-pong mode).

I have used momentary footswitches because I have a lot, but this version can be easily changed to DPDT latching footswitches.

Questions:
-Is the Self Oscillation footswitch added correctly (I'm not sure if maximum or minimum value on the feedback pot gives the maximum feedback - I assumed it was the maximum value)?
-Does the buffer routing look okay?
-Are there any other problems that I haven't been able to spot yet?

Thanks and enjoy!

Christopher

[slacker]

Amazing looking schematics, looks like an interesting project.

I haven't studied the switching in much detail so I can't comment on that, but there's a couple of things you might want to change on the delay sections.
The modulation on/off switches should short out the 1uF caps not disconnect them. so connect the cap between pins 1 and 2 and the put the switch in parallel with the cap.

The self osc switch will work as shown, but if the feedback pot is turned down so the wiper is at ground then it won't do anything because it will just connect the top of the pot to ground. I'd connect the right hand side of the switch in series with a resistor to the junction of the 20k resistor and the 100n cap. That way it should work no matter where the feedback pot is set.

Hope that helps

[FunkyGibbon]

Thanks, Ian!

I, like so many others here, really appreciate the support and enthusiasm you've put into this project.

Regarding the Self Oscillation switch, I'm guessing the series resistor should be 80k, but I may have misunderstood something. I think Gutsofgold tried a similar mod with the Rebote delay, but had some difficulty getting the series resistor value correct.

Schematics are done using DipTrace free.