Gotta do a Loophole - did search, gathered info, let's do a bundle of it here!

[Cortexturizer]

HI guys, I don't know how I missed on the Loophole, it looks like the PERFECT thing I need for my band!
I love that it is lo-fi. I love that it can do down tune, and thanks to JakeFuzz, the vibrato. Fantastic.
I have a problem finding ISD chips, but it will sort it self eventually... [btw, I did make an offer to buy some in the forum predetermined for that kinda stuff]

The project - http://www.madbeanpedals.com/projects/Loophole/Loophole.pdf

From what I have seen here on the forum, there is a vibrato mod [huge thanks to JakeFuzz!], the chip mod [use ISD2560 instead for longer recording times and slightly better sample rate], ground pins 7 and 8 of the ISD2560...

Vibrato mod:



but, make speed a reverse log tapered 50K pot, and bump 4.7K to 33K. Am I right?

Also, does the Detune pitch pot gives you the opportunity to raise pitch or just to tune it down?

I have a dry/wet mixer in a wah pedal enclosure that I plan to use with the Loophole, and sort of mix the recording in and out throughout the song I'm playing. It's gonna rule for ambient type of songs.

Any other mod that I haven't stumbled upon? Any other recommendation you guys could give? now that a bunch of you have been using the pedal for some time, there has to be something that you would add or subtract from the pedal. What is that?

Thank you fine people, thank you.

[Cortexturizer]

Also, what would you do to add highs to the recorded signal? A simple EQ circuit in the pedals effects loop maybe? 

[JakeFuzz]

I am pretty sure the vibrato only tunes down. The way it works is by slightly varying the voltage to the chip which causes it to detune slightly.

As for the ISD250xxx I just grounded those two pins and it was good to go!

I would say bump the 4.7K to 33K. I would try a 5K for depth. I haven't confirmed this value but with the 10K things get extreme real fast. I would test 1K all the way to 10K if you had some time. Definitely 50KC for the speed. You could also tweak around with that 1K to get some different speed extremes. BTW I do apologize for that wiring diagram. Its been a while since i've seen it and it is a mess!

As for bringing treble back into the signal, there is a filter built into the original design. I would look into changing the value of filter for more high end.

[Cortexturizer]

Thank you JakeFuzz!
Hm, I am pretty sure I've heard a clip of a person playing their recorded signal through the Loophole and raising the pitch, I gotta find that clip...
aha, here it is!

I can barely hear what the guy is saying but I think he says "this is not in the documentation but it's really cool"

and my God it cool is.

[JakeFuzz]

So what he is doing is recording while the detune switch is pressed. This records the pitch shifted signal and when the voltage on the chip returns to 5volts the pitch is shifted back up and the guitar signal is now at a higher frequency than when it was recorded.

The way the vibrato works is it is only enabled when the pedal is playing back the signal. This allows you to do realtime changes to the vibrato parameters. I think you could probably enable the vibrato only while recording and that may do an only up shifting vibrato.

To get a true up and down vibrato you would have to bias the ISD voltage to the middle of the vibrato swing voltage at all times (during both recording and playback). Then the vibrato would swing above and below the isd voltage giving you high and low pitch shifting variations. The problem with this is that as you change the depth setting the vibrato swing will change and you would have to alter the isd bias once again. It is a little involved but you could make the depth pot a dual gang pot with the second gang on a really tiny voltage divider (someone said the major depth variations were between 4.0 and 4.7 volts!). This voltage divider would slightly alter the main supply voltage from the regulator to the ISD chip. If you tune the divider correctly you could get it to follow the center point of the vibrato swing voltage.

The other way to do it would be to make the vibrato swing above and below the original supply voltage. I am not 100% sure this is safe as you will be feeding the ISD more voltage than it is designed for but for really minor variations like this I would think it would be fine. I am not sure how I would do this. I might put in a huge blocking capacitor (time constant must allow for really low frequency to pass) and then feed that into the original supply after that. The detune would have to be moved past the blocking cap and onto the supply voltage (like the original detune feature).

[Cortexturizer]

Alright!

So I made a Loophole, and I have some problems...
Both LEDs are on when I record which is OK [used a momentary switch to record] then when I press Play, it plays the loop but it plays the whole available time in the ISD chip! Not just the time I used to record a loop, everything. That, and when I record some more, it records over the last recorded loop and if the new loop is shorter, then when it finishes the old one just continues!!! Like a cassete tape on Walkmans haha.
And it does that, only ONCE, so, it's not looping, it's just playing the recorded stuff once. What a bummer.
I used the ISD1020AP chip.

The detune feature is also non-working.

Weird. Any ideas to what may be wrong?

Would you guys go through my voltages if I post them?