Subspace Transmission - A fuzz with a recording and playback

Stompboxes circuits published in magazines, books or on DIY electronics websites.
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Freppo
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Post by Freppo »

Hi folks,

Here's a new DIY project release from me - the Subspace Transmission Fuzz.
It's a fuzz with a recording and playback feature based on the ISD1820 voice recording chip.
It can record up to 20 seconds and the playback can be repeated and pitched up or down.
It's a pedal you can have alot of fun with... :)

It's an easy build that doesn't require any programmable chips.



More info in my blog at http://www.parasitstudio.se

I hope you like it
Cheers, Fredrik
Check out my building blog at http://www.parasitstudio.se

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mirosol
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Post by mirosol »

First, would lowering the values for R3, R4, R15 and R18 help with the output level issue?

Second (as i couldn't find my answer in the datasheet), does the chip suport simultaneous rec/play with different samplerates? You probably guess where i'm going with this :)
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Freppo
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Post by Freppo »

mirosol wrote:First, would lowering the values for R3, R4, R15 and R18 help with the output level issue?

Second (as i couldn't find my answer in the datasheet), does the chip suport simultaneous rec/play with different samplerates? You probably guess where i'm going with this :)
Yes, the output could probably be raised by lowering those resistors, but the sweep of the tone would suffer.
I'm working on a revision with a different kind of tonestack (with less volume loss) and a makeup gainstage insted of the buffered Vref (isn't really needed).
It will overall have less components and be able to be quite a bit louder than unity. :)

The chip is a single message chip, so it's not possible to do simulanious playback and recording for overdubs/bouncing.
That would require two chips. I'm actually working on a two chip version already. :)
The tricky part is to have both chips controlled in a logic fashion, perferrable sharing controls.
Setting up the controls for one of these chips was hard enough, as I had to use CMOS flip flops with switch debouncing.

The most annoying drawback of these chips is that they always powers down into a powersaving state before beginning playback again, so fluid repeats is not possible.
There will always be a short (like a half second) delay between the repeats.
Check out my building blog at http://www.parasitstudio.se

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mirosol
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Post by mirosol »

Thanks for clarifying. True, the resistance before BMP-style tone stack would afftect to control. What comes to raw output level. More is always better. At least in my opinion. I seem to favor quite hot pickups, so the lower than unity level performance for a pedal is basically a show stopper.

The idea of dropping/doubling the sample rate for playback would be the key in gaining a polyphonic octave/pitch shift effect - Something that's been sorely missed as (even remotely) simple diy circuit. So it seems that this chip wouldn't work as one.
http://tagboardeffects.blogspot.com/
http://mirosol.kapsi.fi/
"No such thing as innocence" -Iron Chic

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