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Casio SK1/5/8 mods - Phat Philterbank update, SK1 sample expansion and more!

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gmeredith:
Hi everyone! Sorry for dropping off the scene, a combination of hectic work life and also being locked out of logging in to this forum for ages - a stupid "time out" error on this server. Another user had the same issue and posted that suddenly they were back in today, so I logged in, and here I am again!

Lots and Lots of things have happened:

1. I retired, which means I get to play with all my toys more again, and

2. A bunch of people have been messing with my Phat Philterbank (PPB) and other mods and improving them (making it easier to build without making mistakes - it was almost an impossible circuit to build and get functioning with my layout, even for me!). They also got the PPB adapted to the SK1 and it sounds AWESOME on it (Thanks to Joel and Sam!)

3. They have also adapted the SK5/8 sample memory expansion mod to the SK1. This was quite difficult to nut out as the SK1 uses a different sort of ram to the later SK5/8 that run standard SRAM. They are also working on making the sample memory battery backed, so you retain the SK1 samples when powered off, like the SK5/8 does. These guys are heroes!

Watch this space for details and videos

Cheers, Graham

wax+wire:
Thanks Graham

Joel here. Would be good to see a little more action on this forum again.

With the Phat Philter Bank a few things that have been done:

1. Making the envelope points and the audio points on the CASIO SK1 correct. There were a few instructions around the net that resulted in the PPB (and the SLOW AD mod) not working perfectly. I'll share a schematic with exactly where to get those spots on the CASIO SK1's PCB.

2. Modifiying Graham's initial circuit slightly so you can control how much the envelope from the Casio SK (1/5/8) effects the filter cut-off AND also mix an LFO signal with an envelope signal. allows for some really nice filter opening combinations

With the Memory Expansion it is :
* 64x Memory expansion for the SK1 (so 64 samples, AND I'm fairly sure 64x 400 note sequences AND memory retention when switched off).
* Same with the SK5/8 except only 16x expansion (but that is 16x4 samples, so 64 samples) and no sequencer (actually, I'm not sure about that.. I've never used the record function)
* fairly cheap, about $30AU for all the parts (SK1 is a bit more expensive)

gmeredith:
Awesome work Joel. Dug out the SK8  loaded with all the mods yesterday and noodled around playing stuff. I'm going to rebuild it. Either you or Sam got hold of those really tiny quad pots I think - where did you get them? I'm going to replace all mine

wax+wire:
Mouser:

https://au.mouser.com/ProductDetail/652-PTD904-1015FA104

~$4.00AUD -- and free postage if you order over $60 in australia atm. I recommend doing 3, one for the cutoff, one for the resonance and one for the envelope in.

Have you every played with the "record" function of the SK8? I just checked on the SK1, and because it writes the sequences to one of the RAM chips, with the SK1 64xMemory Expansion you can store 64 sequences.

gmeredith:
Yes they are really shallow, the 4-gang is only 17mm deep. It just might do it.

I have just confirmed that indeed the memory expansion also expands the sequencer - on each of the memory banks, I can record a different sequence and it retains it for that memory slot. Like you, I don't really use that feature, especially since my SK8 has MIDI in, so i sequence it from my MMT8 sequencer, so I never knew if it ever did work, until just now

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