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

[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

[wax+wire]

I've put up a little video of the SK1 memory expander here.

https://www.reddit.com/r/CircuitBending/comments/if0r40/casio_sk1_sample_memory_expansion_x64/

It is a bit more challenging than the SK5/8 and needs 2xRAM chips, 1 logic controller, 2 RAM chip controllers, 6 resistors, 3 switches and the rotary encoder. Having spent a fair bit of time doing it, I actually think it is the sort of thing that could benefit from a unique PCB being made up. You could have it so that you basically just desolder the old two RAMs and then solder in this PCB on top.

Not sure if that is something people would be interested in?

The other challenge is mounting the controller stuff. I really wanted the encoder and bank switches close to the sample button. It just makes sense! To do that I had to chop the legs off my mini DPDT switches to get them down to 7mm deep and then solder onto the stumps. a bit silly I know. I reckon you could make something that mounted onto a plate that you installed onto the SK1and cut a whole through it with the wires.

[gmeredith]

I expect this thread is going to get very busy over the next few days. I just joined a Facebook group of toy keyboard noodlers and mentioned what we had been doing with the SK samplers. Expect a barrage of new members!

https://www.facebook.com/groups/966873446990657

[kloroplaster]

Has there been any developments here? A pcbs would be great!

[wax+wire]

PCBs for the memory expander or the Phat Philterbank.

The answer to both is no. Sorry.

I was just down at the state library in my city. It has a fabrication lab (3D Printers, Lasercutter etc). Anyway, I was really impressed by how easy SMD soldering looked using a hot air gun.

If you are interested in doing up some PCBs I'm happy to help. I'd recommend using SMD and making them fit easily inside the casio.

[kloroplaster]

PCBs for the memory expander or the Phat Philterbank.

The answer to both is no. Sorry.

I was just down at the state library in my city. It has a fabrication lab (3D Printers, Lasercutter etc). Anyway, I was really impressed by how easy SMD soldering looked using a hot air gun.

If you are interested in doing up some PCBs I'm happy to help. I'd recommend using SMD and making them fit easily inside the casio.

Ok. I have very limited PCB routing experience (I've only made two eurorack modules, both passive) but I could give it a try. Could you please post details and schematics here?