Adjusting the 1200's filters?

Deck Daddy · Adjusting the 1200's filters?

www.emulatorarchive.com/DrumMachines/SP1200Overview/SP1200Tech/sp1200tech.html

"The remaining two channels (the toms) each use a dynamic VCF. They use the SSM2044 with a simple AR enevelope generated by the Z80. They create a 5ms sloping attack, followed by a decay. The frequencies can be internally adjusted."

"There are 7 trimmers on the main circuit board. Four are for the DAC's, one is for the sample offset, and the last two trim are dynamic filters."

Has anyone tried adjusting the filters? What does the controls do, what do they adjust?

HavDeaf!

interesting. my filters are disabled, id like to make a switch or something to turn them on and off. any knowledge about it? drop it if u know fellas

Something Like That

Bruce at Forat can do all that for you.

Adjust filters internally or even install switches for you to use but 1st he'll recommend that you just use a Ycable.

I'm getting the on/off switch installed on mine, not because I plan on using them frequently but more so b/c carying around a trs snake or y cable is a pain to me when I could just use a switch. Plus the mod will increase the value of your machine and one day it will be pretty hard to come across working eye pleasing sp's.

Deck Daddy

I'm not interested about other ways of turning the filters on or off. They can be enabled easily with balanced TRS cables.

I'm interested in the part about "The frequencies can be internally adjusted."

And I'm not interested in ruining anything, so I would love to hear some experiences of doing it, or about how it's done, if it can be easily changed back to the default settings again, and mostly: how will it sound.

Deck Daddy

BTW: I have seen that the topic has been discussed several times before on this forum, but it don't seem like anybody has tried to adjust them, no answers that really clears this up...

Deta!L

yeah deck I don't think anyone has stuck around here, that has done it to their SP sooo enter with caution

kb · I've messed with the 2044's

In the midst of fixing my sp12t, I wanted to play with the filters a bit.

I think the trimpot in the sp already adjusts the cutoff frequency, so I pulled out the ssm2044 datasheet (freely downloadable out there) and figured out the necessary control voltages to adjust the resonance and rigged up a potentiometer.

I think I had to lift a pin out of the socket to connect to the rigged pot - gotta be careful with that, always scary that you might break it and 2044's, while not too hard to find, aren't too cheap either.

Anyway, I ran one of the stock drum sounds through it in a pattern and twiddled the cutoff and resonance in real time. You can definitely get the filter to resonate and squeal and you can muffle the sound with the cutoff. It was kinda cool, but I decided not to make it a permanent mod just yet. I always figured the sp sound was so unique I didn't want to goof it up, but that's just me.

Using resonant filters on drum sounds is different than on synths because the envelopes are so short. I'm working right now on an Oberheim DX modification that has a tweakable VCF on every sound and I think I might have to add a VCA after each filter because...

One major issue with adding the resonance is that you don't have a VCA after the filter, so if the res starts squealing, it may not shut up even when the drum sound is through.

Good luck!

essence

@DeckDaddy : apparently you did not search thoroughly, here's what phase one found out (http://sp1200.myfastforum.org/about284.html) :

DFACE DXA

yeh its been covered

Adjusting the 1200's filters?

I've messed with the 2044's