ARP VCF's - 3 in my Odyssey

Broadwave · Posted: Mon Sep 28, 2009 5:56 am Post subject: ARP VCF's - 3 in my Odyssey

I recently managed to get a MKIII Odyssey on ebay... not working... VERY cheap Razz

After spending a few hours, I got it fully functional and have since added both the 12db 4023 and the "Moog Infringement" 4035 to go along side the 4075, which has been fixed (swapping the 4 x 4k7's for 2k2's) for full frequency response.

I tried two attempts at the 40235 board with no luck, so I just copied the buffer sections for audio, CV and feedback and used the output to feed all 3 VCF's - works like a dream.

Now that I've finally had the chance to compare the "Moog infringement" VCF with ARP's later Norton design, I have to say that the difference is very subtle. They sound remarkably similar, although I think the 4035 has the edge, but only slightly - the resonance is smoother and drops off slightly at the lower frequency end, and FM control is punchier (maybe that's to do with the log converters?)

I've also installed a switch to invert and level shift the saw output of VCO 1 to the S/H mixer - The "White Face" Oddy's output is sawtooth, while the MkII & III is ramp, which makes a difference when you sample the LF output of VCO 1.

I now have the choice, by way of 3 simple switches, to choose which version of the Odyssey I want - All I have to do now is tidy up the wiring, fix the boards in and drill 3 small holes for the switches... I'm waiting until I have a steady hand Very Happy