CV-3 MIDI-CV Converter Review

[gstopp at fibermux.com]

     Hi DIY List,
     
     I've been playing with my JKJ Electronics CV-3 MIDI-to-CV converter 
     recently and I like it so much that I figured that I could relate my 
     thoughts on the unit to the list.
     
     When I first took it out of the box I had the idea that I would try to 
     see if I could hook it up without even thinking about it, as a test of 
     its ease-of-use. I cabled it up to a Minimoog, stuck a MIDI cable in 
     it, set the channel switch, and hit some notes. Music! Not in tune, 
     however - the volts/octave was a little off. However as you may know, 
     this is normal with CV/Gate stuff, so I wasn't surprised. Now normally 
     a volts/octave trim means tuning at the instrument, which can range 
     from easy to excruciating, but the CV-3 has all of the scale trims 
     accessible from the from panel, through little holes, and JKJ even 
     gives you a trim screwdriver with the unit. I was in tune in about ten 
     seconds.
     
     The default settings include a nice vibrato depth on the mod wheel, a 
     nice vibrato speed, and a two-semitone range on the bend wheel, so 
     right away everything feels very comfortable. I got so wrapped up 
     playing wild pitch-bendy vibratoed solos on a five-octve Minimoog that 
     it was an hour before I started messing with other parameters. Next 
     came portamento tests - the pitch glide is very smooth, and the range 
     from no glide to max has excellent resolution. Now quantization to the 
     point of not noticing the steps is one thing, but *this* felt like it 
     was analog. This of course caused me to get distracted for a while 
     messing around again...
     
     Next on my list was the LFO stuff. I wanted to see how many features 
     there were, because I wanted to know if I'd rather have a mod voltage 
     for a VCA on a modular instead of an internal LFO. I was not 
     disappointed - the CV-3 LFO section has a lot of things to offer. All 
     standard waveforms are available (tri, up saw, down saw, bipolar 
     square, positive square, negative square, S/H, etc.) plus some 
     arpeggiator-like staircases (with up/down/up-down modes) that I think 
     will get used a lot. All of these waveforms form very precisely tuned 
     musical intervals when the mod wheel is moved to max, with the default 
     settings. Another dedicated vibrato LFO is also provided, which can 
     free up the configurable LFO for special effects.
     
     The CV-3 unit also has an audio-in jack plus a pair of audio out 
     jacks. I patched the audio out from the Minimoog to the in jack, and 
     ran the out pair to a pair of mixer inputs. Now I had volume and pan 
     control of the Minimoog's output, via MIDI! There's a lot of 
     possibilities here as well (for example you can auto-pan with the LFO 
     while syncing it to MIDI clocks, etc.). I think the most important 
     thing here however is now there is sequencer control of the MIDI-CV 
     instrument in the mix. What a concept.
     
     The CV-3 also has a Filter CV output (with assignable sources all over 
     the place) and an AUX CV output (likewise assignable). Gate outputs 
     include a V-gate plus an S-trig us Moog-heads.
     
     All operation modes are set up using MIDI program change commands. The 
     important real-time parameters are mapped to Continuous Controller 
     values. The further I got into the patch change mode chart, the more I 
     realized that there's an awful lot of parameters in there. I'd 
     recommend that those interested go to the JKJ web site and look at the 
     chart to see how much stuff there is. I really did try to test 
     everything, but it soon became apparent that it would take days to go 
     through all of the possibilities.
     
     I did some side-by-side testing with my old MPU-101 and found some 
     interesting things. The MPU will handle the pitch CV range from note 0 
     to note 127 in one sweep, while the CV-3 will only output the pitch CV 
     in five octave (61 note) spans at a time. However you can send patch 
     change commands to shift the range of those five octaves across the 
     whole 128 note range. Not a big problem for me, since none of my 
     controllers have more than 61 keys. Not only that, if I want to play a 
     note range of wider than 5 octaves in a sequence, I can always insert 
     a patch change in the event list.
     
     The MPU has only a two-deep buffer for the low-note priority. That is, 
     if you do a Minimoog-style two-note trill it will remember the upper 
     key when the lower key is down, so the trill will work like its analog 
     counterpart. However, if you do a three note trill, for example:
     
     high-middle-low-middle-high
     
     the MPU will play:
     
     high-middle-low-middle-nothing
     
     It forgets anything after two notes. The CV-3 remembers much more than 
     that - I think JKJ told me it's 11 notes but I haven't played that big 
     a trill yet. But it does act more like a true analog keyboard than the 
     MPU. There are also high-note priority and last-note priority (buffer 
     disabled) modes.
     
     The MPU has no panel trimmers for the CV scale, and the CV-3 does. 
     Like I said before, this is an absolute God-send for us CV heads. 
     Thank you thank you thank you.
     
     The MPU splits out the various CC and controller voltages to separate 
     jacks. The CV-3 routes them in software (firmware really). The default 
     routings are exactly where I'd patch them with the MPU anyway, in most 
     cases. However it is very dramatic how much modulation you can do with 
     the CV-3's internal pitch control alone, thereby freeing up several 
     modules on a modular that you'd need to do the same effects with the 
     MPU. It's like there's half a standard synthesizer already inside, for 
     modulation stuff!
     
     The MPU has nothing to do with audio. The CV-3 gives you volume. 
     panning, and modulation possibilities of any audio signal, but mainly 
     intended for the audio output of the controlled synth. (Does any other 
     MIDI-CV converter do this BTW, out of curiousity?)
     
     The MPU gives you four CV/Velocity/Gates, the CV-3 gives you one plus 
     one Filter CV plus one AUX CV.
     
     The MPU has an AC power cord, the CV-3 has a wall wart.
     
     The CV-3 is probably a lot cheaper than an MPU (which is out of 
     production and pretty pricey these days). I'm not sure of the 
     price/performance comparisons with other currently-available MIDI-CV 
     boxes, such as the Kenton, Clarity, Big Briar, etc., so I can't give 
     any comparisons to those. Perhaps somebody else can provide some 
     comparsion data - I'd love to see that.
     
     Anyway there's the scoop on the CV-3 box from a user's standpoint. 
     JKJ also offers the CV-2 (same as CV-3 but no audio control) and the 
     CV-1 (same as CV-3 but no audio or Filter/AUX outputs). The JKJ 
     webpage has all the details.
     
     - Gene
     gstopp at fibermux.com