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Blue Lantern Lunar Modulation Center VCO (revisited)
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Blue Lantern Lunar Modulation Center VCO (revisited)
Hello out there! Now that the Blue Lantern Lunar Modulation Center has been around for a while, any owners care to share their experiences? Any unforeseen anomalies or has it been smooth sailing?

The main reason I ask is that I have been building my first rig since the spring. And now that I've finally got it where I'm pretty comfortable with the pieces I've assembled, I've begun to take it out for a spin a bit deeper. But that's when I noticed that the octaves are not tracking that well (or "scaling" forgive me if I'm not using the correct term but hopefully you guys get what I mean) about 20 cents off per octave, so I chalked that up to needing a calibration.

With that said, being a noob, this is my first crack at calibrating a VCO (or any module for that matter) and I'm having a time with making any progress. Now it has me thinking "Was it always like this". Hell I've only had this thing for a few months. And I'm also thinking "Is this as good as the tracking is gonna get?"

So I'm just curious if any of you guys have experienced the same issue? Or do I need to just stay after this calibration thing or even take it to a pro? I'm doing mono synth type work so staying in tune (or the lack thereof) is an absolute deal breaker for me! I'm hoping that it's me and not the machine because I do enjoy the sound of it! Btw, I've got his latest module, I bought direct from him this spring (in case anyone was curious about that).

Any feedback would be greatly appreciated!
All the analog VCOs I have owned could be calibrated to track reasonably well across 3.5 to 4 octaves. The best could track pretty accurately across 7 octaves.

One thing to check before you try and calibrate the octave scaling on your VCO is whether the VCO settles down to a stable pitch once it has been powered up for say 15 minutes. If the pitch doesn't settle, then you are trying to hit a moving target when you come to calibrate the octave scaling.
My advice for calibrating a VCO:
First, as Blairio mentioned, make sure your system is warmed up. I tend to leave mine on for 30-60 minutes beforehand just to be absolutely sure, but that's probably overkill.
Next, check the manual to see if there is a specific calibration procedure. There may be multiple trim pots on the back that control tracking so knowing how it was intended to be calibrated can be very helpful.
Then, start fiddling. All your adjustments should be very small, using a scope or tuner as reference. Make sure you're playing across several octaves as you go to get a feel for how the tuning works (I had one module that scaled from the middle of the range outwards which was confusing before I had it all figured out). It may take a little while, but you should be able to get it tracking nicely without too much trouble. Longest I ever took on an oscillator was about half an hour because there was a finicky octave switch that needed calibrating as well.

The reality is with an analog osc it's never going to be perfect. I usually call it good once I'm within around 5-10 cents every octave, because trying to get better than that just leads to frustration. That much isn't noticeable to the ear in my experience anyway.

Don't be scared to just get in there and try it. I considered taking modules to my local shop for calibration a few times when I was just starting, but once I'd calibrated one I realized it wasn't at all the big deal I thought it was. You can't hurt anything, and I highly doubt it'll be hard at all to get it tracking to a point that it's useable. Tracking is definitely an "if it sounds good, it is good" situation even if it's not technically perfect.

Hope this helps!
Hey thanks for the info guys! Yeah I gave it a shot, I started out with a tuner and just relying on my ears but it got a lil frustrating after a while with the cents moving to and fro and I eventually turned in for the evening. I then found an oscilloscope program that I got going today and when I put a signal on it, I was surprisingly closer than I thought I was (and closer than where it was before I started) so that is encouraging.

Yeah the LMC has a high and a low trim. I've got a good bead on the low side and now I'm gonna attempt to dial in the high side. Quincas over at VBrazil sent me an informative (albeit pretty technical and granular) method on Youtube so I've been doing a hybrid of that and a lil freestyling lol. But I definitely feel more comfortable now than whence I began.

I'll see how close to 0 I can get it to scale between as many octaves as I can before I start a Reverb listing lol. Thanks again for all the advice!
Good luck!

As mentioned before, with an analog osc, you're never really going to get to 0. It's not physically possible. And even if you did, as soon as the weather changed, it'd be off again. Look away from the scope once you get it close, and if it sounds good to you, don't worry about it. There's no such thing as perfect with analog, and that's the fun of it!
OTOH, and slightly OT, it is possible to have excellent 1V/octave tracking and stability across temperatures with analog VCOs, eg. this design from Ian Fritz
Thanks again all for the advice! So I gave it a good ole college try and it is now definitely tracking better than it was however it is a far shot less than 7 octaves. With that said, I don't see my self doing anything too musical in the upper octave ranges so I'll keep an eye on it and make sure that it's capable of doing what I need it to do.

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