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FreqBox calibration/tuning

Posted: Fri Feb 29, 2008 7:36 pm
by toryjames
I finally hooked my FreqBox up to my modular and found that it wasn't tracking very well. I couldn't find information on here relating to how a person could calibrate their FreqBox so I called Amos today and he was very helpful. When you open up the back of the unit there are two white square trimmer pots. The one at the center of the circuit board relates to the VCA/Env response, the one in the lower left corner calibrates the FreqBox for 1V/Oct modular use. It's fairly coarse so you have to be gentle when turning it, I suggest marking the factory setting with a thin black Sharpie (in case you get way off base you can at least get back in the general ballpark). I tuned mine right away without too much trouble then let it sit a while to stabilize/warm up. I came back about 15 minutes later and tuned it again and now it tracks beautifully, about 5 octaves.

I don't recommend doing this unless you have experience tuning VCOs, you may end up worse than where you started. But for those of you who are somewhat familiar:

Instructions from the MOTM VCO manual:

"Play a note on the keyboard. Play a note one octave higher. Adjust the trimmer for proper pitch. Keep playing/adjusting back and forth until this 1 octave is set. Now play 4 or 5 octaves apart. Readjust the trimmer as necessary."

Instructions from the Paia 9720 VCO manual:

"During calibration one oscillator will be used as a fixed reference tone while the other oscillator (in this case the FreqBox) is adjusted. Use triangle outputs and arrange for both to be heard at the same time at equal amplitudes.
Apply a 1V/Octave controller (or Midi>CV converter) to the frequency input (on the back of the FreqBox) and cause the controller to output 4V (typically by pressing the 5th C on a keyboard). Adjust the FreqBox until the pitch is 2 octaves above the reference tone. Now cause the controller to output 0V (typically by pressing the lowest C) and adjust the internal trimmer until the pitch (of the FreqBox) is 2 octaves below the reference tone.
Once again cause the controller to output 4V and again adjust the Frequency knob (on front panel of the FreqBox) for 2 octaves above reference, then 0V again while adjusting internal trimmer (on the inside of the FreqBox) for 2 octaves below the reference. Repeat until satisfied with both the high and low end."

Please correct me if I'm wrong or something is unclear. I'm hoping this helps someone out. Please don't do this if you're unsure, that's what Paia kits are good for: experimentation and learning. Don't mess up your expensive Moog equipment.

Posted: Sat Mar 01, 2008 12:01 pm
by narrowcaster
Thanks bosshog, that will come in handy.

Where did you keep the Freq knob on the top of the Freq Box during all this?

Posted: Sat Mar 01, 2008 12:45 pm
by c7sus
Thanks for the tip. I calibrated my 107 last night. Seems it will only track accurately over about a 3 octave range.

To Narrowcaster: on my FB the knob wound up just about DFC and the trimmer is backed off just about to the min. I played the lowest C and tuned the knob on the FB to 2 octaves above that tone. Note that you'll want to use a patch with a triangle wave and a single oscillator. I tuned everything with a Peterson VSII but there's really no need to tune the source because you're looking for a tone two octaves above any other given tone. Because the tracking seems to run sharp I settled for tuning my 3 octaves solidly in the mid-range of the audio spectrum.

YMMV.

I'm gonna try again this afternoon and see if I can dial in better tracking over at least another octave. If the trimmer went down just an RCH more I bet that would get it.

I'm interested to know that the ENV trimmer controls-- is it the tracking of V/octave as in the case of the oscillator or is it some other fine-tuning for the depth of the quack?

Posted: Sat Mar 01, 2008 3:44 pm
by toryjames
The MOTM manual suggests the reference tone be around A=440hz, that would make the lower frequency (2 octaves down) 110hz and the higher (2 octaves up) 1760hz. I suppose the logic is that anything too far above or below that might make it hard to hear accurately. I didn't use a frequency counter, I just found a reference tone where a range of two octaves above or below was still easily distinguishable. I believe the FB Frequency knob was just below halfway (≈4.9).

Posted: Sat Mar 22, 2008 3:10 pm
by CTRLSHFT
thanks for the information! mine has tracked my voyager pitch cv out for ~5-6 octaves out of box pretty much, but it's good to know there's a way to tweak this if neccesary.

has anybody messed w/ the env pot?

Posted: Wed Dec 09, 2009 5:23 pm
by Neekau
I just bought a second hand MF107, which did not track that well with my voyager... but now it tracking is perfect on 5 octaves !

(I used another way to calibrate: with MP201 displaying VOLTS, and a chromatic tuner, easy way to proceed :D )

Re: FreqBox calibration/tuning

Posted: Thu May 27, 2010 10:43 am
by moremagic
I recently picked up a Freqbox secondhand myself, my first moogerfooger with the old smooth paintjob, but have yet to get a MIDI->CV box or a keyboard with CV outs, so I haven't gotten around to worrying about the tracking yet...

However, the input seems cold as ice, which really sucks because the envelope follower isnt nearly as useful when the signal stays low. Is there a trimpot or jumper or sth to change this? I'm keeping the drive dimed and it's pathetically weak running a guitar into it, and on most patches I need to use a line level instead of inst level output from my Polysix.

I was really wanting to be able to (eventually) run CV into the Freq and the Osc out to a synth mixer while running a guitar thru it (sync off, env, FM, and mix @ 0) to put fx after the env follower but before my MF 101, so I can have a nice animated curve controlling the filter envelope over a fuzzed out guitar.

Re: FreqBox calibration/tuning

Posted: Thu May 27, 2010 11:00 pm
by c7sus
The calibration is about trying to temper the response of the oscillator to the widest octave range, rather than setting the VCO at a specific tuning itself.

The trim pot adjusts the volt/octave scaling for the VCO.

Re: FreqBox calibration/tuning

Posted: Fri May 28, 2010 10:16 am
by SteveD
Hi All -

Needless to say, I don't recommend popping open your freqbox to mess with the calibration unless you know what you're doing.
However, if you are attempting this, set the panel frequency control to 12:00 when tuning the V/Octave scale trimpot. Also make sure env. amount is at zero. The panel pot is summed w/ the freq cv input, as well as the envelope follower signal post-env. follower amount VCA. The trimmer calibrates the gain of these signals going into the VCOs core. You'll want anything other than your CV input close to zero for the best results in calibrating. With careful tweaking, I've gotten 6 octaves of tracking. The procedure descriptions quoted by tory james are basically valid approaches. Note that this calibration may drift slightly if you don't have AC in your studio in the summer, or if you're on a stage w/ hot lights. Just so you know... It's really old-school analog!

The other trimpot is for setting the threshold of a gate signal that turns off the output VCA for the VCO when there is no signal so you don't get too much VCO bleedthrough when you're not playing anything into the input. You shouldn't need to mess with it - if you do, you may make the freqbox feel either less responsive or too noisy...

Have fun and freq out...
SD

Re: FreqBox calibration/tuning

Posted: Fri May 28, 2010 3:26 pm
by moremagic
SteveD wrote:The other trimpot is for setting the threshold of a gate signal that turns off the output VCA for the VCO when there is no signal so you don't get too much VCO bleedthrough when you're not playing anything into the input. You shouldn't need to mess with it - if you do, you may make the freqbox feel either less responsive or too noisy...
So the only gain-related trimpot only controls when the gate triggers? Or does affect the VCA level or boost the gain? I can't understand why the freqbox's level led barely reaches green while dimed on a signal that sends all my other mf's into the red

Re: FreqBox calibration/tuning

Posted: Sun Jan 27, 2013 2:58 am
by gruvsyco
I know I'm digging up an old thread but, this was majorly helpful in getting my Freqbox to track to my Little Phatty better. If any of these posters (especially OP) are still around, thank you.

Re: FreqBox calibration/tuning

Posted: Fri Dec 25, 2015 4:09 pm
by PIANODENTIST
Hey guys. Just got a Freqbox. Great fun. Quick question. The env amount knob seems to act as an offset for the VCO frequency even when using the direct OSC out rather than the audio out. Is that correct? I thought the envelope and FM knobs and inputs only effected the audio out (not the raw oscillator).

Cheers guys.

Re: FreqBox calibration/tuning

Posted: Thu Jun 30, 2016 2:42 pm
by ebo
PIANODENTIST wrote:Hey guys. Just got a Freqbox. Great fun. Quick question. The env amount knob seems to act as an offset for the VCO frequency even when using the direct OSC out rather than the audio out. Is that correct? I thought the envelope and FM knobs and inputs only effected the audio out (not the raw oscillator).

Cheers guys.

the envelope is generated from the Audio in.
with extern CV to Freq in and Env in you can controll the raw VCO.