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Calibrating Macbeth Mk1 A Oscillators
MUFF WIGGLER Forum Index -> 5U Format Modules  
Author Calibrating Macbeth Mk1 A Oscillators
BTG
Don't suppose anyone knows how to do this? I've contacted Ken as well.

They track mostly okay over 2 octaves, but are clearly out of tune when I use the octave switch. My Mk B oscillator tracks fine.
JohnLRice
I'm sad to say I've never owned any of Ken's beautiful 5U modules! cry
Adze
BTG wrote:
Don't suppose anyone knows how to do this? I've contacted Ken as well.

They track mostly okay over 2 octaves, but are clearly out of tune when I use the octave switch. My Mk B oscillator tracks fine.




I hope this helps, it's really easy do to it.
BTG
Whoa, thanks! Can you briefly describe the process?
Adze
BTG wrote:
Whoa, thanks! Can you briefly describe the process?


This is how I do it (there is probably more HI-TEC way of doing it)

From cubase I am sequencing C1 and C4 (or something like that), and than I make sure that the oscillator plays exactly 4 octaves (not important is it C or any other note at this point) you tweak 1V/OCT trimmer to get there. After you make the oscillator track, let’s say 4 octaves, from the front panel (yes that big knob) tune the oscillator to C.
Than I am switching octaves via switch from the front panel and tweaking octave trimer to get things in tune, sometimes it is necessary to play with high end trim to get everything right.
If needed you can go back to repeat some steps until you are satisfied with the results, but that’s the drill. In my experience Macbeth MK1 oscillator A needs this more regularly than my other oscillators, but it sounds really amazing, as you already know smile

I hope this will help!
BTG
I have a Standards module from dotcom, so what I was thinking of was:

set to 2V or whatever
tune to reference A220
set to 6V
check that it's 3520hz

That should have the range set for 1V Oct.

What do Octave Trim and Hi End Trim actually control?
sduck
If you have a good midi?cv module you can use VCO tuner - discussion in this thread - https://www.muffwiggler.com/forum/viewtopic.php?t=164286 or download it at https://github.com/TheSlowGrowth/VCOTuner/releases/tag/v0.2.4
Adze
BTG wrote:
I have a Standards module from dotcom, so what I was thinking of was:

set to 2V or whatever
tune to reference A220
set to 6V
check that it's 3520hz

That should have the range set for 1V Oct.

What do Octave Trim and Hi End Trim actually control?


Hi end trim is for correcting high frequencies, and octave trim is for setting the range of the octave switch.
Thalassa
BTG wrote:
I have a Standards module from dotcom, so what I was thinking of was:

set to 2V or whatever
tune to reference A220
set to 6V
check that it's 3520hz

That should have the range set for 1V Oct.

What do Octave Trim and Hi End Trim actually control?



I would do like this :

1 - Set the standards to 0V and tune the oscillator to A1 ( 55Hz )

2 - Change the standards to 1 V
2A - The VCO doesn't track perfectly- Move a bit the 1V/Oct Trimmer. Come back to step 1
2B - The VCO tracks perfectly go to step 3

3 - Change the standars to 2V
3A - The VCO doesn't track perfectly- Move a bit the 1V/Oct Trimmer. Come back to step 1
3B - The VCO tracks perfectly try the next octave ( standards 3V )

Once the VCO tracks correctly 3 octaves it's time to check the high frequencies. Change the standards to 4 or 5V. If it goes flat or sharp turn a bit the high frequency trimmer ( remember in what direction for future corrections ). Go back to the step 1 and check the tracking. The high frequency trimmer also affects a bit the middle frequencies.

After the tracking is calibrated it's time for the octave trimmer.

As you can see is a tedious process but it's not hard at all. And I know that I shouldn't say that but.... WTF , 500€ VCO and single turn trimmers for calibration!!! Come on it's not 1975 anymore!! Mr. Green
BTG
Cheers for that.

Out of curiousity, how calibrated is "calibrated" for most people?
Thalassa
For me calibrated means calibrated hihi hihi

In my VCOs it means perfect tracking for 6-7 OCtaves
BTG
Thalassa wrote:
For me calibrated means calibrated hihi hihi

In my VCOs it means perfect tracking for 6-7 OCtaves


Well, "perfect" can mean different things. If you're at A0 at 55Hz, do you expect to be at exactly 1760Hz a few octaves up or would you be okay with, say, 1765Hz?

I just spent an hour measuring my various oscillators but I don't trust my figures too much because I believe the frequency counter on my scope (a cheap Siglent) likely isn't sufficient to give me precise measurements.
Thalassa
It's not perfect but it should be enough. The difference is only 5 cents of semitone. Also at higher frequencies the ear is not so perfect. The inly problem is when you have a couple of oscillators and each one has different tracking curve. I always advice to have at least 2 identical vcos.

Your scope should be enough to measure the frequency. Also you can use an app like the Boss Chromatic Tuner ( It's free )
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