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Tuning VCOs to each other & A440?
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Tuning VCOs to each other & A440?
Mr. Pete
HOW DO You tune VCOS together? hmmm.....

What's the quickest easiest way?
Is it possible to do it without relying on a MIDI connection to the VCO?
kpreid
Together, as in matching each other? By ear, listening for the beats. To a note? Use a tuner module (displays the pitch of a note). You can tune one VCO with a tuner and then the others by ear, if you're intending them to match.

No MIDI involved unless you're using a MIDI controller or sequencer, in which case make sure to send the note you want to tune to and then match it on the tuner (otherwise your notes will be transposed).

This is assuming your VCOs have correct 1V/oct calibration (or whatever standard your system uses). If that's not the case you need to recalibrate them.
cycad73
I tune one to A440 using a tuner app

With the second, I take both VCOs' saw wave output and mix them together. I tune the second until the beating completely stops. Saw waves are best in terms of being able to hear the beating.

I repeat the above for additional oscillators.
sduck
If I need to tune vcos together, I just use my ear. When I need to tune to a specific pitch, I use one of a bunch of tuners I have laying around - I'm kind of a tuner junky, there's always one within reach here. I even built a modular specific one a while back -
Mr. Pete
WILD I NEVER HEARD OF A TUNER MODULE …oops all caps sorry Thanks!
How is that different from using an external iPhone app /Guitar Tuner

I would assume a simple sine wave is the cleanest signal out ¯\_(ツ)_/¯
…but then they don't all do necessarily do sine waves

kpreid wrote:
Together, as in matching each other? By ear, listening for the beats. To a note? Use a tuner module (displays the pitch of a note). You can tune one VCO with a tuner and then the others by ear, if you're intending them to match.

No MIDI involved unless you're using a MIDI controller or sequencer, in which case make sure to send the note you want to tune to and then match it on the tuner (otherwise your notes will be transposed).

This is assuming your VCOs have correct 1V/oct calibration (or whatever standard your system uses). If that's not the case you need to recalibrate them.
Mr. Pete
oh i LOVE this! thanks applause
by "built" you mean you just stuck a jack in the clip? hihi

ie …no soldering necessar, right?
sduck wrote:
If I need to tune vcos together, I just use my ear. When I need to tune to a specific pitch, I use one of a bunch of tuners I have laying around - I'm kind of a tuner junky, there's always one within reach here. I even built a modular specific one a while back -
sduck
Mr. Pete wrote:
oh i LOVE this! thanks applause
by "built" you mean you just stuck a jack in the clip? hihi

ie …no soldering necessar, right?

There was soldering. Not a lot, but the back came off, a hole was drilled, and wires soldered onto the correct places, and then reassembly. There's a thread about this in the DIY section I think, somewhere. Not my idea, I copied someone elses idea and took a picture.

Thread: https://www.muffwiggler.com/forum/viewtopic.php?t=74376
kpreid
Mr. Pete wrote:
WILD I NEVER HEARD OF A TUNER MODULE …oops all caps sorry Thanks!
How is that different from using an external iPhone app /Guitar Tuner

Not all that different, it's just what I thought of first. Being a module means it's always there to use, definitely OK with modular levels, and also often has a built-in multiple so you can just keep the signal patched through it rather than having to split the signal with more cables or unpatch to tune. I have the Noise Engineering Soleo Vero (Eurorack) — it's a strobe tuner so it's really fast to use but you have to tell it the note you're tuning to.

Mr. Pete wrote:
I would assume a simple sine wave is the cleanest signal out ¯\_(ツ)_/¯
…but then they don't all do necessarily do sine waves.

The wave shape doesn't usually matter too much — sine, saw, square, and triangle are definitely all good. And if you're trying to tune something with a complex wave you could also tune it by ear to match a simpler oscillator you already tuned.
davebr
The second module I made for my system was a final output mixer setup to drive an external amplifier. I incorporated a three channel mixer with clipping detector, spring reverb, and an A-440 sine oscillator which is the fourth input to the mixer. That way I always can generate a tuning reference without patching. I used a DTMF generator for the 440 Hz which is actually 440.295 Hz. Details are on my DJB-002 Module page.

Since then I wrote some AVR code to generate 440.00 Hz Reference Oscillator but I have never bothered to upgrade my module. It generates a square wave but also generates the 100X frequency to drive a switched capacitor filter for a nice sine wave output.

I used to sell some parts and others incorporated the oscillator into their designs, some with LEDs to indicate tuning. I just use my ears.

Dave
Dave Peck
Mr. Pete wrote:


I would assume a simple sine wave is the cleanest signal out


Actually it may be more difficult to try to tune by ear using sine waves than using other waves. Sawtooth waves work best for me. I can more easily hear the up/down 'flanging' harmonic movement of the two oscs when they are slightly detuned from each other and this makes it easier to do the fine adjustment and get them tuned the way I want them (which is often NOT perfectly in tune, it is often with some small amount of intentional detuning to create that 'motion' between the two oscs).

TIP: It can be easier to tune oscs by ear if they are both playing a low-midrange note. If they are playing a much higher pitch it can be more difficult to tune them to each other.
abelovesfun
I use a mordax data to tune oscillators. I have a sequencer preset that just sends out c3 and mordax tells me not only the note but also the number.
Most analog oscillators are tri or saw core, and use shaping to get sine, so if I'm picky, I would choose a triangle wav, but all of the tuners I've used have accepted any waveform.
cycad73
Dave Peck wrote:
I can more easily hear the up/down 'flanging' harmonic movement of the two oscs when they are slightly detuned from each other and this makes it easier to do the fine adjustment and get them tuned the way I want them (which is often NOT perfectly in tune, it is often with some small amount of intentional detuning to create that 'motion' between the two oscs).


A confession: I almost never use this intentional detuning to create motion, because the beating frequency scales linearly with the oscillator frequency, so high pitches will have this horrible dissonant fast beating, also the varying speed of the motion creates a lot of messiness in the mix. (I know most people love detuned oscillators, but I am an exception) The fix is detuning by constant Hz, but then the oscillator would have to support linear FM and then it's more cumbersome to set up. As is I just lock the frequencies as best as I can, with or without sync and then use vibrato or PWM to create motion. PWM can have the opposite effect, being more extreme at the lower frequencies.

Quote:
TIP: It can be easier to tune oscs by ear if they are both playing a low-midrange note.

If they are playing a much higher pitch it can be more difficult to tune them to each other.


Assuming tracking is perfect, though, you'll get the most exact tuning by doing it at higher pitches. I'd say 800-1000 Hz is my practical limit though, which may be closer to the mid-range you suggest, and is little more than an octave above the 440Hz standard. But it helps, a 1 Hz deviation at 1000Hz will translate to 0.05 Hz deviation at 50 Hz. If you start with 50 Hz and think you've got it "right" because there are a couple of seconds between beats, and play a high note, then you realize you didn't do such a good job.
Dave Peck
cycad73 wrote:
I almost never use this intentional detuning to create motion, because the beating frequency scales linearly with the oscillator frequency, so high pitches will have this horrible dissonant fast beating, also the varying speed of the motion creates a lot of messiness in the mix. (I know most people love detuned oscillators, but I am an exception) The fix is detuning by constant Hz, but then the oscillator would have to support linear FM and then it's more cumbersome to set up. As is I just lock the frequencies as best as I can, with or without sync and then use vibrato or PWM to create motion. PWM can have the opposite effect, being more extreme at the lower frequencies.



There are some tips to help with this:

1. make a note of which osc is calibrated with the keyboard tracking 'wider' and which is 'narrower' and set the wider osc slightly flat relative to the other osc, with a slow beat frequency on a mid-range note. As you play higher, the tracking difference will cause the flat osc to become 'less flat', relative to the other osc, closing the frequency gap between the oscs as you play higher notes, and causing the beat frequency between the two oscs to be a more consistent rate all across the keyboard.

2. Yes, PWM works great for creating a controlled type of motion, and you can fix the problem with PWM 'messiness' on low notes by using a VC LFO that slows down when you play lower notes, creating a similar effect to #1 above.
b9
ornament and crime's references. I use it for a dozen other things as well.
cycad73
Dave Peck wrote:

There are some tips to help with this:

1. make a note of which osc is calibrated with the keyboard tracking 'wider' and which is 'narrower' and set the wider osc slightly flat relative to the other osc, with a slow beat frequency on a mid-range note. As you play higher, the tracking difference will cause the flat osc to become 'less flat', relative to the other osc, closing the frequency gap between the oscs as you play higher notes, and causing the beat frequency between the two oscs to be a more consistent rate all across the keyboard.

2. Yes, PWM works great for creating a controlled type of motion, and you can fix the problem with PWM 'messiness' on low notes by using a VC LFO that slows down when you play lower notes, creating a similar effect to #1 above.


Thanks, both awesome ideas!
Longjonlebon
Oh I love this! Just ordered one on eBay
monads
Dave Jones O'tool+
DAW w/tuner plugin

The above is what I use mostly. The Futhrrrr Generator by endorphin.es has built-in tuners
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