Hapax CV v/oct range options

Hi - I have just unboxed my Hapax and started to use it tonight with Plaits. Plaits uses -3v to +7v/oct range, and it looks like, as of now, there is only -5v to +5v and 0v to +5v available with the Hapax. I am just a few months into eurorack, what is the best path forward here?

honestly, this is a common dilemma in eurorack, as v/oct range is not standardised.

I think the key thing here, if you are new to eurorack, is always v/oct is RELATIVE.

1v does not mean C5 , it means 1 octave above the base frequency of the oscillator.

so the fact that the ranges differs does not matter at all!

so, I often just use 0-5v, as 5 octave is enough esp. given tracking of some oscillators.
though, you can use +/-5v , so you get -3v to +5v, so get 8 octaves.

in both scenarios, you can use the frequency knob, to decide where the start of this range is.

if you want the full 10v range… you’ll need essentially need
a) a precision adder
b) a (reliable!) voltage source to generate 2v

basically you can then add a constant 2v to get -+5v to -3 to +7v - easy.
important to use a precision adder, otherwise you’ll not get a good result.

you’ll likely find a module that’ll will do both in one module…perhaps look for a ‘transpose’ module.

note: its unlikely you’ll get the full 10v range accurately, as most opamps will tend to drift at the ‘rails’.
so its unlikely either hapax or plaits will track well at the extremes.
(Id say ± 0.1 v … but Ive not checked)

2 Likes

Your explanation has helped me reclaim a bit of sanity! Thanks!

With that being said, there are going to be situations where the note that is displayed on the Hapax screen will be octaves different than what is being played. Is that another thing I should accept and adjust for?

you’re still gonna have an 8 octave range with -3v to 5v so that covers a lot of territory.

also, there is an alternate firmware for plaits that i use that turns the frequency knob into an octave shifter, which i love. you may wanna put this on your plaits as it makes it really easy to shift the range.

this is always going to be true in Eurorack !
pretty much every oscillator has a frequency knob, so depending on its position - will determine what octave range you are in … or if you are doing some other kind of transposition.

as I said, v/oct is relative in eurorack.

I think this is one of the early ‘gotchas’ in peoples eurorack adventures.
most come from midi, where we talk about absolute pitch… where midi note 60 = C4 (ok, or C3 for some manufactures)… its just not like that in eurorack.

for many beginners, they will then just set the frequency so that they appear to get this same relationship… but that builds a misunderstanding in the fundamental nature of v/oct!

another thing you are going to bump into quickly, is v/oct is never 100% accurate !
even if you calibrate everything, you will alway find a certain amount of mismatch.
…if you don’t accept this, theres a chance you’ll continuously chase your tail seeking perfection.

so no, there is no issue… nothing to accept/adjust … this is the nature of eurorack, and nothing is wrong here… set the frequency of oscillators is part of setting up the patch, not a set and forget.

overall, eurorack is delightfully imperfect, embrace this… (or ditch it :wink: )


p.s. whilst in this case, I think its unlikely you need to offset the voltage… a precision adder is a very useful module in eurorack… and helps to get you thinking in relative terms…
e.g. using two sequencers to drive the pitch sequence, where one is used as a relative offset.

(oh, and if you are going to do this, you’ll need a decent S&H module too !)

I suspect this thread has resulted in a eureka moment for some. :slight_smile:
So the Disting Mk4 (and likely other versions) has an algo (A-1) called “Precision Adder” that might be worth considering.

A = X + Y + offset, or X + offset
B = X – Y – offset, or Y ± offset
offset = ±10V in 1V steps derived from Z

Param Val Output A Output B Notes
0 Sum of inputs X & Y, plus the offset. Difference between inputs X & Y, minus the offset. With nothing plugged into input X, B is therefore simply an inverted copy of Y.
1 X plus the offset. Y minus the offset. This is particularly useful for shifting between bipolar (e.g. ±5V) and unipolar (e.g. 0-10V) CVs and back again.
2 X plus the offset. Y plus the offset.