Hexinverter ACXsynth MIDI2CV Manuale utente

HEXINVERTER.NET

presents:

DIY MIDI to CV/Gate Interface

USER/SETUP MANUAL v1.0

Firmware v4.0

Introduction

The ACXsynth MIDI2CV is a DIY (“do it yourself”) MIDI to CV/Gate converter for analogue modular

synthesis. This project was born out of the need for an accurate and readily available eurorack DIY

MIDI-CV project. As a user of modulars myself, I struggled during my DIY modular system’s infancy

to ﬁnd a MIDI-CV interface I could build myself. The only solutions were too expensive, did not ﬁt my

needs or were out of reach at the time.

Rather than develop and code a module from scratch myself to solve the problem, I knew about Alain

Coupel of ACXsynth’s great PIC microcontroller projects for synthDIY hosted on his site ( acxsynth.

com ), so, I asked him if I have his good graces to make a eurorack-centric DIY module out of his

great design. His designs are presented in a mostly open-source 5U format design philosophy, so,

unfortunately the design did not ﬁt into eurorack without a redesign of the hardware.

When I ﬁrst began this project in January 2013 or so, I did not expect for it to take shape the way it

did. A number of bugs in the ﬁrmware were unearthed by people on the forums in which the project’s

development were publicised. Me and Alain communicated through many weeks of long-distance

email tag and worked through much bug-ﬁxing before ﬁnally arriving at the v4.0 ﬁrmware which you

now see present in this hardware design.

This new ﬁrmware adds a number of features and tweaks not present in the older open-source

version on Alain’s site. Do not try to layout your own panel from the panels on his site (or

Re:Synthesis’ for that matter.) The aforementioned panels are for older versions of the ﬁrmware and

will not work with this hardware design.

Please use the 8HP eurorack and eventually 4U dotNET format panel renders present on the

hexinverter.net project page as reference when laying out your own panel for this project!

While Alain and myself strived for perfection with the ﬁrmware and eradicating all of the code

bugs, one bug remains which much problem solving on Alain’s part could not rid of. We have ruled

it out as a shortcoming of the rather modestly specced microcontroller used in the design. If you

are considering this module I urge you to read about this bug and determine if it’s a problem for you

before purchasing:

In Monophonic mode (only), if you bang a whole bunch of keys at once, the module will sometimes

get the GATE output stuck open for a few keystrokes. Seeing as how this occasional error is

Monophonic mode, this shouldn’t be a problem for most users since you play one or two keys at

once only in Monophonic operation, but, if it is a problem for you I strongly encourage you to abstain

from building one of these as it is a problem that cannot be solved without deleting other features

(to free up processing power).

The beta testers agreed that it is not a huge issue, but you may feel differently, which is why I am

telling you. With regular playstyles, it should not be an issue. I can only get it to happen when I’m

trying to make it happen. The beta testers and myself could not replicate the issue during normal

play.

I wish that the ﬁrmware was 100% perfect in every way, sadly the little PIC microcontroller isn’t

quite up to doing everything it does do in Monophonic mode with absolute perfection.

Features and Speciﬁcations

Technical Speciﬁcations

• 8HP eurorack format DIY module

• Requires eurorack standard +/-12V supply

• Stacking board design makes for super slim module

• 55mm depth

Features

• 12bit DACs with Intersil tunable opamps mean great CV accuracy (many commercial MIDI-CVs

have only 8bit DACs)

• 4x CV/Gate outputs allow for 4-note polyphony

• Monophonic mode features full control of one voice (mod, pitch wheel, etc.) as well as full

sequencer controls (stop, run, reset)

• Sync output emits sync pulses when MIDI clock is received

• MIDI channel autolearn at startup means no pesky conﬁguration and very simple hardware

Detailed Feature and Control Descriptions

Mode Select Switch

MIDI2CV has three different main modes of operation. I will do my best to explain them here. The

pitch wheel is active in all modes, but, the mod wheel only functions in Monophonic mode.

Polyphonic 1 Channel (position = UP): In this mode of operation it is possible to play up to 4 notes of

polyphony. The ﬁrst is sent to CV/Gate output 1, the second to CV/Gate output 2, and so on.

Polyphonic 4 Channel (position = CENTRE): Each CV/Gate output is a different channel. The MIDI

channel auto-learned at startup is output 1, then, the following three outputs are increments of one

channel up from that. For example, if the ﬁrst channel is 3, the next channels will be: 4, 5, 6.

Monophonic (position = DOWN): The module operates in full single note mode. While only one note of

polyphony is achieved, this mode allows for full control of one synthesizer voice over MIDI: velocity,

mod wheel and trigger. Additional run/stop/reset outputs allow for control of an analogue sequencer

on top of the single full voice. The note-handling mode in Monophonic is legato. This means the

GATE output only starts a new gate when all previous notes have been released.

SYNC Output

This jack outputs an analogue version of the MIDI clock in the digital data stream. It is 24ppqn and

can be divided down for use driving sequencers and the like. It can be used alongside the run/stop

and reset outputs to control a sequencer while playing in Monophonic mode.

ACT Indicator

This LED is a status indicator for the module. It is lit when the module is ﬁrst initialised and has yet

to detect a MIDI channel. When MIDI clock is being received, it blinks along with the beat which is

emitted at the SYNC output.

NOTE: The following 5 outputs are only present in Monophonic mode. In all other

modes they are CV/Gate outputs for the respective notes/voices...

VEL Output

This jack outputs an analogue control voltage based on the velocity of the struck note. Use it to

control ﬁlter cutoff, VCA volume, whatever you like!

MOD Output

This output produces an analogue control voltage based on the position of the mod wheel on the

input MIDI keyboard/controller.

TRIG Output

This jack outputs a short trigger pulse every time a note is struck, regardless of whether or not it

is actually a new note. You can use this output to retrigger envelopes to get staccato style playing

rather than the legato style note handling offered by the GATE output in Monphonic mode.

RUN/STOP Output

Use this digital output to start and stop a sequencer from a MIDI sync source. RUN = high, STOP =

low.

RESET Output

Use this digital output to reset a sequencer from a MIDI sync source. This output is active high

(RESET = high)

Tuning Your ACXsynth MIDI2CV

In order to achieve accurate CV conversion, it is necessary to tune your MIDI2CV module once you are

ﬁnished building it. In order to accurately tune the module, you will need a decent multimeter. A $10

multimeter will not yield perfectly accurate results. Spend $100 on a decent quality meter and you

will be very happy you did (not just for this project, but for others as well).

Tuning the module is quite easy. Just follow these steps:

1.) Plug the module into your system, turn it on and let it warm up for 30 minutes.

2.) Make sure the module is in MIDI learn mode by quickly resetting the power to your system. Don’t

press any keys on your MIDI controller yet or send any SYNC data to the module via MIDI.

3.) Plug your multimeter into each CV output and tune the OPAMP TUNING trim potentiometer for

the CV output you are tuning so that the respective CV output reads as close to 0.000V as possible. If

you cannot get to 0.000V, it’s probably because you did not listen to me and used CA3140AEZ opamps

instead of CA3140EZ like I said to use in the Bill of Materials!

4.) Now, plug in your MIDI keyboard and tune the CV outputs for V/oct scaling. Plug a CV output into a

VCO in your system and either:

Read the frequency of the VCO and adjust for v/oct

Read the voltage out of the CV output of the MIDI2CV module and adjust for v/oct.

I like the second method, myself.

Whatever method you choose, you tune the CV output by stepping up and down octaves on your

keyboard and verifying that the voltage/frequency has doubled each octave you step up.

Whichever method works best for you is the one you should use!

Your MIDI2CV is now setup and ready to use!

Indice

Altri manuali hexinverter Apparecchiature di registrazione

hexinverter

hexinverter SYMPLESEQ MKII Manuale utente

Manuali Apparecchiature di registrazione popolari di altre marche

KV2 Audio

KV2 Audio 500 Series Manuale utente

Robotics Technologies

Robotics Technologies microBus-Cam II Manuale utente

Seca

Seca 460 Manuale utente

Cognex

Cognex MVS-8000 Series Manuale utente

Mect

Mect MPNC006 Series Manuale utente

Bad Caf

Bad Caf THE LEASH Manuale utente

Strymon

Strymon NIGHTSKY Manuale utente

Mitsubishi Electric

Mitsubishi Electric 16CH DIGITAL RECORDER DX-TL5000U Manuale utente

Tews Technologies

Tews Technologies TPMC465 Manuale utente

Honeywell

Honeywell Excel 50 Manuale utente

SeaLevel

SeaLevel COMM+8.LPCI Manuale utente

Arturia

Arturia AUDIOFUSE STUDIO Manuale utente

Rukra

Rukra RK-1240 Manuale utente

Samson

Samson SCOM Manuale utente

Dynacord

Dynacord DPS260 Manuale utente

Nice

Nice Core Manuale utente

Pyle Pro

Pyle Pro PSS8 Manuale utente

RF-System

RF-System TinyGate Manuale per l'uso e la cura

hexinverter ACXsynth MIDI2CV Manuale utente

Manuali Apparecchiature di registrazione popolari di altre marche