Line 6 VDI Interface

Started by Elantric, January 30, 2015, 09:31:21 AM

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Elantric

All Variax's employ the Line -6  VDI 8 pin CAT-5 RJ-45 Interface.

This transports standard 24 bit  AES/EBU Digital Audio and standard MIDI I/O
http://bencraven.com/?p=1616










Its possible to design an interface that allows the Variax to be a MIDI controller for third party gear  - using a MIDI Solutions Processor Plus

Or the opposite - use MIDI to remote control the settings on the Variax Guitar

Must initiate AES/EBU and MIDI I/O by transmitting to Variax the special MIDI SYSEX MESSAGE -Its contained within the graphic of this photo at center bottom

SYSEX F0 00 01 0C 07 00  2A F7

mbenigni

QuoteIts possible to design an interface that allows the Variax to be a MIDI controller for third party gear  - using a MIDI Solutions Processor Plus

Cool tip!  I never thought about which protocol Line 6 was using for Vetta/PODxt control - I just assumed it was something proprietary.

HAMERMAN409

Keep in mind that while the signals are MIDI in this implementation the optical isolation happens inside the VDI interface box so you lose that when you go direct to the RJ-45. The signals still run to a RS422 buffer so it's not like it's dangerous - just different. :-)

LinzHenderson

I've been using a modified VDI cable for years as a means to remotely change Variax sounds via MIDI. It's very simple and works great.

However, I've recently been testing a setup using the digital out from the VDI. It's a simple conversion - AES-SPDIF-Analog. However, I'd just assumed that Line 6 were able to access the mags and modelled sounds separately by feeding one to the left channel and one to the right, but that doesn't seem to be the case. It's always the same signal that the Variax jack socket gets, i.e. if the model button's on, it's modelled sounds, if it's off it's mags.

Does anyone know how Line 6 get the separate signals into the Pod HD/Helix/etc.?

Elantric

#4
There is probably a MIDI command from Helix / HD500X used to inform the Tyler Variax DSP board to route both mag and DSP Modeled tones at same time down the VDI cable

A MIDI packet sniffer utility might assist.
https://www.vguitarforums.com/smf/index.php?topic=2975.0
Given the numerous complaints about  warbling or normal PU bleed when DSP Alt Tuning is activated on the Line-6 Forums  - I always assumed Tyler Variax transmitting both Mag PU tones and DSP Modeled tones down the VDI cable via AES/EBU  at same time was a "bug"  -


Use FiiO D3 DAC Box with AES/EBU signals



FiiO D3 DAC Box
https://www.vguitarforums.com/smf/index.php?topic=9163.msg66031#msg66031


LinzHenderson

Good thinking on the MIDI commands, Steve. I'll try something this weekend and report back.

I'm using little DAC similar to the Fiio, and the quality's excellent!

XavierB

And? Did you find a way to send the mag signal?

Elantric

It can't happen on older hardware

Need a JTV DSP board if you want to send mag PU signal down VDI cable

XavierB

Fair enough... Do you know which MIDI signal you have to send to the Variax so that it outputs both the virtual and mag to the AES port?

Elantric

#9
No - start at first post, read entire thread to read suggestions for discovery

XavierB

For now I'm mostly interested in changing the Variax presets via MIDI. I've ordered a cheap MIDI cable that I can sacrifice, and looking at the diagram at the top of the post it looks like I need to make a DIN to RJ45 (VDI) cable that "follows" the green arrows (the ones going from DIN 5 & 4 connected to pins 6 & 3 of the RJ45). I should then be able to connect this cable to the MIDI OUT of my MIDI interface and I should then be able to send Program Change MIDI messages, and my Variax (a JTV89) should switch the presets accordingly.

Is this correct? Has anyone (LinzHenderson?) done that successfully?

The reason I thought I would check is that it's a MIDI OUT but the arrows go out of the Variax, I would expect them to go in since that's the direction the data should flow.

Elantric

#11
This is accurate

Variax VDI Debug Interface with a RJ-45

Arrows for MIDI data flow direction are accurate

Quotelooking at the diagram at the top of the post it looks like I need to make a DIN to RJ45 (VDI) cable

Its a break out adapter comprised one  RJ-45 (Variax side) to CAT-5 cable that breaks out as follows:

1 = GND
2 = PWR (+7VDC)

4 AES/EBU- (24 bit PCM Audio @ 48k)
5 AES/EBU+ (24 bit PCM Audio @ 48k)

3 TX+ (MIDI Out +)
6 TX- (MIDI Out - )

7 RX- (MIDI IN + )
8 RX- (MIDI IN - )

Parts required  Two 5 pin DIN Plugs (MIDI I/O)
* One XLR Male (AES/EBU Out) and
* DC Coax plug conected to source for +7VDC Power @ 500mA

QuoteFor now I'm mostly interested in changing the Variax presets via MIDI.
That should be possible with original Variax 300/500/600/700 and pre HD 2.0 JTV series



But rumor is HD 2.0 or newer firmware on Tyler Variax (JTV-59, JTV-69, JTV-89) now uses undocumented MIDI Sysex / NRPN messages   

XavierB

@LinzHenderson, do you have as JTV on firmware 2 or more?

tone_crafter

Sorry to resurrect an old thread.

I'm wondering if anyone got anywhere further with reverse engineering the Variax control protocol (JTV with 2.0 firmware or newer). I have read in several places that with this new "HD" firmware Line6 no longer use standard midi PC and CC messages to switch models and tunings and adjust volume/tone knobs. Is this true? I would like to make a simple VDI to midi interface so I can use my midi foot controller to adjust Variax settings.

I would attempt to reverse engineer the protocol myself but I don't own a Helix or similar, only a JTV59.

Elantric

#14
The JTV VDI hardware interface is same as old Variax  - and described here
https://www.vguitarforums.com/smf/index.php?topic=13484.msg128343#msg128343


if you build this "Variax VDI Debug Interface with a RJ-45", you should be able to connect to the JTV RJ-45 Ethercon connector  and use standard MIDI Message monitor techniques to reverse engineer the JTV MIDI message packets

   standard MIDI Message monitor techniques are all described here:

MIDI controller Setup / Debug
https://www.vguitarforums.com/smf/index.php?topic=2975.0

tone_crafter

Yes I understand this but I don't own a device I can interface my JTV59 with (such as a Helix) in order to reverse engineer the commands so I am wondering if someone has done this already (with a JTV with firmware 2.0 or newer).


XavierB

#17
@tone_crafter I made myself a cable that works (can send/receive MIDI to/from Variax using my PC) by following the diagram in this post, and the cable looks like Ben Craven's breakout cable, as per this page:
http://bencraven.com/?p=1616

https://web.archive.org/web/20150810124803/http://bencraven.com/?p=1616

tone_crafter

I'm fine with the electrical side of the VDI interface.

I'm wondering about what midi messages are used to change guitar models and knob settings etc. I've read that for JTVs with firmware newer than 2.0 Line6 are now using a custom messaging protocol (sysex messages?).

admin

#19
Quote from: tone_crafter on August 31, 2017, 12:41:31 AM
I'm fine with the electrical side of the VDI interface.

I'm wondering about what midi messages are used to change guitar models and knob settings etc. I've read that for JTVs with firmware newer than 2.0 Line6 are now using a custom messaging protocol (sysex messages?).

I'd start with attempting the known Variax control messages and see if you get a response from the JTV




XavierB

@tone_crafter - I can confirm that the standard PC MIDI messages still work with the JTV and newer firmwares, I have v2.21 on my Variax and it works fine.

I used a MIDI monitoring software (IIRC one of the REAPER plugins) to find out the SYSEX used to switch to another tuning using MIDI, and sending that to the Variax worked. Basically, you plug the Variax OUT into the IN of a computer and watch the MIDI messages it sends - you can find out anything the Variax will reply to that way. Another SYSEX that was useful was for the one to switch to mag (instead of piezo) pickups and vice versa, but these days I use a model that has a mix of piezo and mags, that's a lot easier.

cags12

#21
Quote from: XavierB on September 19, 2017, 01:58:35 AM
@tone_crafter - I can confirm that the standard PC MIDI messages still work with the JTV and newer firmwares, I have v2.21 on my Variax and it works fine.

I used a MIDI monitoring software (IIRC one of the REAPER plugins) to find out the SYSEX used to switch to another tuning using MIDI, and sending that to the Variax worked. Basically, you plug the Variax OUT into the IN of a computer and watch the MIDI messages it sends - you can find out anything the Variax will reply to that way. Another SYSEX that was useful was for the one to switch to mag (instead of piezo) pickups and vice versa, but these days I use a model that has a mix of piezo and mags, that's a lot easier.
Would you mind sharing the list of SYSEX messages you mentioned and any other CC and PC that you know about? Let's start building the MIDI reference guide :)

Magiamusical

Excuse my ignorance, would this be useful for controlling the JTV from a midi pedalboard, ej. Changing the models with a MIDI command, or with Set List Maker?
Godin LGXT, Les Paul Studio w/GK3, JTV89F w/GK3, GR-55

Elantric

#23
Quote from: Magiamusical on September 19, 2017, 08:35:38 AM
Excuse my ignorance, would this be useful for controlling the JTV from a midi pedalboard, ej. Changing the models with a MIDI command, or with Set List Maker?

Correct!

QuoteWould you mind sharing the list of SYSEX messages you mentioned and any other CC and PC that you know about? Let's start building the MIDI reference guide :)

So far we know these

tone_crafter

Quote from: XavierB on September 19, 2017, 01:58:35 AM
@tone_crafter - I can confirm that the standard PC MIDI messages still work with the JTV and newer firmwares, I have v2.21 on my Variax and it works fine.

I used a MIDI monitoring software (IIRC one of the REAPER plugins) to find out the SYSEX used to switch to another tuning using MIDI, and sending that to the Variax worked. Basically, you plug the Variax OUT into the IN of a computer and watch the MIDI messages it sends - you can find out anything the Variax will reply to that way. Another SYSEX that was useful was for the one to switch to mag (instead of piezo) pickups and vice versa, but these days I use a model that has a mix of piezo and mags, that's a lot easier.

I'd be really grateful (as I'm sure a lot of others would too) if you could share the messages you have found to work!