Eurorack Synth Build for Roland GK-3 & Cycfi Nu Guitar Single-string Processing

Started by GuitarBuilder, June 10, 2019, 09:32:52 AM

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GuitarBuilder




With this thread I hope to provide regular updates on my latest idea: a guitar processor (mostly analog) that retains single-string audio processing all the way to the output, including the ability to drive synths.  I'm a huge fan of control voltage (CV) systems (I built my first guitar synth in the late 70s using CV control from the guitar and foot pedals) for synth control, so the Eurorack format was a natural choice for me.  I like the performance of my Fishman TriplePlay (FTP) system, but there is something about guitar to MIDI conversion that feels unnatural to me; my motivation is partly driven by the superb playability of my Roland GR-300 - I would like to see if I can come close to that with this new processor.  Of course MIDI will be used for presets - there can be no knob twiddling while playing guitar.

The concept is as follows for a 6-string guitar (but can be expanded/reduced for any number of inputs):

Guitar with hex pickup > Eurorack hex breakout > Hex pitch shift > Hex audio controlled oscillator (ACO) > Hex audio mixer > Hex voltage controlled filter (VCF) > Hex voltage controlled amplifier (VCA) > Hex output mixer

The main goal is to retain analog audio processing as much as possible; this is obviously not the case with pitch shift.  At the ACO stage the signals will be split for parallel processing (guitar + oscillator) with a voltage-controlled mixer ahead of the VCFs. Of course the requisite support modules (Hex VU meter, low frequency oscillators, envelope generators, CV-MIDI-CV, etc.) will all be there.  Another advantage of the Eurorack approach is the ease of experimenting with different modules, either home-made or commercially available ones, with essentially unlimited parallel/matrix processing.

Modules that are currently not commercially available include the hex breakout, hex pitch shift, hex VU Meter, and hex ACO.  For the hex breakout I have three designs: a) GK 13-pin input breakout with amplifier/attenuator, b) GK 13-pin output breakout with amplifier/attenuator, and c) Cycfi Nexus 19-pin input breakout with amplifier/attenuator.  The GK 13-pin input and output breakout modules have just been completed; the Nexus 19-pin input breakout module is in the PCB fabrication stage. For convenience all modules have input/output pin headers on the back which are useful for permanent connections, such as audio paths.

GK 13-pin Input Breakout close-up:


Next to Antares ATG module and input Hex VU Meter:


GK 13-pin Output Breakout close-up:


Next to output Hex VU Meter:


The 16HP input module breaks a GK guitar output into 6 individual string channels and 1 traditional pickup channel. These are fed into 7 amplifier/attenuator circuits with up to 10x gain to match the typical Eurorack module signal levels. This module also supplies +/- 7V to the guitar, just like a Roland/BOSS synth would. All GK control voltages are broken out as well.

The 16HP output module does the reverse: 7 attenuator circuits bring the signal back down to GK levels and provide a 13-pin output to your favorite synth, as well as all GK control voltages.

In another post I showed my first attempt at an Antares Autotune for Guitar (ATG) Eurorack module:
https://www.vguitarforums.com/smf/index.php?topic=25404.0.  This module uses the ATG Luthier Kit parts and replicates the entire guitar installation in a 10HP Eurorack module.  Since Antares would not provide a hexaphonic output (not sure why, the DSP is processing 6 channels in parallel!), I decided to splurge and create six Eurorack ATG modules, each processing only one string! Brute force and expensive, but I happen to have a lot of ATG Luthier Kits! The hex pickup inputs are routed inside the case via a custom ATG connector breakout board, so no patch cords are needed on the front!
One unintended benefit of this approach is the ability to process each string with different ATG settings; this opens up a large number of new tonal possibilities beyond even the Axon or FTP fretboard split approach. Not shown is a master module that controls the parameters of all six ATGs at once, as well as MIDI control via iPad with MIDI Designer.

I love visual level indicators and a Hex VU Meter is a must for proper input and output level control.  I couldn't find one of those either, so here is my design.

Hex VU Meter 10HP Module:


The ACO module will essentially be a Sonicsmith ConVertor+ (https://sonicsmith.com/products/convertorplus/) in Eurorack format, based on the new ACO160 audio controlled oscillator available this summer (https://secondsound.com/aco160/).  Since that is a monophonic device, six modules will be necessary for this application.  The outputs are triangle, square, and sine waves; CV out includes pitch (V/oct), envelope, and gate/trigger.  There is the option to create MIDI note out via an SPI interface as well. although that is not my first choice at the moment.  As mentioned earlier, the six ACO synth outputs will have their own parallel channels from the six single-string channels.  The key mixing points are at the Hex VCF and/or Hex VCA inputs, voltage-controlled of course!

I plan on using commercially available VCF, VCA, Hex Mixer, LFO, AR, and ADSR modules to start; another key feature will be the ability to use effects loops on each single string processing channel and patch in cool guitar pedals either before the VCFs or at the VCAs.  The output section will be hexaphonic - I feel this is an important feature: why process single-string audio only to mix it back to mono or stereo in the end?  I'd like to experiment with six amplifiers and speakers in different spacial arrangements (perhaps I'm still in awe of my first Pink Floyd live quadraphonic concert!).  The VCAs will come in very handy in moving the sounds around spatially!

Below is a shot of the Eurorack chassis I will be using for the initial phase of this effort:


This was taken at an earlier time when all I had was one Hex VU Meter and a bunch of blank panels!  BTW - all panels were made using Front Panel Express (https://shop.frontpanelexpress.com/index.php#Shop).  The TipTop Audio Mantis case (http://tiptopaudio.com/mantis) is quite nice, but not large enough to hold all modules in the final configuration.  I will likely move to two Intellijel 7U Performance Cases (https://intellijel.com/shop/cases/104hp-84hp-7u-performance-case/) in the end - these have cool 1U strips where I can place the effects loops, MIDI, and various pro audio connections.

Progress is slow but steady due to my guitar build projects (stay tuned for a triple Cycfi Research Nu Multi pickup Strat with electronic hex pickup switching and built-in hex VCF/VCAs!) and I will make a point of providing regular updates as I progress.  Sometimes I wonder why I took on such a huge project!

One interesting intermediate product is the standalone fully Hexaphonic ATG; this is not extremely large like my crazy idea above - only 112HP total in a single 3U rack; here's a mock-up using MODULARGrid:

I plan on building this first using a Roland VG-99 stand and iPad; with MIDI Designer controlling all six ATGs it should be usable without any patch cables!

Finally, I will be looking for VG guitarists who would be willing to test and record demos of the Hex Autotune Processor and the Single-string Analog Guitar Processing monster in my studio when finished.  PM me if you're interested!
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973


whippinpost91850


chrish

RIGHT ON!!!!!!

Quote: "perhaps I'm still in awe of my first Pink Floyd live quadraphonic concert"

Right there with ya. I saw the Dark Side of the Moon concert at the Merriweather Post Pavilion, Maryland. They sent that "on the run" riff circling all around the audience and it was incredible.


Fwiw, Here is how to create that sequencer patch.



AlakaLazlo

This looks extremely interesting! This reminds me of the original 360 systems guitar synth which had 6 pitch to voltage converters driving 6 Oberheim SEMs. Hopefully, this will track better!!! Do you have any plans for some form of patch control system?  I'm a 5U guy, but If you actually pull this off, I may well have to jump into the Eurorack world...
Hexstainocaster, Fender Strat and Electric XII, Godin ACS, Axon AX50 - Moog One, IIP and Mini, SEM, Dot.Com/Moon/STG/FSFX 110, Cubase Pro, 2xMR816, HR824, NS10M, Komplete, Omnisphere/RMX/Trilian, Z3ta+, Analog Lab, Slate MTi2, ML1 and Everything Bundle, Social Entropy Engine, ESQ1, DX7, Lavalamp.


chrish

Quote from: AlakaLazlo on June 10, 2019, 02:26:09 PM
This looks extremely interesting! This reminds me of the original 360 systems guitar synth which had 6 pitch to voltage converters driving 6 Oberheim SEMs. Hopefully, this will track better!!! Do you have any plans for some form of patch control system?  I'm a 5U guy, but If you actually pull this off, I may well have to jump into the Eurorack world...
the converter+ by sonic smith,  which uses the ACO100, chip, tracks great. But it is monophonic and playing more then one string at a time or sympathetic string resonance produces pitch tracking artifact noise.

The solution is having one converter+ type unit assigned per string which is what Guitarbuider is doing and what I hope to accomplish as soon as I get some more swag together. I'm thinking of  just using two VCfilters and VCAmps however, in order to cut expenses.

That hexaphonic system is of course also how the GR300 accomplished it's excellent pitch tracking performance with one voice card per string along with some analog circuit Magic.

https://www.joness.com/gr300/GR-300.htm

BTw, The latancy of the converter+ is measured in microseconds, whereas the GR300 has 3.32 milliseconds of latency.

https://www.joness.com/gr300/MIDI_SPEED.htm



I own a GR300 and one converter+ and the tracking makes both feel like the guitar string is the oscillator and directly responsive to guitar technique.

Hard to describe, but pitch to midi systems feel somehow detached from the playing experience, imo.


GuitarBuilder

#7
Quote from: AlakaLazlo on June 10, 2019, 02:26:09 PM
This looks extremely interesting! This reminds me of the original 360 systems guitar synth which had 6 pitch to voltage converters driving 6 Oberheim SEMs. Hopefully, this will track better!!! Do you have any plans for some form of patch control system?

The cool thing about this approach is that there is no tracking required for the single-string guitar audio channels.  The parallel synth output tracking will be governed by the ACO160 in the ACO modules; I plan to evaluate this chip as soon as it is available later this summer.  Its predecessor, the ACO100 has shown some promising results - check out the Sonicsmith ConVertor+ demos on Youtube.  My primary goal is to avoid pitch-MIDI unless absolutely necessary.

I have not yet thought about a patch control system; like I mentioned, I make all front panel jack connections available on headers in the rear of the modules so I can put the permanent patches inside the case.  In principle that makes it possible to rearrange patches via analog switches and MIDI presets.  I'm already planning on using MIDI Designer on my iPad to control the ATG modules, so adding the other modules would be a matter of a creating MIDI analog switch patch and CV control board and updating the existing MIDI Designer interface.  Like I said, I haven't worked it out yet!
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

GuitarBuilder

#8
Quote from: chrish on June 11, 2019, 11:17:50 PM
BTW, The latency of the converter+ is measured in microseconds, whereas the GR300 has 3.32 milliseconds of latency.

I have a GR-300 as well and consider that the benchmark for my system (and any other for that matter!).  I still don't understand how Wayne Joness got a 3.32 millisecond latency out of that purely analog circuitry, which generates the synth waveforms directly from the guitar signal.  I would love to see that measurement repeated!  ;D ;D

On the flip side, I also don't understand how the ConVertor+ can have microsecond latency when it does have a digital pitch detection algorithm that takes exactly one audio cycle to execute! This will be one of the first things I'll measure when evaluating the ACO160.   ::) ::)

Quote from: chrish on June 11, 2019, 11:17:50 PM
I own a GR300 and one converter+ and the tracking makes both feel like the guitar string is the oscillator and directly responsive to guitar technique.

It's an absolute joy to play the GR-300 compared to all the other synths I own (GR-55, GP-10, SY-300, VG-99, FTP).  I really don't like the idea of changing my guitar playing style to accommodate the synth.

Quote from: chrish on June 11, 2019, 11:17:50 PMHard to describe, but pitch to midi systems feel somehow detached from the playing experience, imo.

Totally agree; this is why I'm trying very hard to avoid pitch-MIDI!  8)
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

jim-analog



Greetings,

Keep up the GREAT work Guitar Builder. Everything looks fantastic. You may want to look into some of the newish "pico-processors" such as the Teensy or Aurdino as a knob/switch position memory system and patch recall. You know what I had i mind, but this could be a much simpler method to use. There seems to be quite a lot of programming expertise on these devices by people who are also musicians. Might be worth a look..............

Regards, Jim

vanceg

This really does look stunning.  The 6xATG is insane... and beautiful.
I'd personally LOVE to try this system someday.

chrish

.
Quote from: GuitarBuilder on June 12, 2019, 08:06:29 AM

On the flip side, I also don't understand how the ConVertor+ can have microsecond latency when it does have a digital pitch detection algorithm that takes exactly one audio cycle to execute! This will be one of the first things I'll measure when evaluating the ACO160.   ::) ::)


Perhaps the clue is in this statement by sonicsmith.

"and play analog synth along with the source"

I'm thinking the latency is measured with the source audio added to the equation.


" The ACO chip can track the fundamental frequency (aka pitch) of an incoming audio signal and play analog synth along with the source at extremely high and dynamic rates so latency is imperceptible. In fact, the ACO's latency cannot be measured in milliseconds. You'll have to steer off to single-digit microseconds to measure latency from this silicon marvel"

https://sonicsmith.com/audiocontrolledoscillator/

GuitarBuilder

Another module almost done!  This is the Eurorack Nexus Breakout Module with a 19-pin LEMO-compatible jack by Cycfi Research.  This is a great alternative to the 13-pin GK Breakout Module: 15 Channels of audio or control voltages, +12v/-12V/+5V supplies.  Channels 1-8 are brought out to single jacks, while channels 9-15 can be assigned to separate audio or CV jacks via a header on the back of the board.  Here are some preliminary photos of the board and 19-pin jack while I wait for the front panel to be fabricated:





A companion Nu Internal Breakout Board was also created to be used inside the guitar.  This board has two headers for Cycfi Research Nu Multi 6 pickups, as well as breakouts for Channels 7-15, each with +12v and GND.  All headers are horizontal to conserve space in the guitar.




A future thread will feature my Triple Cycfi Research Nu Multi guitar with hex electronic switching, touch control, and on-board VCF/VCA module.  Stay tuned!
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

gumbo

"A future thread will feature my Triple Cycfi Research Nu Multi guitar with hex electronic switching, touch control, and on-board VCF/VCA module.  Stay tuned!"

...no coffee maker ??    ::)
Read slower!!!   ....I'm typing as fast as I can...

billbax

Hi GuitarBuilder,

Your 13-pin creation is at the forefront with other forum elite hardware endeavours! What you have achieved looks like a lot of hard work, and the forum is better for it. Brilliant!

Bill

GuitarBuilder

Quote from: billbax on July 05, 2019, 05:59:25 AM
Hi GuitarBuilder,

Your 13-pin creation is at the forefront with other forum elite hardware endeavours! What you have achieved looks like a lot of hard work, and the forum is better for it. Brilliant!

Bill

Coming from you that means a lot to me, Bill!  Cheers!
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

Brak(E)man

Man this looks nice!
I'm already into modular
so I guess I'm going down this rabbit hole to.

Great stuff!
swimming with a hole in my body

I play Country music too, I'm just not sure which country it's from...

"The only thing worse than a guitar is a guitarist!"
- Lydia Lunch

GuitarBuilder

Quote from: gumbo on July 05, 2019, 02:41:30 AM
"A future thread will feature my Triple Cycfi Research Nu Multi guitar with hex electronic switching, touch control, and on-board VCF/VCA module.  Stay tuned!"

...no coffee maker ??    ::)

Regular or Decaf?
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

GuitarBuilder

Quote from: vanceg on June 12, 2019, 09:05:18 PM
This really does look stunning.  The 6xATG is insane... and beautiful.
I'd personally LOVE to try this system someday.

I'd be honored to have you try it, Vance!
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

GuitarBuilder

The Eurorack Nexus 19-pin Breakout Module is done!  This module is specifically designed for the Cycfi Research Nu Multi/Nexus polyphonic pickup system:

https://www.cycfi.com

I essentially created a Eurorack version of their Nexus breakout box, with a few changes:


Front panel view of the Eurorack Nexus 19-pin Breakout Module

Instead of 1/4" TRS outputs on the back of the Cycfi Research Nexus, this module breaks all 15 audio and CV channels out into 3.5mm jacks on the front panel.  In addition, a 16-pin header on the back provides another breakout for permanent wiring (all my Eurorack modules have this).  Channels 1-6 are assigned to audio only; channels 7-8 can be configured on the guitar's Internal Breakout Board as either audio or CV - this was done to accomodate 7- and 8-string polyphonic pickups.  Channels 9-15 can be directed on the back of the Eurorack Nexus Breakout module to either a dedicated audio or CV jack on the front panel.


Rear view of the Eurorack Nexus 19-pin Breakout Module showing 16-pin Output header and Channel 9-15 Audio/CV Selection header


Closeup of the Channel 9-15 Audio/CV Selection header

So what are the differences between the GK 13-pin Input/Output Breakout Modules and the Nexus 19-pin Breakout Module?

1.  GK 13-pin modules have the standard 6 strings + guitar audio channels (for a total of 7), while the Nexus 19-pin module has a total of 6 audio and 9 audio/CV channels (up to 15 audio)

2.  GK 13-pin modules have the standard Roland/BOSS CV signals broken out (GKVOL, MIX SW, SW1, SW2) while the Nexus 19-pin module has up to 9 CV channels available (the companion guitar Internal Breakout Board has dedicated headers for each along with either +5V or +/- 12V power)

3.  GK 13-pin modules have a built-in 7-channel amplifier/attenuator (zero signal - 10x amplification) to match the input audio to Eurorack module levels and back down to GK levels, if necessary.  Amplification is selectable on the back as either 1x or 10x.  Nexus 19-pin module does not have this built in, since the audio levels are already at +/- 12V.  However, a stand-alone 7-channel Amplifier/Attenuator Module is already in the design pipeline!

4.  The GK 13-pin Input Breakout Module supplies +/- 7V to the guitar just like a Roland/BOSS Synth.  The Nexus 19-pin Breakout module supplies +/- 12V and + 5V to its companion guitar Internal Breakout Board to power the Nu Multi pickups, CV pots, and any on-board electronics (more to come on this: the Triple Nu Multi guitar with on-board hexaphonic switching, VCF, and VCA).

I switched cases!  My TipTop Audio Mantis case is brilliant, but unfortunately not large enough for the final configuration.  I just got the Intellijel Performance 7U 104HP case:

https://intellijel.com/shop/cases/104hp-84hp-7u-performance-case/

Note the 1U strip near the top, which is very handy for I/O modules.  I already have the GK 13-pin and Nexus 19-pin breakout modules on the 1U design list!  In addition, the Audio/MIDI/USB breakouts on the rear panel are awesome; I wonder why other case manufacturers have not thought of this!  The case has a metal lid and is designed for travelling; this will come in handy when shipping the processor to a few lucky guitarists who will assist me with demos!  The final configuration will be two Intellijel cases that join together with joiner plates within a few seconds.

Here are all the modules completed to date in their new case:


Top row from left to right: Nexus 19-pin Breakout, Hex VU Meter, ATG, GK 13-pin Output
Bottom row from left to right: GK 13-pin Input, Hex VU Meter
Not shown: Five additional ATG modules, GK +/- 7V power module


Close-up of modules completed to date

Stay tuned - there's lots more to come!
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

jim-analog

 
Greetings,

GREAT work Peter! Keep it going and us posted on progress. I'm way behind here..........

Regards, Jim


scratch17

Thanks for doing this amazingly deep project. In essence, I regard your efforts here as a proof of concept lab for my own project with Nu2 Multi and Fishman Fluence pickups.

QuoteThe Nexus 19-pin Breakout module supplies +/- 12V and + 5V to its companion guitar Internal Breakout Board to power the Nu Multi pickups, CV pots, and any on-board electronics (more to come on this: the Triple Nu Multi guitar with on-board hexaphonic switching, VCF, and VCA).

I am patiently waiting for details on the Triple Nu Multi guitar because I cannot decide on whether to add a single Nu Multi or two of these pickups to my Hamer Duotone.

I know I will replace the stock Seymour Duncan humbuckers with a pair of Fishman Fluence Open Core humbuckers wired as dual mono.

Your experiences with the Triple Nu Multi will inform me as to the tonal benefits of two Nu2 Multi pickups versus one.

If I go with 2 Nu2 Multi's, I will have to use 2 Lemo cables to handle the needed audio channels (12 Nu2, 2 magnetic from the Fluence Open cores and 1 from the piezo built into the Duotone). By themselves, there will be 15 channels of audio in this configuration. So you'd have no room left for CV controls.

If you did this configuration you would need a second Lemo output plus a second cable and breakout. With two breakouts, you'd have enough channels to have 15 audio channels and 15 CV channels. My Hamer already has two standard 1/4" jacks to handle the mag and piezo pickups. So using two slightly larger Lemo cables in their place is not a big deal to me.

One of the really radical ideas I am exploring is the idea of using CV to select each of the Fluence pickup's three voices. I'd use a CV to MIDI converter to use my RJM Mastermind GT to switch voicing, and pickup on/off on the fly. I'd also like to explore a MIDI controlled balance between the two pickups using an expression pedal.

Note that the Fishman Open Cores are normally wired with a mono output, and they must share the same voice number. So you can only select voice 1, 2 or 3 for both pickups.

You can't select voice 3 (vintage single coil) on the neck and voice 2 (classic humbucker hot rod) on the bridge. This separate voice selection and dual mono outputs is what I am trying to accomplish. By moving voice selection from two toggle switches on the guitar top, I keep the guitar surface area available for more volume and tone pots.

I want to use stacked pots for volume and tone for each of the Fluence pickups.

So I am awaiting your Triple Nu Multi guitar to see how you implement the 18 audio channels as well as the hex switching, VCF and VCA control to give me an idea as to which way I decide to go.
Hamer Duotone, Brian Moore i213, Taylor 710 BCE 

VG-99, FC-300, RMC Fanout
RJM Mastermind GT10
Kemper Profiling Amp
Radial JDV Mk3, X-Amp
Mesa Recto Pre + 20/20
68 Fender Bandmaster (AB763)
Marshal AS80R

UA Apollo X6, Twin X, Logic Pro, Luna, Melodyne Studio

GuitarBuilder

Quote from: scratch17 on July 14, 2019, 01:53:20 PM
Thanks for doing this amazingly deep project. In essence, I regard your efforts here as a proof of concept lab for my own project with Nu2 Multi and Fishman Fluence pickups.

You are most welcome!  Combining Nu Multi v2 with Fishman Fluence is a good choice!

Quote from: scratch17 on July 14, 2019, 01:53:20 PM
Your experiences with the Triple Nu Multi will inform me as to the tonal benefits of two Nu2 Multi pickups versus one.

If I go with 2 Nu2 Multi's, I will have to use 2 Lemo cables to handle the needed audio channels (12 Nu2, 2 magnetic from the Fluence Open cores and 1 from the piezo built into the Duotone). By themselves, there will be 15 channels of audio in this configuration. So you'd have no room left for CV controls.

That is one way of using multiple Nu pickups.  My approach is similar to a Stratocaster 5-way switch, with 3 pickup signals in and only 1 out.  The hexaphonic switch creates 5 combinations (Neck, Neck+Middle, Middle, Middle+Bridge, Bridge) and I only need 6 audio channels on the Internal Breakout Board for Nu.  Add in your 2 magnetic and 1 piezo for 9 total and you still have 6 CV channels!

Quote from: scratch17 on July 14, 2019, 01:53:20 PM
If you did this configuration you would need a second Lemo output plus a second cable and breakout. With two breakouts, you'd have enough channels to have 15 audio channels and 15 CV channels. My Hamer already has two standard 1/4" jacks to handle the mag and piezo pickups. So using two slightly larger Lemo cables in their place is not a big deal to me.

I really don't think you need two cables if you follow the switching approach I outlined above.

Quote from: scratch17 on July 14, 2019, 01:53:20 PM
One of the really radical ideas I am exploring is the idea of using CV to select each of the Fluence pickup's three voices. I'd use a CV to MIDI converter to use my RJM Mastermind GT to switch voicing, and pickup on/off on the fly. I'd also like to explore a MIDI controlled balance between the two pickups using an expression pedal.

Note that the Fishman Open Cores are normally wired with a mono output, and they must share the same voice number. So you can only select voice 1, 2 or 3 for both pickups.

You can't select voice 3 (vintage single coil) on the neck and voice 2 (classic humbucker hot rod) on the bridge. This separate voice selection and dual mono outputs is what I am trying to accomplish. By moving voice selection from two toggle switches on the guitar top, I keep the guitar surface area available for more volume and tone pots.

I want to use stacked pots for volume and tone for each of the Fluence pickups.

It appears that voice selection on the Fishman Open Cores involves simply grounding a pin on the pickup; you may want to experiment with routing those pins via separate channels on the Internal Breakout Board.  A simple footswitch or relay at the RJM Mastermind end is all you would need.  I don't think you have to worry about using CVs or MIDI for this.

Quote from: scratch17 on July 14, 2019, 01:53:20 PM
So I am awaiting your Triple Nu Multi guitar to see how you implement the 18 audio channels as well as the hex switching, VCF and VCA control to give me an idea as to which way I decide to go.

While I do have 18 audio signals coming from 3 Nu Multi pickups into my hex switching circuit, the output is only 6 channels as described above.  This is a much simpler approach and in the end will sound as good as routing 18 individual channels out of the guitar (because you will end up mixing them somehow anyway!).  The hex switching circuit output is fed into a hex VCF with frequency and resonance control, which then leads into a hex VCA for volume control.  The VCF and VCA CVs are generated by pots on the guitar, as well as using 3 CV channels on the Internal Breakout Board.
"There's no-one left alive, it must be a draw"  Peter Gabriel 1973

scratch17

QuoteWhile I do have 18 audio signals coming from 3 Nu Multi pickups into my hex switching circuit, the output is only 6 channels as described above.  This is a much simpler approach and in the end will sound as good as routing 18 individual channels out of the guitar (because you will end up mixing them somehow anyway!). 

After I posted the above reply, it occurred to me that you might be mixing the 3 pickups' outputs in the guitar. I agree that doing so keeps things less complex.

I was thinking of keeping all of each pickup's six outputs on separate channels so I would have extremely fine control over the balance between each pickup on a string by string basis.

BTW, my use case is strictly for in-studio work. As a consequence, I am not restricted to having to do things in real time.

For example, with 2 audio streams per string, I could use a stereo channel in Logic to create a single hex stream which uses the neck pickup for low E, A, D, and the bridge pickup for the G, B, and high E strings. In effect, I can set up a hybrid hex pickup that uses any combination of either pickup or both pickups on a string by string basis.

Also, this would let me use automation to continuously vary the blend between pickups to control tone without the need to use filters. Instead of a fixed position switch, I'd assign automation to the stereo channel's balance control. Then I'd use a pedal to set the tone of the hex output by varying the balance.

I could automate the balance on all channels or automate each string's balance individually, adjusting tone on each string independently.

Your in-guitar switching is easy and makes the most sense for live work. By using a switch, you have and/or choices.

My after-the-fact mixing is much more complex, but it provides me with a way to do any continuous blend between each string's pickups.

BTW, I will use my Mackie Onyx 1640 mixer to provide a mono mix of all 12 outputs so the guitarist can monitor his/her playing during tracking.

The Mackie has direct recording outputs which split each channel's signal immediately after the input trim pot. The 12 direct outs will go to my Apollo interfaces. I plan to always record each input dry, so I can apply signal processing later.

QuoteIt appears that voice selection on the Fishman Open Cores involves simply grounding a pin on the pickup; you may want to experiment with routing those pins via separate channels on the Internal Breakout Board.  A simple footswitch or relay at the RJM Mastermind end is all you would need.  I don't think you have to worry about using CVs or MIDI for this.

I wish I could read a schematic as well as you do. This is fantastic news for me. I will definitely use my Voodoo Lab GCX in relay mode to control the Fluence pickup voicing.

In effect, this is just like using relays to switch amp channels. The GCX is fully supported by the MMGT. So setting up presets which select any voice for either or both pickups will be a snap.


Hamer Duotone, Brian Moore i213, Taylor 710 BCE 

VG-99, FC-300, RMC Fanout
RJM Mastermind GT10
Kemper Profiling Amp
Radial JDV Mk3, X-Amp
Mesa Recto Pre + 20/20
68 Fender Bandmaster (AB763)
Marshal AS80R

UA Apollo X6, Twin X, Logic Pro, Luna, Melodyne Studio

GuitarBuilder

"There's no-one left alive, it must be a draw"  Peter Gabriel 1973