Control Voltage as Expression Pedal?

Started by intergalatico, March 02, 2018, 05:44:11 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

intergalatico

Hi Folks,

I just scored my second SY 300 (my first I sold sometime ago) for a good price and wonder if I can use my Control Voltage Expression Pedal with it.

- It is possible? I can configured my CV to send Voltage between 0 and 5.5Volts.

Another question is:
- When I configure to use the Ctrl 2 and 3 to use as controllers, how can I change the patches with my feet? Is there some trick? Or I do have to use the knob with my hands? That would be a shame...

I didn't plugged in yet, but I can't wait to use with my EHX Synth 9!!! =)

Thank you, guys!

Cheers

ElliotG

Quote from: intergalatico on March 02, 2018, 05:44:11 AM
...wonder if I can use my Control Voltage Expression Pedal with it.
- It is possible? I can configured my CV to send Voltage between 0 and 5.5Volts.
I'm assuming you want to send a CV to the SY300.  You should be able to do this... but you need to determine the max voltage.  The following thread describes the construction of the Boss EV-5 pedal.  https://www.vguitarforums.com/smf/index.php?topic=33.0

Plug a TRS cable into the expression pedal input of the SY300, measure the voltage across the sleeve(GND) and the ring.  This is your maximum voltage, you will want to ensure your CV does not exceed this level, or it could damage the SY300.  Your CV would be applied across the tip(CV) and Sleeve(GND), leave the ring unconnected.  (I have not done this, proceed at your own risk.)

As an alternative you should look at the "Wave", the Wave is effectively a virtual CV inside the SY300 that can be used to modify any parameter.  The LFO inside the SY300 is also very flexible but limited to pitch, amplitude and filter control, the LFO can also respond to playing dynamics.  I'd look to exhaust these capabilities before moving to external CV. 

Quote from: intergalatico on March 02, 2018, 05:44:11 AM
When I configure to use the Ctrl 2 and 3 to use as controllers, how can I change the patches with my feet? Is there some trick? Or I do have to use the knob with my hands? That would be a shame...

If CTL2/3 are not used to change patches the options for foot based control are to use external switches (CTL4&5) and program them to make the program change, or to use an external MIDI foot-controller.


admin

AFAIK - using a Control voltage pedal that sends variable DC voltage to the Expression pedal input jack on the  SY-300 WILL damage the SY-300

the proper Roland / Boss Expression pedal is a 10 K linear pot

all details here
https://www.vguitarforums.com/smf/index.php?topic=33.0

ElliotG

Here is how the expression pedal works:  There is a fixed voltage on the ring, this come from the device being controlled.  Let's assume that is 5V.  This means at the high position the TIP (wiper) is 5v, at the middle position the tip is 2.5V, and at the low position the tip is 0V.  The pedal reads the voltage on the tip.  Using an active CV or a passive pot can work, the receiver can't tell the difference.  Moog synths works this way.   The risk is in exceeding the high voltage.

That said, I see little reason for using an external CV, when there is so much programmability integrated into the SY300 with the LFO and Wave.

If in doubt, contact Boss support by email.


CodeSmart

Most CTRL inputs on BOSS Roland uses a special internal arrangement with balanced resistors to determine if a EV-5 or FS-6/FS-7 is connected at run-time by measuring both the tip and ring voltage (two A/D converters are used). These resistors are matched with the resistance of the EV-5 10K-pot. If the voltages are within a certain min/max range the device "knows" it's an analog expression pedal connected. If not, it's a dual footswitch (or unconnected). The internal voltage used is 3.3V.

If you really want to take the risk and fool the system you may have to provide two voltages. One fixed and one variable. The voltages should be feed through resistors (perhaps 1K) and be probably not more than 2.5V or something for full scale reading. Anything above 3.3V may cause a nice expensive barbecue inside.
But I got more gear than I need...and I like it!

admin

#5
Quote from: CodeSmart on March 02, 2018, 01:40:21 PM
Most CTRL inputs on BOSS Roland uses a special internal arrangement with balanced resistors to determine if a EV-5 or FS-6/FS-7 is connected at run-time by measuring both the tip and ring voltage (two A/D converters are used). These resistors are matched with the resistance of the EV-5 10K-pot. If the voltages are within a certain min/max range the device "knows" it's an analog expression pedal connected. If not, it's a dual footswitch (or unconnected). The internal voltage used is 3.3V.

If you really want to take the risk and fool the system you may have to provide two voltages. One fixed and one variable. The voltages should be feed through resistors (perhaps 1K) and be probably not more than 2.5V or something for full scale reading. Anything above 3.3V may cause a nice expensive barbecue inside.


FWIW - Before these External Expression pedal jacks on Boss gear became "smart" (sometime  after 2001) , there was an old trick that worked on Boss GT and Zoom pedals that allowed using a TRS Y adapter  to connect both an Expression pedal AND a 2 button N.O. Momentary switch

http://ashbass.com/AshBassGuitar/Zoom/
It is important to note that the footswitch will only work when the expression pedal is all the way toe-down.

ElliotG

Very cool.  I learned a few things.  Given all of this... I'd recommend the OP NOT use a direct CV.

intergalatico

Thank you all! So much info!

I want to use CV because on my pedalboard I have already a kind of "expressionator" that I build myself. It is based on Teensy and I use one single expression pedal* to control 4 devices:
- Eventide H9
- Strymon El Capistan
- EHX Pitch Fork
- DIY Analog Filter

It works very good and even the H9 (with a boss sy 300 similar config where exp and two ctrl pedals shares the same jack input) works fine. Here the H9 takes 0-3.3V as CV like described on their manual.

I use a TS jack on all connections.

I don't want to make a blue barbecue, so I suppose the better would be  to write boss support. I am just affraid to receive a standard answer like: "we advice to use only boss/roland products with our device"

I am for the next two weeks really busy with a kind of repertoire that doesn't need (at all!)  the sy 300. Shame... So I will come back here after that, I am sorry!

Thank you all for taking the time!

Cheers

* My expression pedal is my Vox Wah with a Hall Sensor and magnet so I can use these pedal as Wah and expression pedal. That spares me a lot of space on my pedalboard! ;-)


CodeSmart

You seem to be a knowledged guy. How about connecting a EV-5 and measure the ring voltage somehow, then you know the max & range suitable for your input control. Don't think you will harm anything by applying it through a 1K resistor to start with and to see what's happening on SY-300 side. Maybe ok to go directly in. Basically there's just two 12-bit or something AD converters inside with resistors/dividers, pull-ups and probably/hopefully shottky protective diodes clamping out over/under voltage.

We are not saying it will not work, just that it's not recommended normal procedure. It's all up to you and it's all about voltages and your skills. If you get it to work then tell us how you did it :-)

If some sh** happens, ..your $$$ problem 8)
But I got more gear than I need...and I like it!

ElliotG

I measured the ring voltage on mine... 3.29V

Like codesmart, I do expect it would work, but I'm not ready to cover the repair cost of a blue BBQ  :P

Another possible alternative... I don't know anything about Teensy, but assuming you could create a MIDI out port (from a UART), you could safely control the SY300 with your homemade expressionator by sending MIDI CC commands.  This would also let you keep an analog exp out on your pedal free, and let you use the expression input on the SY300 for 2 more switches. 8)

gumtown

If you are using a Arduino Teensy, how about using one of the PWM outputs, which is driving a transistor to pull the Boss/Roland EXP 3.3v to ground in a variable manor.
I have used something similar with an Arduino to convert the GK Vol 0~5v to A/D converter input, to PWM output 0~100% duty cycle. 
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

intergalatico

Hey guys,

thank you for the insides! The problem is that my "Expressionator" is already boxed and I can't put any new connection like a midi output or change anything on the hardware. BUT, the good thing about Teensy is that you can use the usb as a usb midi output!

I would assume that the sy300 usb doesn't take normal easy CC messages, but sys.

I can handle standard midi messages on my code but I never did something with SYS messages. Maybe somebody here can help me on it? For example, how to send a CC message in sys?

That way would be awesome and I would be able to control my 4 devices + the sy 300 with one pedal!

I appreciate so much your help!

Cheers!