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Allow "CV" output to double as a 2nd "Ext Amp" controller.

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There is only one "Ext Amp" controller output on the Helix right now. Many modern and even older amps require at least a couple of "Ext Amp" controller outputs to take full advantage of the channel switching and features available on the amp.

 

Don't know how the "CV" output is wired, but if it is possible it would be nice if there was a way to modify the firmware settings to allow the current "CV" output to double as a second "Ext Amp 2" controller. Both external controllers should allow flexible firmware switching of stereo (TRS) plugs to accommodate as many amps as possible. I think the number of people who have a "CV" requirement will be far less than those who would like to have a second controller output for their amp.

 

You can vote for it here in Ideascale

http://line6.ideascale.com/a/dtd/Allow-CV-output-to-double-as-a-2nd-Ext-Amp-controller/790054-23508?submitted=1

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This is just a guess and I could be wrong, but I suspect this will be impossible. CV = Control Voltage: http://www.sweetwater.com/insync/control-voltage/

 

Anything that's expecting a switch to open or close, like the circuits in the amp where you'd connect a foot controller, is only checking for electrical continuity, or not.

 

I don't have an EE degree, but as I understand it, if the CV output provides specific voltages, then by definition there will be continuity at all times, even at 0 volts.

 

Who knows, maybe I'm wrong and there's some way to do it. I hope so!

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Have you tried it? It might work, especially if your amp reads momentary impulses. I'm not sure though. But with a dim value of "0" and a lit value of "100" it might just work with some amps?

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Have you tried it? It might work, especially if your amp reads momentary impulses. I'm not sure though. But with a dim value of "0" and a lit value of "100" it might just work with some amps?

 

Great suggestion!  I have to admit I am a little nervous about damaging my amp experimenting given that I don't have enough information about how a CV output might impact the electronics on my amp. If there are any electrical engineers or experts on amps who can chime in on this idea I would love to hear their feedback.

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Great suggestion! I have to admit I am a little nervous about damaging my amp experimenting given that I don't have enough information about how a CV output might impact the electronics on my amp. If there are any electrical engineers or experts on amps who can chime in on this idea I would love to hear their feedback.

I have to admit, I'd call my amp guy before I try it, too.

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I wouldn't be plugging a CV output into a switch input. It doesn't sound like a good idea to me at all.

 

However, you could use the CV output to control an external device that took the CV input and converted it into switches using relays. I don't know exactly what you have in mind, or if such a device already exists, but that'd be the way to do it in principle.

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Easiest way is to get an extra Midi Switcher. I have an MS-4 which can be configured for momentary on two different lengths of the impulse or latching. Cost me like 80€ once on ebay and it's just lying around these days because my amps have midi or just one switch  ....

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You could measure the voltage of the amp switch input and then use that voltage as the off signal and 0V as the on signal. A switch shorting the input would place 0V in the input, and an open switch would not alter the voltage from the amp switching input.

 

The potential problem is that a switch is very low impedance and the CV output might not be able to drive the amp switching input if it's too low impedance. If the CV output is done with an op-amp it's very easy to protect it from overload by either placing a resister in the output or choosing an op-amp with built in current limit, so it would be foolish of Line 6 not to have protected the CV output from damage, but it's your call if you want to try it out. I don't think your Helix will be harmed, but on the other hand I'm not going to buy you a new one if it does.  :D

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You could measure the voltage of the amp switch input and then use that voltage as the off signal and 0V as the on signal. A switch shorting the input would place 0V in the input, and an open switch would not alter the voltage from the amp switching input.

 

The potential problem is that a switch is very low impedance and the CV output might not be able to drive the amp switching input if it's too low impedance. If the CV output is done with an op-amp it's very easy to protect it from overload by either placing a resister in the output or choosing an op-amp with built in current limit, so it would be foolish of Line 6 not to have protected the CV output from damage, but it's your call if you want to try it out. I don't think your Helix will be harmed, but on the other hand I'm not going to buy you a new one if it does.  :D

 

Good point, I hadn't even considered the possibility of damage to the Helix, I was more concerned about my amp.

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I am with ozbadman and jaeger28 here. Unless we find out exactly what is the driver circuitry of the CV port on the Helix and the circuitry on the control jack of the amp are, there is just too much risk that something might go wrong and you might end up with one of the following:

 

a) It works (best case scenario) but this is highly unlikely, since the CV port on the Helix was not designed for this purpose.

b) It does not work, but no smoke comes out of the Helix or the amp ( the "dodged a bullet" scenario).

c) You're $1500 in the hole (Helix replacement or maybe less, depending on how much Line 6 will charge for fixing a fried Helix I/O board).

d) You're $1000 - $3000 in the hole (or however much the amp costs or its repair).

e) You're $1500 + $1000-$3000 in the hole, if you fry both.

 

I would go with jaeger28's option of getting a 80€ Midi switcher box or, as ozbadman suggested, look for a box that will convert CV to a switched output. Either option is much cheaper than a Helix and/or Amp repair.

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ANSWERED!!: I'm currently using the CV output of My Helix to drive a relay input on my AMP. I measured the properties of the CV output and it delivers 0-5V at an output impedance of approx 660ohms. This is far too weak to drive a relay coil directly (which my AMP uses) so I've embedded a Field Effect Transistor (FET) into the body of the Jack plug inserted into the CV output socket of the Helix (I used a 2N7000 FET - cheap and easily obtainable).

 

The Gate of the FET connects to the CV output, the Drain connects to the AMP switching line, and the Source connects to ground.

 

I then set up a Helix footswitch (from the control centre on the Helix) to toggle the CV between 0 and 100. This drives the Gate of the FET and turns it ON and OFF (the Gate saturation voltage of the 2N7000 is around 2.1V). When on, the FET effectively shorts Drain to Source, so acts like a mechanical footswitch or relay contact, shorting the AMP switching line to ground.

 

Simples ;-)

 

Doug

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This is very cool Doug!   :)

 

Thanks for sharing - I'm sure most folks who own a soldering iron could manage to solder a FET into a jack socket.

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ANSWERED!!: I'm currently using the CV output of My Helix to drive a relay input on my AMP. I measured the properties of the CV output and it delivers 0-5V at an output impedance of approx 660ohms. This is far too weak to drive a relay coil directly (which my AMP uses) so I've embedded a Field Effect Transistor (FET) into the body of the Jack plug inserted into the CV output socket of the Helix (I used an SN7000 FET - cheap and easily obtainable).

 

The Gate of the FET connects to the CV output, the Drain connects to the AMP switching line, and the Source connects to ground.

 

I then set up a Helix footswitch (from the control centre on the Helix) to toggle the CV between 0 and 100. This drives the Gate of the FET and turns it ON and OFF (the Gate saturation voltage of the SN7000 is around 2.1V). When on, the FET effectively shorts Drain to Source, so acts like a mechanical footswitch or relay contact, shorting the AMP switching line to ground.

 

Simples ;-)

 

Doug

 

Genius! And this solution requires no modifications to the Helix only to the cable being plugged in. Could you please post a graphic on how to wire this if you feel so inclined although your clear instructions will probably suffice for most. Does this provide full TRS (two possible amp input) functionality? If so the Helix can now potentially accommodate a total of four jack switching options on an amp thanks to your work.  Thanks! You just provided some free R&D Line6 might want to include in the next Helix. This post is yet another that should be a permanent addition to the HelixHelp.com page for guitarists who want to switch for example between all the channels on their Mark V or be able to change channels as well as kick EQ and reverb in/out.

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I'm pretty sure that it's just going to give 1 additional switch - just a standard mono TS jack to your amp.

 

The Helix doesn't have settings for CV1 and CV2 - there's just one CV that can be used with an expression pedal with Max/min setting or via a footswitch toggle - whereas with the Ext amp you can select 1 for tip-sleeve, 2 for ring-sleeve or both.

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I'm pretty sure that it's just going to give 1 additional switch - just a standard mono TS jack to your amp.

 

The Helix doesn't have settings for CV1 and CV2 - there's just one CV that can be used with an expression pedal with Max/min setting or via a footswitch toggle - whereas with the Ext amp you can select 1 for tip-sleeve, 2 for ring-sleeve or both.

 

Thanks for the answer!  Still awesome and one more than we had before.

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Minor correction  - the FET I used was a "2N7000" not "SN7000" (typo in my previous post). Also yes, it's only a single channel solution. I did toy with the idea of switching multiple channels when particular CV voltages were set, but abandoned the idea as it would be fairly complex (involving an analog comparator and stable power supply regulator). I only needed the one additional channel, and I liked the simplicity of just modding the cable - no other alterations necessary :-).

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Minor correction  - the FET I used was a "2N7000" not "SN7000" (typo in my previous post). Also yes, it's only a single channel solution. I did toy with the idea of switching multiple channels when particular CV voltages were set, but abandoned the idea as it would be fairly complex (involving an analog comparator and stable power supply regulator). I only needed the one additional channel, and I liked the simplicity of just modding the cable - no other alterations necessary :-).

 

I concur with your decistion opting for the more direct and simpler solution. Would you mind editing your post that was used for the green "Mark Solved" block so the proper FET code shows up in the top post. Thanks!

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Nice idea. It's a real shame the control switching wasn't done with isolated relays, that would have solved a lot of problems for me. I needed relay switching to control a GR-20 guitar synth and ended up going to a Voodoo Labs control switcher.

 

Mike

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I'm guessing the reason isolated relay contacts weren't implemented was that an additional jack socket would have been required (each switching output would require it's own TRS output, with tip and ring being the relay contact, and screen being ground). There was no room on the Helix rear panel, I presume...

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Here is the drawing that I posted to another thread regarding Amp Switching using the Helix CV Jack.. I thought that it would be appropriate for this to follow the original thread...

 

Below is a Schematic outlining how the CV MOD for Amp Switching works... (As originally envisioned by Doughadfield)

cv_switch.jpg

I moved the FET from Doug's cable plug to a small box with 1/4" in/ out jacks and a switch to allow you to control one of two functions from the Helix CV... (the TIP or RING on the Amplifier side...)

I hope this helps

seeya

Joe

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I'm guessing the reason isolated relay contacts weren't implemented was that an additional jack socket would have been required (each switching output would require it's own TRS output, with tip and ring being the relay contact, and screen being ground). There was no room on the Helix rear panel, I presume...

 

 

I'm getting ground loops using my Helix Amp switch sockets and wondered if this CV solution would also suffer from ground loops?

 

I suppose the answer is yes - this will still cause ground loops, as there is still a direct connection to Helix ground, which a relay based switch would not have... but is it possible to drive a very small relay with the CV output?

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Hi, I'm flattered at the kind words on this thread - thanks all. The diagram that a2dconverterguy posted is truly impressive, and illustrates the solution beautifully. As for the issue of ground loops, as you suspect, the CV/FET solution is unlikely to make any difference, as the ground loop issue is due to the common ground between the Helix and your amp, which is still present with the FET solution. However, it may be possible to think of a creative solution to your problem. If a resistor is inserted in the common ground, the ground loop current is reduced and your problem may go away. The beauty of the FET is that it's a voltage-controlled device - it requires almost no current at all at the gate. So, we could put a large resistance in the ground circuit and still generate the gate voltage necessary to turn on the FET. Try that - in the excellent diagram above, put a 10K resistor in the ground line between the Source of the FET and the Jack connected to the Helix. Give it a go and let us know how you get on :-)

 

Doug

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On 5/6/2016 at 11:48 PM, a2dconverterguy said:

Here is the drawing that I posted to another thread regarding Amp Switching using the Helix CV Jack.. I thought that it would be appropriate for this to follow the original thread...

 

Below is a Schematic outlining how the CV MOD for Amp Switching works... (As originally envisioned by Doughadfield)

cv_switch.jpg

I moved the FET from Doug's cable plug to a small box with 1/4" in/ out jacks and a switch to allow you to control one of two functions from the Helix CV... (the TIP or RING on the Amplifier side...)

I hope this helps

seeya

Joe

Hey Joe!!!

huge thanks for this. I’m not a really tech savvy (basic skills in electronic and soldering only) so could you send a photo showing the small box you mentioned with the wiring/jacks/FET so I can do it as well?  

 

I’m unsure of how to wire (cause my understanding of electronic layouts it’s almost zero) ... hahaha 

 

I really need to control 3 different channels of my amp and this will be just the perfect solution! 

 

Thank you so much man!

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On 6/27/2018 at 11:58 PM, rsan said:

Hey Joe!!!

huge thanks for this. I’m not a really tech savvy (basic skills in electronic and soldering only) so could you send a photo showing the small box you mentioned with the wiring/jacks/FET so I can do it as well?  

 

I’m unsure of how to wire (cause my understanding of electronic layouts it’s almost zero) ... hahaha 

 

I really need to control 3 different channels of my amp and this will be just the perfect solution! 

 

Thank you so much man!

 

Hi rsan, 

 

I haven't built one of these... I just re-drew Doughadfield's design as a courtesy to show how it could be mounted into a small plastic box...

 

I suggest getting someone in your area who is proficient in electronics to build you one... (the below schematic is much clearer than any pix of an actual wired box could be.)

 

[1] 1/4" stereo jack, [1] 1/4" mono jack, [1] 2N7000 Transistor and [1] SPDT switch and some hook-up wire. The wiring is soldered to the components to match the schematic and mounted in a small plastic box.

 

cv_switch.jpg

 

I hope this helps.

 

seeya

 

Joe

 

P.S. As mentioned before... if you are having hum from ground-loop problems... the above will not help. you will need to isolate using relays and an external power source as follows...

 

mk525_switch_3.jpg

 

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@a2dconverterguy and @doughadfield thanks for the help!! It works! It works! hahaha

I was able to get all the parts and put this together. Everything works fine, HOWEVER, I still have one question:

 

The idea here is to be able to control the voicing modes (three) of my Mesa 2:90 so I can assign a mode for every patch. I was used to simply chose voices using the Triaxis switch buttons on the front panel - but I'm not using Triaxis for all presets so I need to have this done by Helix. The thing which annoys me is that I have to go on every preset > command center > assign to a footswitch > chose the mode I want for that preset > save. 

 

I'm not changing mode within the same preset/snapshot so my question is: is there an easy way to configure this switches for each preset without having all that hassle mentioned above??

 

Thanks a lot!

Ren

amp controller_Page_2.png

amp controller_Page_4.png

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