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Leftzilla

1/4 inch and VDI on JTV series

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Hey stupid question probably but I am away from all of my Variax's and I would like to know if both the VDI and quarter inch outputs can produce output at the same time.  I am asking because I use the VDI to control my patches and and use the output to my Helix but would like to send the dry signal (1/4) output to a TC Helicon voice harmonizer.  I know I could use the helix to send an out but just curious as to whether the Variax could do it also.

 

Thanks in advance!

 

Lefty

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Yes it can do that and I have tried it out a while back and you get sound out of both but I ended up getting a hum as well.   :(

However, as Charlie says it is not recommended and Line6 will tell you not to do it. 

From what I recall the reason stated by Line6 is that the circuits are not designed to allow for both outputs to be used at the same time so you risk overloading them and causing damage to the electronics.

I was fortunate that my experimentation did not cause any issues.  So if you try it then it is entirely at your own risk and on your own head. Don't blame me if it breaks anything on your Variax!    I repeat - Line6 do not recommend using both Variax outputs simultaneously.     :)

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By the way there is nothing in the written pilot's guides that says you can't do this.  But it's been said here.  I'm not sure I buy it but it's a bad circuit design if this can overload anything.  The two interfaces are not the same hardware.  One is digital and the other's analog.  I would love to hear an explanation from one of the Line6 circuit designers but I don't think they are on this forum.

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...but I don't think they are on this forum.

Wouldn't much matter if they were...the Calabasas daily weather report is off limits, never mind the "secret" stuff.

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It has been "officially" stated that over time, using a Variax that way will damage the circuitry.

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I would go with the Helix out as first thing in the chain simply to avoid using two cable to the guitar

 

It may or may not stress the electronics, but dragging two cables around probably does mechanically stress the socket and would stress me - either they are tied together and inflexible (twist them around each other before joining for best flexibility) or you have two cables to trip over!

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Before I bought the variax, I have been using a Radial JDI Direct box with my HD500, I plug the guitar into that, then JDI into the mic input. It's got a nice sounding Jensen Transformer in it and gets rid of some of the fuzziness that I was encountering. I had hoped to use the VDI as a means for patch changes and then run the sound how I have normally run it. Comparing the 2, Variax input vs. Mic Input (JDI Direct Box), the Mic input sounds warmer and better, the Variax input is hotter and more brittle on top. 

 

So If I am only running sound out of one (1/4") and using the other for patch changes it will hurt the Variax? This is pretty much how the Work Bench works right?

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Before I bought the variax, I have been using a Radial JDI Direct box with my HD500, I plug the guitar into that, then JDI into the mic input. It's got a nice sounding Jensen Transformer in it and gets rid of some of the fuzziness that I was encountering. I had hoped to use the VDI as a means for patch changes and then run the sound how I have normally run it. Comparing the 2, Variax input vs. Mic Input (JDI Direct Box), the Mic input sounds warmer and better, the Variax input is hotter and more brittle on top.

 

So If I am only running sound out of one (1/4") and using the other for patch changes it will hurt the Variax? This is pretty much how the Work Bench works right?

The powers that be repeatedly warn against running both outputs from the JTV simultaneously...supposedly it overloads circuitry somewhere. Proceed at your own risk.

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Before I bought the variax, I have been using a Radial JDI Direct box with my HD500, I plug the guitar into that, then JDI into the mic input. It's got a nice sounding Jensen Transformer in it and gets rid of some of the fuzziness that I was encountering. I had hoped to use the VDI as a means for patch changes and then run the sound how I have normally run it. Comparing the 2, Variax input vs. Mic Input (JDI Direct Box), the Mic input sounds warmer and better, the Variax input is hotter and more brittle on top. 

 

So If I am only running sound out of one (1/4") and using the other for patch changes it will hurt the Variax? This is pretty much how the Work Bench works right?

 

When using the Workbench interface dongle the VDI is not powering the JTV - you need the battery in the JTV and then a 1/4 inch cable to complete the circuit and also to take the sound to an amplifier source so you can hear what you are doing.   This is per Line6 design and documented in the manual..

However, using the VDI connected to an HD500 which is providing power to the JTV as well as processing the sound signals, and then using the 1/4 inch output to take the sound output to another amplifier or to another input on the HD500 is not recommended by Line6 and it is this situation that they state can lead to JTV circuitry overload.

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I would love to see the physics behind that statement.  In the worst case, an additional audio load might be as low as 100k ohms which isn't about to stress anything.

 

I am told by a third-party that the real issue is a handful of cases involving steering diode failure.  I believe the doomsday scenario was a mono 1/4" plug in the analog signal output while power was being supplied over VDI.  There is a diode that's supposed to prevent +7V from the guitar electronics from finding its way to ground through the barrel of the 1/4" mono plug.  If that diode breaks down, I can well believe that something will get toasted.

 

The same source points out that using a TRS stereo plug at the guitar (with ring floating) will completely sidestep the already small chance of a problem.  In that case there is no path to ground through the 1/4" jack.

 

Line6 does no one any favors by obfuscating the issue.

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The same source points out that using a TRS stereo plug at the guitar (with ring floating) will completely sidestep the already small chance of a problem.  In that case there is no path to ground through the 1/4" jack.

 

 

Any chance you can describe how to float a ring?

 

Never mind. I looked it up. Thanks for the info though.

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In case anyone else has the same question:  "Float" is a commonly used electronics technical term meaning "not connected to anything" :-).  Essentially, you connect the cable shield to the shell of the connector (as always) and the center conductor to the tip.  The ring connection simply goes nowhere.

 

Having said this, I cannot take any responsibility for problems that might occur.  Since Line6 is not forthcoming with technical details and schematics of the JTV Variax electronics are not available I am going by my own 45+ years of electronics technical background and a clear explanation from a third-party with good reason to know what he's talking about.  All I can say is that if I had a need to use both outputs, I wouldn't hesitate to take this approach. 

 

I want to tread carefully here:  I'm not saying that anyone is deliberately misrepresenting matters, just that blanket statements about output stages being stressed don't jive with anything I know about audio circuit behavior.  Connecting a 2-ohm load to a power amp designed for 4-ohm minimum is definitely going to cause stress.  Connecting a 100K ohm load (worst case guitar level input impedance) to an audio op-amp output?  Not likely.  It's not even in the right order-of-magnitude to cause loading issues.  The steering / blocking diode explanation makes far more sense.

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This discussion is starting to remind me of the "Reefer Madness" propaganda films from the 50's...

 

"You'll go insane...trust us". ;)

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