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What does the powered A/B footswitch actually do?


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I'm new to the Line6 Variax, I've just bought a JTV59.  I know that the footswitch which you have to buy separately acts as a combined A/B unit and passes on power to the guitar from the external supply.  But what does it send where?

 

Am I right in thinking that it is the simple logical system you would expect?  +9V direct to the Ring and Sleeve when connected, with the signal on the Tip and Sleeve, signal fed to the switch which then sends it on to either the 1/4" jack or XLR connection as outputs?  If so, surely it should be a piece of cake to actually make one of these from a converted standard footswitch and the correct 9V/200mA supply.

 

Can anyone point out where that is wrong?  Has anyone done this?

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Errrmm!  For anyone interested here is an update.  You know what I said about a cheap LM317 regulator?  Now where is that 'embarassed' emoticon......... 

 

Have a look at the attached pic.  It shows both sides of the internals of that footswitch.  I have to take my hat off to Line6, that's something comprehensive for what it does.  It certainly isn't a simple regulator and switch is it?  And the build quality is first class.

 

Glad I had a look as it seems I have demonstrated to myself that it was money well spent.

 

 

post-2401514-0-29677200-1466078072_thumb.jpg

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I don't think that can be all that is going on there GH, there are about 8 or 10 transistors and 5 or 6 surface mount chips in there too.  It doesn't take active devices like that to make switching pop free.

 

You're right with the regulator chip, though the code number had been wiped as is common on this type of device.  There will be a balanced line driver for the XLR out which will either take a dedicated chip or a few opamps, and maybe an unbalanced driver for the jack out.  Heaven knows what the rest is for, sensing of whether the guitar is attached, sensing of the TRS plug inserted into a two pin socket so the power on the ring is shorting?

 

And Charlie has to be right too, the power supply is AC so rectify it.  I would have chased it out but as it was surface mount it would have taken an age and maybe not even given any hint as to what some parts were doing.

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The XLR is for going into mixing consoles and recording gear the

use balanced inputs. A/B is for switching between the XLR and 1/4".

 

Recommend not engaging phantom power on the mixer when using

the XLR output on the XPS. Otherwise, use the 1/4" signal line.

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