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Spider iv 75 Channel volume changes Effect #1 as well.


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What the title says. A Spider IV 75.


When I turn the channel volume control, the effect one control setting changes to what it would be had the effect 1 control dial been set to the same position as the channel volume control. The channel volume also changes, but the last thing on the display is the value (and selected effect) for effect #1. 


When I turn the Effect 1 control, the effect 1 setting and value take effect for about 1 second, and then revert to what the setting would be had the effect 1 dial been set to the same position as the channel volume dial (i.e. the channel volume dial seems to be transmitting constantly, and then sending the same value to the effect 1 control as well). 


Fortunately presets still work, and I can edit both values through the FBV USB. 


Very annoying though. And a serious problem for using the amp on stage.


Has anyone seen this? Is there a user-servicable fix for this? Can't afford to send this amp in for service.


I'm perfectly willing to crack the case to look at this problem. Is it worth cleaning the pots, or something? 




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Hmm. Ok. Pulled the schematics for the Spider IV. Those two controls are on an analog multiplexer chip. I probed the the outputs of the mutiplexer. Works fine. Signals look good. The multiplexer is multiplexing. Interestingly, this looks like a SOFTWARE PROBLEM. Not enough settle time between changing the multiplexer select and sampling the control values off the shared input ADC line.


The symptom again: changing the Channel Volume control knob causes immediate changes in both the channel volume value and the Fx1 control value. Changing the Fx1 control causes an immediate change in the Fx1 control, followed by a subsequent reset of the Fx1 control value to the value read from the Channel Volume control about 1/2 second later. I'd have to guess that there's some funky de-bouncing code handling the ADC values for the Channel Volume/Fx1 ADC line. And that the output of the MUX is not settling fast enough following toggling of the MUX select.


I can't see any other way to explain the observed behavior.


Is there any way to get this comment to be relayed to Line 6 developers for consideration as a software bug?



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  • 3 months later...

Have you had any luck with resolving this issue?  I have a similar issue, just with Master and FX2, not Channel Volume and FX1.  I have opened a ticket with Line 6 and will more than likely send it back for repair if there is no other option.

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