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Junior Varsity
Multiple amps suddenly stopped working in stereo mode but still work in bridged
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<blockquote data-quote="Art Welter" data-source="post: 216735" data-attributes="member: 52"><p>Joey,</p><p></p><p>Probably a change in input drive cords or source is the problem.</p><p>As you wrote in DIY audio :</p><p><em>"I understand the amp is not a mixer but it's not difficult to sum a stereo signal to mono. I've done it very easily while building a 3.5mm stereo jack to XLR adapter."</em></p><p>Your input wiring (common to all four amps) is likely the problem.</p><p></p><p>You can "easily" connect (short circuit) the tip and ring of a stereo 3.5mm (or 1/4") TRS together, then wire the shorted pair to the XLR pin 2 (+), and the sleeve to XLR pin 3 (-) to sum to mono.</p><p>Not a good choice, the tip and ring should be isolated with resistors.</p><p></p><p>To function properly, a 3.5mm stereo jack to XLR adapter would require <em>two</em> XLR connectors, one for left, one for right.</p><p></p><p>The standard connection of a 3-pin XLR to a 1/4" TRS (AKA stereo jack plug) is:</p><p>pin 1(shield) to sleeve, pin 2(+) to tip, pin 3(-) to ring.</p><p></p><p>If a mixer stereo headphone out was used to drive the amp input using that configuration, the L/R of a mono signal (exactly 180 degrees out of phase) would cancel if driving the amp XLR switched to "stereo", while the inverting "bridge mono" connection would not.</p><p></p><p><a href="https://qscprod.force.com/selfhelpportal/s/article/How-to-Connecting-stereo-outputs-to-mono-input" target="_blank">https://qscprod.force.com/selfhelpportal/s/article/How-to-Connecting-stereo-outputs-to-mono-input</a></p><p></p><p>Art</p></blockquote><p></p>
[QUOTE="Art Welter, post: 216735, member: 52"] Joey, Probably a change in input drive cords or source is the problem. As you wrote in DIY audio : [I]"I understand the amp is not a mixer but it's not difficult to sum a stereo signal to mono. I've done it very easily while building a 3.5mm stereo jack to XLR adapter."[/I] Your input wiring (common to all four amps) is likely the problem. You can "easily" connect (short circuit) the tip and ring of a stereo 3.5mm (or 1/4") TRS together, then wire the shorted pair to the XLR pin 2 (+), and the sleeve to XLR pin 3 (-) to sum to mono. Not a good choice, the tip and ring should be isolated with resistors. To function properly, a 3.5mm stereo jack to XLR adapter would require [I]two[/I] XLR connectors, one for left, one for right. The standard connection of a 3-pin XLR to a 1/4" TRS (AKA stereo jack plug) is: pin 1(shield) to sleeve, pin 2(+) to tip, pin 3(-) to ring. If a mixer stereo headphone out was used to drive the amp input using that configuration, the L/R of a mono signal (exactly 180 degrees out of phase) would cancel if driving the amp XLR switched to "stereo", while the inverting "bridge mono" connection would not. [URL]https://qscprod.force.com/selfhelpportal/s/article/How-to-Connecting-stereo-outputs-to-mono-input[/URL] Art [/QUOTE]
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Multiple amps suddenly stopped working in stereo mode but still work in bridged
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