zappazapper Posted November 22, 2020 Share Posted November 22, 2020 I'm experimenting with a stereo guitar setup. I was previously using 4CM with my Mesa Boogie .50 Caliber+, but right now I just have the Helix 1/4" outputs connected to the FX Return of both the Boogie and my JCM 900, with the speaker outs of each amp going to either side of a Marshall 1960A cabinet (300W stereo 4x12). "But... you should be using an FRFR setup or a Powercab!!" I know. Not an option right now. I'm using the gear I have. Moving on. So the problem I have is that the signal is out of phase - if I pan the signal to either side, the signal sounds full, but if it's panned to the center, it sounds thin and like it's coming from behind me. If I use a dummy block to engage the B path, pan either path hard left and right in the Merge block, and flip the polarity on the B path, a signal panned to the center now sounds as full as it does panned to either side, and coming from in front of me. But using a dummy block and having to diddle with the Merge block in every preset is not a very elegant solution. Since there are no polarity options in the Output block, a hardware modification seems to be my only option. The likely culprit is that for whatever reason the power amp (or whatever line-level circuitry exists in between the FX Return and the power amp itself) in one of the amps flips the polarity of the signal. Doing an amp modification isn't something I'm interested in, so forget that. My remaining two options are (as far as I can tell) are to rewire either one of the 1/4" instrument cables connecting the Helix to one of my amps to reverse polarity (wire connected to sleeve of one end wired to tip of other end), or to rewire one of the speaker cables. Is there any reason why one approach would be better than the other? I'm leaning towards modifying the speaker cable. It seems to me that in an instrument cable, the two wires have different purposes (one carries the signal, the other provides ground and acts as a shield), and rewiring them in reverse might compromise the shielding. In a speaker cable, both wires are essentially doing the same job, as a powered audio signal is AC, and neither wire acts as a shield for the other one. I'd appreciate any thoughts on my situation, my proposed solutions, and any potential solutions I'm not thinking of. Thanks. Quote Link to comment Share on other sites More sharing options...
CraigGT Posted November 22, 2020 Share Posted November 22, 2020 Reversing the connection on a signal cable will just short out the signal and leave you with nothing, reversing a speaker cable should do the trick. Have you tried going into both amps through a splitter or an A-B-Y box just to prove that is the problem? Maybe check your speaker cables to make sure one's not reversed already too. Quote Link to comment Share on other sites More sharing options...
zappazapper Posted November 22, 2020 Author Share Posted November 22, 2020 58 minutes ago, CraigGT said: Reversing the connection on a signal cable will just short out the signal and leave you with nothing My apologies. As I was walking down the street to get food, I started thinking about it and how wrong I was. A line-level signal is still AC. The signal wire carries both positive and negative voltages, and like you said, reversing the connection on one end will just short the signal to ground, not reverse the polarity of the signal. I'm guessing there is no way to reverse the polarity of a signal by modifying an instrument cable. Seems like modifying one of my speaker cables is my only option. 58 minutes ago, CraigGT said: Have you tried going into both amps through a splitter or an A-B-Y box just to prove that is the problem? Maybe check your speaker cables to make sure one's not reversed already too. I don't have an A/B/Y, and AFAIK I don't have a 1/4" unbalanced splitter. I checked both the instrument cables and the speaker cables to confirm correct wiring. Quote Link to comment Share on other sites More sharing options...
CraigGT Posted November 22, 2020 Share Posted November 22, 2020 31 minutes ago, zappazapper said: Seems like modifying one of my speaker cables is my only option. Well it's easy enough to do and might solve your problem. Quote Link to comment Share on other sites More sharing options...
zappazapper Posted November 23, 2020 Author Share Posted November 23, 2020 Yup, that did it. Thanks. Quote Link to comment Share on other sites More sharing options...
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