Weird result when moving from stereo to mono

    Hi all,


    I usually play in stereo with my main band (main XLR outs to 2 x Headrush 112" speakers as backline with the send and return loop as stereo sends to the PA). I auditioned with a different band last night, and the soundguy asked for a mono output to the PA, so I changed the OUTPUT settings so master out was just master mono, and gave him the left XLR out.


    However, this led to some weird stuff going on, such as the sound cutting out like there was a hard gate effect in place. He was adamant it wasn't anything his end, and I was sure it wasn't anything on the Kemper. Has anyone else encountered anything like this? I'd hit a distorted chord, and as it faded out it would suddenly disappear. Playing clean stuff was a nightmare as it just came in and out all the time.

    And as a related question - what's the best way to go from playing stereo to playing mono? Is it literally just to change the master outs to master mono from master stereo?

    I'd change the entire cabling. Use the main outs to FOH and the new feature of monitor and direct out for your personal stereo monitoring because I'm not sure if send and return is the right way to go FOH.


    When you switched to the main outs for going mono to FOH, how did you connect to your two Headrushs?

    Was the right main out also occupied? If yes, where did it go?

    I could have farted and it would have sounded good! (Brian Johnson)

    Like 1

    Hi mate,


    I used the main outs to my 'backline' of the 2 Headrush speakers as I can then use the output volume knob to change the levels easily. I use the direct out and monitor out to the desk as I lock the output level for these. I don't go through the PA, it's only a feed to allow the guitar to be heard in our in ears from the mixer.

    Last night, I didn't use any backline - it was going direct to FoH, so I switched it to master mono and took the left XLR feed. No other outputs were used.

    If using the two Headrush speakers in a mono output situation - am I right in saying I can just use the two XLR outs from the kemper into each of them, and it'll still be mono (just 2 x mono signals)?

    Phase issue?

    Altough it would have been there running stereo...switching to mono may cause it to be more apparent.

    In short, a phase issue occurs when speaker A moves forward, while speaker B backward at the same time, resulting in the speakers canceling eachothers output.


    The cause is either a setting in a device (not possible with kpa), or faulty speaker wiring.


    Idnk how to check If your speakers are properly wired. (Easy with passive cabs)

    First thing I would do is switch one off, If the problem disappears you have a very strong indication of a phase issue.

    Anything stereo in your setup that has “invert” options that might cause it?

    Quote from FarleyUK

    so I switched it to master mono and took the left XLR feed

    This cabling is correct for the situation last night. What comes to my mind is that there are some desks which automatically engage mic preamps when XLR is pluged in. This will lead to a too high input signal on the desk and maybe your soundman compensated this by dialing in the channel gain very low.


    Quote from FarleyUK

    am I right in saying I can just use the two XLR outs from the kemper into each of them, and it'll still be mono (just 2 x mono signals)?

    Not sure about this but I think it will work. Switch main ouputs to master mono and then on left and right ouput there should go out the same mono signal.

    I could have farted and it would have sounded good! (Brian Johnson)

    Quote from FarleyUK

    Hi mate,


    I used the main outs to my 'backline' of the 2 Headrush speakers as I can then use the output volume knob to change the levels easily. I use the direct out and monitor out to the desk as I lock the output level for these. I don't go through the PA, it's only a feed to allow the guitar to be heard in our in ears from the mixer.

    Last night, I didn't use any backline - it was going direct to FoH, so I switched it to master mono and took the left XLR feed. No other outputs were used.

    If using the two Headrush speakers in a mono output situation - am I right in saying I can just use the two XLR outs from the kemper into each of them, and it'll still be mono (just 2 x mono signals)?

    You can decide, which outputs you want to link to Master Volume and which outputs you don't want to link and run at a constant level. You can unlink MAIN OUTPUT for FOH and link MONITOR OUTPUT for your monitoring on stage. If you pair MONITOR OUTPUT and DIRECT OUTPUT ("Monitor Stereo"), any settings for the MONITOR OUTPUT affect the DIRECT OUTPUT as well - including the link to Master Volume.


    If you are monitoring in mono or stereo and if you are feeding FOH mono or stereo are also completely independent decisions. You can select the Output Source of the MAIN OUTPUT independent of the MONITOR OUTPUT (potentially paired with DIRECT OUTPUT).


    In that particular issue situation I have disconnected FOH from that XLR output and connect the Headrush to that XLR output. Any issue? If not, FOH problem. I would for example check, if the mixing desk is sending phantom power, which should never be the case. Perhaps that is hammering down the output amplifiers of the PROFILER.

    Quote from Burkhard

    You can decide, which outputs you want to link to Master Volume and which outputs you don't want to link and run at a constant level. You can unlink MAIN OUTPUT for FOH and link MONITOR OUTPUT for your monitoring on stage. If you pair MONITOR OUTPUT and DIRECT OUTPUT ("Monitor Stereo"), any settings for the MONITOR OUTPUT affect the DIRECT OUTPUT as well - including the link to Master Volume.


    If you are monitoring in mono or stereo and if you are feeding FOH mono or stereo are also completely independent decisions. You can select the Output Source of the MAIN OUTPUT independent of the MONITOR OUTPUT (potentially paired with DIRECT OUTPUT).


    In that particular issue situation I have disconnected FOH from that XLR output and connect the Headrush to that XLR output. Any issue? If not, FOH problem. I would for example check, if the mixing desk is sending phantom power, which should never be the case. Perhaps that is hammering down the output amplifiers of the PROFILER.

    Cheers - I didn't have my Headrush speakers with me last night to test, but if I'm asked back I'll just use the FrFr speakers as a backline I think - will make things easier for all involved!

    Did the sound-guy complain about your level being too high?


    Are your Headrush speakers inputs set to mic or line-level?


    The KPA's main outputs are line-level and thus too hot for many mixing-desks unless you limit the output. Some mixing-desks produce weird results when input gain is set at or close to minimum. You should thus turn down the output and set your speakers for mic-level input if you run through them to FOH.


    I have my KPA's main output set more or less permanently at -25dB or so. Further, I detach the main outputs from the master-volume and use monitor-out (+ direct out if I want stereo) for monitoring. This way I always deliver consistent levels (mono or stereo depending on the sound-guys wishes) to FOH regardless of how I adjust my stage-level with the master-volume on the KPA.

    Quote from Burkhard

    Since OS 4.2 there is a -12 dB PAD for the MAIN OUTPUT in the Output Section.

    Damn, those XLR outputs are hot =O


    I used the main outs XLR in mono straight to the desk in a rehearsal studio last night. I always have the -12db pad on my main outs and the -20db pad engaged on the desk itself. Even with this setting their desk was overloading massively. I reduced my main output volume to around - 35db and it was still running hot on their desk. The studio owner ended up using an XLR to TS adaptor (if I'd know that's what he was away looking for I would just have changed to the TS output myself :D). The cause was clearly that the desk had Mic Pres which couldn't be bypassed on the XLR ins. I know this is quite common with audio interfaces but I have never seen it so bad on a desk. My own desk (an old Mackie 32:8 handles the XLRs with -12db pad no problem even with the KPA master set to full.

    Quote from Wheresthedug

    I always have the -12db pad on my main outs and the -20db pad engaged on the desk itself. Even with this setting their desk was overloading massively. I reduced my main output volume to around - 35db and it was still running hot on their desk.

    Just curious: what make/model of desk was that? I use to set my main outputs at -25dB or so, and that is OK with most desks. Only once have I been asked to turn down 5dB further and that was a guy with a Midas Pro1 mixer. It is nice that Kemper has implemented an optional output "PAD", but I wish it had been -25dB instead of -12dB.