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KC-500 is quieter on R side...so I have a question about the mono inputs


I just got a great deal on a used Roland KC-500 Sounds NICE. The only drawback is that when plugging in any stereo inputs, the L (mono) side input is always louder. Probably almost twice as loud. I have not been able to fix this yet, so I don't know if this is a setting I am not aware of, or if it's just what makes this amp special.
In testing, I was able to work around this by plugging in the keyboard L plug on the L side of the channel 1 input, and the R side on the R side of the channel 2 input, and the just cranking 2 up a ways to match the output of channel 1.
If this is what I have to deal with, is this bad to do? To plug in a mono input on the non-mono side of a channel?
I only need this amp for keyboard and a drum track, so I will never need more than two instruments going into the amp. I do not want to settle for mono inputs or a quiet R input, so I am hoping to figure out a good solution.
Any suggestions appreciated!
January 1, 2012 @02:40am
Dave Burris

Are you running the line outputs to a house mixer?
Have you tried using the other channels for stereo input to see if the problem is only channel 1?
Have you tried swapping L & R inputs?
The owner's manual has an interesting footnote:
* The volume of a mono connection will be louder than that of a stereo connection; this is normal.

Still your description of the operation does not seem normal. Might want to have a tech check it out.
January 1, 2012 @02:31pm

Not sure about house power. Yes, all channels do this...I should have made that clear. Swapping doesn't matter.
Is it possible this is an optical illusion? Such as...all is fine when they are plugged in as stereo, but when I remove one, the mono gets loud and the R gets quiet? Because the amp goes quiet when a change is made.
The guy testing this discovered this, so maybe this is totally normal. I just assumed the R side would also be quieter while in stereo mode.
I sure am glad you found this footnote, because I am starting to think there is no problem at all.
January 1, 2012 @04:06pm
Dave Burris

I suspect the jacks are wired such that a signal plugged into L (Mono) goes to both L & R until you plug in something to R, then they are split. Something plugged into R probably goes to R only.
As I think about this scenario, I think it's probably normal for this unit. Still something in your description seems unexpected. Without seeing a schematic, I suspect that plugging a mono signal into the R input would only feed the R channel while the same signal into the L would feed both L & R until you plug into the R on the same channel.
While it will not do any damage, plugging half of a stereo signal into L on one channel and R on a different channel would most likely behave exactly as you have described.
January 1, 2012 @05:12pm

This is the normal state for any stereo hookup I've ever seen.
I stand to be corrected by an audio engineer, but I believe that most of the program info is carried on the L channel.
In fact, on my Kurzweil PC2R-O, you are instructed to connect only the L output if you are going mono.
Same on any of the mixers (mostly Mackie) we use at work.
You can skew the volume balance by panning to the R side, but this
just degrades the overall sound.
April 26, 2012 @11:42am