Bob L Posted March 26, 2013 Share Posted March 26, 2013 Guys, I know some have no love for Roland keyboard amps on this forum, but that is what I currently use. I have a KC 150 that frequently will hum. It doesn't seem to be isolated to a channel (there are 4). The signal source doesn't seem to matter (privia px3 or vintage korg cx3). I have tried using a two prong adapter (some called a ground lift??) and that doesn't work (sometimes it seems to make a difference, but it probably is a safety issue also). Are there other techniques to minimize hum? Would getting it serviced make sense (has anyone gotten their Roland amp serviced to fix this kind of problem)? I don't want to waste money on techniques that don't work. I also have problems with hum when taking the line out to the PA. I use a TRS to male XLR cable ( perhaps a balanced versus unbalanced problem)? This month I gigged more than usual and it has really gotten to irritate me. Aside from "replace the amp" advice are there steps I can take to isolate and overcome this problem. Since I use the amp as a stage monitor primarily (leverage the PA for heavy lifting) I would like to hang on to the amp and get this figured out. Please no flames if I am clueless. Korg CX-3 (vintage), Casio Privia PX-5S, Lester K, Behringer Powerplay P2, Shure 215s http://www.hackjammers.com Link to comment Share on other sites More sharing options...
Joe Muscara Posted March 26, 2013 Share Posted March 26, 2013 "I'm so crazy, I don't know this is impossible! Hoo hoo!" - Daffy Duck "The good news is that once you start piano you never have to worry about getting laid again. More time to practice!" - MOI Link to comment Share on other sites More sharing options...
RudyS Posted March 26, 2013 Share Posted March 26, 2013 Damn Joe! Beat me to it!!! Rudy Link to comment Share on other sites More sharing options...
J. Dan Posted March 26, 2013 Share Posted March 26, 2013 Does it hum with NOTHING plugged into it? Just sitting idle? Does adjusting the volume increase/decrease the hum, or is it a constant level regardless of volume? Dan Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth. Link to comment Share on other sites More sharing options...
Ekewaka Posted March 26, 2013 Share Posted March 26, 2013 Is the hum something that you could hear on top of the music played, then it's indeed not good. My guess -- and it's been ages since I did electrical engineering work and fixed keyboards -- is in the transformer, especially if nothing is connected in, you use a good power source and you still hear the hum. If you are handy you could open it up and maybe hear where the hum comes from. If the transformer, might be you could find a replacement one and put that in. But be careful with electrical systems so you don't get hurt or burn the whole thing. If humming with specific equipment, then you need to isolate the issue, cables, mixer, keyboard... Small chance there's something wrong with the input jack/circuits, as well. Link to comment Share on other sites More sharing options...
Joe P Posted March 26, 2013 Share Posted March 26, 2013 Does it hum with NOTHING plugged into it? Just sitting idle? If not this, then did you try different cords? Link to comment Share on other sites More sharing options...
J. Dan Posted March 26, 2013 Share Posted March 26, 2013 Kenekahuna is refering to something in the amp physically humming - in which case, he's right, it would be the transformer. My interpretation was that you meant hum coming from the speaker - like a ground loop or something along those lines. I guess please clarify which you mean. Dan Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth. Link to comment Share on other sites More sharing options...
RudyS Posted March 26, 2013 Share Posted March 26, 2013 I think it is just the design of the amp. You could check the same amp at a store to see of your model has more hum. Rudy Link to comment Share on other sites More sharing options...
kanker. Posted March 26, 2013 Share Posted March 26, 2013 have a KC 150 that frequently will hum.Apparently it doesn't know the words? A ROMpler is just a polyphonic turntable. Link to comment Share on other sites More sharing options...
Bob L Posted March 26, 2013 Author Share Posted March 26, 2013 It will hum sitting idle. It hums with nothing plugged in (hum gets a little worse with something in channel one, the other channels don't seem to increase hum when something plugged in). Turning the volume up increases the hum whether something is plugged in or not. Hope this helps.... Korg CX-3 (vintage), Casio Privia PX-5S, Lester K, Behringer Powerplay P2, Shure 215s http://www.hackjammers.com Link to comment Share on other sites More sharing options...
J. Dan Posted March 26, 2013 Share Posted March 26, 2013 OK, so that verifies that it's in the amp and not an issue with ground loops with different devices, or cords, or anything like that. Since increasing the volume increases the hum, that tells us that the problem is at the front end - i.e. the mixer/preamp stage. This is verified by the fact that you get hum through the line out, which comes off the mixer prior to the master level adjustment (referring to the block diagram in the Roland manual). Input 1 has a mic input, which means it probably has more gain than the other channels, which will increase the noise. I would say the source of the hum is in the mixer. It's possible it could be from just one of the channels, or a bad ground somewhere in the mixer circuit. Do any of the channel volumes make a difference with nothing plugged in? In other words, start with all channels all the way down, turn up main volume til you hear some hum, then turn up each channel and back down one at a time....is there any difference from channel to channel? Dan Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth. Link to comment Share on other sites More sharing options...
Bob L Posted March 26, 2013 Author Share Posted March 26, 2013 Tried turning up each channel one by one. Channel one introduces hiss when turned up. Channel two I have had trouble with (have stopped using as the volume level is always weak) and when turned up emits a "pop" occasionally. Channels 3 and 4 have no impact on the hum. Turning the master volume up and down (as already stated) makes the hum louder/softer. Korg CX-3 (vintage), Casio Privia PX-5S, Lester K, Behringer Powerplay P2, Shure 215s http://www.hackjammers.com Link to comment Share on other sites More sharing options...
Joe Muscara Posted March 26, 2013 Share Posted March 26, 2013 I had one of those (which I finally sold recently to a guy who was replacing his that died. I wasn't going to argue with a sale...). Channel 1 hummed so much that I found it unusable. "I'm so crazy, I don't know this is impossible! Hoo hoo!" - Daffy Duck "The good news is that once you start piano you never have to worry about getting laid again. More time to practice!" - MOI Link to comment Share on other sites More sharing options...
mikecorbett Posted March 26, 2013 Share Posted March 26, 2013 Considerable restraint on display around here today, not 1 mention of chainsaws We are all slave's to our brain chemistry! Link to comment Share on other sites More sharing options...
Tonysounds Posted March 26, 2013 Share Posted March 26, 2013 And this isnt only at home, or in one location, right? If its at home (and not other locations), try plugging it in elsewhere to verify its the amp and not the house wiring. (Ive seen wiring flipped in locations which will cause amps to hum if nothings plugged into the amp; Ive heard reverse wiring cause massive hum if keyboards or guitar pedal board are plugged into one circuit, and the amp in another when the reverse wiring is only on one circuit.) Hitting "Play" does NOT constitute live performance. -Me. Link to comment Share on other sites More sharing options...
Bob L Posted March 26, 2013 Author Share Posted March 26, 2013 Hum happens at home and at gigs. Some places it seems worse than others.... Korg CX-3 (vintage), Casio Privia PX-5S, Lester K, Behringer Powerplay P2, Shure 215s http://www.hackjammers.com Link to comment Share on other sites More sharing options...
Dana. Posted March 26, 2013 Share Posted March 26, 2013 All this talk about humming, things plugged in or not plugged in, technique, irritation... what kind of forum is this?! Link to comment Share on other sites More sharing options...
J. Dan Posted March 26, 2013 Share Posted March 26, 2013 Tried turning up each channel one by one. Channel one introduces hiss when turned up. Channel two I have had trouble with (have stopped using as the volume level is always weak) and when turned up emits a "pop" occasionally. Channels 3 and 4 have no impact on the hum. Turning the master volume up and down (as already stated) makes the hum louder/softer. Ok, it's quite possible that what's causing the hum is the same thing that's wrong with channel 2. Most likely a broken ground. If the volume pot isn't doing anything, maybe the leg that's supposed to be tied to ground is bad, or the pot itself is bad. That could end up being an easy fix for a technician. If you're comfortable doing it, you may first want to open it up and see if you can spot anything obvious on channel 2, like broken connections, etc. Dan Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth. Link to comment Share on other sites More sharing options...
mate stubb Posted March 26, 2013 Share Posted March 26, 2013 http://medieval.mrugala.net/Armes%20de%20siege/Images/Trebuchet%2005.jpg Moe --- Link to comment Share on other sites More sharing options...
J. Dan Posted March 26, 2013 Share Posted March 26, 2013 http://gameswalls.com/wallpapers/k/knights-of-honor/trebuchet-1.jpg Your trebuchet attempt failed, LOL. Apparently they don't like you linking to their pictures. Dan Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth. Link to comment Share on other sites More sharing options...
J. Dan Posted March 26, 2013 Share Posted March 26, 2013 How about this one? http://img.rlt.com/m/10441.jpg Dan Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth. Link to comment Share on other sites More sharing options...
Bob L Posted March 26, 2013 Author Share Posted March 26, 2013 thanks for all of the advice. I will see about the issues with channel 2 on the mixer. I do appreciate everyone's restraint with the chainsaw comments. If I was playing keyboards full time ( or independently wealthy), I would spring for new amplification...... Korg CX-3 (vintage), Casio Privia PX-5S, Lester K, Behringer Powerplay P2, Shure 215s http://www.hackjammers.com Link to comment Share on other sites More sharing options...
Joe Muscara Posted March 26, 2013 Share Posted March 26, 2013 http://blue-funk.com/NonBandPictures/smileys/chainsaw.gif "I'm so crazy, I don't know this is impossible! Hoo hoo!" - Daffy Duck "The good news is that once you start piano you never have to worry about getting laid again. More time to practice!" - MOI Link to comment Share on other sites More sharing options...
Michael Wright Posted March 26, 2013 Share Posted March 26, 2013 http://blue-funk.com/NonBandPictures/smileys/chainsaw.gif Knew it couldn't last. "I cried when I wrote this song Sue me if I play too long" Walter Becker Donald Fagan 1977 Deacon Blues Link to comment Share on other sites More sharing options...
Bossbandbob Posted March 26, 2013 Share Posted March 26, 2013 For what it is worth, I just sold my KC350. Never had any inherent hum or problems and it was bullet-proof as my stage monitor/DI out for 12 years. Sounded fine to me in that capacity. Basically only sold it to buy lighter (weight) amplification. Hammonds:1959 M3,1961 A-101,Vent, 2 Leslies,VB3/Axiom, Casio WK-7500,Yamaha P50m Module/DGX-300 Gig rig:Casio PX-5S/Roland VR-09/Spacestation V3 http://www.petty-larceny-band.com Link to comment Share on other sites More sharing options...
Lone Stranger Posted March 26, 2013 Share Posted March 26, 2013 have a KC 150 that frequently will hum.Apparently it doesn't know the words? I knew this one was coming. It was the first thing I thought of as well. PCLinuxOS user Link to comment Share on other sites More sharing options...
t9cstudio Posted March 26, 2013 Share Posted March 26, 2013 Probably a loose filter cap, wire or something else inside causing the hum. Take it to an amp tech and have them check it out. Kurzweil PC4, NS3-88, Kronos 2-61, QSC K8.2's. Link to comment Share on other sites More sharing options...
ITGITC Posted March 26, 2013 Share Posted March 26, 2013 Tried turning up each channel one by one. Channel one introduces hiss when turned up. Channel two I have had trouble with (have stopped using as the volume level is always weak) and when turned up emits a "pop" occasionally. Channels 3 and 4 have no impact on the hum. Turning the master volume up and down (as already stated) makes the hum louder/softer. Owner's Manual See the Block Diagram on page eleven. I suspect the op amp for channel two may be the problem here. Or... there is a ground problem, cracked solder connection, or a cracked circuit board. Channel one will indeed introduce more hiss because it is a mic input and has more gain. This is normal. Since channel two has a history of giving you low levels and intermittent pops, I would suspect the problem is a bad op amp IC. If so, then adjusting the master volume would indeed make the hum louder or softer. I'd take it to the Roland tech. Good luck. Tom "Music expresses that which cannot be put into words and that which cannot remain silent." - Victor Hugo Link to comment Share on other sites More sharing options...
kanker. Posted March 27, 2013 Share Posted March 27, 2013 have a KC 150 that frequently will hum.Apparently it doesn't know the words? I knew this one was coming. It was the first thing I thought of as well. Quite frankly, I was surprised it was there for the taking by the time I saw this thread. Buncha amateurs around here.... A ROMpler is just a polyphonic turntable. Link to comment Share on other sites More sharing options...
Ekewaka Posted March 27, 2013 Share Posted March 27, 2013 Me thinks the popcorn eaters are the amateurs :-). Link to comment Share on other sites More sharing options...
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