What you are experiencing is caused by a ground issue. It can sound like a high pitched zinging noise when different devices are connected to a single computer. The noise will change character as your computer is asked to do a task like search for an item. It is not really the fault of just one device but a sum total of all connected devices and the ground status. This can be extremely easy to fix or very tricky depending on the electrical sources in your studio, and where in the world you live.

Start with where your computer and all devices are plugged in - try to avoid plugging items into separate electrical lines in your studio. Try getting everything plugged into a single electrical line avoid two separate sources. Consult articles on ground and your computer ... Magazines like Keyboard and SoundOnSound have great articles about ground issues when computers are involved.

http://www.soundonsound.com/sos/dec08/articles/qa1208_2.htm

Thanks I will test out your suggestions. What is strange is that I am plugging the CP4 into my system where the Kawai MP10 had previously been and I never had any noise issues with the Kawai. I also have no noise issues with any of the other equipment in the studio. I only have three USB MIDI instruments plugged in - the CP4, Roland Integra 7 and Motif Rack XS.

I have an old Yamaha P250 and I might try using this as my studio master keyboard in place of the CP4 and see if there are any noise issues with this in the system.

My mixer is Firewire rather than USB

I'll keep testing

Ground issues when connecting to a computer can exist in any type of connection, USB, FW etc. You need to find a method to address your ground issue. All your gear uses electricity and all gear is susceptible to adding to a ground issue. Test all you wish, but you'll need to correct the ground issue.

Set up my old Yamaha P250 piano now in place of the CP4 in the studio and using exactly the same USB connection. No problems now with any USB noise. I'll use this old classic instrument as my studio master keyboard again and keep the CP4 for gigging.

Thanks for your help and advice

This is a common problem and can happen with any manufacturer. I agree with Bad Mister: it's a ground loop problem. I also agree that regarding ground loops, there's no difference between Firewire and USB, and no difference between using just one or the other, versus using both, since they share a chassis ground.

It does seem odd that you have it with CP4 but not P250. In both cases, are the audio connections the same, too? If you're connecting the CP4 audio to anything at all, try with and without the audio connection and let us know if that changes anything. If so, there may be another option to try, which works only if you have audio gear with balanced inputs, or an isolator.

One easy and inexpensive fix is to get a cheap "MIDI/USB adaptor cable", which I see for under $6 on ebay, and all reports from folks using these is that they're fine. In their great wisdom, the originators of the MIDI spec required that MIDI connectors (the actual round "DIN" MIDI connectors, not the MIDI/USB) be optically isolated at the receiver, to prevent this kind of problem. So, if none of Bad Mister's suggestions fix the problem, try one of these, and be happy that your CP4 has DIN MIDI connectors in addition to the USB.

I believe that for the CP4, there is no difference in features between MIDI/DIN and MIDI/USB. The biggest difference is transmission speed, which shouldn't be noticeable for any application on CP4 that I can imagine. If I'm mistaken about this, hopefully Bad Mister will correct me.

I have a similar situation with the CP4 that I don't experience with my ole' buddy CP33 when using the USB out to control an iPad Mini2 128gb (using the recommended Apple USB to Lightning camera adapter) to layer additional voices from the iPad. There is a buzz with the CP4 that is wholly absent with the CP33.

I thought maybe the issue could be averted by running the iPad's 1/8"TRS output directly into the CP4's 1/8"TRS input rather than into a separate mixer channel, since then there is no additional electrical power source being introduced into the setup and the signal loop is CP4 USB > iPad > CP4 1/8 stereo input - but the buzz persists.

I then thought it was perhaps because the CP33 has an external power adapter vs. the CP4's internal that somehow plays a part (and reading about the use of the P250 vs. CP4 above would be a similar situation), but also seeing that the same thing happening substituting the CP4 for a Kawai MP10 (which both have internal power adapters and both accept a standard 3-prong IEC electric cable end) shoots that theory.

Have not had an opportunity to try it with my S90ES (I get all the layers I need with that board coupled with a SK1, so no real need to add the iPad to that rig), but have tried the CP4/iPad direct-into-CP4 setup with all AC components running from a single Monster Pro 2500 PowerCenter to have everything running with common grounds and still get the buzz.

Once more, it is a simple ground issue, in all likelihood. Means it is a total system issue - each device has an electrical footprint in your system, including the speakers. Solvable usually without a lot of trouble. Any setup, anywhere can be susceptible, in spite of everything you may do... you can continue to swap gear and you might still be unable to nail down the exact cause. Because it manifests itself as a high pitched whine, influenced in pitch by your computer's mouse and hard drive activity, should be all the clue you need!

Listen closely, and if your computer has a drive activity light - watch that light flicker. Ask it to search a hard drive, listen as the high pitched whine changes in sync with the drive activity light.

I solved a similar issue for a college lab system setup (USA) where they had 30 computers in a room setup in a teaching network where the instructor could direct the class's attention to any individual station setup, etc. etc.. Tons of modules, I/O's, computers, controller keyboards, all networked - each with that high-pitched whine you are experiencing - solution: Ebtech's Hum X adaptor (www.ebtechaudio.com/humxdes.html) plug the computer into this and this to your Power source, done. I mentioned that was here in the USA, as the SoundOnSound article's author says he has not found and equivalent for other voltages... But don't suffer trying to "maybe" solve the issue by swapping gear, or cables or crossing your fingers or pointing blame at one thing or another... Recognize the cause is electrical, minor (in 99.99% of cases), and quickly solvable when approached with the knowledge of what it is... A ground issue. Approach it as such, solve it, get back to making music!

Hope that helps. If you are not in the USA, consult an electrician who understands your voltage... Double insulated power supply unit for your computer, or USB isolators, are always an option. The article mentions running the computer on batteries (if you're running a laptop - this instantly solves the issue) but be careful, the specs of your computer are vastly different when running on batteries versus when plugged in.

I'm running an iPad, it is on battery power (since the USB input occupies the same port that would be used to power or recharge) and it is not plugged into anything but the CP4 on both input and output. The CP4's 1/4 line-outs into the whole setup produces no noise whatsoever; connecting the iPad's 1/8"TRS output to the CP4's 1/8"TRS input likewise introduces no noise and iPad content played through the CP4 is clean and clear; the "buzz" only appears when the USB port on the CP4 is used.

Have tried it with four different USB cables and two separate iPads, which all work perfectly with the CP33 substituted for the CP4.

The CP4's 1/8"TRS input also works beautifully (and cleanly) when inputting a Hammond SK1's (which has its own separate power supply) stereo outs into it, and then running the CP4's XLR outs to a FOH mixer and the CP4's 1/4" outs back to two powered speakers. The hope was to simply substitute the nice software Hammonds on the iPad for the SK1 for times when quick on-stage/off-stage single-board situation called for it; the only variable changing is removing the SK1 (which also takes away an AC power-source contributor), and substituting an iPad as the component being inputted into the CP4, and then the CP4's USB introduced. Result is then the same as the previous contributors' reported - the introduction of noise only when the CP4's USB is utilized.

Thanks for all the additional info and time and attention you've directed to this, very much appreciated; will continue to chew and re-chew on all of it and see if a solution results.

I'm sorry, Rick, your issue is not really, at all, like the other issue discussed in this thread. You are connecting the CP to an iPad (?) via what type of USB connector(s)? For what specific purpose?

The CP4 Stage's USB "To Host" port is designed to connect to the USB port on a computer or laptop. You can also connect to an iPad for MIDI via an iUX-1, for example... then, I presume, you're running the audio out of the iPad to the Aux In of the CP4 Stage. Is that correct? That should not sound like a high pitched zinging noise at all, but more like your standard constant hum. (I suppose we should have to begin taking these tablet devices as serious audio tools. And look for solutions to make them musician/stage friendly).

Connecting the audio out from the headphone out jack back to the CP4 Stage (while connected via USB) sets up some kind of loop - that is for sure. Frankly, I'll have to take a look at this. It would help to know what type of connectors/cable/adapters you are using.

Saying you've connected the CP4 Stage to an iPad via USB begs the question - How?
What happens if you connect the audio out of the iPad to your sound system without going back through the CP4 Stage? Or you listen in headphones? Is the hum still present or is it there only when you connect the out back to the Aux In?

Let us know - and then we'll try to duplicate your setup... And send in a report.

Back to the earlier thread points and in answer to Jeff yes when I replaced my MP4 with my old P250 I used exactly the same connections. The same L R jack leads (I used the unbalanced outputs) and same USB lead plugged into same connector on my computer. With the P250 I have no problems, no noise or interference.

In the long run it suits me better anyway as I am not using any actual sounds from the P250 just using it to drive software piaos and taking general master keyboard duties. Even though it is old the action is still pretty good overall. I'll reserve the CP4 for gigging action.

It is odd what happened though with the CP4 as I have no trouble with any of my other MIDI gear.

Thanks very much; the connection is as described in my post above your next-to-last post: USB cable into an Apple USB/Lightning camera adapter, and then into an iPad Mini2 Retina 128gb. The Apple USB/Lightning adapter is used/recommended for several of the software modules available for the iPad (such as Korg Module and Galileo), and you're right - iPads are being used more and more for performance in lieu of laptops, especially the later iPads with 64bit processors that can achieve north of 64 polyphony with negligible latency.

When using this with the CP33, the iPad output was via 1/8"TRS to dual 1/4"TS cable into a mixer's stereo channel (and sometimes through an Ernie Ball stereo volume pedal first to control the iPad's presence/volume), with the CP33 running into a second stereo channel; the mixer's stereo XLR outs went to FOH and the mixer's Control Room stereo outs went to backline powered speakers. But when using the CP4, part of the goal was to eliminate the mixer in the quick-on/quick-off stage setup, so I took the mixer out of the setup and ran the iPad's output into the CP4's 1/8" stereo input with a 1/8"TRS to 1/8"TRS cable (which works perfectly to play iPad music content over/via the CP4), used the CP4's XLR outs to feed FOH and its 1/4" outs to feed the backline powered speakers. So you may indeed be onto something when you ask about using the CP4's USB but not connecting the iPad's audio back into the CP4 and connecting it externally instead (or to headphones). I was going at it a bit the other way; ascertaining a sound/stable setup with the iPad audio out connected to the CP4 and the CP4 connected to systems/amps downline, and then making the USB connection into the CP4 last - so I will check to find answers to your questions when I'm back off the road tomorrow.

Thanks again, greatly appreciated.

...and you're right - iPads are being used more and more for performance in lieu of laptops, especially the later iPads with 64bit processors th

I was partially saying this for humor, because while the digital audio out (Lightning) is okay, the 1/8" stereo mini jack is just not what we, as musicians, should be aspiring to use as a connector... We should be lobbying for better analog audio connectivity for serious play. Even the little Lightning connection makes me nervous as a connector to have to rely on while on stage (of course, this is my personal opinion and my personal wish list).

For example, the MOXF was recently updated to include audio plus MIDI via the USB-to-Lightning connection, and avoids the analog 1/8" audio loop back. Audio is routed digitally from the iPad/iPhone through the MOXF's DAW LEVEL return... Offering a separate level control and pristine audio quality.

The top-of-the-line Motif XF can communicate audio/MIDI wirelessly between the iPad and the synth, and while this has its own set of issues (or can) it is reliable audio that is always noise free.

Anyway going forward, hopefully, the tablet-world will not completely ignore professional use and offer improved connectivity options. We can only hope... The AuxIn on the CP4 Stage was provided simply, as you describe, to playback today's consumer audio devices (like phones, tablets, handheld playback devices) through its audio outs. There is no gain stage in associated with this input. It is a simple play-through input. No mention of any iOS connectivity is included in the documentation.

I will look into solutions and report back.

Bad Mister wrote:

Once more, it is a simple ground issue, in all likelihood. Means it is a total system issue - each device has an electrical footprint in your system, including the speakers. Solvable usually without a lot of trouble. Any setup, anywhere can be susceptible, in spite of everything you may do... you can continue to swap gear and you might still be unable to nail down the exact cause. Because it manifests itself as a high pitched whine, influenced in pitch by your computer's mouse and hard drive activity, should be all the clue you need!

Listen closely, and if your computer has a drive activity light - watch that light flicker. Ask it to search a hard drive, listen as the high pitched whine changes in sync with the drive activity light.

I solved a similar issue for a college lab system setup (USA) where they had 30 computers in a room setup in a teaching network where the instructor could direct the class's attention to any individual station setup, etc. etc.. Tons of modules, I/O's, computers, controller keyboards, all networked - each with that high-pitched whine you are experiencing - solution: Ebtech's Hum X adaptor (www.ebtechaudio.com/humxdes.html) plug the computer into this and this to your Power source, done. I mentioned that was here in the USA, as the SoundOnSound article's author says he has not found and equivalent for other voltages... But don't suffer trying to "maybe" solve the issue by swapping gear, or cables or crossing your fingers or pointing blame at one thing or another... Recognize the cause is electrical, minor (in 99.99% of cases), and quickly solvable when approached with the knowledge of what it is... A ground issue. Approach it as such, solve it, get back to making music!

Hope that helps. If you are not in the USA, consult an electrician who understands your voltage... Double insulated power supply unit for your computer, or USB isolators, are always an option. The article mentions running the computer on batteries (if you're running a laptop - this instantly solves the issue) but be careful, the specs of your computer are vastly different when running on batteries versus when plugged in.

Ground loops are never Simple. Not only the setup is influencing, also the devices it self. So there is a big chance that the Kawai MP is better designed for USB ground loops then the CP4. The solution you suggest is good for ground loops over the mains connections. That is not the issue here. here the loop is betweem the analog connections and the USB ports. I also have problems with Yamaha MP61 and Yamaha P-115 with using USB and I think Yamaha did not designed it optimal for these products. A ground loop isolator is the only solution.

I've had this happen with my CP4 connected to Mac laptop via USB. In my situation, simply using the XLR output instead of the unbalanced 1/4" outputs solved the problem. No problem with S90XS, but I remember when I still had the Motif XF8, I needed to use Ebtech Hum Eliminator or DI with ground lifted.

LK