LED Back Light causing line noise

I couldn't figure out where this noise was coming from (like a real shrill whistle) until the other day I cut the back light off and the noise stopped... I was just curious if any one else noticed this or is my 500 special? any ideas (besides the obvious, cut it off) on how to resolve it also would be tight. Thanks

I've heard that noise too, you could be on to something! Good catch, I shall look deeper into it when i come back from the mall!

might be something we can put into the 1.31 bug list, hopefully its fixable. but yeah ill check it out too, and let you know if it happens for me

does this happen when you record out, or when your recording in?

Never had this issue.

Could be a ground loop of some sort. Not sure about this.

My setup:

PMC-05 out to MPC line in (RCA to 1/4 cable)
MPC out to Beringer mixing board in (1/4 to RCA with RCA to 1/4 adapters)

Backlight always on. Batteries never installed (I've literally never put batteries into my 500), always running on AC power. Amp is on different circuit than mixer and MPC.

namotu wrote:does this happen when you record out, or when your recording in?

Happens without recording at all... just sitting there doing nothing but being on & you can hear it... but it does end up in the recording also if I don't cut off the back light...

I have my mpc with two 1/4" lines going out & two coming in... I run them thru a behringer mixer... and of course the mixer is hooked into a RCA to USB interface that runs to the computer

click my myspace link and go to the reverbnation widget on the left and play the 4th track called NUCLEAR SUN... and in the intro you can hear what I'm talking about, that real shrill whistle.

Yeah I have this as well - I am sure it is a known issue as I believe I read about it before on this site

audiowarez wrote:Yeah I have this as well - I am sure it is a known issue as I believe I read about it before on this site

Yea I searched & couldn't come up with nuthin... be cool if some one finds it & post a link, I mean if there was ever a resolve?

HAHA, thanks. That noise has anoyed me for a while!

Where's guyb when you need him? lol ...

Think we can safely say it's a common issue.

This has pissed me off for some time and figured it was the quality of the thing, and gated it out. Not near my MPC at the moment but will check out turning the backlight off. If this solves the issue I will be a very happy bunny indeed!

No noise on my 500 AC or DC powered.
I use it in the studio with my other gear, in the truck, on the sofa where ever when ever with no noise.

Something you might want to try is to disconnect the 500 from everything and see if you hear it in the headphones.

I would suspect it to be more related to how your 500 is hooked to other gear moreso than a 500 problem.

Poor gain staging, poor cables. connectivity of USB devices etc are all pretty susceptible to noise that a backlight can generate.

I only get noise when I have the USB lead plugged in. Its a bloody annoying high pitched whine which comes through my main monitors. I will try the led backlight switch later. It wouldn't suprise me if the backlight was controlled by a PWM current (basically turning it on and off really quickly) to reduce the power consumption a bit and this could potentially cause interference of roughly the frequency I can hear over the speakers. If this was the case you could potentially desolder the led and attach it to a power rail on the PCB instead of the PWM driver, which would use a bit more power and probably be brighter. This would be a pretty hardcore hack though for not a great gain! If the PWM duty cycle is software controlled then Akai should be able to provide an option to turn it fully on in firmware which should remove the problem.

MPC500 -> unbalanced jack -> EMU 1616 -> balanced speaker cable -> KRK RP5

(The preamp is very noisy at high gain also but what do you really expect!)

I get the noise you guys are talking about, but only when I plug my 500 into the 1/8 in input that leads to my car stereo. Which makes me think it's not the backlight, but rather a power source or unbalanced audio cable (?) or something along those lines. I don't hear it when it's running through my home receiver, dj mixer, board mixer, soundcard or headphones. But it makes it when running through my car.

yeah i noticed that noise when i first got it the first month the 500 came out. it gets louder if your only using batteries and the batteries are dying. i also get a buzz when i put cables in the "record in" jacks.

*when i track it out in my pc, i unplug the jacks that go to the "record in" and i shut off the backlight.