My LXR audio outputs are kind of noisy... [solved]

borfo

My LXR's audio outs are significantly more noisy than any of my other devices...  Has anyone else noticed that?  Not outrageously noisy, and nowhere near unusable, but if I turn up the LXR channel on my mixer while the LXR's plugged in but silent, the noise floor is pretty audible - a lot louder than my other devices when I turn their mixer channels up.

Is there anything I could do to get rid of some of the noise?  Is this just my LXR, or is this a common issue?

djversus01

I was wondering the same thing!

However I was using trs cables when I noticed this, only because thats all I had around at home, and I thought maybe it was due to having turned up the gain on those channels to compensate for the drop in volume you get when using trs cables with unbalanced gear, however this is usually only a 3db difference. On the other hand at the levels that the noise floor typically occurs I suppose 3db could be the difference between noticing the noise floor vs not? Even though the s/n ratio doesn't change in this case it could still account for noticing the noise more due due to psychoacoustics.

Are you using ts cables?

borfo

I'm using TS cables now, but noise is noticable with either TRS or TS cables.

djversus01

I'm not entirely sure, but I suppose the other thing to check are the capacitors c1, c3, maybe c2, c4 as well.

Hopefully someone more knowledgeable can weigh in here, but I guess we would want to check that the components are good, and also that the soldering is good for those components, as I believe these are responsible for filtering out noise from the power supply?

That right, anybody?

djversus01

seriously? nobody?

borfo

Thanks - I'll check those caps.  I wasn't so much concerned that there was anything wrong with my LXR in particular, was more thinking that the LXR might just have a relatively loud noise floor by design, and wondered if anyone had any ideas as to how to quiet it down a bit...

I'd be interested to hear if other people notice that it's noisy as well - I'm not talking about a lot of noise, just that it's noticably noisier than my other devices.

erwanone

I don't really notice a noise, i use 2 jacks that i plug directly in my monitoring

Mesmerised

It must be a problem with your units because my LXR has a really low noise floor. I found the audio quality of the LXR to be really good. (used in a pro studio setup)

julian

do you have USB connected?
Is the LXR using the same outlet as the rest of the equipment?

borfo

USB is not connected.  All of my 9v equipment is powered off one 4amp 9v power adapter with a splitter, everything is plugged into the same power bar.

I'll check the soldering on the caps djversus mentioned - if other lxrs have a low noise floor, I guess maybe it is something particular to mine.

julian

are all 4 outs noisy or only a single pair?

borfo

All four.

str

I noticed a visually perceptible noise floor on my spectragraph VST when I did some quick and dirty DAW processing, but I haven't had time to rule out my recording device and other noise-generating factors in my setup. The noise was inaudible until you cranked up the gain, but it was there. I'll try and test other devices and maybe post the results. 

djversus01

Hey Borfo, 

So the noise went away for me, no idea why. 

One thing that changed since before was I used different cables. Maybe check with a different set of cables, although maybe you've done that already. I'm working without an enclosure (still designing it), which might make it hard to plug the cables fully.

Probably not related but I was also initially plugged into an Alesis IO dock (because it was all I had at home). I have since brought a little submixer from the studio and am now plugged into that.

Lastly when hooking up the submixer I did shuffle a few things around, maybe I had some psu or other device that was too close to the unenclosed lxr.

Good Luck

A

tixiv

All of my 9v equipment is powered off one 4amp 9v power adapter with a splitter

I think that could very well be the Problem: you have created a ground loop. Try powering the LXR from a dedicated, non earthed power supply, or try an audio cable with a lower resistance ground connection.

I had lots of hum from my LXR when I used an earthed powersupply, which also created a ground loop.

You could also try putting a common mode choke into the powercable to the LXR, e.g. this Reichelt Part: http://www.reichelt.de/Stromkompensierte-Drosseln/CAF-0-9-47/3/index.html?&ACTION=3&LA=2&ARTICLE=32283&GROUPID=3183&artnr=CAF+0,9-47

borfo

Well, whaddya know.  Using a separate power adapter fixed it - there's no hum now.  I guess it was a ground loop.  I didn't realize you could get a ground loop where everything was powered off the same power source...  But I guess I do have a weird huge chain of 9v devices, with splitters and long chains of devices.

Strange that none of my other devices hum, even when plugged into the same power adapter output plug.

Maybe I'll look at installing that choke at some point.

Thanks everyone.

str

Ok, I'm getting a hum when plugged into my PC via USB with other powered-via-USB peripherals (like a DJ controller). 

Basically, when my DJ controller and LXR are plugged into my PC, the outputs on both the DJ controller and LXR hum. When I plug my LXR into my LCD monitor (which has 2 USB ports, connected and powered by a USB type B cable), the hum disappears. 

Both cables have ferrite beads, and I've tried other cables. Any ideas? Using my monitor's USB ports is not a problem, but I'm curious as to why it's happening. 

nightworxx

A ground loop is a ground loop, you should try to test to put the wallwarts of both devices into different plugs. My guess would be, that the USB bus is powered by the same power rail internally and so both share the same ground reference.