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Luna2 - noise on analog input!

Posted: Fri Jul 06, 2007 3:59 am
by bojanmil
Hi!
I using Luna2 for a long times ago and I was very happy till few days ago.
I hear the loud noise on analog input at my Luna2. Even when I disconnect all cables from Luna, peak-meter on ST1632 software mixer shows input signal on strip where "Luna Analog Source" is connected. There is not insert or send effects on this mixer channel - only "Luna Analog Source" is connected to the first ST1632 channel. I tried to replace two capacitors on input and one operational amplifier (LM833 dual low-noise) chip but problem still exist. Please help me!
Thanks in advance and best regards!

Posted: Fri Jul 13, 2007 3:14 pm
by bojanmil
Noise level is about -66db, but I have noise for last few weeks only. Never before I had not any noise on my Luna2.
If I use GuitarRig and load an preset with distortion, noise level is raised to very high level and any work isn't available.
What can I do to decrease noise level? I think that this noise is product of AD/DA converters...
Thanks in advance!

BEST REGARDS!!!

Posted: Fri Jul 13, 2007 3:49 pm
by bojanmil
Thanks for reply!
All my cables are separated from power cords and shielded, but problem still exist.
What means "ground all only one times"?

Can I send my card to Creamware service???

Posted: Fri Jul 13, 2007 5:06 pm
by garyb
are you plugging the guitar directly into the card without going through a preamp first? if so, the card can probably produce enough gain, but there will be noise, especially if you are using distortion.

the guitar's level is very low, about the level of a microphone(so a mic pre with a high impeadance input would be the best preamp choice for clean gain). you need to get the level up to line level before it enters the card, that's what a preamp is for....

Posted: Fri Jul 13, 2007 11:01 pm
by bojanmil
garyb wrote:are you plugging the guitar directly into the card without going through a preamp first? if so, the card can probably produce enough gain, but there will be noise, especially if you are using distortion.

the guitar's level is very low, about the level of a microphone(so a mic pre with a high impeadance input would be the best preamp choice for clean gain). you need to get the level up to line level before it enters the card, that's what a preamp is for....
Guitar is connected trough external mixer. My mixer have gain control. I was disconnected all cables from Luna2 (except audio cable from analog output) and peak-meter on ST1632 software mixer shows signal on analog input! Yes, without any sound source! When I start Nuendo and load GuitarRig (without cable connected to the Luna's input) I hear loud hum/noise...
Any idea?

Posted: Fri Jul 13, 2007 11:22 pm
by garyb
well, the 1/4" input on the mixer is most likely for line level, not mic level. in that case, you need a direct box to convert the hiz guitar pickup into a loz(xlr) mic input if you want the lowest noise and highest fidelity(best tone).

you should see the bottom led on the mixer with nothing connected to the the card, but the analog source connected to the mixer, more than that indicates a problem.

it would be normal for a high gain guitar amp patch to be very noisy. high gain distortion makes maximum compression. compression makes the loud sounds quiter and the quiet sounds louder(decreased dynamic range), so the noise that's part of every electronic circuit is magnified mightily. this sound would be mostly white noise.

if the sound is a low hum, then are you sure that the problem isn't between the computer and the monitor amplifier(s)? a ground loop in between the computer and the speaker amps is common, especially if the computer and the speakers are plugged into different outlets.

i hope this helps.

Posted: Sat Jul 14, 2007 4:06 pm
by bojanmil
Now I am sure thats normal to see bottom led on ST1632 mixer. OK...
One and only thing that I don't understand is:
WHY I SEE BOTTOM LED ONLY FOR A LAST FEW WEEKS????
NEVER BEFORE I SAW NOT BOTTOM LED ACTIVE!

THANKS!!!

ALL THE BEST!!!

Posted: Sat Jul 14, 2007 4:07 pm
by garyb
dunno.... :D

Posted: Sun Jul 15, 2007 1:06 am
by bojanmil
Sorry for my bad english, but what means "dunno"? :-?

Posted: Sun Jul 15, 2007 1:16 am
by garyb
dunno=i don't know=i'm not sure...

sorry...

Posted: Sun Jul 15, 2007 3:41 am
by bojanmil
stardust wrote:Regarding your question:

Think about what you have changed in your setup.
candidates have been named:
cables, preamps, interference from power chaords, new cards in PCI slots, different output levels,......
Thank you for answer!
I changed motherboard and CPU.
My new motherboard is ASUS M2N32SLI Deluxe and my new CPU is AMD Athlon64 4600+ X2.
Only Luna2 and nVidia GeForce6200 card are connected to motherboard.
I tried to remove old motherboard and CPU, but problem still exist...

Posted: Sun Jul 15, 2007 6:46 am
by valis
Did you chance the power supply? Even if not the change in components has obviously changed the base noise in the system. Your entire system is grounded via the motherboard to the backplane that comes with the case, and also through the PSU. DIfferent components on the system 'leak' differing levels of 'noise' via RF into the local computing environment as well, so changing motherboard & graphics card changes enough 'polluting' components to have made a difference.

A single lit LED is nothing to be concerned about, as long as your noise floor is below -70dB you're safe. I get -80 dB here on my board with all faders nominal (except a crappy sblive used in one system has poor grounding due to the consumer output and gives -60dB). If you're really concerned use a proper set of analyzers to see what the actual noise levels are (in the stereo as peak & RMS, and in a view that has spectral bands at least every 1/3 octave) and post up a screenshot for us.

Posted: Sun Jul 15, 2007 6:26 pm
by valis
If it was grounding noise of that kind then it would surely show more than a single -70db LED on the mixer's meters. However some leakage is possible if he didn't mount his motherboard properly (using all of the copper ringed holes on the motherboard with the proper grounding hex mounts). Even if properly grounded some motherboards are better than others when it comes to RF leakage, and modern gpu's definately leak a ton of RF.

Posted: Mon Aug 06, 2007 1:12 am
by bojanmil
Hi people!
I was been on holiday for a last few weeks. I will try all your tips and suggestions soon and I will inform you about results.
Thanks a lot and best regards!!!!