VU Meter rising in CW Mixer when nothing playing!

lysergide · Post by **lysergide** » Mon Jul 12, 2004 4:06 am

Don't know if this is supposed to be a problem,

When i connect the Analog INS of the Luna card in the SCOPE software, the Mixer shows some sort of signal enterring the system, although nothing is playing... is this a problem?

astroman · Post by **astroman** » Mon Jul 12, 2004 6:24 am

no, it's just detecting regular noisefloor.
The numbers in the mixer channels show the peak values reached so far and can be reset with that small button at the master fader.

cheers, Tom

alfonso · Post by **alfonso** » Tue Jul 13, 2004 5:51 pm

The VU meters have a dynamic range wider than the range of the analog ins, so they behave correctly....

Post by **garyb** » Tue Jul 13, 2004 6:41 pm

it is the sign of an active connection.

siriusbliss · Post by **siriusbliss** » Wed Jul 14, 2004 12:46 am

I've been getting this behavior since the beginning going back to rev. 1.0.

For me it usually accompanies some crackling coming through the converters (or something), but it's usually during TOTALLY SILENT downtime when nothing is going through the system, so I always thought it was a bug, or DSP problem, etc.

Post by **garyb** » Wed Jul 14, 2004 2:57 am

i think that lysergide is talking about the fact that when you connect to the mixer it shows a small movement on the meters. there IS a noise problem, probably from a ground loop if there is more than a slight movement.

siriusbliss, are you saying that you only have the noise when you make the connection in scope? is it fine the rest of the time?

maybe you mean that you never have crackles in your recordings, but that when your computer is idle it snaps and pops at you randomly....

if the former, that's a little strange, but doesn't seem like a big problem(to me anyway). if the latter, is your luna the clock master?

<font size=-1>[ This Message was edited by: garyb on 2004-07-14 04:03 ]</font>

alfonso · Post by **alfonso** » Wed Jul 14, 2004 11:17 am

Read page 7 of the STM 2448/4896 section of the manual or page 5 of STM 1632 section.

It clearly states that if you hook analog in it's normal to see a little input in the VU's as they represent more than the noise floor of the analog devices. Just for the fact they are connected, the noise is detected.

blazesboylan · Post by **blazesboylan** » Wed Jul 14, 2004 11:46 am

Usually around -80db.

samplaire · Post by **samplaire** » Fri Jul 16, 2004 11:57 am

On 2004-07-14 01:46, siriusbliss wrote:
For me it usually accompanies some crackling coming through the converters (or something),

It's a shame I don't remember the term to call it

It's simple to explain though:If the signal is close to the digital 0 (between 0 and 1) it raises once zero once one and you can hear it as crackles. To avoid it use dither. It produces some noise which is nicer for our ears than the 0/1 crackles.

scary808 · Post by **scary808** » Fri Jul 16, 2004 5:25 pm

On 2004-07-16 12:57, samplaire wrote:
On 2004-07-14 01:46, siriusbliss wrote:
For me it usually accompanies some crackling coming through the converters (or something),
It's a shame I don't remember the term to call it It's simple to explain though:If the signal is close to the digital 0 (between 0 and 1) it raises once zero once one and you can hear it as crackles. To avoid it use dither. It produces some noise which is nicer for our ears than the 0/1 crackles.

You may be thinking of quantization error. I don't think that's the problem though...

The analog ins do have a small amount of self noise(even the A16 ultra does). If it's around -80dB to -75dB, theres nothing to worry about. Even converters that cost 10 times what CW's do have a little self noise.

If it's more than -75dB it may be a poor wiring job on the outlets that your system is plugged into. Or a ground loop as Garyb already stated.

blazesboylan · Post by **blazesboylan** » Fri Jul 16, 2004 6:46 pm

As long as you can get really hot signals I wouldn't worry too much about anything below -50, personally. Seriously. I've used lots of gear that only has 50-60dB of headroom and still sounds great!

Cheers,

Johann

siriusbliss · Post by **siriusbliss** » Fri Jul 16, 2004 10:26 pm

I used to get it when my system was getting hot, or when opening up older projects without swapping in new modules.

It's a distinct crackle most of the time, but there's also times when there is no sound and the VU's are still active.

Sometimes it only does it on one side of stereo or in random channels on the mixers.

It does it with various mixers.

Sometimes it will 'purge itself out' by reloading fresh modules.

Plato · Post by **Plato** » Sat Jul 17, 2004 4:38 am

If it really bothers you, just put a gate on your offenging input channels......I think it's totally normal, though....I see one set of illuminated VU LEDs on my analogue & SpDif ins if I don't gate them, and you can see some sort of activity if you open Wavelab and view the record page......whether you can hear that stuff is a different matter though !

astroman · Post by **astroman** » Sat Jul 17, 2004 4:58 pm

if you have noticable crackling something is wrong with your system.
I remember I could hear harddisk access on one of my installations, too, which actually was a long used Win98 with lots of installs/uninstalls, definete ASIO problems etc.

Now that I have a clean install the problems are gone and strangely the general signal-to-noise ratio has improved significantly.
I now have -85 on the empty analog ins of the card and -81 on an external A16.

But now I have a problem to explain my own theory about weak power supplies in the 'Noise' thread

Since the system was open anyway, I just re-installed the original 90 Watt pixie and hell, no noise at all

I pushed all channels to the max, added 24dB gain and nothing but plain sea-sound, no hums or crackles... whatever I did with the disk, or how I moved windows around on screen.
I swear the noise was there and changed with the PSU - the only differences I can think of are a new harddisk and no CD-writer installed and there appears some Intel driver for the disk interface I never noticed before.

cheers, Tom

blazesboylan · Post by **blazesboylan** » Sat Jul 17, 2004 5:31 pm

Maybe the hard disk sucked a lot of current? If the PSU is being overloaded that would certainly affect the voltage.