-85 db Background Noise , is this normal ?

[Barbad]

Hi Friends ,

When I Turn off my Avalon 737 preamp , the digital level meter on input channel shows -inf , OK !
when I turn on the preamp with lowest output level ( Mute ) , input level meter
shows -85 db ... and when I put the output level of preamp to "0" then level meter shows -75 db and ffffffff noise start and I don't like that ...

are these numbers normal for analog devices & connections ?
is ( -12~-6db : -75~-70db ) ratio normal for ( audio signal : Noise ratio ) ?

if these numbers are not normal , then what should they be ?

Thanks for your helps .

[Keybeeetsss]

Grounding problem?

[Craig F]

sounds like the tubes need to be replaced

[nucelar]

Hmm, my guess is there is something wrong in the preamp. Are you going directly into the 192 I/O?
Acceptable S/N should be way above 85 dB, and I'm sure the avalon can do better than that. If it's a used unit it may be that the tubes are worn out and need replacement. Or it could be a ground issue.
Can you put a spectrum analyser plug-in in the track and see what frequencies are causing the noise? This will give us a clue to what's wrong.
Cheers

Edit: Keybeetsss and Craig F beat me by seconds!

[Keybeeetsss]

Nucelar gives a good point; or maybe u could even record it & post a file of the noise & we maybe able to tell u; I definitely kno what it'd sound like if the tubes are bad which could be it; I've put British mullards in after mine went bad... (a swooshing like wind noise)

[Barbad]

Thank you all ,

I don't think it's because of tubes , because it's a new preamp ... ofcourse my TC gold channel that is not a tube preamp is the same ... direct connection to 192 IO or LE 003 Rack ... the same noise level ! could you please guide me about analyzing ground issues in my circuit ? a preamp , an XLR Cable & Rack LE 003 ( 192 IO and LE 003 has have the same problem ) . I have uploaded the result image of spectrum analyzer for you friends , please check it and guide me . thanks .

Spectrum Analyzer Result :
http://www.4freeimagehost.com/show.p...2daa2a633d.jpg

[Keybeeetsss]

What type cables do u hav & are they balance? (XLR to TRS) Its either that or a ground problem...

[FajitaTone]

pin 2 or pin 3 hot problem?

[Dizzi45Z]

Originally Posted by Barbad

Hi Friends ,

When I Turn off my Avalon 737 preamp , the digital level meter on input channel shows -inf , OK !
when I turn on the preamp with lowest output level ( Mute ) , input level meter
shows -85 db ... and when I put the output level of preamp to "0" then level meter shows -75 db and ffffffff noise start and I don't like that ...

are these numbers normal for analog devices & connections ?
is ( -12~-6db : -75~-70db ) ratio normal for ( audio signal : Noise ratio ) ?

if these numbers are not normal , then what should they be ?

Thanks for your helps .

I'd like to know what they should be too. That seems right for tube gear to me, but I don't deal with tons of tube gear.

On my ADL 600, if the trim is turned all the way down and I switch to show pk on a Pro Tools track, I get -90.3. It takes quite a bit of volume and compression to get it coming through on my tracks. If I turn my trim up 10 db (0 on the trim knob), I get a pk of -80.8.

I've been told that the ADL 600 is suppose to be a super quiet tube pre, and from what I see and hear, it seems that way to me. I will run into a problem though if I have a microphone pad on a microphone or the -20 db pad on the preamp when I shouldn't. In this case, the noise starts becoming more audible (obviously!).

The hiss noise that comes through the Waves Plug-ins with the "analog" switched on for the CLA76 seems waaayy noisier than these sort of things.

Also, is there a definite bad tube sound? Doing these tests, I noticed that my Channel 2 tube sound is way different from my Channel 1 sound. I replaced tubes about 3 months ago on the unit. I cranked Trim and Gain maximum on both channels and recorded the noise. Download this link and tell me if the Channel 2 must have a bad tube or something. The tracks I record through it sound fine as far as I can tell.

Download Tube hiss files:

[Barbad]

Thanks Again ,

My Cables are XLR<>XLR ( F&M) ... I read a lot of documents about ground loops all the night ... I found that ground loops make Hum or Buzz , but Hisss may be something different . AC cords are 2 pins ( without ground pin ) therefore no ground loop here ... I took out the gears from rackmount to avoid looping by rackmount ... avoid using different AC outlet ... used balanced cables ... all inputs & outputs are balanced ...

I found some techniques like ground lift on male XLRs and routing the ground & ground signal to the chassis . i'm going to do them and see what happens ... thinking about RFIs & EMIs ... I'm gonna be mad !