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Audio Noise - Please Identify
Old 26th December 2007
  #1
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CJ1973's Avatar
 

Audio Noise - Please Identify

Could any engineer please identify this noise I am getting when I send my synths through my Demeter VTMP2a preamp. Its clear when the music is quiet, especially at the start and end. Im trying to figure out if its tube related or otherwise. I have tried various cable options. Also have tried installing a JDI radial Duplex between the SYnths and the Demeter and the sound is still prevalent. Could you please tell me what it could be? My signal path is short so I feel its a preamp issue but have not had experiences in dying tubes or tubes that need replacement so I dont know what Im looking out for.
Thanks and Happy Holidays!
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Audio Noise.mp3 (521.5 KB, 111 views)

Old 26th December 2007
  #2
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Sounds like line interferance. You need clean power..

or are you recording into a computer? Is this onboard audio? If the machine has onboard audio - Sometimes poor Audio chipsets and poorly placed motherboard components can cause this problem.
Old 26th December 2007
  #3
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Its just that I have an ISA430 and tried the same steps with that and its as clear as anything. I also have a top of the range power conditioner...
I am recording into a Multiface II and into Nuendo. When I go into my 02R from the Demeter, the sound still exists, and the 02R is routed via adat optical into the RME as well. So I am thinking its the pre.. could be wrong...

Quote:
Originally Posted by heyman View Post
Sounds like line interferance. You need clean power..

or are you recording into a computer? Is this onboard audio? If the machine has onboard audio - Sometimes poor Audio chipsets and poorly placed motherboard components can cause this problem.
Old 26th December 2007
  #4
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Ok, so if you replace the Demeter with the isa, everything clears up..
Hmm, How are you connecting the Demeter?
Old 26th December 2007
  #5
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Hello. Did you try moviing the Demeter from where it's located? ( some times transformers picks up this noise) my Ditto does this if I put it near certain electronics. Just a thought.. Good luck...
Old 26th December 2007
  #6
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I go from the Synth into the Neutrik Patchbay with standard 1/4" audio cables. Patchbay to Radial DI i use 1/4" TRS to XLR mogami. From DI to Demeter Mic Input I use XLR XLR balanced mogami. From Demeter out into Multiface balanced 1/4" input, I use mogami.
When I use the same link with the ISA, it all clears up. so trying to see what really this could be.....

Quote:
Originally Posted by heyman View Post
Ok, so if you replace the Demeter with the isa, everything clears up..
Hmm, How are you connecting the Demeter?
Old 26th December 2007
  #7
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No I havent yet and there is only one unit next to it, which is the ISA430 and it is off when I use the Demter.
I will however try out what you say for sure. Do you know what a 'bad' tube which potentially needs replacement sounds like?
Tks

Quote:
Originally Posted by Snatchman View Post
Hello. Did you try moviing the Demeter from where it's located? ( some times transformers picks up this noise) my Ditto does this if I put it near certain electronics. Just a thought.. Good luck...
Old 26th December 2007
  #8
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Quote:
Originally Posted by CJ1973 View Post
I go from the Synth into the Neutrik Patchbay with standard 1/4" audio cables. Patchbay to Radial DI i use 1/4" TRS to XLR mogami. From DI to Demeter Mic Input I use XLR XLR balanced mogami. From Demeter out into Multiface balanced 1/4" input, I use mogami.
When I use the same link with the ISA, it all clears up. so trying to see what really this could be.....
After reading this, where you go from the patchbay to the Radial DI with 1/4" TRS, isn't the input of the Radial unbalanced jack? Don't know if this may be contributing to the noise or not....
Old 26th December 2007
  #9
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Hi
I actually tried it without the Radial DI in the link and nothing has changed. But I will try perhaps unbalanced into the DI. My assumption about balanced cables was that they can be used anywhere, as opposed to unbalanced. Hope I didnt make that misunderstanding.
In your ears does it sound like a bad tube related noise in anyway?

Quote:
Originally Posted by Snatchman View Post
After reading this, where you go from the patchbay to the Radial DI with 1/4" TRS, isn't the input of the Radial unbalanced jack? Don't know if this may be contributing to the noise or not....
Old 26th December 2007
  #10
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Quote:
Originally Posted by CJ1973 View Post
Hi
I actually tried it without the Radial DI in the link and nothing has changed. But I will try perhaps unbalanced into the DI. My assumption about balanced cables was that they can be used anywhere, as opposed to unbalanced. Hope I didnt make that misunderstanding.
In your ears does it sound like a bad tube related noise in anyway?
Hi. I'm not sure if it's a tube or not. Have you tried isolating each channel of the Demeter ( sending a signal thru each channel separately) to see if it may be something happening on just one, or both channels? I think sometimes if you plug a balanced cable into an unbalanced input ( especially if the cable is connected balanced on the sending end) that you lose a " leg" and it poses impedence problems sometimes. Not a cable expert.... but maybe if I'm wrong, someone will correct me...
Old 26th December 2007
  #11
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Hi
Yeah I tried it and one channel A feels alittle louder than the other actually. They arent totally equal in terms of this noise level. Again I probably would have to agree that it may well be an impedence thing but I honestly have no idea on how to go about isolating it totally.
I will perhaps try various combinations of balanced/unbalanced cables to see how lucky I could get...
Thanks alot for your advise!

Quote:
Originally Posted by Snatchman View Post
Hi. I'm not sure if it's a tube or not. Have you tried isolating each channel of the Demeter ( sending a signal thru each channel separately) to see if it may be something happening on just one, or both channels? I think sometimes if you plug a balanced cable into an unbalanced input ( especially if the cable is connected balanced on the sending end) that you lose a " leg" and it poses impedence problems sometimes. Not a cable expert.... but maybe if I'm wrong, someone will correct me...
Old 26th December 2007
  #12
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Also what I havent tried is just sending a bass guitar into the instrument input of the unit to see if the same sound is still there. So maybe that could isolate it to cable or tube right? If its tube, sending a bass or guitar into the instrument inputs would actually still keep that bad sound right if its a bad tube?

Quote:
Originally Posted by Snatchman View Post
Hi. I'm not sure if it's a tube or not. Have you tried isolating each channel of the Demeter ( sending a signal thru each channel separately) to see if it may be something happening on just one, or both channels? I think sometimes if you plug a balanced cable into an unbalanced input ( especially if the cable is connected balanced on the sending end) that you lose a " leg" and it poses impedence problems sometimes. Not a cable expert.... but maybe if I'm wrong, someone will correct me...
Old 27th December 2007
  #13
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Anybody else out there who can identify with this noise would be much appreciated!
Tks in advance.
Old 27th December 2007
  #14
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Quote:
Originally Posted by CJ1973 View Post
Also what I havent tried is just sending a bass guitar into the instrument input of the unit to see if the same sound is still there. So maybe that could isolate it to cable or tube right? If its tube, sending a bass or guitar into the instrument inputs would actually still keep that bad sound right if its a bad tube?
Yeah. That might help. what about a mic? Something that doesn't has a lot of inherant noise as synths. If the noise continues with a mic plugged in, it may lead you to it being the preamp/tube itself. Good luck...
Old 27th December 2007
  #15
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OKAY.. now here goes. I just worked it out snatchman and others.....This freaked me out...It was no cable issue nor tube... it was sort of what you said but not really current related or power...
What i did was unscrew the unit from my work station desk and bang it went away... i screwed the unit back on and the noise came back.. i unscrewed the unit and it went away again.. i just unscrewed it and placed it on top of another module with no rack screws and guess what.. NO noise!!!!!! I gathered maybe the vibrations of the unit are interfered with by the rack/screws... Instead of the screws, i tried a screw driver and made contact with the ears as well as the rack and the noise was back.... so i think its due to some internal vibration of being interfered with.... SO strange but I cannot find any other reason....The noise is GONE.. WIth the Wind!!!!! but the pre is not racked anymore but oh well... I would LOVE it if someone can advise me why this could be the case...
Thanks eitherway!!!!!

Quote:
Originally Posted by Snatchman View Post
Yeah. That might help. what about a mic? Something that doesn't has a lot of inherant noise as synths. If the noise continues with a mic plugged in, it may lead you to it being the preamp/tube itself. Good luck...
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