Investigating my hum problem: PC + A16 Ultra *only* = hum fr

mano · Post by **mano** » Thu May 08, 2003 7:00 pm

Seems like I can't get rid of this one...

I took just my PC and my A16 Ultra out of my studio with the simplest connections possible (just 2 ADAT lightpipe cables), and sure enough... As soon as I open one of the A16 inputs in the pulsar mixer, the hum is there... Floor displays: -60dB

-> I record a sample of the noise and listen to it later when plugging some headphones, the hum is there and stops if I don't play (I mean it's in the recording)

It sucks! I read a lot about how to slove those kinds of problems, but frankly here I don't know what to do... PC+A16 only... no audio connection there, just the ADAT cables to interface and that's it.

I do know there should be some noise that's fine, but here the hum makes it unusable.

What should I do? Do you think some PC parts are touching the case and I should isolate them more?

I had the problem from the day I purchased the A16U... I thought it was my unbalanced equipment but it's not, now that I took the time to isolate the problem. Not cool...

Thanks in advance for helping

[ This Message was edited by: mano1.com on 2003-05-08 20:02 ]

at0m · Post by **at0m** » Thu May 08, 2003 7:24 pm

How's the noise on the analog input? Does it compare to the A16?

On the analog input and Luna2496, I get like -85dB when nothing's connected, and between -70 and -55dB when a cable's plugged in.

If there's a compressor on the mix, I usually gate the analog inputs. If the mix is uncompressed, the noise doesn't get pulled up in the quiet parts and it works confortably without gates.

mano · Post by **mano** » Thu May 08, 2003 7:28 pm

Hey

Well here I definitly have a ground loop problem; I don't mind the 'normal' noise

The Pulsar analog input doesn't have the same hum problem. I need to do more capture + comparison but the A16 definitly "HUMS" louder than normal.

at0m · Post by **at0m** » Thu May 08, 2003 7:32 pm

mano · Post by **mano** » Thu May 08, 2003 7:39 pm

On 2003-05-08 20:32, at0mic wrote:
:-/

Don't stare at me like that

[ This Message was edited by: mano1.com on 2003-05-08 20:45 ]

Post by **garyb** » Thu May 08, 2003 10:10 pm

ground loops have been covered ad infinitum.they're impossible to diagnose second-hand..all your components are suspect.

astroman · Post by **astroman** » Fri May 09, 2003 3:59 pm

reverse the A16U's wallwart into the wall outlet, that could help. At least if there's nothing else involved (no other gear on the A16U) the ground problem can be only between the powersupply and the device.
But I never hold my breath on ground probs - too wiered as garyb wrote

forgot one of the most famous: is your house electricity grounded at all ?

good luck, tom

[ This Message was edited by: astroman on 2003-05-09 20:28 ]

bassdude · Post by **bassdude** » Fri May 09, 2003 6:54 pm

So, the pc without the a16 connected doesn't hum? Then the a16, not rack mounted but sitting on its own, with nothing plugged into the analog ins, and connected to the pc via lightpipe does hum? Does the hum go away when you pull the power from the a16? (It should). If this is the case, then the a16 unit itself must be faulty. A ground loop cannot exist over optical fibre. If the hum is there only when you plug gear into the analog inputs of the a16, then you do have a ground loop problem.

Go here http://www.rane.com/note110.html for good information. There is also alot of other info in the Rane library that may help you out. http://www.rane.com/library.html

mano · Post by **mano** » Sat May 10, 2003 1:15 pm

Great Post Bass dude!

let me go though your questions

On 2003-05-09 19:54, bassdude wrote:
So, the pc without the a16 connected doesn't hum?

no

Then the a16, not rack mounted but sitting on its own, with nothing plugged into the analog ins, and connected to the pc via lightpipe does hum?

yes and the hum is louder on IN1 and goes quiter as you go towards IN16

Does the hum go away when you pull the power from the a16? (It should).

yes

If this is the case, then the a16 unit itself must be faulty. A ground loop cannot exist over optical fibre.

what should I do? I line in Seattle area
car someone "fix" the A16 for me?

Thank you so much

Post by **garyb** » Sat May 10, 2003 8:47 pm

could even be a "cold" or broken solder joint on the pc board.if so,a reflow would cure it.not for the uninitiated, though........

bassdude · Post by **bassdude** » Sun May 11, 2003 5:32 am

Well if you were in Canberra Australia, I would be more than happy to have a look at it for you. Oh well.

More than likely it's a problem with the internal power supply for the analog part of the circuitry. It could be one of these scenarios that is causing the hum:-

1. As gary says, a dry joint affecting internal grounding/shielding.

2. Dud filter caps.

3. Powersupply does not have enough balls to drive the unit. Dud regulaters.

4. One of the +/- supply rails gone belly up. Dud regulater.

There are certainly other components that can go faulty but the above are the more common problems and are what I have personally diagnosed in repairs I have done in the past.

If it's out of warranty, maybe you could take it to a local serviceperson? These are the first things that they would probably look at anyway.

Good luck.

[ This Message was edited by: bassdude on 2003-05-11 06:38 ]

mano · Post by **mano** » Sun May 11, 2003 1:18 pm

hey thanks for all the info

i bought it from subhuman about a year ago but only used it a few times since we had a baby and stuff - i always thought needed to fix a ground loop problem and waited too long to realize ...

Maybe subhuman could replace or service the unit ... I will email infinite vortex the link to this thread and keep my fingers crossed

[ This Message was edited by: mano1.com on 2003-05-11 14:20 ]

mano · Post by **mano** » Sun May 11, 2003 1:47 pm

OK I emailed the link + summary of this conversation to Infinite Vortex and added the CW tech support on CC.

I am keeping my fingers crossed and hope they'll be helpful and resolve the problem

Thanks again to those who posted. Others please feel free to post more suggestions if you want.

Manuel

felix o. · Post by **felix o.** » Mon May 12, 2003 12:34 pm

since you can hear the hum, it means that there is more connected than only the pc and the a16. i in my case have the problem, i have to use only one wallwart for all my equipment. as soon as i use two, i have a big hum.
in another case a friend of mine had a hum on his stereo, where also the pc is connected, and as soon he turned on the pc, he had the hum coming back. the reason for his hum was, he had the stereo connected to the house radio antenna.
only two cases of a million reasons for a hum.

good luck, felix

mano · Post by **mano** » Mon May 12, 2003 1:03 pm

Coincidence, Shawn from Infinite Vortex (where I bought the A16 Ultra unit from) lives in my area

He's coming tonight to test a working A16 Ultra with my setup. We'll see what is going on.

Great service!

alfonso · Post by **alfonso** » Mon May 12, 2003 5:08 pm

I don't have A16, but when i encountered very big hum problems with some other gear connected to pc, it was totally cured with this simple rule: only one piece must be ground connected, all others must be plugged in a groundless socket. Only the PC must be grounded.

bassdude · Post by **bassdude** » Mon May 12, 2003 10:10 pm

**** No no no! That's a potentially lethal solution.

If you need to lift earths/ground connections to address hum issues, then it should only be done by lifting the signal ground between interconnecting equipment at one end. Lifting mains earth is potentialy lethal if the equipment is designed to have an earth connection. In my country, doing as you suggest, with groundless sockets, is illegal.

The Rane note 110 in my previous post above shows the *correct* way to isolate hum loops.

[ This Message was edited by: bassdude on 2003-05-12 23:12 ]

mano · Post by **mano** » Tue May 13, 2003 1:45 am

guys, listen to this!

my unit definitely had a problem and Shawn from Infinite vortex was able to run various tests

I have a replacement unit and IT works!

Thanks creamware and infinite vortex - great service!

[ This Message was edited by: mano1.com on 2003-05-13 02:48 ]

bassdude · Post by **bassdude** » Wed May 14, 2003 5:39 am

Ahhh... so the subhuman unit goes by the name of Shawn?

Good news Mano.

Post by **hubird** » Wed May 14, 2003 6:42 am

pwew!
congrats, Mano1!

PlanetZ forums - scopeusers.com

Investigating my hum problem: PC + A16 Ultra only = hum fr