Advice on Ground power supply?

[Pitchfork]

I have the Macbook issue with noise coming from my output, when I have a 2nd DVI monitor plugged in (lots of online problems about this apparently!) as Apple haven't fixed this..

Anyway i have been reading that this noise/hum 'vanishes' if you plug the monitor into a grounded power supply?

I have no real clue as to what this is? I am running from a 4-plug extension with other studio bits plugged in, do they mean plugging directly into the wall?

How do i know if I have a grounded power supply to stop any hum?

Where my setup is now, im running off 4-plug extensions, but at my studio I did have lots of individual plugs fitted, does this make a difference?

Sorry for the ignorance, but I know this is a safety issue, and know this can be dangerous!

[TrickyDicky]

Bump anyone?

[ef37a]

Morning P'

Firstly, would this not get more attention in the Mac Music section?

Ok, power strips. Are they all fed from ONE 13A outlet? If not do that.
I know jack of macs. Do the monitors have mains in IEC connectors or are they fed from separate "line lump" power supplies? If the latter and they have a 3 pole mains in (often a clover leaf style, not IEC)you might be able to get an earth free, two pin version.

Things will only become dangerous if you lift earths in mains plugs so DON'T DO THAT!

Dave.

[chris...]

Are you using the Apple powerbrick with:

(A) the stubby plug the plugs directly into a mains socket

or

(B) the 1-2 metre long AC lead connecting powerbrick to mains plug.

Which ever you're currently doing, try the other, and let us know if that helps.

With my MBP, (B) results in the powerbrick having a ground connection, but (A) does not. This does not matter for safety reasons, as it's double-insultated. But perhaps there might be an affect on audio things.

More info in this thread:

http://soundonsound.com/forum/showflat.php?Cat=&Number=782582

[Pitchfork]

I'm using the standard power brick from Apple but with a (B) the 1-2 metre long AC lead connecting powerbrick to mains plug.

Can I disconnect this and plug the actual 'brick' into the power socket?

[chris...]

Yes - if you can find the stubby plug thing that clips onto the powerbrick in place of the mains lead. If it's like mine and others, this will result in the power brick NOT having an earth connection, but I've no idea if this'll help or not.

Its quite tidy, if nothing else...

[Pitchfork]

Are you using the Apple powerbrick with:

(A) the stubby plug the plugs directly into a mains socket

or

(B) the 1-2 metre long AC lead connecting powerbrick to mains plug.

Which ever you're currently doing, try the other, and let us know if that helps.

Tried the both above and still the same - noise bleeding through when DVI connected to monitor

[Pitchfork]

Having moved this around and tried various plugs/leads/grounded etc

I have now noticed that when I unplug my PC Laptop power supply (its a Mac with DVI Monitor going into a PC as a recorder) that the noise vanishes?!

So im really scratching my head, as this noise/Laptop power doesn't happen when there is no DVI connected, now it vanishes when the PC laptop power is removed?

Is there anyway around this? I am running off other plugs, and this thread now being moved to the Mac forum, may need to be moved to the PC forum?!

[. . . Delete This User . . .]

ahhhh you have a loop between the PC laptop and the Mac, via the Mac external screen.

A) don't use the PC on PSU

B) if you're connecting over analogue audio, lift the ground off the audio cables on the PC end.

C) if you're connecting over SPDIF, use optical, not coaxial.... OR, get 2 optical/coaxial converters anda really short optical cable, , and out them between the PC and Mac audio devices coaxial SPDIF I/O , so you have no electrical connection....

basically, lift the signal (NOT power) ground between the PC and Mac, and it should be sorted.

[Pitchfork]

ahhhh you have a loop between the PC laptop and the Mac, via the Mac external screen.

A) don't use the PC on PSU

B) if you're connecting over analogue audio, lift the ground off the audio cables on the PC end.

C) if you're connecting over SPDIF, use optical, not coaxial.... OR, get 2 optical/coaxial converters anda really short optical cable, , and out them between the PC and Mac audio devices coaxial SPDIF I/O , so you have no electrical connection....

basically, lift the signal (NOT power) ground between the PC and Mac, and it should be sorted.

Hi, sorry for being thick but not sure on how to "lift the ground off the audio cables"?

So in response to your q's

A. I have to use the PSU on the PC laptop as battery is dead, so it needs to run on power im afraid, so thats a necessity.

B. Not sure on how i do this or what that means?! Sorry for being dense but does it mean lifting the cables up in the air? lol

C. Not connecting via SPDIF

Its an analog out Mac to Analog into USB Soundcard on PC, and I get this noise, so any help on "lifting the ground" would be a big help - i'm already with my spade if that helps?

[ef37a]

Having moved this around and tried various plugs/leads/grounded etc

I have now noticed that when I unplug my PC Laptop power supply (its a Mac with DVI Monitor going into a PC as a recorder) that the noise vanishes?!

So im really scratching my head, as this noise/Laptop power doesn't happen when there is no DVI connected, now it vanishes when the PC laptop power is removed?

Is there anyway around this? I am running off other plugs, and this thread now being moved to the Mac forum, may need to be moved to the PC forum?!

Aha! So, the Mighty Mac suffers the same problems as windows laps? You need a power supply that does not have a mains earth connection.

I get the same problem if I run my HP lap' and a fast rack pro then jack the analogue outs into the main pc (my solution cannot be shown here.)

Dave.

[Pitchfork]

Aha! So, the Mighty Mac suffers the same problems as windows laps? You need a power supply that does not have a mains earth connection.

No i do think this is down to the PC Laptops PSU, as removing the Mac power, does nothing, but removing the PC AC power kills the noise

I think its the PC's power supply, and as its an old laptop brick adaptor between standard UK plug and small ac adaptor with cord on other end, im not sure how i remove the ground on this?

Or going by BBQ lighter's post, I need to do this to the "audio" but after much trawling on google, am still no clearer on how exactly to do this with my USB soundcard (Edirol UA25 older version)?

[. . . Delete This User . . .]

take the audio cable that you're using to connect the devices, and open the plug at one end, and remove the shield/ground connection...

from the sounds of it, you're using a stereo mini jack to 2 RCA/Phono connectors, or 2 jack connectors...

if it's moulded plugs at both ends, this will be nigh on impossible, without replacing the plugs

but if it's decent plugs with screw on metal bodies, it's easy peasy....

however, this will mean a potential increase in other noise as the shield will then be floating at one end.... and it also means that if you use the cable in the absence of a ground loop, it won;t work.....

What is probably a better technical solution, and possibly easier to implement, is to get a transformer isolating box, Like the ART cleanbox ,

http://www.google.co.uk/products/catalog?client=safari&rls=en&q=art+cleanbox&oe=UTF-8&redir_esc=&um=1&ie=UTF-8&tbm=shop&cid=14640362188370276509&sa=X&ei=OhovTvmsGsrB8QO-qcF3&ved=0CD4Q8wIwAQ#ps-sellers

and put this in line between the Mac and the UA25

should solve the issue .... in theory./..

[Pitchfork]

Thanks for your reply - yes your right, its a 3.5mm jack out to 2 x phono in, and no i dont think its possible to take the ground wire out as its sealed..

I think the ART box is the only answer.. Thanks

Will this definetly work, I only ask because I did recently get an Audio Hum Eliminator for this same thing (not ART though) and it made no difference and had to return, But if this one works.......?

[. . . Delete This User . . .]

got a link to the one you got and returned??

it OUGHT in theory to work.....

however, i wouldn't guarantee it .....

it is however a cheaper option than my next suggestion....

get 2 audio interfaces with proper balanced Line I/O then connect them using proper balanced cables.....

OR, 2 interfaces that allow optical SPDIF connection.....

OR

why not just record on the Mac ????? using Audio Hijack for example,

then if you must use the PC for something.... you can simply copy files over the network....

or for that matter, investigate cross platform audio networking, like Wormhole.

In essence, the message is , that there are a BUNCH of ways of solving this issue.... ranging from as simple as a modified cable, to expensive audio interfaces and balanced cabling.... (possibly even with the earth lifted on them)

and that lateral thinking can present alternatives... like recording on the mac, or using digital methods rather than analogue.... and so on.,..

[Pitchfork]

Yes your dead right, I could record directly on the Mac, but its cus I have a PC laptop that records fine, and i know I can messily use it to record and edit audio without much thought, and sequence those audio files back on the Mac..

The Ground Loop isolator i returned was :

http://www.ebay.co.uk/itm/Bumper-Ground-Loop-Isolator-/140535094791?_trksid=p4340.m263&_trkparms=algo%3DDLSL%252BSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D8%26pmod%3D250832919484%252B250832919484%26po%3D%26ps%3D63%26clkid%3D1622177013704038937&_qi=RTM637057#ht_1941wt_907

The PC is old now, and everything tells me to chuck it, but as its free (not mine) I feel like I want to use it cus its "there" a bit like an old synth, but use it to record, edit and manipulate audio, as well as a few PC only VST's

(I do have Parallels on the Mac for PC audio editing, but it didn't seem "as snappy" as on a PC?)

Anyway I did look at the SPDIF thing, but it would mean getting a new interface..tried audio hijack and didn't really get on with that

I could try Wormhole which is cross platform and audio via Ethernet?

I'm probably mad and stupid and need to change my ways really

[. . . Delete This User . . .]

it doesn't say how it's isolating....

shame you've sent it back, you could have tested it with a multimeter to see what the ground side was doing....

there are other similar applications to Audio Hijack as well....

AND,

it just occured to me, you already have an optical SPDIF output on the Mac.... the line out socket has a combined Digital output, if you use the right kind of optical cable ....

and the UA25, as i recall HAS an optical SPDIF input.....

no purchase required other than the right kind of optical cable

[Pitchfork]

it just occured to me, you already have an optical SPDIF output on the Mac.... the line out socket has a combined Digital output, if you use the right kind of optical cable ....

and the UA25, as i recall HAS an optical SPDIF input.....

no purchase required other than the right kind of optical cable

Yes your dead right, but been there for over a year...

The only fly in the ointment, is that the UA-25 doesn't monitor in SPDIF mode amazingly!

But yes, I had bought the Optical cable, cus of the headphone becoming the SPDIF output, and the UA-25 has the optical in..

But as it can't monitor, you can either record OR listen back and not both at the same time annoyingly, so you can't play along to a playing DAW in SPDIF, so you can't record on a track while monitoring others like normal recording!

But your right, that would have solved everything....

[ef37a]

That isolator would have done just what the Art would do, break the earth path.
The only difference is in the quality of the transformers, they are said to be pretty good in the Art and reflect in good quality sound but the cheapee SHOULD have cured the earth loop problem and so I very much doubt the Art will.

Buy an RCA 2plugs to 2 line sockets lead. Chop in half then connect only the inner cores together. Fit into the system.
If that does not cure the hum you probaly need an earth free power supply.

Dave.

[. . . Delete This User . . .]

a Client of mine used to have a UA25...

as i recall if you use 44.1 or 48K (little switch on the back) sample rates, you CAN monitor on SPDIF, BUT , it doesn't use the direct monitor knob to set level, against the output of the PC's DAW, it either goes straight to the D/A OR you monitor THRU the PC DAW...

it IS possible.....

just a bit fiddly.... inherently flawed really...

where are you based????

(if i happen to be flying past i'd happily stop and fiddle with it to set it up or find a solution... )