Laptop Noise Problem - Quattro users pls help!

[DavidBanner]

Hi all,

I know it's a bit off topic, I hope no one minds.

I'm having a bit of a problem with my laptop and quattro. As soon as I plug the USB from my laptop to the Quattro I get terrible noise problems, even with the audio leads disconnetted from the mixer!

As soon as I pull the power to the laptop and go onto to battery it goes.

Is there a way to sort this with the current gear WITHOUT pulling the ground pin on the power to my laptop adapter? It's my idea of a nightmare being at a gig on stage / in a DJ booth with an adapter about and no ground, I've had 3 club electrocutions and I'm in no rush for my 4th, also the power isn't the best in a lot of places, especially illegal parties.

Or is the solution the most obvious painfull one - go out and by a MOTU traveller?

[bionix]

maybe i'm not the right to awnser, but i also get some "stupid" noise while using *smth* (equal what, even if usb driven) through my mixer without a stabilized and filtered psu. seems that the switching psu (even a laptop got one) makes that noise but i'm not sure. if you use smth. to filter that out, it disappears. tested with an filtered psu (or just test it against lab psu stations which are normally extreme well)

could you power your stuff with normal an "psu" which could be filtered (rectifiers, l78xx and caps)? this COULD be a solution, at my side it helps while experimenting with psu for the sid station and some other audio hardware like filters and effects. but i'm not sure - i'm not an e-tech freak ;) hope that helps.

best regards...

[audiocommander]

yeah, the ol' ground noised... I can sing a song about that (is that an english expression ???) ;D

I got two ideas for you:

either you tune your sounds to the ground noise frequency ;D haha...

or: a fellow student has built a portable dj music thing with a vinyl player and he uses a rechargeable car battery... he can make quite incredible loud sound for a loooooong time... maybe that's an option to keep away ground-hell at illegal parties?

:)

[DavidBanner]

hello fellas,

thanks for the suggestions!!

uses a rechargeable car battery.

lol, not a bad idea, but I can just imagine the reaction trying to check a car battery  in at the airport  :D

Smash has given me the low-down on the situation, and it seems you guys are bang on - the PSUs I'm using are fighting each other, it's also frying my core chips too :(

But - the solution it would seem is using Isobar filter/surge protectors - i'm waiting on some now, I'll let y'all know how they go...

[stryd_one]

There's always the option of running your gear through a UPS... generally a good idea anyway ;)

[DavidBanner]

hey stryd,

There's always the option of running your gear through a UPS... generally a good idea anyway Wink

true, true, but UPSs aren't that portable either, fingers crossed the Isobars will do the trick.

[bionix]

Ok, back to theme:

i'll try to figure out the problem, because it happens even on my vst server (grmpf, p4 with zahlman switch psu, but still noisy!)

in my op. you could "work around" the noise by using optical or digital audio out. your sound card should provide smt. like spdif/tos/etc.

so i looked for smth. to change the signal from digital back to analogue, because my mixer and also the audio (xlr) are analogue.

this project http://sound.westhost.com/project85.htm could be interestening esp. to kick our noise problem. other (professional) systems are avaible, but not under 200€ (rme produces some DA/AD changer).

let's give it a try. first of all, someone else should try testing the problem itself (noise while psu at net) with digital audio out, because i have really nothing with an optical input, just a few optical outs.  :-\

if the problem disappears, we could try to build the DA/AD changer from project58. any other suggestions?

best regards...

[bionix]

oops i did it again  ;D

http://www.pp.iij4u.or.jp/~shu-nkmr/SN-DAC0501.html contains a VERY WELL schematic for DA/AD conversion via s/pdif to chinch (not digital) out.

these chips cost between 5-7 euro, so it's cheap to build smth. like that. i think most cost would be the adapters etc ;-)

best regards. btw: i start buildin this unit at weekend, if conrad got these chips in stock ;)

damn, they have not. ok, but i found a really cheap distributor (strange to find some, which are really cheap, schuko.de sells for 12€ / chip, but this one for ~6€)

http://www.futurlec.com/cgi-bin/search/search.cgi (sells also ONE chip if required, the other only distributes complete packages ~25 pieces or smth.)

so here is the (chipset) partlist:

1x CS8414 96kHz Digital Audio Receiver IC (4.50 USD at futurlec)

1x CS4334 96kHz Stereo D/A Convertor IC (2.90 USD at futurlec)

1x L7805 (the japanese version name: njm7805) ~30 cent

and a lot of standard resistors and caps, some connectors (spdif, chinch in [u0 seems to be a chinch in, or doesnt?] , chinch out

and finally an 8v supply, but it should run with 9v fine too (look, there's a regulated psu behind the supply input, 7805).

best regards.... hell, that thing is interestening :P

[stryd_one]

Bionix keep in mind that going to digital cabling will reduce cabling noise, but not the kind of noise being discussed in this thread... The thing with going from analog to digital and back, is that there is still an analog stage, and that will still be susceptible to power issues distorting audio :(

[bionix]

sorry, i didn't realized that the m-audio quattro doesn't have any digital outs. these are all only 6,3mm?

[rogic]

David, what laptop are you talking about? I'm having trouble with Gericom, model Hummer.

[DavidBanner]

hey bionix - thanks for the info, but alas Stryd is right.

Rogic - I'm using a Toshiba Tecra M5

This problem has been frying the Chip in my core too - after much help from SmashTv the problem looks like the various PSUs fighting and sending voltage down the midi ground.

I think the solution (i.e. Tim suggested) will be to put the isobar filters on the mains and run a cable from a screw in the chassis on the laptop to ground.

I'm currently completely immobilised with my back at the moment, but as soon as I'm up on my feet I'll be doing some more experimenting and i'll report back on the results.

Once I've got a solution I'll post it and add some info to the Wiki for the next victim of the dreaded ground loop.

[stryd_one]

Hope your back gets better soon mate.

Hey have you called Toshiba about this?

Edit: If it's still under warranty, they should replace it with another model without the problem, which is at least as good as yours, or better :)

[DavidBanner]

Hey Stryd,

The laptop is only a few weeks old and it's got a 3 yr warranty, but I'm not sure it's a problems with the laptop as such, or a better way to put it would be that I think another one would do the same thing.

I think it's a power supply issue and/or a quirk with the Quattro. I've got a feeling that a decent unit like a MOTU traveller wouldn't be giving these problems.  I think the quattro is highlighting a problem with the power supplies I'm using - I have a gigital switch mode PSU for the Laptop, A digital switch mode PSU for the core and a wall wart for the Quattro.

All these PSUs are fighting each other and the result is that some mad voltages and spikes etc are being tranmitted to ground and frying the analogue stuff in the PIC chip in the core.

But the Quattro is nice and small and would be great if I can get it working, if not I'll bite the bullet and go and get a traveller.

But there is also the issue with clean power in clubs that hopefully the Isobars will sort out. I saw Sasha asking for clean power at a club in London a couple of weeks ago and the sound tech nearly died laughing.

[DavidBanner]

here's a couple of snips from a messages from smashTV who explains it much better than I could:

"I think your laptop supply and the quattro wall wart are fighting each other.  Actually I know it is, having fought this issue on my own systems (but with powerbooks and onkyo and aja audio interfaces, and some monitors on the vga port)."

"This explanation/values is theoretical, not sure what you will actually find with a meter considering the differences between our mains standards.....

Let's call the quattro's ground our reference, at zero volts.  If you measure from this ground to the chips in the interface, 5v as expected.  -Usually- thats a linear ps inside, like the one on the CORE.

Now add the PC supply to the mix, it's a switcher (switch mode) design.  These work differently than a linear, taking chunks of the incoming AC wave and using capacitors and a high speed switching circuit to -approximate- a clean DC out.  Switchers are heat/power/weight efficient compared to linear.  The problem here is the way the switcher works, the ground on the output is different than what the linear gives as ground, if referenced to the linear there could be a few millivolts difference, or all the way up to full mains voltage difference depending on the specifics of the design(s).

This difference is your nasty hum, and it will stress everything while connected."

** snip **

"My bet then is we have the ground loop and it's acting like an antenna to the dirty supply power (tainted by the hash pushed out on a ground the analog parts are sharing, laptop charger supplies are apparently bad about this).

I have always fought this issue by using isolation transformers and cap filtered power strips.  I have a power distribution box with isolation transformers in my main FOH rack, and I have a few isobar brand outlet strips that use caps and transformers to block DC and keep it from leaking outlet to outlet.  I have all of my computer equipment plugged in through isobars, all of my outboard racks, etc. "