Can power supply noise and ripple on a PC affect recording ?

[JoseDN]

Are there any upper thresholds that are commonly accepted to ripple and noise on a PC's power supply regarding analog recordings ?

I know quality sound cards have good filters/capacitors to make up for psu related problems but still would like to hear other's experience on this.

 

Cheers:thu:

[t_e_l_e]

not sure if i understand your question

normally in a good setup you should not get any noise from power supplies or computer or whatever

 

we were once recording in a setup

amp->mic->mackie mixer->line-in of crappy notebook onboard sound card

 

notebook was powered with its psu on the same circuit as the mixer and we had horrible noise on the recordings.

we freaked out and tried to fix it, after 2 hours of trying someone unplugged the psu of the notebook and the noise was gone...

 

so yes, you can get noise, but it is a setup problem and which components you plug together.

and no, noise in the recording chain is not acceptable, cause after you recorded it there is almost no way to get rid of it again

 

we bought a proper external sound interface and there were no noise issues anymore since then

on board soundcards and standard soundblaster types are not really meant for audio recording and so are the results of recordings with them not really usefull...

 

if you have noise with a proper external interface, most likely you have somewhere a bad cable or so and you should double check your setup

[WRGKMC]

PC's should not and normally do not induce any kind of AC hum in recording interfaces.

 

AC hum usually comes from poorly shielded cables connecting to an interface where the preamps amplify the hum up, or in some cases you may have a ground loop where one piece of equipment is on a different circuit than anither and theres a difference in potential between the two due to ground resistance. Thats about it. If you use good quality 90% shielded cables you shouldnt have ac hum or ripple and is you do its will be so low in level it would have no impact on recording digitally.

[JoseDN]

Er, I'm not sure we're talking about the same kind of noise, I was talking about the ripple and noise normally referred to on PC PSU reviews and tests. For example, here is a example of a good PSU (look at the graphs bellow and comments it seems to be measured with an oscilloscope): http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story3&reid=202

 

and here is one "not so good but still in spec" PSU: http://www.hardwaresecrets.com/article/OCZ-ModXStream-Pro-600-W-Power-Supply-Review/936/7

 

Whether or not this noise ends up affecting the noise in the recorded audio (analogue) signal is my question, I guess it depends on other factors like the motherboard and sound card in question, but can it theoretically affect it or not ?

[JoseDN]

I understand that this is probably a bit too technical but nevertheless probably important when putting up a system for audio recording.

[Phil O'Keefe]

In my experience, if you have a decent power supply (Antec, Enermax, Thermaltake, etc.) with sufficient wattage to power everything in the computer, (with some power in reserve) then the power supply noise and ripple is usually going to be below the noise threshold of other things, and less of a cause for concern than other things. IOW, you're more likely to have issues with acoustically radiated noise from the fans in the computer (including the power supply fans), self-noise from your condenser mikes and your mic preamps and the noise floor of your recording room than from the computer's power supply. If you want to look for a ultra low ripple / noise power supply, feel free - but you will probably have problems in terms of direct comparisons since there is no defined reference or measurement standard that is universally used industry-wide.

 

Can it affect recordings? Yes, if it's bad enough. It's usually not a cause for concern; especially compared to other sonic gremlins.

[WRGKMC]

The ripple can affect two things. The preamp of the interface which is analog and susceptable to emf, or disruption with digital data.

 

If the ripple was large enough to affect the data then your problems wouldnt be isolated to musical data, it would affect any or all parts of the computer and its processing. Any chip on the board can be affected and if it was leaking into circuits affecting clocks etc your computer wouldnt function. After the point of audio being digitized and sent through the cables boards processors etc, the data is combined with protocol to make sure the data packets arrive intact. If the data packets were being knocked out by AC ripple changing the binary highs and lows, the CPU would detect the loss of data and come up with math errors. In other words, you had a hundred people get on the train, and 98 or 107 gets off then something got on or off while the data was moving, the packet was corrupted during transmission. This would be detected, the packet would be resent untill the correct ammount is recieved. This is called ecm and deals with data compression so large ammounts of redundant data can be sent quickly. If too many errors are received then you can have slow data transmission, transmission failures, blue screens can occur, hardware can drop off line, pop ups in the software, or maybe just digital noise.

 

Where AC noise is more likely to affect is the interfaces preamp section of the interface which is susceptable to AC noise.

The question would need to be if you're using PCI, USB or Firewire interfaces as well.

If you were using say firewire, then its unlikely to be affected by AC rippel. It has its own power supply and its going to be feeding the preamp with clean juice.

so that leaves PCI cards and USB. USB is not only a data terminal, its a voltage source as well. If the USB interface runs on the 5vdc the port provides and that dc volts has dc ripple, then it may affect the interface if the interface has no voltage smoothing and regulation. Most manufacturers will include some capacitence to smooth the voltage and prevent spikes so you dont zap the circuit plugging and unplugging the device hot so low levels of ripple are unlikely to make it to the preamp section. plus many USB devices have another separate supply like firewire and only use the plug as a data port.

 

Lastly are PCI cards. These do get their voltage from the mother board and are susceptable to both radiated and power supply noise. luckily most manufacturers know this and design the circuits so the preamps are well buffered and filterd from stray noise. What noise you may hear gets into the circuit after its been digitized and the recorded or played back wave file doesnt suffere from any ill effects. You can for example crank the gains up and move the mouse and hear zipper noise in the speakers and the playback amp will pick it up. The recorded file wouldnt have that zipper noise imbedded in it though.

 

There are of course low end sound cards, on board sound made up of $2 in parts that will pick up anything but thats not the class of interfaces we're dealing with here.

 

So after that long winded explanation. will a better quality power supply help an computer and its recording abilities? Well it wont hurt. It would likely last longer in the cumputer and maybe have better filtering so you may have less component, drive, card failures etc. But as far as audio performance, even low end supplies do fine so it would be one of those low proirity items on my list. Nearly all have surge and over voltage protection and they are cheap. if a power supply gets noise or fails, then they're cheap to replace. Most supplies outlive the technology so, theres no way I'd spend big money on a supply no matter how good it is. I'd likely upgrade my box before the thing dies.