HydrogenAudio

CD-R and Audio Hardware => Audio Hardware => Topic started by: theoctavist on 2023-02-05 09:58:16

Title: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: theoctavist on 2023-02-05 09:58:16
I know the obvious, ie additional ports and so on;  but are there any (theoretical) performance benefits wrt noise floor, phantom powering of condenser mics, headphone output performance etc?    I have two interfaces.  Steinberg UR22C & Soundcraft Signature 22 MTK. 


Y'all the best.  Thank you. 

TR
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: DVDdoug on 2023-02-05 11:09:08
USB power tends to be noisy which is no problem for the digital data but sometimes that noise gets into the analog electronics.    Some computers have more-noisy power than others and some interfaces have better filtering than others.  

If you hear it, it's usually a high-pitch whine, either from the switching power supply or from all the data/switching inside the computer.   (Even on battery, a laptop has switching voltage regulators.)

The mic preamps are most-sensitive to noise since they are high gain and they amplify noise along with the signal.
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: saratoga on 2023-02-05 20:37:35
Externally powered hubs are nice since you can pick the power supply.  Usually doesn't matter, but for really sensitive instrumentation I've used low-noise linear power supplies with hubs before.
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: fooball on 2023-02-06 08:16:35
Ideally the analogue modules would have their own source of power separate from USB.
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: theoctavist on 2023-02-07 09:50:03


The mic preamps are most-sensitive to noise since they are high gain and they amplify noise along with the signal.
thank you sir! On that note, ive seen this on a pro audio forum :
Quote
"Because of the severe power constraints of USB bus powering, the headphone outputs, and often the phantom mic power (mic current capability) are limited to power levels that are far less than ideal"
  is there any truth to the notion that mic preamps,phantom power ,  headphone outputs etc will perform worse on bus power?
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: theoctavist on 2023-02-07 09:51:57
Externally powered hubs are nice since you can pick the power supply.  Usually doesn't matter, but for really sensitive instrumentation I've used low-noise linear power supplies with hubs before.

Thank you @saratoga @fooball
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: Octocontrabass on 2023-02-07 20:07:11
is there any truth to the notion that mic preamps,phantom power ,  headphone outputs etc will perform worse on bus power?
That depends on how well the device filters noise from the bus power and how much power the bus allows it to draw.

I would guess it's probably cheaper to rely on an external filtered power supply than it is to build adequate filtering into the device, especially if there's no guarantee that the bus can provide enough power in the first place. (Although USB-C might solve the bus power issue, now that there's a standard for supplying up to 240W!)
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: saratoga on 2023-02-08 19:09:21
With care USB can be fine. There is enough power for headphones and noise can be filtered. But it's often easier to just use a cheap external power supply at a higher voltage rather than clean up USB+5v.
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: theoctavist on 2023-02-11 06:50:03
is there any truth to the notion that mic preamps,phantom power ,  headphone outputs etc will perform worse on bus power?
That depends on how well the device filters noise from the bus power and how much power the bus allows it to draw.

I would guess it's probably cheaper to rely on an external filtered power supply than it is to build adequate filtering into the device, especially if there's no guarantee that the bus can provide enough power in the first place. (Although USB-C might solve the bus power issue, now that there's a standard for supplying up to 240W!)
thank you for the input sir!
Title: Re: Advantages re: AC Powered USB Hub vs Bus Powered for audio interface.
Post by: theoctavist on 2023-02-11 06:50:55
With care USB can be fine. There is enough power for headphones and noise can be filtered. But it's often easier to just use a cheap external power supply at a higher voltage rather than clean up USB+5v.
yessir, I've done just that and ordered an external supply.  Thank you so much!