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Audio interface test reports

I'm trying to learn more about the various qualities of the audio interfaces that are on the market, but I am having a great deal of trouble locating test reports.

I'm interested in test reports for all of the currently popular brands of audio interface, but what I really want to see is anything about the XMAX preamps in the presonus products. Everywhere I look they are praised, but not one person cites a single specification, let alone an actual test. Everywhere I look I see people repeating that they have incredibly high headroom, but nobody seems to be able to tell me what the headroom actually is.

Before I went down this presonus rabbit hole I was just idly interested, but now I really want to know. Does anyone have a source for this kind of info?

Re: Audio interface test reports

Reply #3
Everywhere I look I see people repeating that they have incredibly high headroom, but nobody seems to be able to tell me what the headroom actually is.
Headroom is meaningless in a digital interface.   The analog-to-digital converter is hard-limited to 0dBFS, period.    0dBFS is defined as the highest you can "count to" with a given number of bits, and it's limited on the digital side.     You can't go over 0dB, period.   In other words, there is no headroom over 0dBFS.  

But, you can leave yourself headroom by recording at a lower level...   If your peaks are hitting -10dB you've got 10dB of headroom.   Pros often record at around -12 to -18dB.    But, nothing bad happens when you get close to 0dB...  Bad things only happen when you "try" to go over...  Headroom (during recording) is for unexpected peaks, and then if an unexpected peak does come-along you no longer have the same headroom.   ;)        

An analog preamp CAN go over 0dB, so if a preamp goes to +20dB it's got 20dB of headroom.    But, you have to know what the analog reference level is.    It can be vague because the reference level could be dBV, dBu, dBm, or it could be line level which is -10dBV for consumer equipment or +4dBu for pro equipment.

You're probably not going to find "headroom" spec. for a preamp.   Your more likely to find a maximum output spec, such as "+20dBV" or something like that.   Then, if you have a reference level in the rest of your system you can figure-out how much headroom that gives you in your setup.

The main thing I'd be concerned with is noise, but you can't assume the manufacturers all use the same test methodology so it's probably not helpful to compare the manufacturer's specs.    With USB-powered interfaces, sometimes noise can get into the preamp through the USB power.   And when this happens you don't know who to blame because it depends on the computer and the interface's sensitivity to power supply noise.   Interfaces with their own power supply are immune to that.

Distortion and frequency response are usually better than  human hearing so I wouldn't worry about those.

Sometimes gain can be an issue.   Some people complain of not having enough gain.   That depends on the sensitivity of the microphone, the loudness of the sound, and the distance between the mic and sound-source (and of course the gain of the preamp).

Other people complain about the gain not going down far enough to prevent clipping, even with the gain/level control turned down to minimum.    This usually seems to be guitar players with a direct connection to the interface.  

Re: Audio interface test reports

Reply #4
Thanks for the info.

I still want to see reports for the actual tested performance. Why is it that people produce so many test reports for ADCs and DACs, end products who's purchase has consequence to only to a single consumer, but almost nobody's is interested in producing test reports for a piece of music production hardware? Something where the effects of the purchase potentially affect a much broader audience.

I honestly thought that a musician or studio wouldn't want to buy these things without knowing how they actually perform, but that doesn't seem to be the case.

Re: Audio interface test reports

Reply #5
Look at these threads.

The $80 behringer outperforms the focusrite which costs nearly twice as much.

I'm becoming convinced that they're selling snake oil.

The headphone output from the Behringer is very much Not Very Good At All, though.

If you don't need the headphone output, it's great.

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