I'm starting to get slightly annoyed at the wildly different volume levels I get from my CD player vs from my two computers.

I have all three connected to my amp on line level inputs like so:

Desktop computer -> USB -> Edirol UA-1X soundcard -> RCA -> amplifier
MythTV computer -> onboard sound -> minijack-to-RCA -> amplifier
and of course
CD player -> RCA -> amplifier

(The software volume controls on both computers are at 75% which is a notch below where I start to hear distortion in the signal, and the CD player has a variable output attenuation from 0db to -20db, which I have at 0db)

Now, one would probably expect all three of these to play at roughly the same sound level, given that everything is line-level outputs and inputs, correct?

When I use the CD player, about 1/4 the way on the volume control on my amplifier is normal listening level, and 1/2-way up is rather loud (probably the loudest I'd ever want to have it). But when I listen to either of the computers, I have to turn the volume almost to 2/3 the way up to get just a reasonable sound level.

It's not so bad for music, but when I watch my movies from the MythTV computer, their sound levels are generally lower than most of my music, and it is impossible to get a reasonable "movie watching" sound level.

Is this expected behavior, and/or is there something I can do to get similar volume levels from all my inputs?

It's quite jarring to switch the amplifier over to the CD player when the volume was set for the computers

There might be something on your setup playing.

I have the output of my soundcard at 6% (yes, 6. when i watch TV, I pump it to 15% or so), and my Amplifier at 1/4th. That's fine most of the time.

About the output attenuation you mention on the CD, it only reminds me that "Consumer" eletronics use -20dB, and professional equipment +4dB. So, maybe the problem is that you need amplification from the soundcard to the amplifier, if this one expects a signal in the "professional" range.

Of course, you might want to put your CD at -20dB, to equal to the output of the soundcards, but that would solve only half of the problems.

I don't think my amplifier expects a 'professional' line-level signal. It's a normal ~10 year old consumer-level Pioneer 2x50watt stereo amp.

Attenuating the signal from the CD player would bring the signals roughly in line with each other, and I have thought about "solving" my problem via that route. But the result would be one of castrating my amp and not being able to play as loudly as I sometimes would like to.

After having some spare time (3 hour train ride) to think it over today, I began wondering if it could be caused by impedance mismatching, although I would think that my Edirol UA-1X USB soundcard ought to have the correct output impedance for coupling with a regular old stereo amp.

The edirol should be a few db louder with a bit-perfect setup (ASIO, no mixers anywhere). You could try kernel streaming on the other computer (ASIO4ALL will do this from ASIO).

"Line level" on consumer products differs considerably from one device to another in my experience; e.g. three different CD players input to one amplifier, playing the same CD, will produce three different loudness levels with the volume control always in the same place.

On soundcards there is "professional" (+4dBu) and "consumer" (-10dbV). I have done too little with the +4dBu settings to know much about that, but the consumer level output differs quite noticeably from one soundcard to another, at least for the several I've played with.

ASIO won't be that easy, considering that both computers run Linux

But it seems that the JACK Sound Server supports ASIO, so I'll give it a go.


And thanks for the advice, AndyH-ha. I foolishly thought that there was some kind of widely agreed-on standard for line-levels, but now I know otherwise


If using ASIO doesn't work (and I'm sorry to say that I don't think it will), could some kind of slight amplification be in order? Something to raise the line level just those few db?

EDIT: The specs page for the Edirol UA-1X here says "Nominal Output Level Line output jacks -10 dBu"

Are you sure that isn't -10dBV?

The soundcard might meet its published specs, but general consumer audio devices are all over the map.

ALSA will do bit perfect output on most cards with little effort, and so can Jack, as far as I know.


A simple line level gain stage could be added. You could build a suitable one with excellent performance for very little money (using OPA2134, for example). You must just be careful not to cause clipping in the extra stage, or in the power amp.

It does say "dBu" on the specs page, so I'm guessing that's what they mean.

I found a user's guide for my CD player here (it's in swedish, though) where it says on page 22 (translated): "Output voltage ..... 2.0V (EIAJ)", which I guess is some kind of Electronic Industries Association of Japan standard.

And the user's guide for my amp here (in swedish again) says "Impedance: CD, TUNER, LINE, TAPE l/DAT, TAPE 2 MONITOR ..... 200 mv/50 kOhm".

Now, it doesn't make too much sense to me, but it's gotta be useful for something

Dis you compare using the same source?
A music CD, and ripped to WAV versions for for computer playback.

My SPDIF hooked up receiver has volume control with discrete dB steps, and going from a loud MP3 (100dB in MP3gain) to a movie, I have to up the volume 20dB!!

I am comparing the very same source material. I have the CD playing in the CD player and the same album compressed with FLAC on my PC and as I switch between them, normal listening level from the CD is barely audible from the PC.

This is not uncommon at all. Not only do different sources ouput different voltages, sometimes different inputs on amplifiers/receivers/processors will have different volume levels.

One 'good' way of setting the levels is to record a 1kHz pure tone (adobe audtion works for this). Play it back on the cd player and using a SPL meter note the level at your seat. Then play the same tone troug hthe computer (and whatever other sources you want to match) and adjust there volume controls to match the SPL reading from the CD player.

On the other hand you could just live with it.

I could do that, but the only place I could adjust the volume would be on the CD player. And turning it down to the level I get from the PCs would mean turning it down way too far.

Plus, the adjustment is lost every time the CD player is turned off.

I can live with it for now. But since we're moving to a digital-only broadcast platform here in Denmark in 2009 and my TV doesn't have a digital tuner, I was planning on using my MythTV box for watching TV (thus also gaining hard disk recording, which is nice ). But without proper volume, that's kinda not going to happen...

It would seem that my only two options are:

1. Building an amplifier box to match the line levels
or
2. Getting sound cards with proper line levels, if such a thing exists.

There is something strange going on. Isn't the Edirol a professional quality soundcard? 75% of its output is way down. I can't think of any reason you should attenuate its output unless the full signal over drives the amplifier input -- and then you would have very loud audio. I've used several professional/semi-pro soundcards. The only reason I would reduce the output level on any of them is if they were being fed from more than one program at once (multi-client driver required) and the sum of the inputs was greater than 0dBfs.

There certainly should not be any distortion prior to the amplifier for 100% through the soundcard. For the built-in soundcard, who can say what screwy nonsense might be involved?

Well, Edirol is a Roland brand, so I would assume that they know a thing or two about good audio. And it does have RCA in- and outputs, toslink, as well as a headphone jack with a volume knob (which I've found really handy).

What happens if I drive it at 100% (-0db) is that the sound distorts very noticably. I have to reduce it to 75% (-32db) for it to stop distorting. This affects both the RCA and headphone outputs.

So perhaps the ALSA drivers are at fault? I'm borrowing a laptop with WinXP on it (I have no Windows installations at home at the moment) and I'm going to test to see if the Windows drivers for USB sound are better this afternoon.

EDIT: Nope, just as bad in Windows XP. Perhaps it simply can't draw enough juice from the USB bus?

"if I drive it at 100% (-0db)"

The input to the Edirol is the USB link, no?
With what do you attenuate the level?

The input is USB, correct. I use alsamixer on Linux and the standard mixer in Windows.

I'm not familiar with any of the Linux stuff. I believe this is the first professional soundcard I've heard of that uses the Windows Mixer. It's unfortunate that it does as Windows it oriented too much towards messing with audio in the name of gaming and multi-media performance. However, while your problem is no doubt real, it still doesn't compute unless the Windows mixer is doing some special busy body manipulations. USB transmits digital data. What the device receives should be exactly what is transmitted, just as with S/PDIF. If it is 0dB at the source end, it should be 0dB at the soundcard.

Some DACs can't handle exactly 0dB, a couple tenths less should always be fine, however. Those defective ones are usually found in less expensive consumer equipment or rather old CD players anyway. It is also possible for some audio samples below 0dB to produce analogue signals above 0dB. This isn't all that common, and decent DACs have enough headroom to handle it without clipping when it does occur. While I don't have any specifics to go on with your particular soundcard, it doesn't sound like it is functioning properly.

My USB card has no mixer panel to allow any level adjustments and does not use the Windows horror either. It can only receives the unmodified source data, and it never has any problem with it.

Odd... Does yours use the default drivers, or is it something you install manually? I plug my Edirol in, Windows messes about a bit, and voila, it's installed. And it uses the Windows mixer.

The chip in it seems to be a TI/Burr-Brown PCM2902, which I would think is a good piece of kit.

After Windows does its basic USB audio dance, there is an M-Audio driver to install.

It isn't exactly true that there is no control panel. One is installed with the driver. It is only for setting a few ASIO parameters, if one elects to use the ASIO driver. It does not include any mixer or level controls.

There seems to be no additional software for the UA-1X. From Windows 2000, Mac OS X and Linux 2.6 onwards, it uses the USB audio drivers built into the OS. Only Win9x and older versions of Mac OS need a driver, according to the website and the box I got it in.

I guess I'm going to have to sell this card, borrow and try some other sound cards and see if I can find one with a proper output. Any suggestions?

There are quite a few decent soundcards on the market. It's unfortunate you didn't discover the problem with yours while the box was under warranty.

It is... But you live and you learn

Thanks for your help everyone!

If I remember there are a few people on the Head-Fi forums who either use linux or have asked about using it. If you search for linux there you will probably see what sound cards there are that work with it.

Excuse me for practicing thread necromancy, but I solved my problem.

First off, I could have sworn the distortion was in the RCA outputs as well as the headphone jack. But after hooking a Behringer HA400 headphone amp up and playing around with it, I simply cannot get any audible distortion on the RCA outputs of my soundcard, only the headphone jack.

My only conclusion is that the headphone opamp in the sound card is a piece of crap. Thankfully, this doesn't matter anymore since I bought the separate headphone amp.

Now I'm kinda feeling stupid for not discovering this before...