How to reduce audio distortion
April 5, 2015 8:53 AM   Subscribe

I use my computer to play music via iTunes and my computer uses two BOSE companion speakers for output. In order to play music I am faced with a total of 3 volume controls each found separately throughout iTunes, Windows 8, and my Bose speakers. How should I adjust each volume setting to achieve the best sound quality?
posted by isopropyl to Technology (9 answers total) 3 users marked this as a favorite
 
Turn up the two volume controls all the way. They are digital and by having them turned to anything but 100% you are losing bits of precision.

Adjust the volume using the speaker volume controls.

The exception is, if you have distortion because the input to the speakers is too loud, turn down the Windows volume until the distortion disappears.

Use the individual applications' volume controls to adjust volume relative to other applications when necessary, but keep them as high as possible.
posted by kindall at 9:06 AM on April 5, 2015 [3 favorites]


Keep in mind, it is only all digital if you are using a digital output built into the computer, or an audio interface with digital outputs and digital inputs on the Bose system (i doubt the Bose has digital inputs). If you are using the normal analog mini plug outputs on the computer (as most people do), there is a DAC (digital to analog converter) just behind the mini plug analog out converting the computers digital signal to analog before exit. This makes that output gain stage subject to being overdriven like any other. When you are using a digital out, the volume controls of that output disappear as the maximum gain is sent to the output automatically. Adding a high quality audio interface will improve that connection dramatically by improving the quality of the D to A conversion. If you don't have that, do not overdrive the analog output of the computer, turn it down until it sounds good to you then set playback volume you want with the Bose system.
Almost all Mac computers have a dual purpose mini plug output that is analog with a normal length mini plug and Digital with a slightly longer digital mini plug cable. The extra length allows it to access the digital section of the output. Windows computers rarely have this digital output as far as I know.
posted by StUdIoGeEk at 10:02 AM on April 5, 2015 [1 favorite]


They are digital and by having them turned to anything but 100% you are losing bits of precision.

No. Bose Companion speakers use an analog interface between the computer and the speakers, so there are two analog amplifiers involved: the one in isopropyl's computer, which is controlled by the Windows 8 master volume control, and the one in the speakers, which is controlled by the knob on the speakers.

Both the computer (via Windows 8) and the speaker volume will need to be tested to find the maximum level they can each be turned up without audible distortion, and then isopropyl will leave the one that is less convenient to adjust at the distortion-free maximum and use the more convenient one to adjust volume. (The more convenient control depends on speaker placement, what's in reach, and the intrinsic audio qualities of the amplifiers - so isopropyl, that's up to you after experimentation.)

I agree that the one in iTunes likely doesn't matter here, and is mostly there for convenience.
posted by eschatfische at 10:10 AM on April 5, 2015 [4 favorites]


Years ago (circa 1996, probably), I read in the manual to a DAW product that one should always have the software volume controls turned to 100% in order to prevent "dropping bits" at the DAC. I have stuck to that advice since then, although I do not think that modern DACs actually have that problem or work that way, and it's thus fairly cargo-culty.

But if you see or hear that particular piece of advice floating around, I think that's where it comes from. For people who were raised on analog audio equipment, it feels "truthy" in the sense that it is similar to the way you'd set up gain structure throughout an analog audio signal path. (In the analog world you generally want to keep the signal as strong as possible without distortion all the way through to the end stage, the amps or headphone output or whatever, and that's where you adjust the volume.)

There's still some merit to that gain structure argument when you have a digital source driving an analog source, like speakers attached to your computer, particularly if they are connected via an unbalanced Line Out jack which picks up a lot of 60Hz line hum if the speakers are turned up too far. (It doesn't make sense if you have digital speakers, though, with an integrated DAC and amp.)

However, I wouldn't obsess too much over gain structure at the expense of convenience. If it's convenient to control your volume at the speaker controls, do that; but if it's more convenient to use the Windows volume controls, go ahead and use them. I'd just try to find a 'sweet spot' for your speakers' analog volume controls that ensures there's no audible line hum when nothing's playing (which means they're turned up too loud or you need to move the cables away from power cords), and lets you play music as loud or a bit louder than you'd want to play it when Windows is at 100%. If you do that, you can then use the Windows controls to reduce/mute it (using your keyboard volume buttons or whatever), and balance applications against each other (so that Exchange's new-email dinging doesn't wake the dead, etc.).
posted by Kadin2048 at 10:55 AM on April 5, 2015


I'm fuzzing the tech here a bit. But you don't lose 'bits of precision' by having your application volume control in Windows 8 lower than 100% because Windows upconverts all internal audio streams to 32-bit floats before any volume processing takes place. In Ye Olde Days of software processing where your audio output was 16 bit and your software processing was 16 bit you would lose bits by changing internal volume on apps, but that hasn't been the case since Vista I think. So your audio file is 16-bit, upconverted to 32-bit for all volume/mixing/etc processing, then sent to your sound card which almost certainly converts back to 16-bit before it goes analog. So it doesn't matter what your internal volume controls are set to, your sound card is still getting a high enough bitrate stream that it's not losing any data when it outputs. So just set your actual sound card/speaker volume low enough so that you don't hear any audible distortion.
posted by Jairus at 12:42 PM on April 5, 2015 [2 favorites]


iTunes max, windows 1/2-3/4, Bose speakers whatever you want.

Low volume from the sound card will have a crappy signal to noise ratio. iTunes volume is just an arbitrary toy if you want quiet background music while having sound from something else louder. The volume on the speakers is your true "master" volume.

There's some good advice above from studiogeek and jairus.

If you have consistent distortion or a bad SNR/noticeable static then your sound card probably sucks. Get a cheap usb DAC. The Fiio ones are fine. If your motherboard has optical out, the cheapo optical ones will be fine too.

I got better sound and a WAY better noise floor/distortion than I've gotten from any onboard sound with a cheapo Yamaha USB mixer I paid maybe $50 for.(that used one for $39 is an EPIC deal)


On preview, someone in my office has those speakers. They just distort fairly easy. Have you tried other speakers?
posted by emptythought at 5:27 PM on April 5, 2015 [1 favorite]


To defend my initial post, it seemed unlikely to me for a PC sound card to have a separate DAC to control the amplifier volume, especially given that the PC must also support outputs that do not have such and control the volume on them as well. Far more likely, I thought, for the amp on the analog output to be fixed to unity (for line out) and the system volume control to be done in software.

If y'all are telling me that's wrong, well, at least my advice won't hurt anything.
posted by kindall at 4:01 PM on April 7, 2015


it seemed unlikely to me for a PC sound card to have a separate DAC to control the amplifier volume

While DACs are often packaged with amplifiers, DACs don't control amplifiers. They convert a digital bitstream into an analog signal which is then passed to an amplifier. This isn't a splitting of hairs - DACs have nothing to do with amplification or the adjustment of volume.

Every sound card or integrated HD Audio chipset that has a stereo line out or headphone jack has multiple analog amplifiers with software-addressable gain control for each amp, and that's been the case since the days of the Sound Blaster. You don't want the amplifier to be continually active at a high fixed level due to noise and power consumption.

Electronic devices absolutely can and do have multiple DACs and amplifiers. The Wolfson WM5102 codec, a high end integrated audio chip found in many mobile phones, has 7 DACs, 6 ADCs, and five analog amps all in one tiny package. It's 24-bit, so there's no loss of resolution if you adjust the volume digitally. Even with all of that, they cost around $7 each in quantity, and you can buy a complete sound card based on it of very good quality for less than $40.

the PC must also support outputs that do not have such and control the volume on them as well

Every modern operating system has been able to support multiple audio drivers to control different types of audio output devices, whether those devices are fully digital or that have analog amplifiers and outputs, for some time.
posted by eschatfische at 11:49 AM on April 9, 2015


Every sound card or integrated HD Audio chipset that has a stereo line out or headphone jack has multiple analog amplifiers with software-addressable gain control for each amp

Said software-addressable gain control needing to be converted from digital to analog by some kind of component... a kind of digital to analog converter, if you will...
posted by kindall at 5:06 PM on April 10, 2015


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