[grhellen]

Hello, All.

I was wondering if anyone would mind relating their experiences with DACs (AVA or other) used with digital sources such as MP3 players, satellite radio, etc.

Thanks.

[Rashiki]

As far as I know, very few MP3 players have digital outputs. I don't think you can get digital output from an iPod without modifying the hardware.
I have an older MP3 player (iRiver H140) that has an optical digital output and I've used it with a couple of different DACs and it has worked very well. With lossless files the sound quality was in the same league as my CD player and SqueezeBox.

Speaking of the SqueezeBox, that's a non-CD source that works well with DACs. You can stream "ripped" CDs from your home computer, internet radio stations or services like Pandora. It will also handle 24 bit data up to 48kHz if you can get your hands on it and if your DAC supports it.

I haven't tried satellite radio. The Polk home XM tuner has digital optical and coaxial output and I would assume that it outputs 16 bit samples at 44.1 or 48kHz which would be compatible with most DACs, but I don't know for sure.

 -Rob

[Brett Buck]

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I haven't tried satellite radio. The Polk home XM tuner has digital optical and coaxial output and I would assume that it outputs 16 bit samples at 44.1 or 48kHz which would be compatible with most DACs, but I don't know for sure.

       I haven't tried any digital output sat radios, but I can't imagine that running through a DAC of any type would help very much. The low bit rates and compression on either Sirius or XM makes it sound *horrifically awful*. I had my Sirius PnP receiver connected to my good home system (AVA Omega preamp/amp, B&W 803s), through analog, of course,  and it sounded like it was being transmitted from a bus station restroom, even on the good channels. All sorts of high-frequency metallic "reverb", and having all that extension up to 20khz was not helping. This was the first time I used the "filter" button on my OmegaEC. Analog TV sound is actually an improvement over Sirius and XM broadcast. It's a shame, too, because it really is a convenient way to go, if you could listen to it for more than an hour.

   The Sirius streaming service is 128K and it as least tolerable to listen to - it would be worth using as a home source, and would probably benefit from a better audio chain than using the analog output from a computer sound card.

    On a related topic, does anyone know what bit rate/compression is used in ATSC (over-the-air digital TV) for audio? I have noted that the digital TV sound from a local jazz station (KCSM JazzTV, digitial 43.3 for Bay Area residents) is fantastically good. It really surprised me how well that works.

     Brett

[Berndt]

brett, kcsm is my best sounding source point, via a 50$ FM tuner.
A great radio station!

[avahifi]

Other sources?

Well, our source at the Audiokarma show last week was Jim's computer feeding a Squeezebox into our DAC from uncompressed CDs copied onto the computer hard drive.  It worked just fine to my ears, aside from a nasty room boom from the small Howard Johnson hotel room.  Both my engineer and prototype builder have brought in computer connections here that worked just fine too.  Compressed MP3s?  Forget it, the Spam approach to fine dining.

Radio?  I have an Ultra hybrid tube audio circuit built into my own Philips FM/AM tuner.  It is a one off and not for sale. Very nice on good classical stations here.

Regards,

Frank

[grhellen]

Thank you all for your responses.

Is the problem with satellite radio the same as with compressed files such as MP3?

Greg

[Rashiki]

       I haven't tried any digital output sat radios, but I can't imagine that running through a DAC of any type would help very much. The low bit rates and compression on either Sirius or XM makes it sound *horrifically awful*.

I haven't listened to sat radio, but I did assume they were using very aggressive compression. Too bad.

    On a related topic, does anyone know what bit rate/compression is used in ATSC (over-the-air digital TV) for audio? I have noted that the digital TV sound from a local jazz station (KCSM JazzTV, digitial 43.3 for Bay Area residents) is fantastically good. It really surprised me how well that works.

I can't tell you what KCSM uses for ATSC transmission because I don't get that channel over the air, but a random sampling of my local OTA HD ATSC stations gave the following results:

384 Kbps AC3 2-channel, 2nd program at 96 Kbps AC3 2-channel (PBS)
384 Kbps AC3 5-channel (NBC)
448 Kbps AC3 5-channel (Fox)

If KCSM is using 384 Kbps 2-channel AC3, it would explain why it sounds good -- that's a reasonable bitrate.

 -Rob

[Rashiki]

Is the problem with satellite radio the same as with compressed files such as MP3?

Greg,

Most MP3 players will play lossless files or high bitrate MP3. Lossless files should sound as good as CD and high bitrate MP3 should sound pretty good, possibly just as good as lossless to your ears. I personally can't distinguish between high bitrate MP3 and lossless in most situations, but I can clearly hear the difference between high bitrate MP3 and 128 Kbps MP3. Unfortunately, most online music is encoded at around 128 Kbps. AAC or WMA might sound slightly better than MP3 at those low bitrates, but you'll probably still be able to tell the difference between low bitrate encodings and lossless. If you want high bitrate or lossless data on your MP3 player, you'll have to either rip your own CDs or find an online store that caters to people wanting higher quality.

The issue with satellite radio is that the data is encoded at a fairly low bitrate. I don't know the actual rate or encoding format, but from comments on sound quality, it seems like it may be lower than 128 Kbps.

 -Rob

[Rashiki]

Out of curiosity, I checked the bitrates of the audio channels available over digital cable (Comcast). The "Music Choice" channels all seem to have their audio encoded as 192 Kbps AC3, while the local radio stations are encoded as 128 Kbps AC3. I know that doesn't answer the question that Brett asked, but I thought it was relevant to the original topic.

 -Rob

[Brett Buck]

The issue with satellite radio is that the data is encoded at a fairly low bitrate. I don't know the actual rate or encoding format, but from comments on sound quality, it seems like it may be lower than 128 Kbps.

    Much lower. I experimented with different encoding rates (from a CD source) and the very best channels at the very best of times were like 48kbps MP3s, which is pretty bad in and of itself, but with a strange metallic reverb sound that's like fingernails on a blackboard that makes it more difficult to listen to. The "regular" quality Sirius streaming service usually reports 48Kbps on it's control panel. and it sounds about the same as the broadcast. The Sirius "premium" service is 128Kbps and it sounds like most 128K sources, i.e. not great but pretty decent. So the regular service is, at best, much worse than that.

    My understanding is that the total bandwidth for the entire service is 12Mbps, so with ~150 channels you can see it's not going to sound very good.

   By the way, the 128kbps "premium" service is advertised as "CD Quality" but of course that's just a lie. I pointed it out to them and they said "we'll get back to you". That was about 2 months ago.

     Brett

[grhellen]

Do you think that hooking up a Sirius home tuner (SR-H550) to a T8, or similar, will result in anything listenable?

Greg

[dB Cooper]

As a Sirius customer, I can say that I doubt it very much. I listen to the talk stations and (mainly in the car) music. It's good enough for that, but even over a car system, a good FM station is obviously better.

[Brett Buck]

As a Sirius customer, I can say that I doubt it very much. I listen to the talk stations and (mainly in the car) music. It's good enough for that, but even over a car system, a good FM station is obviously better.

    Exactly what I found, as well. The music is not nearly as good as standard FM with good reception, and the "Talk" stations are much worse than a decent AM station, even when you listen in a car going down the road at 80 mph. I'm reasonably certain that it doesn't matter what you hook it up to - the downlink bit rate is so low that the quality of the analog end of  the system has virtually no effect.

   The one and only "killer app" for the broadcast version is that you can go all the way across the country with good reception and no interruptions. That alone makes it worth it.

    As I mentioned earlier, the 'premium' streaming audio over the internet is listenable and I plan on using that as a home source when I get a sufficient TCP/IP connection. I use it at work all the time.

     Brett

   

[geezer]

Would someone talk a bit about HD radio? I don't know anything about it, but what little I've read looks interesting. How does it compare with ordinary fm or cds? What hardware is needed in what price range? How would all this relate to an existing DAC?

[Toka]

HD Radio... 

The short story is thus: A scam

Long version? Lets see...MP3 quality at best (the "HD" stands for hybrid digital, NOT high definition), poorer broadcast range vs. analog (you'll notice this if you ever drive around with an HD receiver in a car...the two feeds will likely pop in and out, and they are timeshifted, so the song will skip ahead/back several times if you are on the fringe of the broadcast radius), interference with adjacent stations (even worse now with recent FCC legislation), and yes, you need new hardware. Has nothing really to do with DACs and such. I'd suggest waiting for it to die out, shouldn't be too long. I work in the radio industry FWIW.

[geezer]

The short story is thus: A scam

Well, that's to the point Toka, thanks.

Any contrarians out there?

[dorokusai]

I've used the Polk XM tuner and haven't noticed any difference in SQ in regards to using digital vs analog, thru multiple DACS. XM is satellite/terrestrial, it is what it is and I never really expected much.

I'm betting on some things to really change in regards to the formats that can be found and streamed on the internet. It's already heading that way and if a really nice wireless option can be used, that works internally....XM/Sirius may have something to worry about. I was recently amazed at how many internet radio stations are available, as I just never looked. I feel old.

Mark

[Toka]

I agree that internet radio has the most potential, both in terms of sonics and programming...of course, the recent ruling by the Copyright Royalty Board will kneecap the whole wazoo unless it is altered (internet broadcasters will have to pay both the composers AND performers, while terrestrial is exempted on the latter). I've just started checking it out more myself, so I certainly hope it stays...we will see, I guess.