2. digital
  3. 1137005401

mp3 bit stream to DAC?

I have an mp3 player (archos av340) which in addition to the headphone analogue audio out, has an SPDIF out. I used to plug the SPDIF out to my yamaha tuner/reciever/amp SPDIF in and play through my stereo system. The SPDIF out/in gave much better sound than the archos analogue out/ yamaha analogue right/left in's I used before I learned I could go the "digital" route (I guess the yamaha had a better DAC than the archos?).

The question - I bought new speakers (quad 989's), a tube amp and an ACK DAC 2.0 to be able to again play my mp3's the digital route through my new system. I get NO sound or indicator light "on" on the ACK indicating the ACK is getting a digital signal fed to it. Should the ACK (or any other DAC for that matter) be able to get and DAC mp3 bit streams (like my yamaha reciever did)? If so, any thoughts on what I could be doing wrong.

Finally, I know mp3's through a "nice" system is an oxymoron (i.e. the mp3 signal is compressed compared to a raw CD signal), but, most of my music is mp3's so I still want to make things work.

????
hovendic
peak
26 posts
 

The SP/DIF port on the Archros player is not an output but an input.
hovendic OP
9 posts
 
Peak, it is labeled input, but the manual says it is both in and out, and it has worked out to my yamaha digital in. That is the only reason I have kept it so long (the newer versions do not have it, I believe some worry about digital rights).
hovendic OP
9 posts
 
Just wanted to close the loop on this, I bought another DAC and it does work on the mp3 bit stream from the spdif out of my mp3 player.
steuspeed's avatar
steuspeed
501 posts
 
Hovendic,

I looked around for an answer to your question, but I could not find anything specific as to what requirements a DAC needs to play an MP3. MP3 players have decoders built in them, but outboard decoders or DACs seem to be lacking. Perhaps MP3 decoding is built into more modern DAC chip sets? Your Yamaha must have this capability. If a component says, "It can play MP3" that is a bit ambigious as this can mean before or after it has been decoded to analog.

What DAC did you buy? Was there any improvement?
edesilva
768 posts
 
GCE.

The bitstream created by an mp3 is format identical (although not content identical) to a CD transport; the player has a digital algorithm in it to convert mp3s to a PCM stream that is probably 16 bit 44.1 kHz, maybe 16 bit 48 kHz (used by a lot of computers). The Ack DAC might not like 48 kHz sample rates, so that might be it. Most DACs are more tolerant.

The content difference is that your mp3 is going to sound compressed, even though the stream is no different technically. It still has to create the same sample rate and reconstruct the bits, its just that it has less information to do it with and will therefore interpolate a lot more.

Try running wav files off your Archos. Those will probably sound a lot better.
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