Lewinskih01... Zoot 45

When you asked.. where will you store the music? That's where I hit the wall. The DAC has USB... so I won't need USB HDD. Is that correct?

Thanks again
DAC has nothing to do with storing digital music.

The DAC's USB is an input intended to receive a stream of data from the computer. You connect the computer to the DAC through that USB connector.

If the laptop has a large enough HDD you can store the music inside the laptop. Otherwise you need an external drive and the most widely spread type of connection between external HDD and computer is USB. But if your laptop happens to have another type of connector, such as firewire, eSATA, or Thunderbolt, you could buy an external HDD with that type of connection and be done. But again, using a USB HDD will work too; my point is another type of connection for the HDD will just sound better.

I hope this is clearer. If not, keep asking!

Type of interface should not matter since HD stores data and not the music stream.

What you say is true. However, it is my understanding the data retrieval from the HD affects the sound quality because of the serial nature of USB and the real-time nature of streaming.

Frankly, I never had a computer/HDD that allowed for this comparison to be experienced first-hand. But it's a commonly accepted "fact" by those who claim they did try it. So in the case of someone who is to buy a HDD for this application, like Zoot45, I try and steer them in that direction. In my system I do abide by this, but can't say I campared it to a USB HDD.
Data on hard disk has no timing. It goes thru all sorts of buffers to audio card or converter where timing is recreated. Different type of Hard Drive might have influence possibly reducing overall system noise (if lower power) but it won't affect serial stream. Playback program, or computer speed might affect data stream but they will change timing and not the data itself. Variation in time is jitter - removed by reclocker. I use wireless to completely isolate noisy computer from my system. Receiver, Airport Express is known to have a little bit more jitter than desired (258ps peak-peak while >50ps peak-peak becomes audible). Reclocking in my DAC reduces jitter to inaudible levels.
Exactly. I'm talking about jitter too. Not sure I'm following 100%, though, or that I am making myself clear enough.

The point I'm trying to make is that if you have an asynch USB DAC connected to the computer, adding a USB HDD to the same computer is likely to add jitter. Which is why I was recommending a non-USB HDD IF the laptop has another type of connection available. But I'm not saying music will sound better because a non-USB HDD sounds better.
I don't know asynch USB, you're probably right. Firewire HD has advantage of not involving main processor in transfers (has its own processor).