Hello-

[drewm1980]

Hello-

I'm a grad student in EE at the University of Illinois, Urbana-Champaign. Though my specialty is in computer vision and unsupervised learning, I am quite a music lover and also love working with my hands. Audio hardware is a recent obsession of mine, triggered primarily by an analog circuits class I am taking.

I currently play music from my ibook's built-in audio, through an onkyo TX-8511 stereo amp (about $200) and a pair of Phase technology Teatro 4.5 bookshelf speakers (about $300). I suspect that my ibook's DAC is currently the weak link in my audio chain, but I've had two USB audio adapters go bad on me so its the best I've got, besides a couple onkyo CD players that I bought in a garage sale are repaired.

My first audio project will probably be to build an outboard DAC, maybe with a chip based headphone amp if I have enough $$. I had a job soldering circuit boards for one summer and have also successfully hardware over-clocked my ibook.

Musical tastes include Duke Ellington, Bela Fleck, Bjork, Chicago Symphony (family), Glen Gould, Solas, Osvaldo Pugliese, Jimi Hendrix

Still haven't learned to like Punk, Ska, Country, Rap, most electronic, most rap, most mass produced radio music

[Geek]

Hi, welcome!

Heh, looks like our musical tastes are pretty close.

Outboard DAC is a great idea. Feed it into a 6DJ8 tube for a sound you won't forget

Looking forward to some of your ideas and projects

[drewm1980]

Thanks for the advice, Geek!

Though it may be ambitious for a first project, I'd like to look into building my usb or IEEE1394 interface as well, possibly on the same board as the outboard DAC depending on how many signals are required to interface the chips.

One of my broken mass market usb adapters (UA-1X) may still have a working optical SPDIF output though, so that is a possibility as well. I presume a TOSLINK receiver would be simpler and more commonly supported, so I may start there.

The tube you are recommending is to be used as a unity gain stage in the outboard DAC, or as a headphone amplifier? Could you please refer me to the circuit(s) inspiring your comment?

Drew

[Geek]

http://pw2.netcom.com/~wa2ise/radios/tubedac.htm

Scroll down. Robert Casey did some great groundwork here. The ensuing discussion on Usenet led to some others tweaking around with it. Sorry, I disn't save those threads.

The tube I mentioned can be used for unity gain, or fairly linearly with a gain of 20 or so per section. Other than the above link, another good configuration is known as the mu-follower (some gain) or Loftin-White cathode follower (near unity gain [0.98 or so]), because it has a high input impedance (several hundred K ohms), so to not load down the DAC and a low enough output impedance to drive a line

But, I'm babbling. Just an idea. Not everyone likes "hollow-state"

[drewm1980]

Cool! Now I see the dual purpose of the near unity gain tube stage. At first I thought it was to improve sonics only in the very vague sense of adding that "warm tube sound" to the signal, which I take to be some slightly non-linear distortion of the signal that people have grown to like.

Thanks for the link to the website, it is very thorough in explaining the motivation behind all of the aspects of the design modifications proposed.