The OP wrote:
"I'm a musician with a bit of a fascination with audio gear, and it's been a fairly longstanding goal of mine to do some measurements to characterize the sound of different instruments, techniques, spaces, etc.. I'm also interested in being able to characterize the performance of my gear - frequency response, THD+N, etc - both as a reference for further experiments and so I can see the effect of different configurations or modifications."The way I read this, is he wants to tweak his equipment to a get better sound, and understand the effect of the tweaks. His goal is not to get better numbers only (he does not work for a commercial business where it can be interesting for marketing to build the first 32 ENOB-dac with an SN of 194db :-) so all audiophiles consider this the next Walhalla and sell their house to buy this new gear).
So we should advice gear that is :
- capable of measuring “audible” differences (and a bit below audioble so the cumulative effect of multiple changes is also possible)
- relatively easy to use and to understand (he will not use this 8 hours a days, 5 days a week…)
- affordable (so the OP can spent the rest of his available budget on other nice gear for an electronics lab :-) )
So I think the recommended QA401 will be perfect for measuring the electronics (differential inputs are a very big plus), and use a sound card with ARTA or equivalent software (he can play around with as many free tools he wants) will get him going on the acoustics side.
I recommended this as an “ex-audiophile”, as once upon a time I also really believed in the benefits of using ultra expensive audiophile capacitors, ultra-low jitter clocks, buying expensive signal cables…
and wasted quite some money doing that until I started reading.
One of the things that cured me from my “audiophile illness” was the following software tool:http://www.foobar2000.org/components/view/foo_abx
It allows you perform blind ABX comparison between two music tracks. For example you can test if you can hear the difference between a compression less music and MP3@320, the effect of 0.01% THD added, the effect of some phase distortions,the effect of adding some reflections …) For manipulating the audio tracks (THD distortion, phase distortion, low and high pass filters, adding reflections) use the typical musician tools which I suspect will be not an issue for the OP.
By doing lots and lot of ABX testing (use a good headphone) you will be amazed how difficult it is to actually hear some differences. For example I was really sure I would be able on any music to recognize MP3 (even at 320kbps) from compression less, but this proved to be not so easy.
Combine this with a good book on psychoacoustics and acoustics, and you soon realize you will have been wasting your time on the wrong things (and the wrong audiophile gear). Your new goals will be to manage early reflections in your listing room, having a speaker with constant directivity and having multiple subs in many positions to get a reasonably flat frequency response in this modal sound region. All of these are dictated by the way sound waves travel (and the wavelengths involved) from the speaker to your ear, and the way our hearing works. The electronics cannot alter these new goals (only exception, having a speaker with steers the sound beams using DSP and multiple speakers). So once you know your electronics are “good enough” (which should not be a problem for modern affordable gear), you can start tinkering on how the fool the laws of physics…