The Cordell distortion magnifier is a pretty good tool. With modern op-amps that same idea, plus a halfway-decent sound card should have no problems measuring the distortion of even a SOTA power amplifier.
Alternatively, here's an interesting option:
https://e1dashz.wixsite.com/index/cosmos
Alternatively, here's an interesting option:
https://e1dashz.wixsite.com/index/cosmos
If you don't want to build something yourself, then the QuantAsylum QA40x is currently the best device with the best price-performance ratio. Above all, the measured values are displayed well and the whole level controlling works. Even Bob Cordell uses the box.
I've had very good results with a Topping D10s and the Cosmos ADC, with an Autoranger in between.
This post is what inspired me to purchase the D10s: PMA Measurement system
does anyone other than me get a kick out of reading some of these old threads over time?
i kicked this one off WAAAY back in 2001 when I used to have unlimited access to an AP at work and wanted something I could use at home.
now, 20+ years later, we've seen several folks build great looking revised versions of Bob's THD analyzer (from Audio magazine years ago), the high performance but affordable QA-4XX series of HW & SW, we've seen the appearance of the wonderful RTX6001, and lots of great software (some free like REW and more recently ARTA) and audio interfaces for less than $200 that can do amazing things.
if only there was a device that could create more free time and provide access to discontinued parts from the past ....
now where did I put that timemachine ...sigh ...
i kicked this one off WAAAY back in 2001 when I used to have unlimited access to an AP at work and wanted something I could use at home.
now, 20+ years later, we've seen several folks build great looking revised versions of Bob's THD analyzer (from Audio magazine years ago), the high performance but affordable QA-4XX series of HW & SW, we've seen the appearance of the wonderful RTX6001, and lots of great software (some free like REW and more recently ARTA) and audio interfaces for less than $200 that can do amazing things.
if only there was a device that could create more free time and provide access to discontinued parts from the past ....
now where did I put that timemachine ...sigh ...
Now, if you'd only started a thread about that subject back in 2001, we'd be in fine shape. 🙂
I also like reading old posts. It's amazing how some ideas keep popping up as if they are new, how some bold and emphatic ideas of the day seem, umm, "quaint" now, and how some debates never get resolved.
Anyway, for the benefit of anybody who decides to read this thread a few years from now, here's what my current test set-up can do. It's a little more expensive than the $200 you mention (especially with this week's tariffs...) but not a ton.
Topping E50 (has both balanced and unbalanced outputs - using balanced here) > Filtered by E1DA Cosmos LPF > Notched by E1DA Cosmos APU > E1DA Cosmos ADCiso. Software is REW, although Multitone gives pretty much the same results.
Of course, I can do other measurements with this system, too.
In addition, I also have one of Victor's 1 KHz test generators as a sanity check source, an E1DA Cosmos Scaler that is used for lower level DUT measurements (preamps and so on), and a Jan Didden AutoRanger used for higher level DUT's, like amplifiers.
I'll make one of those bold statements here myself: This is probably more than good enough for any home audio testing. The distortion levels are well below the ambient noise levels found anywhere and (probably) well below the human auditory threshold.
Besides, who knows if people will actually build their own audio gear or even much care about listening to reproduced music 20 years from now. Then again, long established technologies like tape decks, vinyl playback, vacuum tube amplification, and even John Curl's original JC-2 design have kinda "valleyed" out, but have hardly disappeared. So, again, who knows?
Anyway, for the benefit of anybody who decides to read this thread a few years from now, here's what my current test set-up can do. It's a little more expensive than the $200 you mention (especially with this week's tariffs...) but not a ton.
Topping E50 (has both balanced and unbalanced outputs - using balanced here) > Filtered by E1DA Cosmos LPF > Notched by E1DA Cosmos APU > E1DA Cosmos ADCiso. Software is REW, although Multitone gives pretty much the same results.
Of course, I can do other measurements with this system, too.
In addition, I also have one of Victor's 1 KHz test generators as a sanity check source, an E1DA Cosmos Scaler that is used for lower level DUT measurements (preamps and so on), and a Jan Didden AutoRanger used for higher level DUT's, like amplifiers.
I'll make one of those bold statements here myself: This is probably more than good enough for any home audio testing. The distortion levels are well below the ambient noise levels found anywhere and (probably) well below the human auditory threshold.
Besides, who knows if people will actually build their own audio gear or even much care about listening to reproduced music 20 years from now. Then again, long established technologies like tape decks, vinyl playback, vacuum tube amplification, and even John Curl's original JC-2 design have kinda "valleyed" out, but have hardly disappeared. So, again, who knows?