JohnRoberts

Re: Audio test set
« Reply #20 on: January 15, 2013, 01:29:45 PM »
This is the catch-22 for designing test equipment... What do you plan to measure with it? If you want to tweak out performance of a THAT 1646 you need a path significantly better.

Back in the '80s when I designed a practical Audio range test set for trouble shooting I accepted less than bench level performance to keep costs down. The product was successful because when you troubleshoot gear it usually misbehaves pretty grossly (and a lot of equipment back then was not as flat and linear as today, like old tape recorders).

 These days you could cover my old unit with a sound card... To get significantly better than a sound card takes some effort. Perhaps that might be a direction to pursue. Hot rod a sound card to extend the resolution/noise floor/whatever.

That way the available software to repurpose sound cards could be utilized.....   or not.

For example to extend the measurement range for using a computer sound card to measure noise floor, build in a SOTA front end gain stage, maybe with noise weighting built into the front end gain stage. That way the sound card noise floor is effectively scaled down by the gain stage and now limited by that gain stage noise floor.

As Sam has documented with some of his exploration of test equipment design limits, you always run into some threshold. So pick your poison.

JR

PS: Decades ago to extend the measurement range of my (budget) test bench I used a heathkit distortion analyzer in front of an old used spectrum analyzer. Neither unit by itself was very remarkable, but together I picked up a couple ten dB of more range. FWIW I had to run the Heathkit audio path at -10dB from nominal zero, for the heathkit's own distortion to not dominate my distortion measurement floor.

 
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.


ruffrecords

Re: Audio test set
« Reply #21 on: January 15, 2013, 04:06:28 PM »
This is the catch-22 for designing test equipment... What do you plan to measure with it? If you want to tweak out performance of a THAT 1646 you need a path significantly better.

What I would plan to measure with it would be the sort of gear we design/build here.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

audiomixer

Re: Audio test set
« Reply #22 on: January 15, 2013, 06:35:16 PM »
I have been looking at sound cards today and it seems that this path is a possible option indeed. I looked at:
- Prism lyra - very nice but probably to pricey.
- Lynx Studio has a beautiful Hilo AD/DA...
 Dante DSP like the new Symetrix Edge units. Dante would be cool, but unfortunately no linux support yet.
dspecialists aubion - cool, but no linux support either, and pricey

the front end would really make the difference. an other option would be to use a pimped frontend on something like Uwe Beis AD and DA boards and then straight into a digital I/O.
the I2S interface on the Raspberry Pi seems not fully functional right now, I haven't seen any success story - specially no input for the moment. otherwise this would still be a nice option. I would want to keep a onboard sine gen to check absolute levels and make sure there is no system software messing with them, otherwise its just an other RMAA thing.

In the office we have a duran audio interface. that it uses USB but doesn't send audio through the Windows Audio subsystem but through a proprietary driver. that makes repeatable measurements easier. no linux support either. I didn't test it regarding low THD but I will give it a go eventually, just to see how it performs.

I think I might build uwe beis AD/DA boards an test them..... may be with modified gain ranges / attenuator - seems a viable option for most of my uses.

- Michael



 

Related Topics

  Subject / Started by Replies Last post
2 Replies
2558 Views
Last post February 18, 2005, 06:03:17 AM
by mig27
35 Replies
8702 Views
Last post February 04, 2007, 08:34:13 PM
by bcarso
17 Replies
3164 Views
Last post June 14, 2008, 12:11:54 PM
by Emperor Tomato Ketchup
16 Replies
1213 Views
Last post April 30, 2019, 12:22:56 PM
by Dualflip