Electronics > Projects, Designs, and Technical Stuff
Analog Disovery as Audio Analyzer
halej1:
Jaxbird- this is Awsome! I'm new to EEVblog-- and have seen some of the Audiophoole/Audio Geek bashing. Some of it is well deserved but frankly much of the electronics world is represented by audio and audio analysis. which is why I'm here. Actuallyout of necessity I'm am an Audio guy with limited funds (like all of us) and my gear is aging and failing, so I've had to start learning repairs and testing (albiet I'm new to that part). Really interested in your work and want to use it to analyse some of my gear (sub amps, amps, processers). I have recently purchased (ebay cheap) a Keithly 2015. two reasons- 1) A great bench multi meter 2) the ability to Do THD measurements. Not so much for the ansolute measure but to see if my amps are providing rated power. Sorry such a long lead-in but my question is:
When you connect your output signal to test equipment do you attenuate the signal? Basically input would be 0-2V ish and output may get to high voltages for high output amps.
Anyway glad there are audio folks on the Blog as well.
Thanks
jaxbird:
--- Quote from: halej1 on February 20, 2016, 09:32:18 pm ---Jaxbird- this is Awsome! I'm new to EEVblog-- and have seen some of the Audiophoole/Audio Geek bashing. Some of it is well deserved but frankly much of the electronics world is represented by audio and audio analysis. which is why I'm here. Actuallyout of necessity I'm am an Audio guy with limited funds (like all of us) and my gear is aging and failing, so I've had to start learning repairs and testing (albiet I'm new to that part). Really interested in your work and want to use it to analyse some of my gear (sub amps, amps, processers). I have recently purchased (ebay cheap) a Keithly 2015. two reasons- 1) A great bench multi meter 2) the ability to Do THD measurements. Not so much for the ansolute measure but to see if my amps are providing rated power. Sorry such a long lead-in but my question is:
When you connect your output signal to test equipment do you attenuate the signal? Basically input would be 0-2V ish and output may get to high voltages for high output amps.
Anyway glad there are audio folks on the Blog as well.
Thanks
--- End quote ---
Thanks, the goal for this project was to provide a cheaper alternative to the already reasonably affordable older HP etc audio analyzers, but adding more features. Performance level should be about the same, it will never get anywhere near the Audio Precision equipment level, but certainly good enough to tell whether an amplifier is faulty and help locate any faults. IMO in reality these 0.000001% specs don't really matter, I am confident no living person can successfully identify the difference between 0.01% and 0.000001% distortion in a true blind test.
There is a big difference between audiophoolery and actual audio engineering, many inexperienced people are confused by this difference, thinking everything is audiophoolery and hoping to gain community recognition by calling it out.
The immediate limitations are that the Analog Discovery will start clipping at +/-25V input, so that does limit the usability with large amplifiers, but I can easily add a feature to use any division factor, as in add any attenuation (couple of resistors) at the inputs and just enter the factor into the software to scale everything. I can make a board with auto attenuation up to 1000W if anyone is interested.
Other limitation is that the outputs are limited to near +/-5V peak (single ended), anything higher than that will need external amplification, but I think most amps will never require more than for full wattage output. Balanced output will also require some external components.
Great thing is that the inputs are differential (not floating, but within limits), so measuring things like bridged amplifiers is not an issue.
This solutions is much more useful than a Keithley 2015 for amplifier characterization.
Cheers
jaxbird:
Here is a good example of using this software to check the performance of an amplifier, a slightly ridiculous 300B single ended tube amplifier in this case:
halej1:
Jaxbird - still awesome! and thank you for the input to my question. Your software/hardware solution looks really good! I watched your video and was wondering --- you are able to look at the graphs and pretty easily tell if things are good or not so good. Obviously pretty simple on something like THD or THD+N but can you share or direct me to where I can find out, for example -- what is acceptable output impedance (tube, solid state) or input impedance (tube, Solid state) etc... I guess what I'm asking is lot's of people can probably set the system up and get graph but the skill comes with the interpretation.
It may be a little while before I spring for an Analog Discovery and your software -- cause I just blew my budget on an Oscilloscope (Rhode and Schwarz 1202) -- Yeah a bit overkill for this type of analysis but I wanted to treat myself (the FFT function is supposed to be very good, though)
Cheers
John
ci11:
Hi,
I can't get the download to work - got a 'Fatal Error - Unable to find "dwf.dll"'. What am I doing wrong? My PC in Win 7 x64, .Net 4.6.
Thanks.
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