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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Hi Bill, allI had a chance to install your neat little program and play with it a bit.
One fundamental problem with measurements in general is that unless you have experience in both measuring and then hearing a sufficiently wide variety of problems / conditions, that measurements as numbers mean little. I mean this is how the spec race to reach .001% thd began, obsessing on a number without context.
Like with distortion in particular, the summed number “THD†tells just short of nothing about how the spectral distribution of those individual harmonics sound to a listeners ear, thus, two amplifiers with identical specs could sound entirely different.Many test instruments (like most distortion analyzers) take the pure source signal and add it out of phase to the returning test signal and after which you adjust the gains to get the deepest null or cancellation. With +1 added to –1 = Zero, the residual that is left being the difference between the input and output after the amplitude was normalized.
If you have done this kind of un-automated measurement, you know finding the bottom of the null can be a pain or difficult if the residual is large.The concept is unassailable with systems that are not comparatively time dispersive however, it is a fact that a wire, amplifier or what ever, cannot alter the signal, without that alteration also showing up as a “difference†between the input and output.
Your program gives one an easy way to hear THAT difference.
I believe that for those who are interested in hearing actual differences (as compared to differences due to prior knowledge), that this could prove be a useful tool.The idea of setting this kind of test up with Software and a sound card is a great idea, most cards can run 24/96 now too.
If I were you, I would consider promoting using it to evaluate parts which are well known to HAVE a sonic signatures.
For example, all signal transformers, output transformers and such all have audible artifacts; here is a way to “hear†the signature of any transformer under consideration.
As long as the slopes were the same, one could compare reactive parts like capacitors and inductors and such as well.
If you were to add a software hp or lp first order slope option to your source signal, one could directly compare capacitors and inductors against a “theory perfect†version of same. I would think speaker builders would find this valuable tool to audition crossover parts selection is mostly word of mouth.Many say there is an audible difference between a regular good pot and fancy (expensive) stepped attenuator of the same R, here is a tool which would allow you to hear that difference(s). Similarly, for passive resistors, here is a way to hear what ever the difference is between a 20 cent and 20 dollar resistor.
Same for cable loading on a pre-amp if you used the signal going in to the pre amp as the reference and listened to the differences in residuals with each cable type.It strikes me too that if one found a proper connector, maybe like this one:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=091-1045
-that didn’t do anything weird when measured with an RF network analyzer (to assure that electrically it can’t effect the electrical signal), then combined with short, low C cables to the sound card would be pretty un-intrusive from a measurement set up effecting the measurement stand point. Parallel C would be your enemy in low level / high impedance signals.
You might consider adding an active front end and use Oscilloscope probes as there hi-z , low c design would (as intended) have essentially no effect, on high frequency, high impedance circuitry (or anything less sensitive either).
If you are keen to make hardware, perhaps a USB or sound card input head with a cable to the computer would be a way to easily input anything from speaker level (power amp out) to input level, to banana jack inputs, this would be a logical accessory I think.
Anyway, it’s pretty cool, a simple way to audition input verses output is a cool idea!
If you don’t mind, I will make a few posts on some technical forums suggesting these uses etc.
Best,Tom Danley
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Topic - Bill Waslo’s comparator thingy - tomservo 07:22:03 01/07/07 (3)
- Re: Bill Waslo’s comparator thingy - bwaslo 08:37:02 01/07/07 (2)
- It Is a Nice Concept..... - Todd Krieger 15:59:44 01/07/07 (0)
- Wow, thanks I hadn't seen this - Russ57 10:03:57 01/07/07 (0)
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