Monday Monologue: Faults with Audio Testing Methods.

[@mfr58]

There was a time when the technical reviewers decided that simple harmonic distortion was inadequate for assessing amplifiers. They came up with intermodulation distortion and transient intermodulation distortion measurements. I don't see these very often in manufacturer specs, I don't think it caught on as standard harmonic distortion numbers are easier for marketing. Also square wave performance into capacitive loads gives some insight into stability and sound character, but not often shown by companies, or reviewers. Impulse response is shown for speakers sometimes and power bursts in amps, but into resistive loads, in some reviews. You are correct there is much more to be discovered about equipment measurement. I do like that you point out different harmonic content, proportions of odd and even, that give character to amp sound, which is something that can be manipulated to voice to taste. Good luck with the camera project. I'm always in admiration of American,s natural entrepreneurial abilities.

[@ceylonmooney]

luv the mug

[@JohnScheppler]

I totally agree. The processing of multiple sounds at the same time is what makes the difference in all audio products from dac, amplifier, or speakers. The more complicated the music is it well separate a good product from a great product.

[@heronew]

great to see a vintage camera store being saved，vintage camera and tube audio gear would be a great match. 🎉

[@michaeldina1103]

Fascinating conversation as usual and congratulations on your new business venture! Look forward to hearing about all the fun.😊

[@insurrectionindustries1706]

I had an audio precision analyzer and it can do a lot of measurements with high precision. You can actually measure a lot more than is usually published and I know I have personally seen a lot of difference in measurements that are not the measurements we typically look at. If you compare amps under different loading conditions over different frequencies and different power levels the differences really start to show themselves. Great example is the .002% distortion amp that actually has 2% distortion at 20k and rated power. You will never see that on a sinad measurement that is published

[@Keepee66]

Sounds like exciting times are ahead. Best of luck. L💞ve from Canada.

[@dtg474]

Pretty exciting stuff regarding the store and your plans. I love the soap tip on the screws. Ill have to remember that. Good luck. If you open it up with audio auditioning, ill drive there from Dallas.

[@BryanPresnell]

Steph, where can I get a coffee cup like that? That's the coolest mug ever!!

[@SkunkieDesignsElectronics]

His info is in the video description!

[@GiguereSylvain]

Great projects in view Steph! I wish you the best success. Just make sure you keep "having pleasure" first, and that you don't become swallowed by all the administration work and obligations linked to the operation of a store. We don't want to lose you! I'm selfish! ;-)

[@AudioFanMan]

Awesome "Coffee" cup! We do have software that can listen through a calibrated mic, look into room eq wizard. I dabbled with it, but most way over my head. That said it doesn't listen to music but pink,white noise as well as sweeps.. I think knowing what the frequency response using the audio analyzer for the amp is half of what we hear, the speaker and room is the other half.

[@warp2600]

I wish you good luck and all the best for your store plans. 👍

[@cobar5342]

Oh, I love the soap on screw tip!

[@paulgood2218]

That's exciting congrats on the camera and audio opportunities!

[@row4hb]

Great monologue as usual. Why do we stress over speaker spec sheets when we decide with the most sophisticated instrumentation available, our own ears. I really liked where you were going with the calibrated microphone, then playing a high dynamic range musical piece or pieces, and looking at the result. We hear many audiophiles discuss harmonics but we don’t have a measurement for comparing our equipment. Best of luck with the new venture, we need to preserve the vintage camera hobby too. Not to mention a brick and mortar location so you are not opening your home unnecessarily.

[@alwilliams5177]

Exciting news about camera store! I worked there a few times when I worked for AM Photo. Might have to talk with you when you are looking for staff. Have you thought about adding a b&w darkroom? BTW, got a friend of mines R8. He's building a 300B kit. First tube amp. ❤❤❤❤

[@SkunkieDesignsElectronics]

We have all sorts of ideas for the future :)

[@sjhorton1184]

30 years ago, Fluke (maybe not the inventor) had a troubleshooting "system" where they took 5-7 measurements at specific test points on a circuit board to create a "gold standard" of what the measurement should be and then they could automate, to some degree, the troubleshooting of a circuit board. Why can't we take a 30 second snip of a music signal and compare that original signal against the same clip at any point in the chain and compare distortion or frequency differences or heck, just about anything? What is the CD player/streamer/record player & cartridge doing to the original signal? How does that signal change through the preamp? Compare the output music clip out of the preamp into the amp and measure how it changed coming out of the amp? Amp in to speaker audio measured at the listening position? Just a thought.

[@rogerayotte9503]

FFT can resolve multiple frequencies. One could input a pink noise signal. In addition, you could hook up the signal probes in parallel to speaker loads. Even an FFT of a complex signal overlaid with the amp output. Lots of possibilities. Not my area of expertise, but I know a good FFT analysis is possible on verycomplex signals. Good luck.

[@SkunkieDesignsElectronics]

I've never heard pink noise that had a strong bass track.

[@junkyoutube9060]

what about checking for power supply sag..... especially on transients ? also from Rod Elliott "A further test is to apply a low frequency square wave at about half to 3/4 power, mixed with a low-level high frequency sinewave to the amplifier. At the transitions of the squarewave, the sinewave should simply move up and down - 'riding' the squarewave. If there is any misbehaviour in the amp, the sinewave may be seen to be compressed so its shape will change, or a few cycles may even go missing entirely. Either is unacceptable, and should not occur."

[@rickg8015]

Hi Stephe.. Where can I buy that Mug??

[@SkunkieDesignsElectronics]

His info is in the video description!

[@adamfrandsen]

Ideally manufacturers would list MHD (Multitone Harmonic Distortion) and IMD (Intermodulation Distortion) for their speakers/drivers - this should not be so hard. You would only need 124 simultaneous tones/notes played to cover the entire musical spectrum including the 3rd harmonic of the highest note on an instrument (Piccolo 4186Hz), that should be doable - simple tests could be done with mics and more advanced with lasers etc… Audio Science do the 32 multi tone test for the reviews of DACs etc., which is nice. As I understand most manufacturers already do multi tone testing in their labs, but simply don’t publish the results.

[@ThePerkri]

There is a complex signal, varying in frequency and amplitude, going from a dynamically reactive source to a dynamically reactive load - at every step of the audio chain. This is why synergy is everything at every step. And no, that is never measured. Nor is that ever considered when folks dismiss the relevance of cables.

[@paulgood2218]

From what I understand our ears are much more sensitive at higher frequency. So we may not be able to hear much difference in a 3 db gain or drop. At lower end notes but midrange frequency and up yes human ears can hear the difference easily. And we do got way to measure more than frequency. A waterfall graph in my experience is where you see and hear the difference between 2 speakers that measure the same frequency response curve.

[@audiononsense1611]

Your 1st statement is flawed and therefore requires further clarification. 3dB of gain / drop can be heard and is frequency dependent however with the range of frequencies in any piece of music 3dB would be noticeable, 6dB even if one had serious hearing loss...

[@el_arte]

Amir and others routinely do multi-tone frequency tests. AP and REW support them.

[@SkunkieDesignsElectronics]

Still not the same as dynamic music, voices with overtones etc.

[@el_arte]

@@SkunkieDesignsElectronics It is not the same by definition. But, in a away, a multi-tone frequency test is more taxing, since it demands the entire frequency range to be activate at the same time, whereas music content rarely does that. Also, it's important to remember that the first principle of the Fourier Transform is that it can be used to decompose ANY musical waveform into a sum of simpler sinusoidal components, each with its own frequency, amplitude, and phase. Finally, pure tones are known quantities that make them excellent reference signals. Conversely, different music content would potentially yield different conclusions.

[@Keith-ux9ku]

The amount of computing power would be huge. I used in the petroleum industry and exploration is analyzing sound waves. When I worked there my employer was using the largest supercomputers.

[@SkunkieDesignsElectronics]

But the processing power in a modern PC with a high end video card IS huge. I know for example 30 minute videos that took 45 minutes to render on my old PC, now take less than 5 minutes.

[@Keith-ux9ku]

​@@SkunkieDesignsElectronics I thought about that after making the comment and you may be right about the power issue.

[@michael71601]

It does exists, except instead of music it sends white noise, reads back and calculates various stuff. Computer + math. As a minimum it can subtract one from another to see any distortions. I dunno I used to work on white noise testing math back in 80s... Don't Dirac use white noise test?

[@SkunkieDesignsElectronics]

White noise is still not like music IMHO but I suppose is better than a single frequency sine wave.