Evaluate harmonics in audio gear

[buschfsu]

Hi all

Got a new hantech scope that will let me see FFT. So I guess I can evaluate even and odd harmonics when sending a sine through mic pres comps etc Any advice on what I’m looking for as far as ratio of even odd etc. also is this quality intrinsic to the circuit/transformer or can it be tuned using component choice. ?

 

[user 37518]

I guess that the most important are the 2nd and 3rd harmonics, but, most importantly, the total harmonic to fundamental ratio, which is THD. In my opinion, the best would be to not have any harmonics.

 

[JohnRoberts]

It depends on what you are trying to accomplish. Adding distortion to vocals is pretty well explored in the "oral exciter" technology. There was even a patent with some descriptions back in the day. Then there are guitar "fuzz tone" effects, pretty severe soft/hard clipping. When I wrote about these for my column back in the 80s I really irritated the exciter inventor by calling it a fuzz box.

I suspect I will still irritate people these decades later with my pursuit of clean, linear, paths. I recall back in the 80s when exciters were still new, I would find myself trying to tune in the FM radio stations better to clean up the distortion.
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This is one case IMO when dialing in a design by just listening to it makes sense.

JR

 

[ruairioflaherty]

Hi all

Got a new hantech scope that will let me see FFT. So I guess I can evaluate even and odd harmonics when sending a sine through mic pres comps etc Any advice on what I’m looking for as far as ratio of even odd etc. also is this quality intrinsic to the circuit/transformer or can it be tuned using component choice. ?

The A to D on the scope will have much higher distortion and noise floor than most typical audio devices you may want to measure, it's the wrong tool for the job. A typical budget DSO has an 8 bit A to D and is optimized for wide bandwidth rather than low THD.

Any modern audio interface (even very budget ones) paired with the Free REW software makes a much better tool for this task, lots has been written here about this.

As for ideal ratios of harmonics, it's generally understood (and very much backed up by my own bench/mastering experience) that low order harmonics sound more "musical" than higher. So 2nd, 3rd, 5th maybe are "good" but 9th,11th, 15th etc not so much.

The ratio of odd and even is getting into the subjective and will complement different sources in different ways (or not!). There are quite a few digital plug ins and softwares that allow you to play with these effects. In audio hardware some of these harmonic ratio effects are bound to the ways the devices work and are not subject to modification.

 

[Script]

For programm material, I find higher harmonics utterly unacceptable. Just my taste, of course. It all just gets muddy, fuzzy, veiled, bland.

For measuring harmonics in gear, I use soundcard and software.

 

[john12ax7]

Another aspect to consider is how the harmonics translate to musical intervals, then it will make more sense why some are less objectionable and even desired by some.

 

[CJ]

After you figure out a way to measure the harmonics, you would be in a position to design and test a preamp with a knob that emphasizes even harmonics when turned to the left and odd harmonics when turned to the right with center being neutral. That is if you wanted to.

 

[Tubetec]

three words , Room EQ Wizard ,

every amp distorts at some point , single ended class A triodes have the sweetest distortion , higher harmonic content gets worse when class b/c/d amps clip .
its not so much of an issue with pre recorded music , as the levels are known , the transient peaks in live sound and music recording and how there handled matters though .