On 12/22/2015 05:07 PM, whit3rd wrote:
On Tuesday, December 22, 2015 at 8:39:49 AM UTC-8, Phil Hobbs wrote:
On 12/22/2015 11:02 AM, c4urs11 wrote:
On Tue, 22 Dec 2015 05:59:52 -0800, Tim R wrote:

However, my question is about how you would use a 1950s era scope
to determine a sine wave or the degree of harmonics present.

Scopes from that era easily reached several MHz of bandwidth.
That should be considered adequate to inspect audio signals.

The eyeball is a really lousy detector of harmonics, though, especially
odd harmonics.

Not always; I have no trouble looking at a filtered triangle-wave type "sine"
and seeing the distortion, which is presumably under 1%.

You're looking at the residual cusp, though, not the smooth details of
the peak, right?


"Pure" to the ear doesn't require a spectrum analyzer with parts-per-million
resolution and logarithmic display. I think the researchers were applying
a loose definition.

Plus he had to use a 1950s-era microphone, so the scope bandwidth is
irrelevant.

Carbon microphone, maybe, but dynamic microphones were very well
developed by then.

Sure, but they have big heavy diaphragms and coils, so their high
frequency response stinks. (Velocity sensitivity helps, but low
resonant frequency wins.)


A lot of early recordings were transcribed onto DVD,
and the sound quality improved because the SINAD of microphone and tape were better
than the rest of the phonograph process.

I don't doubt that one bit. Record cutters especially.

Cheers

Phil Hobbs



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Dr Philip C D Hobbs
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