John Curl's Blowtorch preamplifier part II

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#64,661
Tom Danley said:
With a 20Hz pure tone, passing through my old BGW pre-amp, the 17th harmonic was the largest seen on the 3562a. I forget the THD (normally the first 10 harmonics) but it was very low% yet passing the 20Hz tone, in headphones, you could clearly hear a “whirr” at 3400Hz that accompanied it.
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Looking for numbers...... that 17th harmonic you could easily hear.... what was the level compared to the fundemental? % can you venture even a guess of what it was?


THx-RNMarsh
 
#64,662
RNMarsh said:
Looking for numbers...... that 17th harmonic you could easily hear.... what was the level compared to the fundemental? % can you venture even a guess of what it was?


THx-RNMarsh
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Hi
I don’t remember the number (more than 10 years ago) but it was quite low.

One can see the why though looking at the equal loudness curve.

http://hyperphysics.phy-astr.gsu.edu/hbase/sound/imgsou/eqlou.gif

One can see that at the threshold of audibility at 20Hz, the required minimum SPL is about 75dB.

At 3400Hz, the ears are about 75dB more sensitive than at 20Hz. That means a 17th at about 1.7^-4 % has the same apparent loudness as 20Hz and far from being masked.
Best,
Tom
 
#64,670
billshurv said:
Wayne is an interesting person. I hope I never get stuck in a lift with him.
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I'll say. I often wonder how someone can maintain certain articles of faith while embracing, and even being good at, more-or-less hard science. But then I guess my own current beliefs in areas well outside of these forums would raise plenty of eyebrows.

I'm reminded of the late Charlie Townes. According to a guy who was the night assistant at Lick Observatory when Townes was there one night, he attempted to engage CT in philosophical conversation. He began by asking what Townes thought about the nature of reality, a sort-of Hitchhiker's Guide question about the answer to Life, The Universe, and Everything.

Townes didn't speak. He grabbed his briefcase, extracted a single single-spaced typewritten sheet, and handed it to the night assistant. End of dialogue.
 
#64,674
#64,678
I'm pretty sure that you lied about what was on the typewritten paper. I checked him out.
 

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