From: jl@glen--canyon.com   
      
   On Fri, 14 Nov 2025 14:51:26 +0000, liz@poppyrecords.invalid.invalid   
   (Liz Tuddenham) wrote:   
      
   >Jan Panteltje  wrote:   
   >   
   >> >Bill Sloman wrote:   
   >> >>On 13/11/2025 5:02 am, john larkin wrote:   
   >> >> On Wed, 12 Nov 2025 17:28:04 GMT, Jan Panteltje    
   >> >> wrote:   
   >> >>   
   >> >>>> john larkin wrote:   
   >> >>>>> On Wed, 12 Nov 2025 16:11:03 +1100, Bill Sloman    
   >> >>>> wrote:   
   >> >   
   >> >   
   >> >   
   >> >> The problem is to find an audio spectrum analyzer with -150 dB   
   >> >> distortion.   
   >> >   
   >> >Not if you filter out almost all of the fundamental before you feed the   
   >> >residual signal into the spectrum analyser.   
   >>   
   >> In the old days I tested the Eurovision sound connection from otehr   
   countries   
   >> by having them send a 1 kHz tone, and then measured the harmonics   
   >> with a selective voltmeter.   
   >> Some math and you got a distortion value.   
   >>   
   >> Simple.   
   >   
   >Two-tone intermodulation distortion measurement is even easier to use,   
   >the resullts are read directly off a meter. It deserves to be used more   
   >often.   
      
   What meter goes to -150 dB?   
      
      
   John Larkin   
   Highland Tech Glen Canyon Design Center   
   Lunatic Fringe Electronics   
      
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