Yet another update. I have exchanged a couple of emails with Mathieu Pernot. He has asked me to produce two more recordings, using a "silent" track on the test record, and another track that has the 1 kHz tone at -20dB. These I have produced today and emailed to Mathieu.
Analysing these tacks myself, one thing is clear, silence is quite noisy on vinyl. The test record has a degree of surface noise, and is it is also very fractionally warped. I mentioned in an earlier post that there was a slight "thlump" noise in the 1 kHz recording, I can now see this visually matches a fractional "hump" in the pressing. Thanks to all this, silence clocks in at a whacking -49dB peak at 25Hz, and -44dB at 8Hz. (and yes, this is with RIAA 1976) Although above about 200Hz, silence measures between -92 and -115dB. Consider that the infamous "hiss" comes in with a peak of about -81dB (again peaking at lower frequencies), this perhaps gives a degree of perspective to this matter. Indeed, in the past I have stated that the hiss is annoying because I know it is there, but I do not notice it when actually playing records. This rather subjective view appears to be in line with the measurements. What the measurements do show is how the noise follows the RIAA curve, so with hiss, surface noise or whatever, the RIAA curve is boosting this at low frequencies. Back on the RIAA 1976 issue. Mathieu has advised me that the RIAA curve includes a 20Hz 1st order high pass filter. "This filter is of the lowest possible order and only provides a limited rumble attenuation."
Attached below is Mathieu's FFT plot of my 1 kHz test recording. This shows the harmonic effects quite clearly, and how the RIAA curve adds stacks of noise at the lower frequncies. Mathieu uses Adobe Audition for this analysis. (which clearly produces vastly better plots than Audacity) According to Mathieu "The distortion is of course mainly a cartridge/mechanical thing. I wonder if @f1eng could help on the amount of distortion commonly found on vinyl playback. The phono preamp does have some unwanted harmonics but the levels are simply not comparable at all. That's part of the "LP way of life". (Mathieu used @f1eng 's actual name, but I edited it here as it would be a little impolite to post on-line)
Analysing these tacks myself, one thing is clear, silence is quite noisy on vinyl. The test record has a degree of surface noise, and is it is also very fractionally warped. I mentioned in an earlier post that there was a slight "thlump" noise in the 1 kHz recording, I can now see this visually matches a fractional "hump" in the pressing. Thanks to all this, silence clocks in at a whacking -49dB peak at 25Hz, and -44dB at 8Hz. (and yes, this is with RIAA 1976) Although above about 200Hz, silence measures between -92 and -115dB. Consider that the infamous "hiss" comes in with a peak of about -81dB (again peaking at lower frequencies), this perhaps gives a degree of perspective to this matter. Indeed, in the past I have stated that the hiss is annoying because I know it is there, but I do not notice it when actually playing records. This rather subjective view appears to be in line with the measurements. What the measurements do show is how the noise follows the RIAA curve, so with hiss, surface noise or whatever, the RIAA curve is boosting this at low frequencies. Back on the RIAA 1976 issue. Mathieu has advised me that the RIAA curve includes a 20Hz 1st order high pass filter. "This filter is of the lowest possible order and only provides a limited rumble attenuation."
Attached below is Mathieu's FFT plot of my 1 kHz test recording. This shows the harmonic effects quite clearly, and how the RIAA curve adds stacks of noise at the lower frequncies. Mathieu uses Adobe Audition for this analysis. (which clearly produces vastly better plots than Audacity) According to Mathieu "The distortion is of course mainly a cartridge/mechanical thing. I wonder if @f1eng could help on the amount of distortion commonly found on vinyl playback. The phono preamp does have some unwanted harmonics but the levels are simply not comparable at all. That's part of the "LP way of life". (Mathieu used @f1eng 's actual name, but I edited it here as it would be a little impolite to post on-line)
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