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Old 2nd January 2012, 10:00 PM   #1
SY is offline SY  United States
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Default Phono cartridge noise calculator

I've posted a little Excel-based calculator for intrinsic phono cartridge noise, both flat and with RIAA equalization weighting. Input cartridge nominal output voltage, DCR and inductance, then preamp load resistance and capacitance. The noise voltages assume a unity gain ideal (noiseless) preamp- this sets the noise floor so you can determine what an acceptable preamp noise is for your cartridge. It also allows you to compare the intrinsic S/N of different cartridges.

SYclotron Audio RIAA Noise Calculator
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Old 2nd January 2012, 10:06 PM   #2
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That is pretty cool. Thank you, this is very useful.
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Old 2nd January 2012, 10:39 PM   #3
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I'm surprised others haven't done it before. As I was putting together my MM phono stage and reading about the stunningly low noise of some other preamps, I wondered, "What do I really need? Is there a reason to increase complexity and heat to get an extra 6dB in the preamp?"

It should be pretty easy to add a noise figure function as well. I'll do that at some point...
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Old 2nd January 2012, 10:51 PM   #4
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Douglas Self has done that mathematically but not as convenient as this one.
The best MC stages i can make have -80dB. My Titan i is 81.5dB after your program, so what is the noise figure ? 4.5dB ?
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Old 2nd January 2012, 10:57 PM   #5
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I was thinking of preamp noise figure. So with the en and in known, NF should come flopping right out from the calculated complex source Z. I think your NF is 1.5dB assuming the same weighting and no noise current.
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Old 2nd January 2012, 11:01 PM   #6
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Should the noise of the cartridge and the preamp not add ? Sure, noise figure is 1,5dB because the preamp is 1,5dB worse. Am i right ?
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Old 2nd January 2012, 11:06 PM   #7
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The values i used was :
Loading : 470 Ohm
Cartridge DC impedance : 6 Ohm
Cartridge Inductance : 0.0005mH
Cartridge Output : 0.5mV
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Old 2nd January 2012, 11:11 PM   #8
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Handy calc, it sadly lacks the SYclotron logo and the underscore motto though.
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Old 3rd January 2012, 12:06 AM   #9
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I had noticed the intrinsic phono cartridge noise calculation result in your article for HMV here at diyaudio and I thought to myself at the time how tedious it must have been to come up with that number slice by slice.

Nothing quite like Excel to simplify the task. Thank you, very worthwhile.
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Old 3rd January 2012, 01:06 AM   #10
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Quote:
Originally Posted by Joachim Gerhard View Post
Should the noise of the cartridge and the preamp not add ? Sure, noise figure is 1,5dB because the preamp is 1,5dB worse. Am i right ?
Well, first, how was your preamp s/n determined? Shorted input? Or have you measured en and in separately?
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