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2nd January 2012, 10:00 PM  #1 
diyAudio Moderator

Phono cartridge noise calculator
I've posted a little Excelbased 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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"Pity, wrath, heroism, filled them, but the power of putting two and two together was annihilated." EM Forster 
2nd January 2012, 10:06 PM  #2 
diyAudio Member
Join Date: Mar 2009

That is pretty cool. Thank you, this is very useful.

2nd January 2012, 10:39 PM  #3 
diyAudio Moderator

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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"Pity, wrath, heroism, filled them, but the power of putting two and two together was annihilated." EM Forster 
2nd January 2012, 10:51 PM  #4 
diyAudio Member
Join Date: Mar 2009

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 ? 
2nd January 2012, 10:57 PM  #5 
diyAudio Moderator

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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"Pity, wrath, heroism, filled them, but the power of putting two and two together was annihilated." EM Forster 
2nd January 2012, 11:01 PM  #6 
diyAudio Member
Join Date: Mar 2009

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 ?

2nd January 2012, 11:06 PM  #7 
diyAudio Member
Join Date: Mar 2009

The values i used was :
Loading : 470 Ohm Cartridge DC impedance : 6 Ohm Cartridge Inductance : 0.0005mH Cartridge Output : 0.5mV 
2nd January 2012, 11:11 PM  #8 
diyAudio Chief Moderator
Join Date: Oct 2002
Location: AthensGreece

Handy calc, it sadly lacks the SYclotron logo and the underscore motto though.

3rd January 2012, 12:06 AM  #9 
diyAudio Member
Join Date: Jun 2004
Location: Hillside

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. 
3rd January 2012, 01:06 AM  #10 
diyAudio Moderator

Well, first, how was your preamp s/n determined? Shorted input? Or have you measured en and in separately?
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"Pity, wrath, heroism, filled them, but the power of putting two and two together was annihilated." EM Forster 
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