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
SYclotron Audio RIAA Noise Calculator
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...
It should be pretty easy to add a noise figure function as well. I'll do that at some point...
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 ?
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 ?
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.
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 ?
The values i used was :
Loading : 470 Ohm
Cartridge DC impedance : 6 Ohm
Cartridge Inductance : 0.0005mH
Cartridge Output : 0.5mV
Loading : 470 Ohm
Cartridge DC impedance : 6 Ohm
Cartridge Inductance : 0.0005mH
Cartridge Output : 0.5mV
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.
Nothing quite like Excel to simplify the task. Thank you, very worthwhile.
Well, first, how was your preamp s/n determined? Shorted input? Or have you measured en and in separately?
Measuring the background noise. With input shorted and also cartridge connected.
Then playing an actual test record and overlaying the plots. What is of cause visible is the 1/f noise that worsens the plot in the bass, especially with Fets.
I do simulations too.
Then playing an actual test record and overlaying the plots. What is of cause visible is the 1/f noise that worsens the plot in the bass, especially with Fets.
I do simulations too.
Hi,
I have used a spreadsheet like this for years, except I also had input fields for Ein from Datasheets and for other resistances in the circuit, so if you got Ein right for your complete circuit (easy for Op-Amp's, less so for tubes) it would tell you you output noise.
I have a rummage around to see where it is. I't probably in Excel 2003 or earlier though.
Ciao T
I have used a spreadsheet like this for years, except I also had input fields for Ein from Datasheets and for other resistances in the circuit, so if you got Ein right for your complete circuit (easy for Op-Amp's, less so for tubes) it would tell you you output noise.
I have a rummage around to see where it is. I't probably in Excel 2003 or earlier though.
Ciao T
Noise Figure is 10 log ( (noise output power of actual system)/(noise output power of noiseless amp i.e. noise of source multiplied by gain of amp) ). 3dB noise figure means the preamp and the cartridge contribute equal amounts of noise. Complication is that the noise spectrum might be different for each.
Doesn't groove noise dominate most preamps?
Doesn't groove noise dominate most preamps?
In my experience, yes, but others have claimed that they can get improbably low noise. Maybe it's my lousy phono system. In any case, it's nice to know at which point the preamp is blameless...
Perhaps we could characterise groove noise (with a particular stylus) by giving a noise temperature in record reviews? How about cryogenics - not for treating components but cooling preamps and cartridges. Barmy, I know, but someone has probably tried it. As we know, some audiophiles have hearing as good as a radio telescope.
Many years ago I remember reading an article on FM tuners in which the author showed the plausible theoretical limit for sensitivity for a room temperature solid-state circuit, which curiously was worse than some manufacturers seemed to claim for their tuners.
Many years ago I remember reading an article on FM tuners in which the author showed the plausible theoretical limit for sensitivity for a room temperature solid-state circuit, which curiously was worse than some manufacturers seemed to claim for their tuners.
I make phono stage as low noise as i can. Groove noise dominates mostly but some customers go to the speakers and simple put an ear on them. If they hear noise, they complain, even when the record is not spinning.
If a super low noise stage sounds better then one with a little more is hard to tell.
Talking of the noise spectrum, there are big differences for sure. Tubes and Fets have a quite soft treble but there is more noise in the deeper regions starting at 1kHz or so. BJT´s are much better there. Burkhard Vogel went so far that he does not recommend Fets for lowest noise MC phonos. Subjectively i can not second that. The ear is less sensitive for noise in the bass so psycho acoustics help out a bit here.
If a super low noise stage sounds better then one with a little more is hard to tell.
Talking of the noise spectrum, there are big differences for sure. Tubes and Fets have a quite soft treble but there is more noise in the deeper regions starting at 1kHz or so. BJT´s are much better there. Burkhard Vogel went so far that he does not recommend Fets for lowest noise MC phonos. Subjectively i can not second that. The ear is less sensitive for noise in the bass so psycho acoustics help out a bit here.
And they turn up the volume to its fullest also while sticking an ear to the tweeter I suppose. To win that over a horn system with high gain line preamp would be the coolest party trick. To no avail, but go figure. Its a system grounding thing to have no trace of hum also in such conditions plus the chain being up to scratch and balanced XLR though.
Nice! Something I've never understood is choosing between FETs and bipolar. With opamps it's well published that below some source impedance bipolars have the noise advantage, whereas above that FETs rule. It would seem that bipolars (with a fairly high current) would be the low noise choice for MC cartridges, yet many go with FETs. What am I missing?
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