But in your analysis in the video you multiply the noise curent only to cartridge impedance ignoring the input resistor (47k or 150k). This introduce significant error at higher frequency.
You have to include the noise current flowing through the load resistor. This gives the total Enoise + Inoise integrated over 20Hz to 20 kHz of (0.5H + 1k)//(47k + 100 to 200pF) of circa 3uV. The higher the load resistor value, the greater the noise.
This is the inescapable noise. You can use a JFET input stage to minimize the noise current contribution but you can’t get much better than 3uV noise.
This is the inescapable noise. You can use a JFET input stage to minimize the noise current contribution but you can’t get much better than 3uV noise.
I made a quick and dirty analysis of the Johnson's noise at the phono input. Excuse me for bad handwriting.
RL - load resistor (47k or 150k)
Rc - cartridge resistance
Lc - cartridge inductance
Unc - noise voltage from cartridge
Unl - noise voltage from load resistor
It superimposes voltages from two sources of Johnson's noise by summing modulo squares of two contributing voltages at the input. U1 is noise voltage at the input coming from cartridge, U2 noise voltage from input resistor at the input.
Using the final expression, I got these charts showing noise power referenced to Johnson's noise just from cartridge resistance Rc.
For the sake of simplicity I didn't included input capacitance in calculation.
Diagram shows that 47k input is somewhat noisier (2-3dB) at mid frequencies. At higher frequencies, 150k takes the lead.
RL - load resistor (47k or 150k)
Rc - cartridge resistance
Lc - cartridge inductance
Unc - noise voltage from cartridge
Unl - noise voltage from load resistor
It superimposes voltages from two sources of Johnson's noise by summing modulo squares of two contributing voltages at the input. U1 is noise voltage at the input coming from cartridge, U2 noise voltage from input resistor at the input.
Using the final expression, I got these charts showing noise power referenced to Johnson's noise just from cartridge resistance Rc.
For the sake of simplicity I didn't included input capacitance in calculation.
Diagram shows that 47k input is somewhat noisier (2-3dB) at mid frequencies. At higher frequencies, 150k takes the lead.
"Any DIYer can do it in 5 minutes, and ordinary housewife, after she finds out which end of the soldering iron is taken takes no more 15 minutes"
Any DIYer that modifies his HiFi equipment voids the warranty. I am in awe that Nick can teach a housewife to solder in 15 minutes. I say just select the load for a Q of 0.6 and that is close to phase linear. The FR may suffer but so what? There isn't much music on the high end anyway.
Any DIYer that modifies his HiFi equipment voids the warranty. I am in awe that Nick can teach a housewife to solder in 15 minutes. I say just select the load for a Q of 0.6 and that is close to phase linear. The FR may suffer but so what? There isn't much music on the high end anyway.
I was looking on forums for a recent phono devellopement and found this thread which contained rather interesting discussions.I tried Nick's feedback riaa filter and input loading on an ideal op amp topology with a simple 1350ohms+600mH replacement for Shure V15type 3.I've seen Hans has more complicated models, but the simple model that circulates on the internet for decades, when loaded with 91...110kohm +25pF gives indeed very linear response up to 21...28khz depending on the riaa network I used.Nick's riaa values give better linearity to 28khz, my preffered values give 21khz linearity.The bonus my preffered riaa has is in the SNR which hits a maximum of 4uV below 1khz, while Nick's values are around 13uV.My values also allow for 5 times higher input headroom and there is where I think this preamp is really poor. These are values obtained from ideal simulations with ideal op amps. Nick's circuit is a cool circuit, but I'd trade the linearity over 20khz for noise and headroom...Besides Shure cart is one of the most reactive cart outhere, other carts would send this preamp deep into bats communication systems domain.I'd keep lighter loading for turntables that incorporate a phono preamp, but I'd dump that riaa filter in the feedback path for a more silent and lighter one or the low noise jfet input will become irrelevant.
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My circuit has transadmittance output stage with overall NFB RIAA loop to the input stage. Therefore I have not any problems both with linearity and headroom (the circuit has almost constant loop gain 40 dB from 0.2 Hz to 80 kHz) as well as noise. If you dump 75 uS from input NFB you reduce the HF overload margin and at the same time revive the Miller input capacitance.
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At higher freqs you must keep in mind both RIAA curve with -20 dB @ 20 kHz and IEC-A (or ITU-R) with -10 dB (or -30 dB) also @ 20 kHz ref mid freqs.
Very strange! Is this your scheme? A decent person should say this: I borrowed the circuit from a Japanese manufacturer and took credit for many decades, taking advantage of the fact that the Soviet Union was behind the Iron Curtain)
By the way, I could be wrong if you paid royalties to KENWOOD for using their circuit) In that case, I bring apologies)))
Nick used the Kenwood circuit as a prototype, which he contributed to the article. but you, as a member of a terrorist country, could self-destruct here
Dear "Artmaster"!
Please refrain from doing this' just because a person on one side of the front / border has said something quite correct.
Remember, we can't reinvent the wheel.
Friendship,
HBt.
Psst.
Nick used the Kenwood /TRIO circuit as the basis for his own circuit and was the editor of his own newspaper. And that's perfectly fine, there's nothing wrong with that. We all know that fact now.
Anyone who reads the opening post #1 will immediately know what this thread will be / all about.
Please refrain from doing this' just because a person on one side of the front / border has said something quite correct.
Remember, we can't reinvent the wheel.
Friendship,
HBt.
Psst.
Nick used the Kenwood /TRIO circuit as the basis for his own circuit and was the editor of his own newspaper. And that's perfectly fine, there's nothing wrong with that. We all know that fact now.
Anyone who reads the opening post #1 will immediately know what this thread will be / all about.
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