instead of simulating and tweaking the riaa network and loading for the best to counter the mechanics of the cartridge you could have a more direct approach ,by fighting the cartridge currents tweaking a current feedback topology like the one you find scrooling down at the end of this document:
Website of Wayne Stegall - Phono Equalization Calculations
or as in this much older compensation of shure v15typeIII :
US4470020A - Virtual ground preamplifier for magnetic phono cartridge
- Google Patents
Website of Wayne Stegall - Phono Equalization Calculations
or as in this much older compensation of shure v15typeIII :
US4470020A - Virtual ground preamplifier for magnetic phono cartridge
- Google Patents
Virtual ground techniques on MM only work on a limited subset of cartridges. On those it works with its very good.
Hans,
1) What's the little box after E1? How will LTSpice read that?
2) The first curve on the left was taken from where? Stereophile?
3) Why did you change the output values and are they supposed to be kept on the actual circuit: inductor, cap and resistor?
As I asked Marcel, I still do not quite understand which are the actual values for his input model.
1) What's the little box after E1? How will LTSpice read that?
2) The first curve on the left was taken from where? Stereophile?
3) Why did you change the output values and are they supposed to be kept on the actual circuit: inductor, cap and resistor?
As I asked Marcel, I still do not quite understand which are the actual values for his input model.
He talks aboutthe links i provided here: https://www.diyaudio.com/forums/ana...vs-bjt-input-phono-preamp-31.html#post6365819
Again he claims something that nobody verified...We argue about this for some years now...In the beginning he claimed they they don't work at all...It's a step forward saying that they work on a limitted subset of whatever he thinks somebody veryfied only on Mars and on some planet in the Andromeda.
Again he claims something that nobody verified...We argue about this for some years now...In the beginning he claimed they they don't work at all...It's a step forward saying that they work on a limitted subset of whatever he thinks somebody veryfied only on Mars and on some planet in the Andromeda.
And this is what things are becoming when replacing the 75usec pole behind the first OPA by a lower termination resitance.
R = L/Tc = 0.46/75usec = 6k13
This 6K13 minus the 1k35 fron the Cart gives 4k783 as a termination load.
Because of this, the FR will significantly change in the HF area, so C9 will have to be increased to 2n5.
In the image below you will see again the FR without Cart mechanical resonance in red and after Cart resonance in Blue.
FR will now be practically insensitive to the input capacitance.
Hans
R = L/Tc = 0.46/75usec = 6k13
This 6K13 minus the 1k35 fron the Cart gives 4k783 as a termination load.
Because of this, the FR will significantly change in the HF area, so C9 will have to be increased to 2n5.
In the image below you will see again the FR without Cart mechanical resonance in red and after Cart resonance in Blue.
FR will now be practically insensitive to the input capacitance.
Hans
Attachments
Hans* has thoroughly characterised the electrical transfer characteristics of a number of MM cartridges and simulated response into a virtual ground preamp. What verification would you like?
*and to be sure George replicated a number of the tests to ensure they were correct.
*and to be sure George replicated a number of the tests to ensure they were correct.
1) this Box is the subcircuit of Marcel's replacement circuit for the V15III
2) yes
3) What output values ??
Hans
Attachments
I'd preffer Hans to talk about this instead of you.But you can provide a link to it...can you?
Just to finish with this annoying problem for some...and why i don't agree with Bill no matter what he sais. Not even if it happens for him to be right!
Dirty records are a huge problem for almost any phono preamp ever made, especially those based on discrete j-fet input transistors, low supply and high offset.Apparently bipolar input phono preamps don't exhibit the same saturation problems although Fet input has lower transconductance than BJT . It might be due to much easier matching for a differential based on bjt with his higher gm or the lower junction capacitance which makes feedback task easier. No wonder APT-Holman used a bipolar transistor in the feedback part of the differential.
No such problem arises with playing 45rpm records either as the SNR is much higher hiding the distortions and the dust influence on reading the grooves on 45rpm records at that speed are much lower also due to the higher kinetic energy of the cart-tonearm being able to displace the dust much easier and settle back into the grove faster .Plus you can use more rigid DJ-ish carts .reading the dusty 33RPM records is the biggest problem.
There was a guy here telling about his Denon PRA 1100 high end preamp having problems with dusty records.There was the same problem i made clear with the Marantz PM 62 that was a poor copy of Technics SU-V6. Denon PRA and Marantz had one common problem : they didn't use 2sk170, but 2sk369 , even paralleled ones, which has double the transconductance of 2sk170 and also double the capacitances making the feedback task harder .
I heard about less than 10 fet-input of the vinyl golden age vintage preamps that can handle dusty records with acceptable distortions or no audible distortions , but if a phono preamp is compressing the sound by itself , there's no problem for the ADC to take it, while the sound will be clearly distorted.
The true art is to have a phono preamp that is compressing the sound in a pleasing way before going to ADC where there's no other solution than removing the clicks and pops in the digital domain , but what remains after that processing is debatable because the clicks and pops by themselves are just one part of the problem, the distortions created by them can't be removed.
I thought Bill knew about Scott Wurcer phono preamp already as he was part of those very long discussions on Scott's thread arguing also about digital riaa and digital click and pops removal:
https://www.diyaudio.com/forums/ana...erential-single-phono-preamp.html#post5042118
Now besides having a folded cascode there LSK489 is a very low capacitance j-fet too, even much lower than 2sk170 and feedback action there is lightning fast too so the clicks and pops come out with little side effects...
Scott's preamp is not your usual phono preamp though...and i'm not sure how many would use a computer to run digital riaa or click and pop noise removal when there's better option like cleaning the damn vinyl before recording .
By the way...many guys are running their LP's through a tape machine before any ADC to get their preffered sound colour .
Dirty records are a huge problem for almost any phono preamp ever made, especially those based on discrete j-fet input transistors, low supply and high offset.Apparently bipolar input phono preamps don't exhibit the same saturation problems although Fet input has lower transconductance than BJT . It might be due to much easier matching for a differential based on bjt with his higher gm or the lower junction capacitance which makes feedback task easier. No wonder APT-Holman used a bipolar transistor in the feedback part of the differential.
No such problem arises with playing 45rpm records either as the SNR is much higher hiding the distortions and the dust influence on reading the grooves on 45rpm records at that speed are much lower also due to the higher kinetic energy of the cart-tonearm being able to displace the dust much easier and settle back into the grove faster .Plus you can use more rigid DJ-ish carts .reading the dusty 33RPM records is the biggest problem.
There was a guy here telling about his Denon PRA 1100 high end preamp having problems with dusty records.There was the same problem i made clear with the Marantz PM 62 that was a poor copy of Technics SU-V6. Denon PRA and Marantz had one common problem : they didn't use 2sk170, but 2sk369 , even paralleled ones, which has double the transconductance of 2sk170 and also double the capacitances making the feedback task harder .
I heard about less than 10 fet-input of the vinyl golden age vintage preamps that can handle dusty records with acceptable distortions or no audible distortions , but if a phono preamp is compressing the sound by itself , there's no problem for the ADC to take it, while the sound will be clearly distorted.
The true art is to have a phono preamp that is compressing the sound in a pleasing way before going to ADC where there's no other solution than removing the clicks and pops in the digital domain , but what remains after that processing is debatable because the clicks and pops by themselves are just one part of the problem, the distortions created by them can't be removed.
I thought Bill knew about Scott Wurcer phono preamp already as he was part of those very long discussions on Scott's thread arguing also about digital riaa and digital click and pops removal:
https://www.diyaudio.com/forums/ana...erential-single-phono-preamp.html#post5042118
Now besides having a folded cascode there LSK489 is a very low capacitance j-fet too, even much lower than 2sk170 and feedback action there is lightning fast too so the clicks and pops come out with little side effects...
Scott's preamp is not your usual phono preamp though...and i'm not sure how many would use a computer to run digital riaa or click and pop noise removal when there's better option like cleaning the damn vinyl before recording .
By the way...many guys are running their LP's through a tape machine before any ADC to get their preffered sound colour .
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I assumed a preamplifier with built-in analogue RIAA correction and only one set of filter components. When you make the filter coefficients switchable by whatever means (miniDSP is one way, switchable resistor and capacitor banks are another) you can extend it to more cartridges, although it may be quite some work when you want to accurately model each cartridge and optimize the filter coefficients for it.
If I understand it well, the LRC network at the output is Hans's model for the mechanical resonance. They are not to be kept on the actual circuit, as they are just a model for what happens mechanically inside the cartridge.
That was my first plan then I embraced the miniDSP as my active crossover and realised it could make life easier for me (despite my best attempts to make it more complex). I realise that for many vinyl lovers this would be heresy, but optimising for digital playback then adding analog was a better trade off for my personal needs.
As for the work per cartridge time will tell. I'm trying to get down to less than a dozen MMs anyway 😀
Then Denon PRA 1100 is an abnormal design...
https://www.diyaudio.com/forums/ana...vs-bjt-input-phono-preamp-11.html#post6298391
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Yes thank you, that was exactly what I tried to simulate, electrical- plus mechanical properties to get a more complete picture.
Hans
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