The turntables have a great come back and the industry shows new models year by year.
Also many new music productions are released also in vinyl added the offer of many older reproductions in better edition (remastered 180gr records, etc.)
Those made me try to design my new phono preamplifier for moving magnet (MM) cartridges. Please, are there any suggestions on this circuit or any other proposals?
Also many new music productions are released also in vinyl added the offer of many older reproductions in better edition (remastered 180gr records, etc.)
Those made me try to design my new phono preamplifier for moving magnet (MM) cartridges. Please, are there any suggestions on this circuit or any other proposals?
Attachments
Parallel stabilizer are only a nice way to generate heat. Usually are faster than series one but with a good design are comparable faster. Anyhow for line noise you don't need so fast stabilizer and for radio frequency no passive L-C filtration can be surpassed by an active stabilizer. For high frequency just use after 3 pins regulator ferrite beans and well chosen capacitors together with a good layout.
For input try a valve repetor or amplifier (powered with relative low voltage - 60...80V) in front of operational amplifier. You will hear a big good sound differences in this configuration. The valve will clip and limit in a pleasant way noise generated by scratches and dust present on the disc.
For input try a valve repetor or amplifier (powered with relative low voltage - 60...80V) in front of operational amplifier. You will hear a big good sound differences in this configuration. The valve will clip and limit in a pleasant way noise generated by scratches and dust present on the disc.
I would reverse the order of EQ stages: 1st should be the rumble filter, 2nd the bass shelf, 3rd the treble cut. It will cut all noise from the previous stages.
But my proposed arrangement might be more sensitive to high frequency overload, you should try.
But my proposed arrangement might be more sensitive to high frequency overload, you should try.
Thanks for your advise lcsaszar. I’ll try changing the order of sections as you advised and listen to compare about both arrangements.
Try to lower even more f of your rumble filter. I will go for below 15 Hz. In simulations it shouls start its effect well below 20 Hz, not just -3bd. Difference is well hearable.
Think for third input option: no additional cap at all and 200k multiturn pot. Experiment with it, it will pay back.
Experiment with only RC cascades for psu, directly after rectifier. Calculate them as low pass filters. 2 or 3 in a row give very good results. No regulation at all.
For first opamp use one with fet inputs. Later, be carefull, some may see inappropriate capacitive load and be prone of oscilations.
Think for third input option: no additional cap at all and 200k multiturn pot. Experiment with it, it will pay back.
Experiment with only RC cascades for psu, directly after rectifier. Calculate them as low pass filters. 2 or 3 in a row give very good results. No regulation at all.
For first opamp use one with fet inputs. Later, be carefull, some may see inappropriate capacitive load and be prone of oscilations.
Last edited:
1) Using Opamp @ input is not a good idea because jfet-input 2134 has approx 8 nV/√Hz, LM4562 has 6 nV/√Hz input noise voltage density and 5532 has bipolar input with too much shot noise current (for MM cartridge inductance up to 1 H). Much better for phono input is LSK389 or JFE2140 dual jfets (with less than 1 nV/√Hz).
2) 1k8 resistor at IC1-B inverting input generate even more thermal noise ( 5.4 nV/√Hz , www.daycounter.com/Calculators/Thermal-Noise-Calculator.phtml ) than modern LN jfets and bipolars , and also more than MM cartridge DC resistance . Use no more than 200...300 Ohm here.
3) I recommend input 150k\25 pF instead of "standard" 47k\several100th pF, see why here https://www.patreon.com/posts/kritichnost-lcr-68630348
Last edited:
No. OPA1612 has not jfet but bipolar input with high current noise 3 pA/√Hz (approximately the same as AD797 2 pA/√Hz) and therefore has 8...12 dB (!) poorer noise performance than LN JFET 2SK710/LSK389/JFE2140 with high inductance (500 mH typical) source as MM cartridge. Prooflink: Doug Self "Electronics for Vynil" page 310 table 9.2: AD797 noise -72.8 dB ref 5 mV input, and 2SK710 is -80.9 dB. My own measurements of phonopreamps with jfets vs bipolars (with 500 mH\1k cartridge equivalent @ input - https://www.patreon.com/posts/mm-constant-loop-67857060 ) are almost the same.
Last edited:
Are you going to drag any mm phono topic into your undamped cartridge territory?You're utterly wrong about noise perception on vinyl mr Sukhov! There are litteraly billions of mm phono preamps using op amps with higher noise than ne5534 or opa2134...Lm4562 while noisier than others is still excelent exceeding vinyl's own noise in that part of the spectrum where the noise really matters.
The noise is the least problem you need to adress for good vinyl reproduction.
The noise is the least problem you need to adress for good vinyl reproduction.
Not least but one of noise-distortion-freqresp inseparable triad. And Opamp input is not the best (but quite possible is acceptable for you if you are not a very picky listener) for noise and distortion.
Well actually the noise makes a very good job at masking unwanted distortions...yet the cartridge distortions will always be at least by two orders of magnitude higher than the cheapest phono preamp's own distortions unless op amps get into hard clipping.
The only important factors (i think i said that 10 times by now...) in vinyl reproduction are:
1.max input signal allowed by the preamp so that the needle hitting dust particles won't drive the output into hard clipping
2. the MANDATORY ability for soft clipping if your preamp is not inside a chain driving 200 watts speakers with low distortions.
I removed SNR from it because we are in 2022 A.D. and there should be enough lower noise components to deal with that problem.
Hitachi was the company who gave us a first standard in op-amp phono preamps by making op-amps able to take +-26.5v rail supplies which equates to a little bit more than 250mV max input signal at 100db max headroom.
Mitsubishi and Nec with their op-amps allowing +-25v supply rails came close.
Discrete fet input designs up to +-43v made by Kenwood, Technics, Akai are now history allowing for max input of 350mV.
You wouldn't probably consider an equaliser place between phono preamps and power amp a delicate problem but big audio chip manufacturers did in the 80's when they came up with +-25v supply op amps.
I opened once a topic on the noise of bjt vs fet input phono preamps and that topic drove mad some people that hijacked it and lead to me getting mad and the topic being closed.I claimed that bjt input preamps are good enough for vinyl if you vonsider their typical SNR.
There was a small accidental discovery of mine related to bipolar transistor or bipolar op-amp input phono preamps, especially that of Aiwa c 22 that led me to two topics , one on noise , the other on nonaudible hard clipping with a +-15v supplied phono preamp on dusty records. I have a topic on aiwa c22 already...contested too of course...Aiwa c30 was a more common approach where you know exactly how hard clipping is prevented .Now you get those same clamping diodes into any op amp input but they act on the signal which is too weak to make silicon diodes clip on cartridge signal itself.So clamping diodes need to be placed in a higher current circuit.
Then there's bipolar trz current bias that controls the transistor max gain.
I know of only one single phono preamp with fet input that used to limit the bipolar cascode base current while cascodes entered saturation due to very high GM input j-fets(2sk146V contsining the rarest 2sk170V).Yet that preamp also used antiparallel clamping diodes in two amplification stages so all soft clipping methods were used in a phono preamp.
Now bipolar input phono preamps are likely to never get into hard clipping even with +-15v supply rail on dusty records while their current noise being stochastically distributed all over audio range are very good at masking unwanted distortions.
With a friend of mine Iinvestigated about 6 discrete bipolar input phono preamps of the 70's and to our surprise none of them had that annoying hard clipping even when supplied fron unipolar 24v supply. That's someting a fet input preamp usually dream about unless it's supllied over +-22.5v.But output signal passes down the line and the next amplification stage needs to deal with anincompressed signal if it's passed cleanly.
That is why with cheap fet designs I always recommend being followed by proffesional recording compressors.They are designed for that.
Also there's a thing that I never saw it mentioned about current noise vs distortions:
Is current noise creation process taking out the energy from the circuit's ability to create distortions same as harmonic distortions induced in speakers by the amplifier were found to destroy own speaker's nonlinear distortions? I may be wrong but I think so as long as mo other hint was pointed against...
Distortions are substractive processes in amplifiers, they are created from own fundamental energy and there's no perpetuum mobile in electronics! Amplified noises are substracted from the idle device current so less energy for distortion creation is available.
I've seen very few people considering distortions and noise from the electrician's point of view: energy loss!
Now if you have a very low noise input stage you need high dymamic range from input to speakers and vynil asks for a few hundred watts rms output capability on 8 ohms to pass acceptably undistorted signals(compared with own speakers distortions) when the faintest signal on vinyl is heard by a normal human being when the needle hits dust particles.
That asks for +-22.5v phono output signal passing through unity gain eq and an amplifier able to cope with that signal at its input at max amplification...Where are you going to get that without soft clipping?
Our own ears treat distorsions same as noise at hearing tresholds and hearing tresholds are never fixed, that is why I keep saying to people: don't forget Dolby's work!
As for fet input discrete preamps I'm aware of only one design that prevented all possible hard clipping while made sure soft clipping would not be an option but certainty.
As for me being picky or not on phono preamps qualities... just because I always recommend cloning commercial versions it does not mean i didn't build some of the best diy phono preamps ever made of which one was designed by me and had the best sound I was ever able to hear of any setups, but I don't recommend it for its complexity and costs since I discovered way more "magical" cheap ways to get the job done.
The only important factors (i think i said that 10 times by now...) in vinyl reproduction are:
1.max input signal allowed by the preamp so that the needle hitting dust particles won't drive the output into hard clipping
2. the MANDATORY ability for soft clipping if your preamp is not inside a chain driving 200 watts speakers with low distortions.
I removed SNR from it because we are in 2022 A.D. and there should be enough lower noise components to deal with that problem.
Hitachi was the company who gave us a first standard in op-amp phono preamps by making op-amps able to take +-26.5v rail supplies which equates to a little bit more than 250mV max input signal at 100db max headroom.
Mitsubishi and Nec with their op-amps allowing +-25v supply rails came close.
Discrete fet input designs up to +-43v made by Kenwood, Technics, Akai are now history allowing for max input of 350mV.
You wouldn't probably consider an equaliser place between phono preamps and power amp a delicate problem but big audio chip manufacturers did in the 80's when they came up with +-25v supply op amps.
I opened once a topic on the noise of bjt vs fet input phono preamps and that topic drove mad some people that hijacked it and lead to me getting mad and the topic being closed.I claimed that bjt input preamps are good enough for vinyl if you vonsider their typical SNR.
There was a small accidental discovery of mine related to bipolar transistor or bipolar op-amp input phono preamps, especially that of Aiwa c 22 that led me to two topics , one on noise , the other on nonaudible hard clipping with a +-15v supplied phono preamp on dusty records. I have a topic on aiwa c22 already...contested too of course...Aiwa c30 was a more common approach where you know exactly how hard clipping is prevented .Now you get those same clamping diodes into any op amp input but they act on the signal which is too weak to make silicon diodes clip on cartridge signal itself.So clamping diodes need to be placed in a higher current circuit.
Then there's bipolar trz current bias that controls the transistor max gain.
I know of only one single phono preamp with fet input that used to limit the bipolar cascode base current while cascodes entered saturation due to very high GM input j-fets(2sk146V contsining the rarest 2sk170V).Yet that preamp also used antiparallel clamping diodes in two amplification stages so all soft clipping methods were used in a phono preamp.
Now bipolar input phono preamps are likely to never get into hard clipping even with +-15v supply rail on dusty records while their current noise being stochastically distributed all over audio range are very good at masking unwanted distortions.
With a friend of mine Iinvestigated about 6 discrete bipolar input phono preamps of the 70's and to our surprise none of them had that annoying hard clipping even when supplied fron unipolar 24v supply. That's someting a fet input preamp usually dream about unless it's supllied over +-22.5v.But output signal passes down the line and the next amplification stage needs to deal with anincompressed signal if it's passed cleanly.
That is why with cheap fet designs I always recommend being followed by proffesional recording compressors.They are designed for that.
Also there's a thing that I never saw it mentioned about current noise vs distortions:
Is current noise creation process taking out the energy from the circuit's ability to create distortions same as harmonic distortions induced in speakers by the amplifier were found to destroy own speaker's nonlinear distortions? I may be wrong but I think so as long as mo other hint was pointed against...
Distortions are substractive processes in amplifiers, they are created from own fundamental energy and there's no perpetuum mobile in electronics! Amplified noises are substracted from the idle device current so less energy for distortion creation is available.
I've seen very few people considering distortions and noise from the electrician's point of view: energy loss!
Now if you have a very low noise input stage you need high dymamic range from input to speakers and vynil asks for a few hundred watts rms output capability on 8 ohms to pass acceptably undistorted signals(compared with own speakers distortions) when the faintest signal on vinyl is heard by a normal human being when the needle hits dust particles.
That asks for +-22.5v phono output signal passing through unity gain eq and an amplifier able to cope with that signal at its input at max amplification...Where are you going to get that without soft clipping?
Our own ears treat distorsions same as noise at hearing tresholds and hearing tresholds are never fixed, that is why I keep saying to people: don't forget Dolby's work!
As for fet input discrete preamps I'm aware of only one design that prevented all possible hard clipping while made sure soft clipping would not be an option but certainty.
As for me being picky or not on phono preamps qualities... just because I always recommend cloning commercial versions it does not mean i didn't build some of the best diy phono preamps ever made of which one was designed by me and had the best sound I was ever able to hear of any setups, but I don't recommend it for its complexity and costs since I discovered way more "magical" cheap ways to get the job done.
I'm sorry that all your records are covered in dust and scratches.
Fets vs bjt @ input is as simple as Ohm`s law. Typical MM inductance of 500 mH creates @ 20 kHz impedance of 63 kOhms. OPA1612 bipolar input with current noise of 3 pA/√Hz creates (according to Ohm`s law) noise voltage (3 pA/√Hz) x (63 kOhms) = 189 nV/√Hz. Compare with typical noise voltage 5 nV/√Hz of lownoise jfet input opamp and typical 1 nV/√Hz of lownoise jfets like LSK389, JFE2140, JFE150 etc.
And also do not forget that for the same input AC voltage, the non-linear distortion of the bipolar differential stage is much greater (approximately Ugs/Ut times, where Ug (typical 2.6 V) - gate-source cutoff voltage of fet and Ut (=26 mV) - thermal voltage of bjt, prooflink @ Table A10 of Paul Skritek book "Handbuch der Audio-Schaltingstechnik") than the non-linear distortion of the differential stage.
Noice floor of vinyl, plus non perfect next stages ,speakers, room, human ears, makes any discussion regarding currenr/thermal noice at above levels complete nonsense, unles we are not going into academic discussion and only measuring. For normal listening - at least non sense
Just to ask, what is the ratio of above 'defects' and signal (yes,signal) generated by mechanical traction of neddle and even perfect silent grove?
Just to ask, what is the ratio of above 'defects' and signal (yes,signal) generated by mechanical traction of neddle and even perfect silent grove?
Last edited:
You do not keep in mind that noise floor of vinyl @ freqs upper 2 kHz is even lower than CD - "LP's noise floor is actually quite low over most of the spectrum, ranging from -84dB around 1kHz to -96dB for frequencies above 10kHz . In other words, the LP recording has a lower noise floor than the CD recording for the majority of the spectrum (frequencies above 2kHz )" prooflink https://www.audioholics.com/audio-t...ynamic-comparison-of-lps-vs-cds-part-4-page-2 . So if you want at "normal listening" hearing hiss of preamp, you may use simplest phonopreamp on 3 bjts or single 5532 with -65 dBA noise.
Hello,
"Typical MM inductance of 500 mH creates @ 20 kHz impedance of 63 kOhms. "
Yes, but only the real part of the impedance generate noise.
Only the resistor generate noise, not the inductor.
"Typical MM inductance of 500 mH creates @ 20 kHz impedance of 63 kOhms. "
Yes, but only the real part of the impedance generate noise.
Only the resistor generate noise, not the inductor.
Inductor inself does not generate noise, but according to Ohm`s law it converts noise current from bjt (known as shot noise - https://www.idsemergencymanagement.com/2021/04/11/what-causes-the-noise-in-a-bjt/ ) to noise voltage. { (3 pA/√Hz) x (63 kOhms) = 189 nV/√Hz } isn`t it? Do you disagree with George Simon Ohm 🙄 ?
I'm sorry that all your LPs are covered in dust and scratches 😢
Fets vs bjts @ input is as simple as Ohm`s law. Typical MM inductance of 500 mH creates @ 20 kHz impedance of 63 kOhms. OPA1612 bipolar input with current noise of 3 pA/√Hz creates (according to Ohm`s law) noise voltage (3 pA/√Hz) x (63 kOhms) = 189 nV/√Hz. Compare with typical noise voltage 5 nV/√Hz of lownoise jfet input opamp and typical 1 nV/√Hz of lownoise jfets like LSK389, JFE2140, JFE150 etc.
And also do not forget that for the same input AC voltage, the non-linear distortion of the bipolar differential stage is much bigger {approximately Ugs/Ut times, where Ugs (typical 2.6 V) is gate-source cutoff voltage of fet and Ut (=26 mV) is thermal voltage of bjt, prooflink @ Table A10 of Paul Skritek book "Handbuch der Audio-Schaltingstechnik"} than the non-linear distortion of the jfet differential stage. Therefore, jfets are much (at least 2.6V/26mV = 100 times) less sensitive to overloads due to dust/scratches "clicks", than bjts.
Sorry I repeat my #14 message because accidentally missed a word "jfet" @ the end
Last edited:
Hello,
"(3 pA/√Hz) x (63 kOhms) "
It will depend of the resistive path in the front end of the AOP.
21K or 47K or 75KΩ.
By the way: https://sound-au.com/pdf/an-104.pdf
"(3 pA/√Hz) x (63 kOhms) "
It will depend of the resistive path in the front end of the AOP.
21K or 47K or 75KΩ.
By the way: https://sound-au.com/pdf/an-104.pdf