A question of loading...

@daveyf 
@atmasphere 

I suspect Ken got tired of people calling about noisy tubes and SUTs are a way to get around that.

Yep, I know from experience that customers were complaining about their Koetsu's with the CAT - not enough gain & too much noise.
The problem was that you only needed a transformer with about 10db ( turns ratio 1:5 ). Most off the shelf audio SUT's are up around 20/26db - which resulted in too much gain. I think this is why he has addressed the gain issue in the way he has.
Daveyf, the gain is also impacted by the system gain - how sensitive is your power amp input - so there are always exceptions.

@dover   Good point about the overall gain in the system. However, my ancillary gear is exactly the same, with the exception of the old preamp vs the new preamp. So. I would have to believe the overall gain should be the same. My amps ( i use both a ss stereo amp and a tube mono block..(not at the same time) do have similar gain structures ( the ss amp has a gain switch to switch between two settings- a very useful feature that I wish more amps featured)) .

47 steps in attenuators seems to be another inexplicable industry standard.

@fsonicsmith That's because if you don't go entirely electronic with the volume control, its insanely expensive to get a custom switch built with the exact number of steps you want. So you get a switch that someone already makes. That part is expensive too- but you don't have to buy 1000 in order get it.

Dear @fsonicsmith  : In 2018 J.Carr made a in deep analysis, modeling/simulations, with white papers including charts of the behavior of loading an LOMC cartridges with different impedance values along different capacitance values too.

He he did not shared the information in this forum but in other different to Agon and I took from there highligths of what he posted about:

""  To claim that the loading affects the measurable frequency response of the cartridge is bogus. However, if inappropriate loading bathes the phono stage in copius amounts of high-frequency noise, it may start to distort (unless the designer implemented various techniques to make sure that this won't happen), and the result will likely be intermodulation distortion.  ""

""  If the phono stage does not have high overload margin at ultrasonic frequencies, or not-so-favorable linearity at ultrasonic frequencies, the ultrasonic spike resulting from high-value resistive loads (the spike can be in excess of 30dB at 5-7MHz if the phono stage input termination is 10kohm or higher) can easily result in ringing and intermodulation distortion which will obscure real information.

But if the designer does give his phono stage high overload margin and good linearity at ultrasonic frequencies, the phono stage will treat the ultrasonic spike as simply another signal, and no intermodulation distortion products will be generated that could otherwise be low enough in frequency for the ear to hear.   ""


He never posted that loading to hard a cartridge will cause stiffness to the cartridge cantilever enough to mistracking. Was other gentleman in that forum who posted that he talked with JC and he understand him that kind of statement.

In the other side JC never said he had white papers of that cantilever stifness as a consequence of the cartridge loading, not even gave any single example with any of his cartridges or other ones where he measured that issue, so no measures about by him and certainly not for any one in this thread.

Now, by coincidence in that same year here in Agon the MC loading was the main subject in a thread ( exist other threads with the same subject. ) and the discussion was more or less that here in this thread but in that thread participated an Agon new comer with several posts, named Wyn and these are what he posted on him self for we can know about:



"""  may not be a renowned Audio Designer, but I am a somewhat renowned IC designer with credits that include cell phone transceivers and high performance opamps.

 I did not design the AD797. That was Scott Wurcer- a colleague at ADI ( Analog Devices competitor to TX/B&B ). and, incidentally, for whatever it's worth, also an ADI design fellow. However, I know the design quite well.

He and I were colleagues in the opamp group in the 80s. He focused on high performance relatively low frequency opamps such as the AD712 and then the AD797, amongst others.

I focused on high performance high speed amps like the AD843, 845 (at one point an audio darling), 846 (also a transimpedance design with some very interesting design aspects that I gave an ISSCC paper on) etc. etc. mostly using a complementary bipolar process that I helped develop that I believe was also used in the AD797.
 I also did things like designing the FET based AD736/737 RMS-DC converter and others.
I moved on to more RF, disk drive read/write, GSM, CDMA etc. transceivers, signal processing, PLL and DSP designs.

The idea of driving a cartridge directly into the virtual ground of an amp either just using the amp input impedance (such as a grounded base transistor) or via a resistor is hardly a new one. Some of the earliest solid state phono stages did exactly that, including one that I sold in the UK in the 1970s. I also used a transimpedance op amp that I designed (the AD846) in that mode- using the device as a current conveyor and operating it both closed and open loop as the extraordinarily high impedance "compensation node" could be loaded by a resistor to provide a fixed, and low, transimpedance for the stage.
I can't say that either approach seemed to be particularly successful ""

He is now retired and living in England and he worked too in the recording industry.
Wyn as any other engeneering at ADI or TX is a engeneering handbook walking.

So, in that thread the issue arrived as here to that cartridge stifness mechanical phenomenom caused by that hard loading issue and after several posts he posted this:


""  is why any of the purported effects of heavy resistive loading you state could be definitively true-

 certainly NOT on TRACKING which is demonstrably FALSE based on IM tests on tracking performance that I have incidentally performed as a function of load.

  ( He measured and is the only gentleman I know he did it. )

While mechanical impact does occur as a result of electrical load- there is some back emf necessarily generated by the signal current that affects the mechanical motion, but a quick back of the envelope calculation using Lenz's law and the 10uH cartridge suggests a 2 orders of magnitude difference between the generated signal and the back EMF for a 100 ohm load at 20kHz- certainly not enough to cause tracking issue.

 As for the rest, well, take the Madake for instance- the resistive load that people (reviewers) claim is best literally varies by nearly four orders of magnitude! I load mine with 60 ohms (as do many users) and I find that the resolution and dynamics is excellent while maintaining a natural timbre, tonal balance and micro/macro dynamics while not creating the unnatural etched image that many "high resolution" MC cartridges produce.

By the way, I constructed a model for the cartridge back EMF using Lenz's law and incorporated it into my simulations.
For those who are interested, the simplest version of the law is V(t)= -LdI/dt.
In this case the parameters can be measured (the LC100A meter from Ebay is a great way to do it) and the back EMF acts to oppose the voltage developed in the coil. The fractional change (attenuation) in the signal voltage is easy to calculate as it approx. equal to -L*2*pi*frequency of interest/Rload. So, it's inversely proportional to the load R and proportional to the frequency.
For example, for a 11.8uH cartridge, with a 100 ohm load the error at 20kHz is c. 1.5%.
The model measures the current through the coil and adds a correction of the form -k*s to the source voltage.
The effect can be seen both on the frequency response and on the transient response of the Phono preamp that I'm simulating.  

One of the "joys" of being an IC designer is the compulsion to measure/model everything! However, once the skills are developed it's relatively easy to do as long as someone else has done the hard work of producing suitable models to use.
Constructing an electrical model for the Madake was fraught with concern as using my own meters to measure the capacitance and inductance was anxiety producing.
Then when I plugged the parameters into the simulation and compared against my measured output I realized that the actual response had precious little to do with the electrical characteristics and everything to do with the mechanical resonances.
And so, the journey began..."""


No one in that thread including atmasphere refuted him. How can any one refute facts/measured information, no way.

Other than FM Acoustics in that different forum where JC posted in the same thread we can read what ORTOFON said about:


"  And here's an interesting comment from Ortofon to me (in a private discussion with them) - it clearly goes against what Jonathan and I have said:

[FONT=&amp]Playing with the input impedance means also playing with the sound character. The influence of the load impedance on the differences in sound is caused by the change of the crosstalk levels and the amplitude raise at the resonance frequency. The lower the load impedance, the higher the current and the more dynamic the sound.[/FONT]   """


Only as an example. If we take the Lyra Etna mated with the Kuzma 4 point tonearm the cartridge cantilever 12cu ( compliance ) has to go to 7cu to stays out of the resonance frequency range. No sense that that loadibng electrical current can stiffness in that way to change from 12cu to 7cu for the possibility of some mistracking that can or can't really occur.

My first hand experiences says that with my phonolinepreamp and in the past with the Classé Audio DR-7 loading at 100 ohms and never happens a mistracking because that kind of loading maybe just the SPL goes a little lower and nothing more.


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

"" To claim that the loading affects the measurable frequency response of the cartridge is bogus. However, if inappropriate loading bathes the phono stage in copius amounts of high-frequency noise, it may start to distort (unless the designer implemented various techniques to make sure that this won't happen), and the result will likely be intermodulation distortion. ""

"" If the phono stage does not have high overload margin at ultrasonic frequencies, or not-so-favorable linearity at ultrasonic frequencies, the ultrasonic spike resulting from high-value resistive loads (the spike can be in excess of 30dB at 5-7MHz if the phono stage input termination is 10kohm or higher) can easily result in ringing and intermodulation distortion which will obscure real information.

But if the designer does give his phono stage high overload margin and good linearity at ultrasonic frequencies, the phono stage will treat the ultrasonic spike as simply another signal, and no intermodulation distortion products will be generated that could otherwise be low enough in frequency for the ear to hear.  ""

These statements are exactly in lockstep with what I've been saying and I agree with them 100%.

In the other side JC never said he had white papers of that cantilever stifness as a consequence of the cartridge loading, not even gave any single example with any of his cartridges or other ones where he measured that issue, so no measures about by him and certainly not for any one in this thread.

No-one has ever made a claim that there were any white papers. But FWIW they aren't needed; anyone versed in electronic theory (or anyone who has worked with generators or alternaters) understands how this works.

[FONT=&amp]Playing with the input impedance means also playing with the sound character. The influence of the load impedance on the differences in sound is caused by the change of the crosstalk levels and the amplitude raise at the resonance frequency. The lower the load impedance, the higher the current and the more dynamic the sound.[/FONT]  """

And here we see again (with exception of the last sentence) that Ortofon agrees with Jonathon Carr and myself, although their English is a bit clumsey. The 'more dynamic the sound' bit is false though. It likely has no effect with regard to dynamics as that is a function of the groove modulation. Add this portion to what Jonathan states above and you have nearly the complete picture.

My first hand experiences says that with my phonolinepreamp and in the past with the Classé Audio DR-7 loading at 100 ohms and never happens a mistracking because that kind of loading maybe just the SPL goes a little lower and nothing more.

That's good- but this sort of anecdotal comment isn't evidence or proof of anything in particular.

Raul, its painfully obvious that electronics isn't your field. There is something called Kirchoff's Law (google is your friend), which is taught in engineering and technical classes on the very first day of class, so this is engineering 101. It essentially says that if you put a certain amount of energy in a system, there will not be any more or any less energy in that system at any other point. So if you're going to make a cartridge (which makes energy, we all know that) do more work by making it drive a lower resistance, it would be a violation of Kirchoff's Law for the cantilever to not get stiffer. The cantilever motion is what makes the cartridge generate energy.


Quite literally this isn't rocket science. Its basic technical and engineering science :) taught on the very first day of school. You can prove what I'm saying very easily if you have a bicycle with a wheel equipped with an alternator for lighting. When the lights are not on (simulating no or a light load for the cartridge) the wheel spins easily and for a long time. When you turn the lights of the bike on (simulating a low resistance load of a cartridge), the wheel is harder to spin. There are millions (literally) of other examples.

Now I can put this another way: If what you say (that loading the cartridge has no effect on the stiffness of the cantilever), is true, then you have just solved the world's energy issues! All the world would need to do is build millions of cartridges and load them at low impedances and just collectively move the cantilevers. Since they don't get any harder to move, we get **free energy**!! Yay! a new branch of physics is born, brought to us by YOU! You'll be a famous world hero!


The Greek philosopher Aristophanes once said “Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but stupid lasts forever.”

Frank Zappa once said “There is more stupidity than hydrogen in the universe, and it has a longer shelf life.” This was probably a comment about how people will stubbornly hang on to their mistaken ideas, even in the face of reality....


You have a choice: you can have your ignorance cured, or you can choose willfully to be ignorant. The former is smart, the latter stupid. Which is it going to be??