Cartridge Loading for a phono pre amp

Dear friends @holmz : Here and in other threads I told you that you read but sometimes you did not because those equations ( not all the development but help you. ) are twice posted in this thread.

Look something interesting:

" 1-

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. IMD products can go low enough to fall within the audible band (even when the stimuli are ultrasonic), and IMD nearly always is not harmonically related to the signal, making it particularly grating to the ear. ""

That came from J.Carr and next what was posted by other expert gentleman around EMF and tracking that involves IM too:

" 2-

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. 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 issues . 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. "

R.

Why ARC featured such function in their reference phono stage that serve no purpose? So they can charge more?🤔

We have a loading strip on our preamps too, and I advise customers with LOMC cartridges to not use it. But if you have a higher output cartridge, the loading strip can be quite handy! Because of their higher inductance, high output cartridges have that electrical peak at a lower frequency, which can be at the high end of the audio band or just outside of it. The winding of a higher output cartridge tends to have a lower Q value so loading can be helpful to reduce ringing. 

" The industry spec is 47K for all cartridges.  " where is the " official " announcement about, say by the AES that coul confirm it? where?

@rauliruegas 

Cripes. If one is grounded in audio history then this is obvious. ARC SP6: 47K phono input impedance; similarly H/K Citation 1, Marantz 7, Conrad Johnson PV12, etc., etc.

"  less able to trace high frequencies. " again: where are the white papers that can confirm it.

It has to be published to be real?? Since JCarr published something, you're not challenging his statement (despite the obviously recursive aspect of that argument...), you're employing a double standard. In order for the cantilever to not get stiffer a fundamental rule of physics (law of energy conservation https://energyeducation.ca/encyclopedia/Law_of_conservation_of_energy) has to be violated. IOW you would have free energy and the world's energy issues would be solved 😂 

So no papers needed- just a grounding in basic physics (high school level), in particular how alternators and generators work. A 'Sheesh!' is in order here.

That is ridiculous and with no facts or diagrams/equations that shows exactly that. I That " can easily get you outside of this target window ( ideal resonance frequency range. ) " is not proved here or in any other subject threads. Again: only IMAGINATION.

Ohm's Law and the power formulas are not a figment of someone's imagination 😁

The cartridge is being asked to do just under 2 1/2 orders of magnitude more work with the example you provided:

47,000/100 = 470

-meaning 470X more current is drawn from the cartridge; because 47K is so high a resistance value relative to the impedance of the cartridge winding, the output voltage is essentially unaffected so the current increase also represents the wattage increase).

Anyone with an elementary school education can work out the math here. Perhaps, knowing that, you can tell me where that current is coming from??  If you can answer that, a bonus question: what is the consequence of that current flow?

This is such simple math I don't see why a paper needs to be written about it, but maybe even though its basic, some people simply haven't thought it thru. Or didn't do so well in math.

Please do answer the questions.

These only 2 of your examples about that 47k input impedance:

SP6

50K ohms, all inputs. (Magnetic phono may have any value from 10 ohms to 100K ohms substituted. Also has provision to add input capacitance for matching certain magnetic cartridges.)

PV12

• Frequency Response: 2Hz to 100kHz
• Distortion: 0.25%
• Gain: 49dB (mm), 16.5dB (line)
• Input Sensitivity:
• Signal to Noise Ratio: 78dB (mm)

" In the PV12 with phono stage, this input provides the amplification and equalization required by moving magnet and high output moving coil cartridges. " This information came by CJ directly, not mine.

One of them not even handled LOMC cartridges that’s the real issue.

Useless that you insist about. No one active high gain phono stage came or comes by default with fixed 47k input impedance, no one. I posted here around 8-9 today phono stages ranging in price from 3K to 95K that’s is not only enough evidence but a true evidence and not as your CJ or SP6 and the like.

In the other side you did not gave us the answer to what you posted before:

" can easily get you outside of this target window ( ideal resonance frequency range. ) "

where are those cartridges that with today decent medium mass tonearms shows what you said coming from 100 ohms to 47k or the other way around. We need to see/read those numbers out of the ideal frequency range due to loading. Where ? and don’t try to distract with other kind of information or other question: JUST SHOWS THOSE NUMBERS AND LOMC CARTRIDGE MODELS WITH TONEARMS.

R.

J.Carr: " Regarding loading of low-impedance MC cartridges, in general I recommend trying to reduce any capacitances present between cartridge and phono stage input to as little as possible. Use the lowest-capacitance phono cable that seems decent, turn off any additional capacitance in the input stage of the phono amplifier etc.

The reduced capacitance should make it possible for you use a wider range of loading impedances without having the sound go bright, peaky or thin-bodied. Conversely, any excess capacitance between cartridge and phono stage input will almost certainly force you into choosing lower loading impedances to save your ears. "

Why JC? because he is a true expert in any cartridge design and a co-designer of one of one of the great ( all time ) active high gain phono stages.

With out diminish here any one he has a way higher whole knowledge levels on the thread issues that any one of us. He is the " SOURCE " of true.

R.

50K ohms, all inputs. (Magnetic phono may have any value from 10 ohms to 100K ohms substituted. Also has provision to add input capacitance for matching certain magnetic cartridges.)

The preamp has a 49.9K resistor to ground, but has other elements in parallel. It measures out at 47K.

You know we can do this all day.

In the other side you did not gave us the answer to what you posted before:

 

" can easily get you outside of this target window ( ideal resonance frequency range. ) "

Sure I did. Whether you are able to understand what I posted is another matter.