Cartridge Loading- Low output M/C

@almarg 
... in a hobby where a lot of audiophiles concern themselves with dubious and unexplainable minutiae such as which way a fuse is oriented an explainable and potentially significant phenomenon such as this seems to me to be a reasonable thing for audiophiles to be aware of.

Good Lord, Al, that's physics! It strikes at the heart of all that we stand for! Say 4 Hail Snakeoils and depart!

Use your ears....get the sound that pleases you.   I use 1000 ohms on my Ortofon. 

Whether to use the extra pole is an interesting question.
So, here is some more information, and a repeat of some old information so you can judge for yourself.
1. The additional pole serves not only to reduce the RF but also to reduce the deviation in the RIAA stage noise transfer function at high frequencies. Effectively the noise from the circuit peaks higher than it should at supersonic/lowRF frequencies.  This might not be a problem, but then again any non linearities in the amplification system might serve to mix the noise down to audio bands so why have it?
However, it does come at a small cost as the extra input pole 
rolls the RIAA stage off, making it flat to extended frequencies but does not compensate for the roll off that may be introduced due to a sub optimal loading on the input stage- basically you are tweaking the Q of the input stage load to flatten the response at 20kHz and that is hard to do.
2. Don't forget the MC mechanical characteristic may cause a significant peak. Reducing the input stage Q to be essentially a LR system adds a single pole low pass characteristic which, combined with the resonance, may produce a characteristic that for example might be +/- 1.5dB 20Hz-20kHz with a dip in the 4-10kHz region rather than -1.5dB (due to a 20Hz infrasonic roll off)  to +3dB (due to the resonance peak). 
3. The recording process (particularly analog) imposes restrictions in the frequency response- limiting the HF and LF responses. These restrictions are not set in any standard and are usually due to limitations in the equipment used (Tape recorder and lathe frequency responses and dynamic ranges for examples). Good recording engineers try to minimize the effects, but they still exist.

If you are like me where my HF sensitivity has been reduced by age etc. where I really can't hear above 13kHz, but my response is still excellent below, including down to 20Hz, then making sure that things remain flat to 10kHz or so is what really counts. Thus, over compensating the response to make the measurements have a minimal deviation from nominal over the "full" audio band is probably not the best approach.
Again, listening is best, but be careful not to delude yourself. 
Audiophiles (myself included) tend to get seduced by what are essentially deviations from what the real listening experience provides- such as excessive detail, ability to resolve supposed room artifacts etc. etc. 
These effects, in my substantial experience of live performances, just do not exist in a live listening environment, but what really matters are things like instrumental timbre and dynamics (both micro and macro) and that often gets lost in the shuffle, and in the recording.
Yes, others have emphasized this last point in this thread, but it bears repeating.

Dear @almarg  and friends:  """  Thus, over compensating the response to make the measurements have a minimal deviation from nominal over the "full" audio band is probably not the best approach.
Again, listening is best, but be careful not to delude yourself.
Audiophiles (myself included) tend to get seduced by what are essentially deviations from what the real listening experience provides- such as excessive detail, ability to resolve supposed room artifacts etc. etc.
These effects, in my substantial experience of live performances, just do not exist in a live listening environment, but what really matters are things like instrumental timbre and dynamics (both micro and macro) and that often gets lost in the shuffle, and in the recording.  """

""" Unfortunately accentuated dynamics and resolution all too often mean a really nasty peak at the HF. In my experience, getting a good test record and testing the RIAA response can be a real eye opener. """

As I said the contribution by @wynpalmer4 was and is an audiophile lessons for those that are willing to learn as me.

Both fragments/high ligths from the wynpalmer4 are ( for me ) the crucial/critical subject for all of us ( again for the ones that are willing to change. ).

The ones that read or seen my posts in Agon knows that I always ( form some years now. ) posted ( with different words ) exactly what we can read in those high ligths and almost all of you posted that I'm " wrong " but almost neves said why.

I like to learn every single day because it's what can confirm or not that what I'm doing or thinking is wrong or rigth.

As I posted I don't have the technical level of wyn or Al so those great contributions are for me as true " oasis " in the desert.

Yes, to learn we have ( at the same time ) willing to change willing to start with some system tests willing to start again with system evaluations willing to make a check up of our MUSIC/sound priorities because as happened to me many times those priorities are way wrong even if we are " jumping " of hapiness for what we are listening for months/years.

And remember that all of us have high ignorance levels in many audio regards and in other subjects that ignorance level is lower.

Through the wyn posts I learned that what I was thinking/posting over years was and is true only that I never had how to prove it. Thank's wyn.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Hi Al,
so, let’s look at some simulations of the RIAA stage input.
Let’s assume that a minimum capacitance has been achieved of 100pF, which as it includes the cartridge winding capacitances, the internal wiring of the pickup arm, the interconnect to the preamp, the wiring to the preamp input and the preamp input capacitance. is probably optimistically low and beyond absurd for anything that involves a SUT or a tube amp. Let’s also assume that mechanical resonances do not exist and the only thing that matters is the electrical response.
Let’s also use our ideal MC cartridge with 5mH and 5 ohms series resistance and lets start with a 47k load.
The peak is at 663kHz and the magnitude is 28dB, the 10MHz rolloff (relative to 1kHz) is 48dB, the boost at 20kHz relative to 1kHz is 70mdB.
For RFI- conducted RFI is generally c. a few kHz to 30MHz. Conducted RFI can be converted to radiated RFI in the power cords, power supplies etc. Radiated RFI is generally considered to be 30 MHz and above, except where conversion occurs. What domain are we concerned about?
I’ll choose the loss at 10MHz as a metric.
OK, lets increase the capacitance to 1000pF, which is a realistic cap based on the values originally presented as available, and see what happens.
The resonant frequency decreases to 223kHz, the magnitude drops to 26dB, but the 10MHz roll off is now 65dB! The gain at 20kHz is 68mdB.

Which of these would be more benign to RFI while keeping an acceptable audio response? I would argue the 1000pF case.

Now lets change the load R to 1k.
In the 1000pF case the peak is c. 3.5dB, and, of course, the loss at 10MHz remains the same at 65dB. The 20kHz boost has decreased to 53mdB.
In the 100pF case the peak has gone and the gain is now 4mdB and the -3dB bandwidth is about 400kHz. The 20MHz loss is 48dB.
Again, the 1000pF case is better from an RFI perspective, provided you don’t care about a 49mdB increase in RIAA error at 20kHz.
Now change the R to 100 ohms. For the 100pF case the gain at 20kHz is -1.3dB and the 20MHz loss is 51dB.
For the 1000pF case the 20MHz loss is now 66dB, but the 20kHz loss is slightly less than the 100pF case, so it appears that a bigger cap might be better, so lets try that.

Increase the cap to 10000pF. The 20kHz loss is now 0.8dB, and the 20MHz loss is 77dB!
Now increase it to 28600pF- the error at 20kHz is now 0mdB, the attenuation at 10MHz is -77dB, and the -3dB point is c. 40kHz which is generally at about the limit that the cartridge manufacturers specify.

So which of these scenarios gives the flattest 20-20kHz ELECTRICAL response AND the highest rejection at 10MHz?
And who knows, a real cartridge might actually have a slightly more ideal audio frequency response with a small loss at 10kHz and a larger one at 20kHz, depending on where the mechanical resonance lies.
By the way, I am the owner of two Miyajima Madake cartridges, one that’s approaching end of life and can’t be retipped and a second one with 12 hours of play, and I’ve been going through this exercise with them both with a SUT/tube amp combo and the AD797 based preamp and it’s proving very hard to reach a conclusion as to what is best...

Wyn