MM Phono Input impedance change 47k to 100k ohms

Raul & Pryso, I certainly don't disagree with your comments about the potential benefits that can result from experimentation, and from making the design as flexible as possible.

However, the original post appeared to reflect an understanding that 100K loading is a necessity for best results with this cartridge. For the OP to make an informed choice about how to invest his time, effort, and perhaps money (if he were to have a technician do the work), it would seem appropriate to advise him that that is not necessarily the case, and that a possibility exists that the performance of the cartridge or the phono stage or both will be worse with that loading. That is what I and others attempted to do.

Regards,
-- Al

An additional point that occurs to me. Tics and pops contain a considerable amount of energy at ultrasonic frequencies (i.e., greater than 20 kHz). The increase in bandwidth that would occur with 100K loading, presumably to the 45 kHz number that is specified for that loading, may result in tics and pops becoming significantly more objectionable. That would be particularly true if the phono stage implements RIAA equalization in a feedback loop, rather than passively. Atmasphere, for one, has emphasized that point a number of times in the past.

Regards,
-- Al

I'm using a ridiculously modified Bottlehead Seduction as a MM phono stage. And yes, I read Raul's post and I was curious to find out if there was a difference. I used inexpensive variable resistors at the inputs--disconnecting the standard 47K ohm, of course-- and played with the loading. I have both a Grace F9E and a ruby . In my tests, 100k sounded a bit too shrill; but, in comparison, 47k sounded a bit too dark. They both preferred-- to my ears-- 62k ohms , splitting the difference. So I swapped the stock 47k resistors for TX2575 replacements and couldn't be happier. It's worth the effort IMO to play with the loading to get the best performance from these two fine cartridges. Good luck.

Dear Calbrs03: That's all about: test and decide, good!!!

Regards and enjoy the music,
R.

I'm with Pryso, by the way. I installed a 100K load R in my MM-only phono stage with the eventual intention of installing a rotary switch so I can change the load R downward and/or add capacitance. The switch will optionally parallel another 100K ohm resistor with the base one, so as to obtain a load of 50K, etc. I've got the parts; I've just been too pleased with the status quo to bother to do it.

Al, Tim may charitably place me in your company in terms of electronics knowledge, but I do not. I respect your superior level of understanding, yet reading all your possible warnings about changing the load R up to 100K from 47K, I cannot find any that would scare me away from trying it (or even any that would make matters worse with 100K vs 47K), even with a bipolar transistor at the input. The only valid caveat might be the increased audibility of ticks and pops. So, use clean LPs.