MM Phono Input impedance change 47k to 100k ohms

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.

Thanks very much, Lew.

To clarify my comments, I too don't see any reason to be scared away from trying 100K or other loads. However, a lot of people do not have the time or inclination to experiment to the extent that you, Raul, and a lot of others here do. And there are other factors that will be concerns to some, such as the possibility of damaging their equipment while doing the work, effects on resale value, downtime and expense that will be incurred if the person prefers to have a technician do the work, etc.

The OP started the thread apparently under the impression that changing to 100K is a clear necessity, and asking how to go about doing that. I believe that my comments, and the experience-based comments from several of the others, provide perspectives from which he can make a better informed decision as to how to proceed, based on his own circumstances and preferences, not ours.

Best regards,
-- Al

My experiment took the better part of a weekend, playing a single track (Daddy, from Julie London's Julie, Liberty-LRP3096) while going up and down with the loading, raising the resistance by 10K units until I reached 100K, then backing down 10K in resistance until I found a range that was was acceptable. Within that range I took 5K jumps up and down to find a narrower range. Then 2K jumps and so on to lock in on 62K.

Time consuming? You bet. Worthwhile? Certainly. I adore my Graces. And I use the Bottlehead specifically for them. I wanted to build a preamplifier that suited this specific cartridge and to enhance it's character. I've listened to other MM cartridges using this pre and I don't find the setting to be optimal, but that wasn't my intent. I believe loading is cartridge dependent, and matching a MM cartridge at 47K is hit or miss.

However, would I want the OP to mess with his phono pre without his knowing it like the back of his hand? No. It can be damn dangerous. But if he/she does know the risks, then why not take the time to bring out the best of a wonderful cartridge? The benefits are manifold, as long as he/ she knows what they want. On the other hand, if this job for a technician, and I have to pay for his time-- and we're talking at least 18 hours of which most of the time I wouldn't be there--so i'm paying mostly for his/her subjective opinion, then no thank you, 47k is good enough.