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.

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.

Lewm: that's a very impressive system. If anything, I think we share the same interest in modifications. Tinkering, my wife calls it--something I picked up from my dad who was an EE and fearless when it came to taking complex things apart and putting them back together.

I have Cary SLM-100 monoblocks that I gutted and rebuilt; a Cary SLP98P which I also modified; my maxed-out Bottlehead for MM cartridges; and an ASR Mini Basis that I have yet to touch for MC cartridges. The speakers for now are ProAc Response D28s, Silverline SR17s and Altec Valencias that I've rebuilt and willed into shape from the ground up. I go back and forth, changing one set for another as I feel.

The source is a rebuilt (not by me) Garrard 401 in a Woodsong plinth with a Schick arm. I use this with a Denon 103R. I used the Graces with a Graham 1.5t on a variety of other tables, but that arm won't work on the 401's plinth, and I believe the Schick is too heavy for the Grace suspensions. For now they'll have to sit in their boxes while I look for another 12 inch arm to use specifically with the Ruby and its brother.