MM Phono Input impedance change 47k to 100k ohms

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.

I fully agree with everyone else; there is nothing "wrong" with using a 47K load with the Grace or any other MM cartridge. (And, as I think I wrote above, I was not aware that Grace recommended a 100K load, if that is the case.) It's just a matter of taste and tonal balance. Ironically, many/most of the best vintage preamplifiers (which in those days ALWAYS included a first-rate MM-capable phono section) included front panel controls for adjusting cartridge load in terms of capacitance and resistance. I have long contemplated buying one of those old-timers for this purpose, but then I would find myself trying to upgrade the sonics. But we've been over this ground before. Candidates I've considered include the one from Yamaha, one of the old Krell preamps (KPA, I think), Accuphase C200 (I think), possibly the HK tube preamps, etc. Unfortunately, others recognize the virtues of these TOTL units and they ain't cheap.

Calbrs03, I share your love of the Grace Ruby. It would interest me to know something about the rest of your system, to learn whether there is some particular synergy we are both tapping into. My system is posted here. Suffice to say I use huge ESL speakers driven by OTL tube amplifiers. The Grace is mounted on a Dynavector DV505 feeding a (tube) Silvaweld SWH550, which I use exclusively for its MM phono section. The Silvaweld feeds the high level section of my Atma-phere MP1 preamp. Unable to keep my hands off anything I own, I am in the midst of some major upgrades to the Silvaweld, even though I liked it as it was when purchased. It will be a whole lot better when I finish my work.

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.