MM Phono Input impedance change 47k to 100k ohms

The well-written AudiogoNer Raul states that the Grace F9 Ruby MM cartridge is best matched with an input impedance of 100k ohms vs the standard 47k ohms. May be a dumb question, but is this a simple resistor swap that I might be able to handle or should I best take the preamp to a technician?
Hi Erik,

I don't think it's possible to say without having a schematic and/or being familiar with the details of the design. There could very well be a 47K resistor between the input for each channel and ground, that could be changed to 100K. But even if that were the case, without knowing the details of the design I would not have confidence that the change would not result in unwanted side-effects.

Also, see my post here. Contrary to widespread belief, 47K could very possibly be a suitable load for the F9 cartridges.

Best regards,
-- Al
I agree with Al. I have sold, (I was a Grace dealer) and personally owned many various F9 cartridges and have found that in most cases, the 47K setting is perfect. I currently have several F9E's and have tried many different phono stages with them.

I have owned a couple different phono stages that allowed the 100k setting, but I always went back to 47K. IMHO, the 47K setting is just fine.

I've had a Grace F9E in my collection and system, non-stop for over 30 years now.
Thanks to both Al and Mofimadness, really appreciate the response and will stick with 47k ohms. Incidently the Grace F9Ruby seems to mate very well with the Herbies Most Excellent mat
FWIW, I have a Grace Ruby which I load at 100K, and I love that cartridge. However, I would not say that 47K is not also appropriate, only that I perceive no downside to using 100K. Now I have to go read Al's treatise on why he prefers 47K.
OK. Now I know that Al actually uses 100K, too, and with a SS phono stage, whereas mine is tube-based. Actually, I never knew that there was any written statement from Grace to the effect that 100K is preferred; I am using 100K because that's the load resistor that In installed in my phono stage input.

As to Elunkenheimer's question, I cannot imagine how the circuit could be harmed, if you were to change the 47K load resistor for a 100K one. If you know how to solder, get some high quality 100K resistors and go for it. Most phono stages I have ever seen will use a 47K resistor between hot and ground to set the input impedance. Since the grid of the tube or the gate of a transistor have a very high impedance, in the megohm range, 47K will become the dominant value at all audio frequencies. Likewise if you change to 100K. The issue is a bit more complicated if you have a true balanced input; let us know. Beware of dangerous voltages; always unplug your device, and leave it off power for at least a full day before doing any soldering. (A full day does not make it perfectly safe, however.)
Mofi, thanks for the excellent and valuable empirical information.

Lew, thanks for your inputs as well. I think that you are correct that in MOST cases changing the 47K resistor to 100K would not have any adverse effects on phono stage performance, especially if the input stage is tube or FET-based. But it goes against my technical instincts to incorporate a design modification, albeit a seemingly minor one, without having a full understanding of what the existing design is.

And in particular, I was envisioning the possibility that the active stage at the input may utilize bipolar transistors, and therefore most likely have a much lower input impedance than a tube or FET-based circuit. Conceivably, also, some of the passive components associated with RIAA equalization could be located at that point. I seem to recall having seen some Bryston schematics, for example, to which both of those points would apply.

Finally, given that the cartridge is a MM I would assume that its inductance is somewhere in the vicinity of 100 to 500 mH. That means its impedance at ultrasonic frequencies at which it may output significant energy may be upwards of several 10's of Kohms, perhaps even approaching 100K. That would clearly be significant in relation to the phono stage input impedances we are talking about, implying the possibility (if the input impedance of the active stage is not high enough to be insignificant) that the resistor change could result in adverse effects on noise levels, frequency response, intermodulation distortion, etc.

It all adds up to caution being called for, as I see it. Especially since, given Mofi's experiences and my theoretical speculation (in the other thread), 47K stands a good chance of working just as well or perhaps even better than 100K.

Best regards,
-- Al
With no disrespect to Raul, you just can't always go by what he says. He uses ADS speakers, that have always been lacking in the midrange, to somewhere where they blend with the treble. I've tried those speakers a short time in their day. A friend changed from ADS to other brands, after he heard a major improvement in music, that he says sounds real, and alive now, as it should, years ago. He doesn't miss them. A lot of us heard them at dealers in their day also. Maybe that is why Raul speaks so high of Empire cartridges. Plus there's the personal taste involved.

I've tried various Empire cartridges in their day, and can't recommend them. I also tried some again, after reading what Raul said, years later, on a total different system. They still have a bright unnatural characteristic, that is harsh and poor, on a well balanced system. When Empire was making those cartridges, they where selling speakers like these speakers that had serious midrange problem and other problems too. So it's hard to rely on results, that was done on a system that uses these speakers for a reference, that has problems like this, in both of these cases. Some said ADS speakers were good for masking poor gear flaws.

I sort of got volunteered into saying this, as many friends that read these forums, don't agree his results either. They are familiar with his equipment, and tried a lot of the cartridges he speaks about. We just want everyone to know a lot of variables are involved. And, we know he spent a lot of time, with good intentions.

I had this enjoyable Grace cartridge in the past, and traded it with a turntable (I believe). I ran it at 47k ohms from what I remember. If it needed a different load, I think I would remember.
Al, you, Lew, and many others are way above my knowledge of electronics. But as I understand this one can load down but not up.

Therefore, changing the hard-wired input from 47K to 100K still allows it to be loaded down to 47K (with parallel inputs or Y adaptors) as well as 1K, 470, 40 ohms, etc., to find the best match for a given cartridge. But one cannot upload from 47K to 100K or any higher value.

Indeed, a few older preamps provided switched loading and included 100K as an option.

I'm a strong believer there are no best/single answers in this hobby, too many variables. So it usually comes down to trying any option for ourselves in our own system. It seems changing the phono input to 100K simple gives us one more option.

Hello Hifitime,

They still have a bright unnatural characteristic, that is harsh and poor, on a well balanced system.

With all due respect,that doesn't sound like an Empire 4000dlll or an Empire 1000ze/x but as you said " plus there's personal taste involved".

What cartridge's do you like personally so we/I can get a feel for your taste in cartridges? If it's not a problem, would you mind letting us know your system?
This would be for reference not for any kind of attack.
Dear Gentlemans : Through the years I always ( time to time ) " think " things out of the " book " that's why I re-discover the MM/MI alternative and when I gone inside the alternative I made the same about the load impedance for these cartridges. Over the years too that time where I think and take actions in an non-orthodox way gives me some fails and some rewards, the MM/MI alternative is one of this rewards.

The Grace 9s different models shares the cartridge same motor and here you can read the FR at 100K with 80pf:

this is the response of those cartridges for CD-4 or NOT.

The Empire 4000 series was designed to run at 100K too and many other MM/MI cartridges. I tested several load impedance options with different cartridges even several cartridges that were designed for 47K and even these ones performs better at 100K.
Problem is that even on those times only a few phono stages came with 100K option where the 47K was and still is the standard but even knowing this standard I tested higher load values ( non-orthodox. ) and till today no one I know is running at 100K posted any kind of " anomalies " in the quality cartridge performance level.

I agree with Hifitime: no one has to belive in me what IMHO has to do is to test it to try it and decide about.

Btw, Elenkeinheimer you can try 100K and if you don't like it you just return to 47K: no big deal and remember that as critical is the MM/MI load impedance as critical is the MM/MI capacitance that must be mated in between.

Hifitime, certainly you can speak about ADS speakers but IMHO you can't speak in specific of my ADS loudspeakers not only because nothing of what you posted happen in mines but because you don't know maybe I can say: you don't even can imagine the quality performance level of my system. If in the future you could have the opportunity to live that experience IMHO you will be " heavy " surprised.

When I made and make " discoveries " that's because I don't believe in " standards " like that 47K till I prove to me that that standard is " right ".

There are almost no-rules about because as Lewm knows several times what in theory things have to be in practic/live does not happen and that theory can't be confirmed.

Audio and analog LP playbak in specific is terrible imperfect at least this is what I learned and I'm still learning.

That 47K sounds good does not means that other load impedances, as 100K , can't sounds better.

Finaly, each of our systems is different and more critical that that is that our music sound reproduction priorities are different too and that's why different opinions.

My advise is: test/try it always and decide.

Regards and enjoy the music,
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.

-- 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.
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.

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

Regards and enjoy the music,
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.