I seem to remember hearing that 530-580 ohms is recommended in most circumstances.
42 responses Add your response
Nil, the 25X rule (that I have been endlessly promoting and which you'll find discussed in depth on other threads) is, I keep reminding people, a theoretical optimum, based on the more or less universal objective of good impedance matching.
However, based on the other elements of a given system, I always urge people to explore loading by ear using a range +/_ 50%. In your case this would be from roughly 70 - 200 ohms.
Everything else about your cartridge setup should be right beforehand (VTF, SRA, AS, overhang, azimuth, etc). Start at or near the optimum (125 -150) If you listen and it's bass-shy, reduce the load. If the bass is muddy or bloated, increase the load until the bass tightens up. If the load gets too high, you'll start to lose the bass, so back it off a little.
Thanks for lot of inputs and data points for me to work on. 47K for set up I am trying is definitely way too thin sounding. 40 ohm is a tad fat. 400 ohms leans towards lower side of lean, closer to flater, very tight bass but little hot on high freq still. Which means 100, 150, 200 ohm might work for the set up. Although I will try out 1000 ohm just for another data point.
Hi Jeff, re: impedance matching of cartridges:
A device which is generating a voltage into a load (could be a source like a tuner or CDP into a preamp, or a preamp into an amp, or a cartridge into a phono preamp) has to "see", or work into, enough of a load (resistance or "impedance") so there will be voltage registered at the other end. Or to flip it over, if the other end were just a short circuit (no load) no voltage would register and there would be nothing to amplify.
Depending on the difference between the ouput device's inherent impedance and the input (load) impedance of the driven device, there is an optimum combination that will deliver the best signal transfer, i.e. the most voltage and the most faithful (to the source) frequency response.
You hear more about "impedance matching" between preamps and amps, when someone experiences problems like not enough gain out of their amp, or poor frequency response (usually loss of highs) when their impedances are not optimally matched. Another instance where you often run into this issue is amp-to-speaker impedance matching, which is the reason for the use of auto-formers like the ones Paul Speltz markets.
The cartridge-to-phono preamp interface is no exception. Although to be absolutely fair, I should point out that cartridges are really current producing devices, but there are very few current amplifying phono preamps, so we always speak of a cartridge's output in terms of (micro) volts.
If one takes the time (and it is a bit tedious I admit) to experiment with a variety of load values, it's actually quite easy after awhile to hear when you're getting the flattest response and strongest output from a given cartridge.
The "25-times cartridge impedance (or coil resistance)" convention is a bit like setting an initial 1.5 degree Stylus Rake Angle. It's just a quick way of getting yourself firmly "in the ballpark" so that you don't have to go too far one way or the other in order to find just the right spot.
Jeff: Well, yes, you are endeavoring to impedance-match the cartridge to the phono preamp. The 25x value may turn out to be right on the nose (after experimenting a little up or down and making listening comparisons, taking notes -- always take notes!)
But if it isn't right on the nose, the 25x value will still be pretty close, thus saving you a lot of time.
If you're using a MC cartridge with a typical output and coil resistance of +/_ 10 ohms (optimum loading around +/_ 250 ohms) you could also follow another approach which would take about the same amount of time. And that would be to start at the low end of value range (i.e. optimum less 50%) and work your way up in increments of say 25 ohms. In this example, 125, 150, 175, 200, etc.
I've done it this way too, and it may actually work better (in terms of training one's hearing) for someone who has never done it. You are guaranteed to start with sloppy bass which slowly tightens up and (if you keep going) eventually gets very thin, or disappears. That's when you back down 25 or 50 ohms and can be confident you've found the best match.
Years ago, all Lyra's were made for 47k, but only a few Phono Stages made that, so the manual changed the loading recommendations. I think, it is System dependent, too. When you have an adjustable one, you can check it out, from from setting you will loose high frequency information. I use most of the time 47k with a Klyne Phono Stage and it's own Filter settings, but there is not only 1 right value I guess.
Nil, the 25x rule emerged from experience and experiment and also compiling data from those (few) cartridge manufacturers who actually publish optimum load values for their products (like van den Hul).
Anyway after compiling a lot of data (on normal output MC cartridges that is) and comparing it with various internal resistance figures, the multiple always seemed to come out at or near 25. To save time, since most cartridge maker's load specs are so vague, it seemed like starting with a value around 25X the internal resistance would put you at or very near the goal; instead of stabbing all over the place from 5 to 47K ohms!
Dear friends: The cartridge load impedadce is a subject of vital importance. It does not have to do nothing with what audio system we have, it is not matters what sound we like, it is not system dependent in any way and it is not a subjective choice.
The right cartridge load impedance is that where the cartridge frequency response is flat, period.
If you like it/or not that load impedance with the sound from the cartridge it is another subject that has nothing to do with the right/correct cartridge load impedance.
The load impedance is not an " equalizer ", the load impedance is an electrical characteristic inherent to cartridges, again, where its frequency responce is flat.
To say another thing/history/thinks/believes , is not valid.
I always ask directly to the manufacturer which is the right load impedance for their cartridges: I don't ask which one like them but which one is the correct impedance.
Examples, Van denhul told me that my Colibri must be running at 540 Ohms and Allaerts told me that my MC2 Finish at 845 Ohms, these impedance values are strictly the value where those cartridges perform flat.
If any one of you are running your cartridges way out of the correct manufacturer load impedance recomendation, then you really don't know how perform your cartridge: what you are hearing is only something near the real cartridge sound reproduction. Now, if with the right/correct cartridge load impedance you don't like the sound reproduction then you have to look around your system where could be a problem, where something is out of synergy but not change the cartridge load impedance hidding/cover with this the real problems all over your system. Be very carefull about.
Of course, you can use the load impedance that you want but that's does not means that is the right way.
Regards and enjoy the music.
Raul is correct, though I think I already covered all those same points.
It is important to remember however, that installing load resistors of the maufacturer's specified value will most likely not result in your cartridge actually "seeing" that exact load impedance, because there are other factors involved. It will be close, but could be off by as much as +/_ 30 ohms, which is enough to alter the desired flat frequency response. I'm sure Raul knows this, he just forgot to mention it.
My point is, once you get it close, then use your ears to make the final adjustment. (Now I am sounding like Raul!!)
I think your point that the load recommend by the manufacture is a fixed value, which is independent of the system, is indeed an oversimplification of the intent of the recommendation and cannot be sustained by any reasonable technical analysis. I agree with Nsgarch that the recommended load is simply a ball park figure. Ultimately one needs to experiment to determine the optimal load value for the particular system.
The load is system dependent. The impedance of a MC cartridge is not purely resistive, it contains a reactive component. The system in which the cartridge is used will impact the transfer function of the cartridge (flat frequency response, etc). The system here includes tone arm, turntable, phono interconnect cable and the input characteristics of the phono preamp, etc. For example, the cartridge impedance may be impacted by stray impedances due to the presence of external interferences, the interconnect has nonzero impedance and the input impedance of the phono section is not infinite thus it impacts the value of the loading impedance. In summary, one needs to experiment, using the recommended load as a guide, to determine the load value that gives the best-perceived flat response.
If you wish I can go into more technical depth.
I think, most of us are on the right track, Raul with his opinion and Gmorris with his explanations. When the wire in the arm is silver or copper, you can choose different loads, next is the wire from the termination box to the preamp, same story. I agree, that you can go the one and only way with the manuf. recommendation, but do you think, that all of them use a 1.class phono preamp? Or step ups? Or tubes? Or transistor? Even the tonearm material has different damping influences ....
Dear Gmorris: This is only to clarify: when I speak about manufacturer load impedance recomennded I'm speaking not about the very wide impedance value range that usually comes on the manual I'm speaking that I ask directly to the manufacturer for his advice about, so that wide range scale it converts in a single value or a very short value range. Normally the load impedance that " see " the cartridge is: the one from the tonearm internal wires, the one from the tonearm interconnect cable and the input impedance of the phonopreamp that in a well phono stage design is the resistor at the input: the one that we can change it for modified the load impedance value.
These three impedance stages are the ones that we have to taje in count fo to have the right load impedance value where the frequency response is flat. There are others subjects about like what you say: " by stray impedances ", but those other subjects does not affect signify the frequency response. And yes we can go in deep about any time you want: welcomed!!!
" is not purely resistive, it contains a reactive component. ". Btw, is inductive and capacitive.
Regards and enjopy the music.
I have never owned a cartridge that I did not experiment with,regarding proper loading.I only care about how it performs based upon my tastes.Yes,the ultimate loading usually complies with a mfgr recommendation,but not always.Not "set in stone"!
So my conclusions(which is NO guarantee of anything,other than "I like it,in my system,that way")are---
BTW--I still love you both-:)
Don't get too carried away,with my affections though!!!
Dear Sirspeedy: Before you can play the judge role we have to stay, all, on the same " road ".
One thing is what you like and other thing is what it be. I don't care what you like about ( this is another matter ), I care what it be and I'm talking what it be about.
Gmorris: pleare re-read my clarify post. Nothing more than that. My point of view is clear which yours? and remember this is not a contest it is only an opportunity to help to other people.
Regards and enjoy the music.
The complex impedance is given by:
Z = R +iX.
Your formula for the real impedance (amplitude, etc) is incorrect. The amplitude is given by the square root of the complex conjugate product, ie:
|Z|**2 = ZZ* = R**2 + X**2
** denotes exponent, and Z* is the complex conjugate of Z
I was not trying to be dismissive of your opinions. My response was to demonstate that contrary to what you stated (as being definitive and the only correct position) the optimal loading value is indeed system dependent. The recommended manufacturer value is only a guide or baseline.
Dear Gmorris: +++++ " the optimal loading value is indeed system dependent " +++++
Maybe there are something that I missed about because I still can't understand your statement.
For me, for a cartridge perform flat ( frequency response ), exist a precise load impedance that is not system dependent because we have to set it through a resistor change or through a variable resistor or through a impedance switch. What have we to take in count for we can have the right resistor value ( this one is the input impedance of the phonopreamp )?: the manufacturer load impedance value and the sum of the impedance of the tonearm internal wires with the impedance of the tonearm interconnect cable. These impedances sum has to be added to the resistor value for to find the precise resistor value for the cartridge can " see " the right load impedance value where it performs flat.
Sorry, I can't see your " system dependent ".
Regards and enjoy the music.
Jeff, re: mechanical damping affecting total load impedance, I suppose it does contribute by a small factor (you are talking about a reactance-type current in the coils damping the cantilever movement, right?)
Anyway, the effect on the freq. response curve would be small I should think, compared to the deviation from flat that would be caused by a load change of even 20 or 30 ohms.
It's one of those factors like VTA, where a less than optimum configuration will only yield 4th (or was it 8th) order distortions which are essentially inaudible. Whereas even a slight mis-adjustment of SRA is quite audible. It's sort of like that I think.
After reading this thread I went home to experiment with the loading on my Helikon which I had been using at 47K. My phono is currently set up for 100, 200, 1K, and 47K.
The 25 x output impedance suggests 137.5 ohms.
I tried 200 and there was a little more bass but the sound was uninvolving, no punch or energy. I tried 1K and that brought back the energy quite a bit. However, at that setting, it seemed that some records sounded great and others didn't. The ones that didn't had an almost "out of phase" kind of sound. The music didn't project out into the listening room the way I thought it should.
I will continue to experiment but color me confused by the results so far.
Loading affects the frequency balance -- LESS loading (higher value like 1k or 47k) means a more prominent peak in the treble response, but, it also means that the peak and fall off after the peak occurs at a higher frequency. Therefor, it is hard to say which setting has an objectively flatter response.
I tend to like the cartridge running more wide open and extended on top (47k for my Lyra Titan). But, I do somewhat compensate for the tendency of this setting to be a bit sibilant by having the vertical tracking angle set low (cartridge very slightly "tail down"). I tend to treat VTA and loading as complementary, so both have to be fiddled with to find the best combination. Both factors affect tonal balance, as well as other performance characteristics.
Larryi, negative SRA will compensate for the HF tilt at higher loading values, but it won't really restore the bass balance, only roll off the highs a bit. Also you pay a price in record wear because the sharp edges of the backward-tilting (micro-ridge type) stylus are scraping across the tops of the forward-slanting groove undulations, instead of locking into them, as they will at a nominal SRA of 1.5 degrees.
Check out this thread for a very interesting discussion on the subject (complete with photos and illustrations ;-)