Resistance loading your phonograph cartridge will affect it's bandwidth, distortion and tonal balance . There is sometime an effect on the dynamic contrast as well. You should seek advice from the manufacturer (or importer) to find the proper load for your exact cartridge, and then try their suggestion. Certain cartridges can be "tuned" with more or less load than the amount suggested, and often that experimentation is required to find the perfect load in your system. Last, once your chosen load has been determined, your preamp may be fitted with a higher quality resistor than the one supplied by the manufacturer. This is sometime easy, sometime not, depending on your preamp design and what resistor you choose to install. |
Mike Fremer thinks that low output moving coils sound best when "loaded", meaning a low impedance setting. I definitely agree. Generally, if your cartridge is high output, the best impedance will be over 1000 ohms, and usually around 50k ohms. I am using 384 ohms with my Benz Lo4 cartridge, and it's output is .85 millivolts (at 5 cm/sec, I believe). The Glider HO that I previously had, had an output of 2.8 millivolts, and sounded best with either the 50k ohm, or 100k ohm setting. My phono stage also has selectable capacitance loading (either 200 or 300 picofarads), and I've always used the 200, but need to try the 300. The amount of gain in the phono stage can also affect dynamic contrast. If there isn't enough gain, dynamics tend to sound soft, even though you may be able to play the music loud, if you turn the linestage's volume up far enough. Mine is set now, where I don't ever have to go above unity gain on the linestage, and is 55 dB of gain in the phono stage.....................Albert, it seems like the most pivotal area to replace with quality resistors would be in the section that determines gain, and not so much the impedance (since the gain is a pad circuit, where resistors are in both in series and parallel with the signal's path...and the impedance loading section is just different dip switches that select different resistors that are all in PARALLEL with the signal's path)...............ALSO, ALBERT, DOES YOUR AESTHETIX PHONO HAVE A SUBSONIC FILTER? I've decided that many records that have even slight warpage should use them....it'd be nice to be able to toggle between using a subsonic filter, or bypassing it, but I don't know of any phono stages that allow for that. Mine has no subsonic filter, and listening to speakers with cones allows one to see the subsonic noise....and also the load the power amp is being asked to drive...very close to direct current. |
And Albert, I just listened to "Balalaika Favorites" and "Bartok: Concerto for Orchestra" ON 45 RPM....and sheesh, am I NOT interested in DVD-A, SACD, or anything digital for a while....I bet these would just make you die of delight on a "real table" with all those separate dedicated power supplies...heh heh. |
In general, the preamp load setting should be 10x,or greater, the cartridge's internal load. This last number can be obtained from the cartridge manufacturer. |
Hi Carl. I have experimented with cartridge load in the Aesthetix IO phono, and the hand trimmed resistor provided by Lloyd Walker (Walker audio) was an improvement over the standard one. As far as other places in the circuit, I agree that any resistor that parallels the signal path will effect the sound. On subsonic filters, the IO does not have one. My previous unit, the Elliott Magnum Opus Phono (previously the Counterpoint SA-9, less the Infinity caps and tweaks), did have a subsonic filter, and it was adjustable in two positions. I think it was 30 HZ and 10 HZ, but I may well be wrong on those numbers. My experience with the subsonic filter (either position) was negative in my system, but that could be due to the design of the filter in that particular preamp. I previously used a 28K Vishay for loading the Benz Ruby in my system, when it was my reference cartridge. The specifications had called for the Ruby to load at 49K. My Koetsu Rosewood Platinum Signature is running at 1K Ohms, and was determined by the (selectable) choices on the rear of the IO. After that load number was determined, I tried the hand trimmed resistor provided by Walker. The improvement was very nice, considering the little money and time spent for the change. |
1000 ohms seems very high for such a low output mc like that Koetsu. According to the Guide, it's output is .2 millivolts at 5 cm/sec rms lateral velocity. My Lo4 is much higher at .85 millivolts, and seems to sound best at 384 ohms. Again, Fremer never sways from his experience, that very low output cartridges sound best when loaded (even well below 100 ohms). I don't doubt that you are getting excellent performance from your Platinum Signature, though. I also don't doubt that a subsonic filter would have a signature on the music, but feel that it'd still be nice to "switch one in", when needed, otherwise you're unnecessarily straining the power amplifier, asking it to reproduce a noise artifact that isn't part of the recording...and a very loud artifact it can be, even with slight warpage that's common in the pressing of brand new records. |
For what it's worth here are my observations. I am running a Koetsu Onyx Platinum (.2mv, 5ohms) into a BAT VKP10 phono stage into a BAT VK5i into VK60 monoblocks biamped with Llano Trinities. The P10 has gain settings of 50 and 55 db in its direct all tube mode (6 6922 for gain) and gains of 67 and 73db if you switch in the stepup transformer. Loading of 100, 1000, 10,000 and 47,000 is builtin. To me the Koetsu sounds best at 55db all tube loaded at 47k. I believe there is some ringing at the higher frequencies which can be cured by going to 10k but with the loss of some dynamics. Going under 10k turns everything to mud and syrup. The volume at the preamp is generally at 50 I(unity is 62) so there seems to be sufficient gain and no loss of dynamics. The bass is satisfactory but see below. My guess is that the best loading would be around 25k. When I switch in the steup (sounds best at 73db) the sound to me takes on the characteristics of a CD: fast, dynamic, and a bass with terrific extension and control; however I lose all the midrange delicacy and air and timbre and so I go back to the all tube mode. This is loaded at 100 ohms and the sound would probably improve by going even lower. At 47k it is unlistenable. However the volume setting on the P10 is now around 30 which probably is not a good thing--losing music to the resistor. So all this means to me is that loading is very dependent on whether or not you are going into a stepup or all tube. I noticed that the Rowland phono stage only offers loading of 200 and 400 and I believe this is true of other solid states and hyrids. Now if I could only incorporate the stepup bass with the all tube mids and highs.... |
The theory of playback of Vynyl LP recordings is well documented in several professional publications. it is in fact quite complicated. I will try to explain it in simple terms. Fitst, the frequency response on the recording is done to the RIAA recording curve, where the low frequencies are reduced in level and the high frequencies boosted to follow this frequency curve or frequency response. On playback, the frequency response of the Pick-Up Pre Amplifier is the exact opposite providing the RIAA Equalisation or Compensation to end up with an overall flat playback frequency response of the original recorded material. Unfortunately, there are losses in this process, and this is where things get tricky. The recording is done with a "Chisel" shaped stylus having fairly sharp corners. The Playback Stylus is either Spherical (Round) or Elliptical and cannot follow the original cut groove exactly which will cause some loss of high frequencies. A loss which differs from cartridge to cartridge, and dependent on the stylus diameter and type. The stylus assembly in the Pick-Up cartridge also have a mechanical resonant frequency, usually at a frequency higher than the highest frequency of interest, but in some cases involving inferior products unfortunately not. Electrically, the coil on a conventional Moving Magnet cartridge forms an inductor. The technique for best playback results is to "Tune" the cartridge at a suitable frequency by considering the cartridge coil as an inductor, and the cable on the Pick-Up Arm together with the input capacitance of the Pre-Amplifier as a parallel tuned circuit which will resonate at a particular frequency. Better types of Pre-Amps have selectable C to allow this to be done. The tuning will result in a distinct peak in the high frequencies which is then damped out by resistive loading to give an overall flat playback frequency response up to a maximum high frequency determined by the stylus diameter, and the stylus assembly in general. Very tricky to do and requires patience, basic test instruments and a calibrated frequency response test record. By the way, test records only last a few playbacks before they suffer loss of high frequency information. Fortunately, most reputable Pick-Up Cartridge manufacturer do specify the optimum capacitive and resistive loading for each type of cartridge. These specifications only hold good provided the cartridge is fitted with the correct original manufacturers stylus assembly, and that this is in "Good Health". For brand "X" aftermarket stylus assemblies, the situation could be completely different, my advise, for replacements, even if it costs more, purchase the proper manufacturers replacement stylus assembly. |
Actually, the first part is wrong. The RIAA curve cuts the high frequencies before it goes to the cutting amplifier during proeduction, and the highs get reboosted on playback of the end product thru equalization in the phono stage. This is widely known. The stylus could not track the groove if the hf was as loud as the lf. |
If any of you guys remember J. Peter Moncrieff's International Audio Review ( IAR ), he spent quite a bit of time in a few issues charting and documenting what worked best with dozens upon dozens of cartridges. While this was quite a while ago and he obviously couldn't have covered the current models of today, his findings on many of those was that what worked optimally in terms of frequency response and noise characteristics RARELY matched the manufacturers suggested loading characteristics. He produced charts showing the both of these specs with the factory specs and with a few others for you to draw your own conclusions from. Sean > |
You got that backwards Carl. In the RIAA system, records are cut with a constant amplitude up to 500Hz, a constant velocity between 500Hz and 2120 Hz, and a constant amplitude again above 2120Hz. A phono cartridge is a velocity transducer, not an amplitude transducer. So for a flat response the records would be cut with a constant velocity at all frequencies. But that would result in very large groove excursions at low frequencies, which (amongst other things) would necessitate a very large spacing between the grooves. By attenuating the bass frequencies (in the constant amplitude region), the grooves can be cut closer together. By boosting the high frequencies (in the constant amplitude region again) the signal to noise ration is improved. Brian |
Okay everyone, I have been reading all the words regarding cartridge loading on this msg. board but I am still a bit confused. I keep getting conflicting information from different sources regarding "cartridge loading" so I hope someone can clear my misconceptions up. Correct me if I'm wrong but I thought that a resistor with a higher value, ie. 10K ohms reduced more current than a 500 ohm resistor. If so, does it not follow that placing a 10K ohm resistor to "load" a cartridge would alter the signal from the cartridge, ie., reduce the bandwidth and lower the high frequency signals, etc., more so than a 500 ohm resistor. If this is so than how can a resistor with a lower value, say 500 ohms be said to offer more "loading" on a cartridge than a 10K ohm resistor? This is what Mr. Fremer suggests and yet I have dealers telling me this is wrong. I am confused. |
You are right. The terminology is confusing. Also frequently people get it backwards. The term load, when used relating to resistance, comes from a mechanical analogy: a SMALLER resistance generally means more current and hence a LARGER load. Conversely a LARGER resistance is often referred to as a SMALLER load. Confusing - I agree.
In any case with MM cartridges the issue is not current or voltage, the issue is to match the coil inductance and phono stage input capacitance with the correct resistance. MM cartridges have a very high series inductance, typically 0.5 Henries. The combination of the three values behaves like an RLC circuit, which under the wrong conditions will give a highly curved response (in fact an RLC circuit can act as a very effective band pass filter). The loading resistor is selected to dampen the response so that it is almost flat within the audio spectrum. Though there is always a residual hump in the response at around 10-12KHz. Therefore the load is critical, and not only that, the input capacitance of the phono stage is also critical.
As a general pointer, the input capacitance is typically around 250pF, larger values will reduce the frequency of the hump, but will decrease the damping, so should be matched with a slightly lower input resistance (maybe 40K Ohm for 330pF capacitance) I imagine that some sonic improvements could be achieved by carefully matching these values. So trying values of between 30K Ohms and 75K Ohms is a good idea if you have the option.
A benefit of using an MC cartridge is that the coil inductance is very low (around 20 micro Henries as far as I remember, I measured it for a couple of MCs recently, but I don't have the result to hand). So in the case of an MC cartridge changing the load / resistance does not significantly alter the frequency response within the audio spectrum.
Ironically though, you will see more discussion on the MC question. I believe that is because the people who spend $2000 on an expensive MC, are more likely to be serial tweakers, whereas Joe Public, who spend $200 on an MM, just wants to set it up and be done with it!
Hope this helps.
Brian |
Brian,
Thanks for the help. Unfortunatly answering one questions leads to more questions, so it is said. (Especially among people who know more about the biological world than the electronic world.)
Maybe you can address this problem as it relates to cartridge loading. I was fortunate, (or unfortunate as the case may be) in one swoop replace my table, arm and cartridge. The problem is is that I now have much more emphasis in the HF spectrum than before and the surface noise on LP's is accented quite a bit more than in the past.
Since the first cartridge failed after 6 months I hoped the second one would do better. Surface noise is still too prominent. Even on virgin LP's.
So, in talking to Benz I am told that my phon stage, which is permanently set at 560 ohms, is too low and should be at 10K-20K. And that this is a major cause for my problems. The 2 phono stages I have tried have allowed me to either agjust to a 10K or are set at 20K. In either case the HF emphasis was reduced with more emphasis placed in the med-low range and surface noise was improved a fair amount. So, was it the loading charecteristics of the phonostages or the phonosatges as a whole which made this improvement?
Also, sorry for asking what does "RLC" refer to as you mentioned?
Thanks! |
Hi Gerard,
Which Benz do you have? I have never used one so I hesitate to comment.
All of the Benz cartridges are MC, and generally speaking, MC cartridges are not as sensitive to the load as MM cartridges (due to the low coil inductance). However connecting an MC to a low resistance load (such as 100 Ohms) results in a larger current, and this mechanically dampens the cantilever. This may be the more rolled off kind of sound you are looking for.
However, returning to your original observations, the two phono stages you tried gave a preferable sound (ie less HF emphasis), even when the input impedance was set high (10K, or 20K). Since your phono stage is already set to a lowish impedance, and you think you still have too much HF emphasis, then I can't see how you can cure the problem with your existing phono stage. Increasing the resistance will make it worse if anything.
Best regards,
Brian
PS An RLC circuit is a circuit containing a resistor (R), an inductor (L), and a Capacitor (C). |
Brian,
I am using a Benz Ruby2. Up until I bought one I had only heard the Benz LO.4. It sounded good so I thought I would try and do better. Hmmm! It has lots of good praise through out the audio bulletin boards.
I have a very strong feeling that the phono stage is just not compatable for some reason. It took me 2 years to get the RF problem solved with it now the sound semi-sucks. It worked so well with my Linn Klyde that I did not worry. The other issue is the the Michell Orbe is alot more revealing a deck than my LP12 was.
Can you expand a bit on the fact that a low resisive load on the cart. mechanically dampens the cantilever? I would have thought that, (let me try this), increasing the resistive load which leads to a decrease in signal strength (thus loading is reduced) would impeed the signal enough to slow or dampen the cantilever. But your saying that as the resistive load approaches zero the machanical dampening of the cart. increases? I was trying to use the water hose and faucet idea to try and convince myself that when you reduce the water flow by closing the faucet down (increasing resistive flow) you cause a pressure build up behind the faucet and a subsequent dampening effect.
Any more help would be great! |
Hi Geradff, A few points on moving coil cartridges. Decreasing the size of the load resistor (say from 47Kohms to 1Kohms) will tend to dampen the high end, Which may or may not be a good thing depending on the rest of your system. Some say a large resistor is more natural and some say it is too bright. Trust your ears.
I think you may still be a little confused on the subject of loading. A large load is one that draws a lot of current from a device. Small resistors draw more current than large resistors, so small resistors are said to be bigger loads. Your terminolgy of "increasing the resistive load" is a bit confusing. It would be better to say "increase the resistance", which means to draw less current with a bigger resistor.
As far as damping the cantilever, as the coils move in the magnetic field, they generate alternating current. First it flows in one direction and then in the other. As you decrease the resistance of the load, you generate more current. This creates a sort of electrical inertia that has to be overcome every time they change direction. The current in the coils creates a magnetic field that must be reversed to get the current to flow in the opposite direction. You get the same effect when you try to hand crank a generator. It gets harder to crank if you increase the load, i.e. you load it with a smaller resitance and draw more current from it. Hope this has been of some help. |
Bruce,
Hey thanks for the explanation and clarification! I can't tell you how long I have been asking, searching for a clearer precise answer to my questions. At least it now makes sense when people talk about resistive loading and seem to say one thing and mean another.
I now feel confident to at least begin to address my loading issues.
Thanks to all who answered!!! |
