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In the Forum: Analog Playback
In the Thread: Taking the mystery out of cartridge loading
Post Subject: Taking the mystery out of Jonathon.Posted by Romy the Cat on: 2/26/2005
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***The proper loading value is difficult to say without knowing your system, as it is partly a preamp and ultrasonic RF issue as well as one that involves the cartridge and audible frequencies. Some cartridges have frequency abberations within the audible band, and may requre loading to achieve a flat energy response.
OK, this is a well know thing but the selection of the words makes me a little suspicious...
***However, the Lyra cartridges aren't made like this, and don't need to depend on loading for good frequency response within the audible range. In other words, changing the input loading won't have much impact on the frequency response of a Lyra.
Here we go! What an accomplishment! I wonder if the Lyra cartridges sound so gray and so boring because of this “accomplishment” or there is any other reasons.
***OTOH, the inductance of a cartridge can react with cable capacitances and cause a sizeable resonance, but with high-impedance loading (like 47k) and MC cartridges, the center frequency of that resonance is far above the audible range - think 1MHz or so. If the phono stage or preamp doesn't have a problem with that (ie., it is either linear at MHz frequencies, or bandwidth limited at the input so that RF energy can't come in), the RF energy will stay RF and remain inaudible. But if the phono stage has some response at RF frequencies but is non-linear at those frequencies, sum-and-difference modulation between the RF energy and the audio signal will occur, with the result that you may get distortion products at audible frequencies that are not hamonically related to the music signal, and are therefore quite objectionable to the ears.
Once again: it is a correct prostration of facts but why he would imply the high inductance MM cartridges buy presenting those facts.
***The Lyra-Connoisseur phono stages have 47kohm loading and MHz response (although there is some input filtering to remove CB, FM signals et al), but since they remain linear at these frequencies, they are not particularly affected by electrical resonances between the cartridge inductance and cable capacitance. But for some phono stages, 1kohm works better. And with other phono stages, I've had to go as low as 100ohms for subjectively decent results.
I knew that the reference to his high gain Connoisseur phono stages is coming. Would be his response is just buttering of Reality in order to convince himself and others that Connoisseur is the only preamp that “does it right”? I wonder how the Connoisseur own SS hardness affects a listener perception of “correct loading”?
***Also note that environmental RF can come on top of the electrical resonance caused by the cartridge-cable-input network, and make the phono stage's life that much more difficult - and the RF environment for each audio system is different. So the choice of loading is a case-by-case scenario.
Certainly it is but still I do not know where he is going.
***In general, however, I prefer under-damping (higher resistance values) to overdamping. A lot of audiophiles seem to like a warm, super-smooth smooth, and if this describes you, over-damping may be what you want. But for my tastes, over-damping, while inoffensive, also tends to be bland and uninvolving.
Yes, and now. What Jonathan forgets to mention that using the phrases “under-damping” and “overdamping” he implies that there is such a thing as a “correct exact damping”. However, the “correct damping” is unfortunately exist only in a virtual subjective perception and HUGELY depending on very- very- very many others, primary masking factors.
***Electrically, you can obtain a better response by using a capacitor as well as resistor in the input impedance network, but due to the low source impedance of many MC cartridges (including the Lyras), small capacitor values (of the type that you would use for MMs) will not have much effect.
Sure, this is well know facts….
***Also note that you want good phase response as well as good audible response, so the net bandwidth should extend considerably farther than the audible range per se, while overdamping will accomplish the opposite.
OK, now. Why he threatens the poor audiophiles with the fear of “good phase response” and associate the “bad phase response” with the overdamping?
***The best way of loading would probably be to reproduce a square wave with the cartridge and adjust the loading so that the square wave looks the best on a scope.
Probably he is correct, however considering that the loading is very much might be subjectively overwritten by many-many other factors then what would be the purpose of the loading tuning via the scope? I wonder how the square waves test would differentiate itself if for instance the VTA is off for a fraction of degree or is the primary resonance of the arm is overdumped?
***A transformer acts as a band-pass filter, and with the amount of transformer inductance needed for good bass performance, in most cases you won't need to worry about the RF issues that I alluded to in my previous post. Autoformers usually have greater bandwidth extension than transformers, but in this case probably still not enough to get you into hot water.
Sure, for a guy who manufactures the 88dB active gain phonostage it would be understandable to consider a transformer acts as a band-pass filter. In fact his is very much correct but … there are some “howevers”… If Jonathan bring his Connoisseur in my room and raise the input impedance of his phonostage then I will be very glad to connect it to Expressive Technologies SU2 or SU1 transformer and to demonstrate to him how this “band-pass filter” will VERY substantially increase the low and high frequency response of his phonocorrector (not to mention the it will bust the dynamic range inhumanly!) It would be fun to listen the further Jonathan’s theories about the band-pass filtering ability of the transformers after that (even if I do agree that a transformer ordinary do act as a band-pass filter)
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