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A funny thing happened on my way to the Circle the other day. I stopped off at the Asylum. There was a thread about a guy who got a SL-1200 and a $60 Grado. He said that it smoked his Rega Planet CD, and he is looking for a sub $200 cart for a MM gain stage. Somebody got on and said how a LOMC was better, blah, blah. I told the OP that I thought he should consider the Silver 1, DL-110, AT-7V, etc.To make a long story short, the discussion got into loading considerations of a MM vs a MC. Hagermann loading calculator was used to plot electrical high frequency resonance of a Shure V15VXMR. Apparently this cart is 1K ohms and 425mH. This results (loaded at 47K/250pF) in a high frequency electrical resonance at 15.44KHz. It was then postulated that this results in a low pass filter that causes a phase shift in the output (even at the preamp out) and it is 120 degrees out of phase at 20K. This doesn't seem right to me. 180 degrees is opposite phase. 360 degrees is back in phase. I'm not looking for a particular outcome of this question, I happen to prefer MCs usually. I think this analysis is an oversimplification. The effect of a filter on phase depends on the type of filter. Because there are electronics in the signal path after the shunt resistors/cap, I would speculate that this is a design consideration for the preamp. Nobody on the thread seems to have the equipment or program to analyze the output of a phono preamp. Any thoughts?http://www.audioasylum.com/cgi/vt.mpl?f=vinyl&m=953118 neo
Gents, there's an excellent article on this subject at VE written by an Ortofon rep. Although it's nearly three decades old, it should be considered required reading. http://www.vinylengine.com/phpBB2/viewtopic.php?t=33679
Grado coils have a resistance of 440 ohms, and the induction is rated at 45 mh. Phase shifting can be caused by high capacitance ICs, phono preamps and even the RIAA EQ curve the preamp MFGR uses can cause it. 30K is something only my dog could hear, I wouldn't get too worked up ion it, unless it's in the 12-15k region. I haven't read the article yet, but is on my list.Wayner
CD-4 discrete 4 channel vinyl records had the rear channel information present as an FM subcarrier signal at 30kHz. See wiki link http://en.wikipedia.org/wiki/Quadraphonic_sound#CD-4_.28Compatible_Discrete_4.29_.2F_Quadradisc The MM phono cartridge has phase-shift present in both channels equally due to the inductance from the coils that are part signal generation mechanism. This phase shift clear down into the mid-band is what mucks up sound of a MM compared to a MC which has much lower inductance and hence much lower phase shift in the audio band. The inductance of a MM cartridge can be canceled out by splitting the signal from cartridge and connecting an identical cartridge body to ground. You are left with a signal level of 2.5mv in the case of a 5mv output cartridge but there is zero phase shift and no electrical resonances. The only limits to the cartridges high frequency extension are mechanical in nature not electrical. I run a modified AT 440ML this way. Scotty
I'm not against further investigation here, but are we splitting hairs again?
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