Andrew,
I think you may have my comment about 47Kohm loading and negative SRA backwards. Let me explain it this way: If you have a MC cartridge at the correct SRA (stylus nicely locked into the forward-slanting groove undulations) and you set the load at 47Kohms, then you are feeding a perfectly wonderful signal (from the cartridge's output) into a perfectly horrible impedance mismatch. The effect of this particular kind of mismatch is to roll off the bass response more and more starting from about 1kHz on down -- leaving the highs (apparently) dominating.
Now, if you leave the load at 47Kohms, then the highs you are getting are essentially normal, but the bass is attenuated due to the impedance mismatch. The only way to (artificially) reduce those perfectly normal highs, so you can hear whatever piddling bass is still left after the impedance mismatch, is to severely disengage (unlock) the stylus from the groove, setting it to negative SRA in order to reduce the cartridge's HF output. And you wind up with a tonearm that slopes to the rear!
Talk about bassackward!!
47Kohms is ideal for MM cartridges. The Shure "V" series coils have an impedance of 1400 ohms! Times 25 that equals 37Kohms! So naturally a default preamp load of 47Kohms would make perfect sense. Similarly a little 2.5ohm MC coil only needs to "see" an impedance about 25 times its own resistance in order to transfer its energy. If you try driving a 47Kohm load with a MC, all those low frequency bass notes start to look like direct current at the preamp input and get dissipated as heat (if I still remember my electonic theory correctly ;--)
.
I think you may have my comment about 47Kohm loading and negative SRA backwards. Let me explain it this way: If you have a MC cartridge at the correct SRA (stylus nicely locked into the forward-slanting groove undulations) and you set the load at 47Kohms, then you are feeding a perfectly wonderful signal (from the cartridge's output) into a perfectly horrible impedance mismatch. The effect of this particular kind of mismatch is to roll off the bass response more and more starting from about 1kHz on down -- leaving the highs (apparently) dominating.
Now, if you leave the load at 47Kohms, then the highs you are getting are essentially normal, but the bass is attenuated due to the impedance mismatch. The only way to (artificially) reduce those perfectly normal highs, so you can hear whatever piddling bass is still left after the impedance mismatch, is to severely disengage (unlock) the stylus from the groove, setting it to negative SRA in order to reduce the cartridge's HF output. And you wind up with a tonearm that slopes to the rear!
Talk about bassackward!!
47Kohms is ideal for MM cartridges. The Shure "V" series coils have an impedance of 1400 ohms! Times 25 that equals 37Kohms! So naturally a default preamp load of 47Kohms would make perfect sense. Similarly a little 2.5ohm MC coil only needs to "see" an impedance about 25 times its own resistance in order to transfer its energy. If you try driving a 47Kohm load with a MC, all those low frequency bass notes start to look like direct current at the preamp input and get dissipated as heat (if I still remember my electonic theory correctly ;--)
.