Thanks, John (Jmcgrogan2).
Jeff, as the others have indicated SUTs are almost always designed to be loaded with 47K, and if improperly loaded can exhibit ringing or other undesirable effects. Since the MC input circuit of the VTPH-2 has a near infinite input impedance in itself, while providing connectors for external loading plugs, you could presumably load the transformer properly by connecting the 47K loading plugs Keith provides with each unit. With a 24 db SUT that would result in the cartridge seeing a load of about 187 ohms, not too far from the 10 to 100 ohm range that appears to be recommended for it.
***HOWEVER,*** 69 db + 24 db = 93 db, which would boost the cartridge’s 0.05 mv output under the standard test conditions to 2.23 volts, and the peaks of some recordings may result in levels as much as several times higher than that amount. Which in turn could very possibly overload the phono stage and/or the input circuit of the preamp. Keith could best advise on that possibility, of course.
So pending Keith’s advice my suspicion is that if you want to stay with the MC-2000 the way to go would be what was suggested by the others, namely using a higher gain SUT specifically designed for use with such a low output cartridge, connected into the Herron’s MM input.
One further point: Note that the capacitive loading recommendation for the T-2000 SUT, as shown in the datasheet Folkfreak provided, is 100 pf. That corresponds exactly to the specified input capacitance of the VTPH-2’s MM input, but the capacitance of the cable connecting the SUT to the VTPH-2 would add to that. So you would want to keep that cable as short as possible, and preferably choose a cable type having low capacitance per unit length. Capacitance on the secondary side of a high gain SUT can be an important consideration, because it will appear on the primary side (as seen by the cartridge), **multiplied** by the square of the SUT’s turns ratio, which for a 35 db SUT is very high.
BTW, I too use the wonderful VTPH-2, in its 64 db version, with an Audio Technica ART9 cartridge rated at 0.5 mv, with no loading plugs, and with great results!
Good luck. Regards,
-- Al
Jeff, as the others have indicated SUTs are almost always designed to be loaded with 47K, and if improperly loaded can exhibit ringing or other undesirable effects. Since the MC input circuit of the VTPH-2 has a near infinite input impedance in itself, while providing connectors for external loading plugs, you could presumably load the transformer properly by connecting the 47K loading plugs Keith provides with each unit. With a 24 db SUT that would result in the cartridge seeing a load of about 187 ohms, not too far from the 10 to 100 ohm range that appears to be recommended for it.
***HOWEVER,*** 69 db + 24 db = 93 db, which would boost the cartridge’s 0.05 mv output under the standard test conditions to 2.23 volts, and the peaks of some recordings may result in levels as much as several times higher than that amount. Which in turn could very possibly overload the phono stage and/or the input circuit of the preamp. Keith could best advise on that possibility, of course.
So pending Keith’s advice my suspicion is that if you want to stay with the MC-2000 the way to go would be what was suggested by the others, namely using a higher gain SUT specifically designed for use with such a low output cartridge, connected into the Herron’s MM input.
One further point: Note that the capacitive loading recommendation for the T-2000 SUT, as shown in the datasheet Folkfreak provided, is 100 pf. That corresponds exactly to the specified input capacitance of the VTPH-2’s MM input, but the capacitance of the cable connecting the SUT to the VTPH-2 would add to that. So you would want to keep that cable as short as possible, and preferably choose a cable type having low capacitance per unit length. Capacitance on the secondary side of a high gain SUT can be an important consideration, because it will appear on the primary side (as seen by the cartridge), **multiplied** by the square of the SUT’s turns ratio, which for a 35 db SUT is very high.
BTW, I too use the wonderful VTPH-2, in its 64 db version, with an Audio Technica ART9 cartridge rated at 0.5 mv, with no loading plugs, and with great results!
Good luck. Regards,
-- Al