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What's Wrong With My Cartridge/Setup?

Please help this newbie sort out a problem with my cartridge, tonearm or installation.

Here's my system: Shure V15VxMR Cartridge mounted on an older Rega Planar 2 Turntable with glass platter into either an Audio Experience Concerto Tube Phono Preamp or a Conrad Johnson SC-22P SS FET Phono Preamp (in a homebrew box) into a CJ Preamp and Anthem Amp-1 tube amp. This system is new to me (most parts are used with the exception of the cartridge which was bought with 'only a few hours use' and the phono preamp (which I ran for 30 hours burn-in).

So here's the problem: My LPs sound like crap. The highs are badly attenuated, the lows are a weak and the entire sound lacks punch. The sound field is totally flat. I've compared a number of vinyl LPs to CD releases of the same material played on my Music Hall CD-25 and the CDs sound considerably better than the vinyl.

I've played with some of the mechanical parameters of the cartridge (tracking alignment, VTA, weight, anti-skating) using a test LP and a scope (as well as my ears). The changes generally have a audible effect but are small compared to the magnitude of the problem. The loading the cartridge is 'seeing' was measured to be very close to the spec of 47K ohms and 250 pF. The two phono preamps I've tried sound pretty similar, so the problem would appear to be with the cartridge/turntable/tonearm setup.

Any ideas? Could cartridge break-in account for such a major sonic impact? Is it fair to compare an LP to a CD of the same material? Help!!!

.... Brian
odourboy

Showing 2 responses by herman

herman
2,282 posts
 
The LP should sound as good or better than the CD.

With the stylus in the groove check to make sure the botttom of the cartridge looks to be close to parallel with record from the side and isn't tilted when looking from the front. If the tracking force is close and it's not twisted way left or right in the headshell looking from the top then it should sound way better than you describe even if it's not optimized.

Perhaps you got burned with a defective cartridge. I wouldn't trust a used cartridge from anybody. Is the cantilever straight? Is the stylus broken off?

You could buy an entry level cartridge to test with.
herman
2,282 posts
 
I would suspect, as you seem to, that the difference in resistance that you measure when on versus off has to do with some voltage being fed back through the input to the meter rather than the input impedance dropping. Switch your meter to volts and see if you get a reading with the amp on. Whether this is normal or not is impossible to tell without a schematic.

As you are probably aware, a better test is feed a signal to the preamp and then insert resistance in series until the signal at the input drops to 1/2 the original. The inserted resistance is then equal to the input impedance. The problem with conducting this test is that the signal levels are so low it is difficult to get accurate measurements.
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