cart measurement vs quoted spec

Dre, I was thinking the same thing. Axel has a habit of sensationalizing things so I think we should question his technique. But he could also be questioning the results of a particular cartridge that really does have an issue. If that is the case, this thread loses impact. Much like Axel's other threads. ;-)

Be well, Axelwahl.

Axel,

I've done these measurements numerous times and have never seen this kind of a result, so that's why I'm cautious about condemning the cartridge at this point.

I think it would be very educational for you to test another cartridge so you can get a better handle on the likelihood of the measurements being reliable.

There are a few things that could possibly cause your numbers to be off that have nothing to do with the cartridge. The errors could also be cumulative. Again I'm not saying they are just that it deserves consideration.

- Please provide the model number of the O'scope you are using.

- Are you using the 10x probes?

- Have you verified the O'scope inputs track each other by tracing the same input signal?

- Where are you taking these measurements? (What output of your audio system are you using to feed your scope?) there is the possibility of additive and induced error...

- The area of resonance could also be possibly due to the tonearm resonance (or somewhere else in the system which is why it would be good to test another cartridge) on that note, does adding damping to your arm change your measurements?

- are you using a different amplitude settings on the O'scope to take amplitude measurements before you convert the output to dB? these amplitude settings can be off relative to higher settings which could contribute to an error in measurement.

- If this is a modern o-scope, are you using the cursors to take amplitude values OR are you using the measurement features to get amplitude values from the scope numerically? (I ask because these time based measurements can be misleading by containing more than the frequency of interest.)

- Are the gains settings for the phonostage set to the same level?

- Is the cartridge loading the same on both channels?

Depending on how you are gathering the numbers, there could be an entire spectrum of cumulative amplitude which is not exclusive to the frequency intended to be measured and this can also effect your results.

There are a number of variables that can stack up and add errors to the measured results. Some other thoughts are the crosstalk introduced by the system itself- this can be checked by sending the output of one cartridge channel into the both input (L&R) of the phonostage by using a Y-connector.

I hope this all makes sense,
Dre

Dan,

I'm just a little puzzled by the results and wanted to respond to Axel's request:

Has any one got some explanation for how such a major variation can be the case?!"

Hopefully, the information and my thoughts to his request is helpful to him.

Dre

Well, if you can't help him with these measurements, I don't think anyone else could. ;-)

What is valid is that I get distortion at high vinyl levels with massed instruments / orchestra / fortissimo, and it *seems* to tie in with the channel imbalance. At medium level, and less complex music it can not be easily noted, if at all.

AHA! Finally we get to the core of this thread, which I've tried to drive at from the beginning - namely, why are you measuring channel balance and crosstalk?

I've heard exactly the distortions you describe in at least 50 systems, and I've eliminated it in at least one or two. ;-)

It would not occur to me to tackle this common problem by o'scoping a cartridge to check channel balance and/or crosstalk. These distortions are vastly more likely to be caused by resonance behaviors, distortions in the amplification stages and/or speaker problems than by crosstalk or channel imbalance in a cartridge.

99% chance this was a wasted effort, IMO.