cart measurement vs quoted spec

Doug,

if a manufacturer would only share that easily your trash it and dump it approach.
10 thou out of centre, since you seem to refer here to optical inspection, is not to my current knowledge a reject criteria in THAT industry.

Now if it helps, I worked over 30 years in the electronics industry and most of that time in Semiconductor Manufacturing, so I do have some idea about quality issues, if you please. And in the spirit we like to get to the bottom of things...

Axel

Axel,

My attempt to help was more to do with your questions that you asked about your measurements and your results. Many of the questions I asked were because the translation of your posts were unclear to me. There are a number of things that still puzzle me that may be the cause of some of your measurement results. I'm not saying they are flawed but the results are puzzling nonetheless.

Thanks for the response on who did the measurements and what happened. Knowing that the measurements will not be redone any time soon or that another cartridge cannot be checked using the same measurement technique, it may not be helpful to continue discussions on the technical aspects of what may be contributing to the results you asked about in the original posting. This is simply because you are not currently able to double check anything or test any new procedures. I mistakenly thought that you wanted to run more tests and find out if the procedure was solid and you were confident with your results. Hopefully when you have a chance to try this again, you can post about it.

I do know what cartridge you are speaking of. If I had one, I'd be able to help you out by checking it out specifically. But I'm not sure those results would be helpful to you since it would be a physically different cartridge.

To answer your question to me about one of my suggestions. The reason for the Y-connector usage suggestion is because this test eliminates the cartridge inter-channel interaction completely. By doing so, the procedure will only be feeding the same signal into the phono inputs along with any subsequent amplification so you will know the contribution of error/offset of the electronics.

I know you said your consultant is away so you can probably answer this later if you choose to. How did you guys get differential measurements from the XLR output with a ground referenced scope? (did you use differential probes? 2 pairs of single ended scope probes (4 probes) in differential mode?)

I wish you much success in searching for what you are asking. I hope you can find the answers you seek.
Dre

Thanks Dre,

I will follow up on the Y-connector suggestion, some time next week the earliest.

We used:
2 pairs of single ended scope probes (4 probe/clamps) in differential mode.
The scope was quite recently calibrated I might mention also.

I have posted a bit earlier today my assumption that the cross-talk's lowish level, PLUS the 6dB variance L/R could explain an increased 'smearing' problem at higher accelerations / output.

Would this assumption (all things considered equal for the moment) make some sense in your experience?

I actually think it could be a clue to the massed instrument high level distortion / smearing.

I further assume the 2dB channel imbalance is not nice, but the lesser of the related issues.
It would mostly pull images more to the higher output side, AND produce some image 'fluffing' i.e. the opposite of a 'carved-out-ness'?

Lastly, could you give some indication if this 0.15ohm DCR diff. between the L/R coils is unusual, or is this of no import within your range of testing carried out?

I'm much obliged for your constructive engagement and it might just serve more than only my curiosity.

Many thanks,
Axel

Hi Dre,
as my consultant is back from Munich, please find the rest of the pending answers :(+++)
- Please provide the model number of the O'scope you are using.
+++ Hitachi Model V-212 Megahertz Scope

- Are you using the 10x probes?
+++ NO, we used the pre-amp (326S) XLR output, assumed to be more correct then 10x probe.

- Have you verified the O'scope inputs track each other by tracing the same input signal?
+++ Yes, using 5V square-wave signal to verify both channels are still calibrated.

- 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...
+++ ML326S pre-amp XLR out-put, but using the probes between PLUS and GROUND pin.

- 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?
+++ We will follow up with measurement of another cart, and I'll be in touch. Damping with the arm's silicone trough had no influence on the 100Hz ~ 7dB resonance at all.

- 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.
+++ We convert to dB by calculation and value derived from amplitude measurements of scope's screen grid.

- 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.)
+++ No numerical output, but amplitude calibrated to screen-grid.

- Are the gains settings for the phono-stage set to the same level?
+++ Yes.

- Is the cartridge loading the same on both channels?
+++ Yes.

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.
+++ Having discussed this suggestion, I'm told this was highly unlikely as there were no indications noted that would have supported such.

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 phono-stage by using a Y-connector.
+++ As mentioned already, we will use this suggestion for additional verification and I'll keep you posted.

Thank you again for all these valuable inputs,
Axel

Hey Axel,

Do you have the Cardas Test Record and if so, can you guys try this approach? (It may be similar to what you are doing but I'm not sure, so here goes). I probe from the phono stage output to keep other unknowns to a minimum, but probing from the preamp out should work. Also, I don't use my o-scope. Instead I use a DMM with MAX feature and at least 3 decimal place accuracy.

There are two, 1kHz test tone tracks. One is for the left channel and one is for the right channel.

Play the track for the left channel and record the peak voltage at the left output. That is V1.

Play the track for the right channel and record the peak voltage at the LEFT channel output. That is V2.

And, naturally: dB = 20 * log(V2/V1)

Now reverse the process for the right channel measurements. I don't get the published -30dB specs, probably only about 1/2 of that, for my XV-1s but I'm sure cartridge manufacturers have a better way to measure all of this without putting stylus to vinyl. However, I do get 1.0 to 1.3 dB of crosstalk which is very close to the published 1 dB spec from Dynavector. IIRC, I was getting -15dB on the right and -14dB on the left. Or something like that, which doesn't sound far from your original numbers.

HTH