cart measurement vs quoted spec

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

Yes, well I posted too quickly here at work. That is,of course, 1 dB of channel separation. ;-)

Anyway, your Ultimate Analog Test LP has the tracks I mention. Tracks 1 and 2 on side 1. They are used for az adjustment but work pretty well for this also.

I think we both need Dre on this one.

I also used the Ulti. Analog test LP.

With titan i, phantom 2, tw raven ac, tricon phono cable into Allnic phono. I played track 2 and 3 and measured the output of the phono with PAA3 meter. I also tried using the Einstein TT choice and results are not sig. diff..

Playing the L track: Recorded 1V output at L channel, 15-25mV ( fluctuating) R channel

PLaying the R track: Recorded 1.1V output at R channel, 15-25mV ( fluctuating) L channel

I took the average value of the crosstalk so approx. 20mV. I was told to take the lower value because the higher value indicated noise in the cart.. If my wife tried to annoy me and turn on the washer & dryer, the cart puts out additional random 5-10mV. For more accuracy, you can use a filter to get rid of noise. I should apply the output ratio to the crosstalk measurement to be more precise. I am just too lazy and want to get the azimuth in the ballpark.

Crosstalk: 20log 0.02/1= -33.9db for one channel;
20log 0.02/1.1= -35.6db

Channel matching 20 log 1.1V/1V = 0.82db

This is not that accurate because I assumed the gain of the phono stage is perfectly matched. I should reverse the channel on the phono to idenfy the gain mismatch in the phono. The tracks itself may not be perfectly matched too.

My math is crude and I am not an engineer. Please correct me as needed. Always love to learn.

What's surprising to me in this exercise, I can get the most channel separation on the Phantom, second on the triplanar, no azimuth adjustment on the Davinci. Both the triplanar and Davicni throws a wider soundstage than the Graham. When optimize, Graham arm sounds very focused like some SS gear.

I cannot contribute to using an oscilloscope. Have not used one since college.

I think -15db crosstalk at 1Khz is poor. Once you lose it, you are not getting it back. I would interested in how the numbers compare at 10Khz, 15Khz and 20Hz.

The window for the >25db azimuth is small, it is easy to jump right pass it. If I make big adjustment, it never went < 20db As the numbers improve, make smaller and smaller adjustments until your back, neck, eyes gives out or reached equal and minimized crosstalk.

With the my sonic lab ultraeminent on the davinci with no adjustment, I managed a -28 to 29db crosstalk on both channels. I was either lucky to have a near vertical stylus or QC is very good. Same goes for airtight and Lyra. I will check out the dynavector next week.

After this exercise, most will see that adjusting azimuth to minimize summed output amplitude of the L & R channel playing opposing phase recording do exactly just that. It compensate for channel mismatch anywhere along the sound reproduction chain: cart, phono, pre, amp, speaker, rm acoustics ( unequal dist. to speakers). It does nothing to put the needle in the middle of the groove.