Analog Corner #321: EMT JSD Novel Titan MC cartridge, Fozgometer V2, Mat Chakra, WAM Wallyscope

Let’s get right to it: The best way to set azimuth, as I recently wrote in this space, is to measure crosstalk using either a high-quality voltmeter or a digital oscilloscope and a good test record like Analogue Productions’ The Ultimate Analogue Test LP (AAPT1). The traditional, qualitative procedure—setting the headshell so that it’s parallel to the record surface—assures only cosmetic satisfaction.

The AP test record’s second band contains a 1kHz tone, on the left channel only. The third band repeats that tone on the right channel. Measuring output on the unmodulated channel, in comparison to the output on the modulated channel, gives you the crosstalk, which ideally should be zero but never is.

I went over how to measure and calculate crosstalk in that same recent column, so I won’t repeat it here. Except for a personal, hands-on lesson, a video in which you can see the oscilloscope is the best way to learn how to do this.

The oscilloscope approach requires creating an RCA or XLR-to-oscilloscope probe interface box, repeatedly pushing some buttons, converting voltage ratios to decibels, and then doing a series of math calculations. It isn’t exactly difficult, but it’s tedious, and it may be more work than some vinyl fans are willing to do.

The original $250 Fozgometer, introduced by Musical Surroundings in 2010—has it really been a dozen years?—was supposed to make the process of setting azimuth easier and produce oscilloscope-worthy accuracy using the same test record. But some Fozgometer users reported results less accurate than they achieved with a digital oscilloscope, and the jumpy meter made accurate readings difficult. Calibrating the Fozgometer increased accuracy, but the results were far from perfect (footnote 1).

Musical Surroundings recently introduced an updated Fozgometer, the V2, which sells for $400—about the same price as a decent digital oscilloscope (footnote 2). The V2 features higher sensitivity than the original version, which means that in most instances, even using the lowest output cartridges, you can plug your tonearm wires directly into the Fozgometer: No need to run it through a phono preamp first. The accuracy of the new meter is said to be better, the resolution higher. You can power the meter either from the wall via a wall wart or with batteries. The instructions don’t mention this, but Musical Surroundings’ Garth Leerer told me that the V2 also includes a two-pole band-pass filter that rolls off below 1kHz at 6dB/octave and also above 10kHz. That reduces meter bounce and makes it easier to get a more accurate reading.

The Fozgometer gets its name from Jim “Foz” Fosgate, who developed the sensitive “Log Ratio Detector” used in the Fozgometer. The circuit simultaneously reads the modulated and unmodulated channel, calculates the difference, and presents a reading on the meter. You adjust then repeat the measurement until the reading on both channels is either identical or close.

For adjusting azimuth, it doesn’t matter what the number is; you just want the L–R and R–L numbers to match. It’s best to repeat the measurement at least five times starting with the headshell a few degrees from parallel to the record surface to make sure you haven’t missed the sweet spot.

To test the Fozgometer V2’s accuracy, I first used a digital oscilloscope to set azimuth while reinstalling the 0.25mV output Lyra Atlas Lambda SL. This is a time-consuming process, but worth the effort.

Converting the voltage to dB volts and repeating the subtractive math is another pain, but a new Excel-based program from WAM Engineering, available now as a free download on AnalogPlanet, does all of the math for you. Just type in the voltages read on the oscilloscope and the program does the rest (footnote 3).

As you can see from the screenshot of the program, the top reading shows a “crosstalk differential” of more than 6dB. The bottom reading—taken after tweaking—shows a 0.2dB difference. Incremental headshell rotation produced a major measured (and audible) difference.

Sometimes when running these tests, it’s possible to achieve excellent balance but with crosstalk numbers far worse than the manufacturer specifications. (Crosstalk isn’t reported for the EMT Novel Titan, which I review elsewhere in this column, but the measured values are excellent.)

It’s important to not just accept that result but to keep experimenting until you get both good and closely matching channel-separation numbers (25dB or higher and within 1.5dB). I’m not sure exactly how this works, but if you keep fiddling with azimuth, those crosstalk numbers may eventually improve.

Next, I plugged the tonearm leads directly into the Fozgometer. The test record’s first track is of a 1kHz tone in both channels (in other words, mono). The Fozgometer’s green center light should illuminate, indicating that the two channels are closely balanced. As you can see from the photo, it did.

Then I played the second track, which has the left channel modulated with the same 1kHz signal. The left red light illuminated and the Fozgometer read 17. The third track, in which the right channel is modulated, produced 16.5, a L–R/R–L difference of just 0.5. This comparison shows that the Fozgometer’s accuracy was very good—not meaningfully worse than the oscilloscope’s—and the results were far more quickly and easily obtained. That’s great news.

But it also raises a question: 17 what? 16.5 what? Is that dB? If it was, then we’d be able to check channel separation/crosstalk against manufacturer specifications.

I’m going to enjoy the Atlas Lambda SL for a while before I install a different cartridge, but when I do, I’ll use the Fozgometer V2 for azimuth adjustment and check the results with the oscilloscope. I’ll report back next time, but here’s my tentative conclusion: The $400 Fozgometer V2 is a convenient and seemingly accurate device that’s easy to recommend for setting azimuth. Making house calls—helping friends with their turntable issues—will be much easier thanks to the Fozgometer V2. It beats having to shlep around the oscilloscope, a computer, and an oscilloscope-probe-to-RCA/XLR interface. Every audio club should have a Fozgometer V2 available for members to use (footnote 4).

One last note: WAM’s J.R. Boisclair checked azimuth using a variety of test records. The good news: He found Analogue Productions’ Ultimate Analogue Test LP “about in the middle” of all the many test records he auditioned. The bad news: The results were “all over the map.” In other words, you can use the Analogue Productions test record to set azimuth and be confident that your setup is good, but because groove geometry varies, there’s no guarantee that crosstalk will be optimized for all or even most of your records. The results depend upon how the cutting stylus was installed in the cutter head chuck for a particular record, and that varies.

The WAM Wallyscope
Do you suspect a money drain going from my pocket to J.R. Boisclair’s—or vice versa—because of how many of my columns end up devoted to his wares and his research? It might seem like that, but who else should I turn to for information like this? Who else should any of us turn to? Who else is doing the research and releasing so many useful products? Products like the new WallyScope (footnote 5).

The WallyScope marries a high-resolution digital camera with an optical microscope on a platform designed for fine-tuning of height and focus while maintaining rigidity. The combination produces higher quality images with better pixel resolution (1920×1080) than you can get with the typical digital microscope. It will soon be available for monthly rental at around $300. Boisclair says his biggest problem right now is getting enough cameras, because the WallyScopes keep selling out, at $1250 a pop, to dedicated vinyl fanatics.

In addition to providing high-quality stylus images, the software lets you take measurements of the angles between the stylus and the cantilever, as in the photo. (The photo shows the EMT Micro Ridge stylus on the JSD Novel Titan; the procedure is somewhat different for Shibata and Replicant styli.) Plug the numbers into a calculator on the Wallyanalog.com website, and it gives you the contact edge to cantilever angle. In the case of the EMT JSD Novel Titan cartridge (used for the EMT 128 phono preamp review elsewhere in this issue), that angle is 67.5° (footnote 6).

Footnote 1: I described the calibration process in a 2015 AnalogPlanet story.

Footnote 2: Fozgometer, Musical Surroundings, Tel: (510) 547-5006. Email: [email protected] Web: musicalsurroundings.com

Footnote 3: The WallyTools spreadsheet refers to “crosstalk” but as the ratios are positive, the correct terms is “channel separation.” (Separation is a positive ratio in dB; crosstalk is either a value in volts or a negative ratio, ie, crosstalk at –30dB is equivalent to separation of 30dB.)—Technical Editor

Footnote 4: They must already be doing exactly that. At the time of writing the Fozgometer calibration story has been read by nearly 105,000 vinyl enthusiasts, and yet, Musical Surroundings claims “almost 5000 sold worldwide.” That’s 21 readers for every Fozgometer!—Jim Austin

Footnote 5: WallyScope, WAM Engineering LLC Tel: (707) 210-5345 Web: Wallyanalog.com

Footnote 6: The photo shows a fiber of some sort that’s not visible to the naked eye growing out of the front of the cantilever. Brushing didn’t remove it, and I wasn’t about to try tweezers, so I left it alone.

NEXT: Page 2 »

ARTICLE CONTENTS

Page 1
Page 2

Click Here: Tottenham Hotspur soccer tracksuit