Are you talking about aligning the heads on tape recorder? A phono cartridge? An antenna?
That's a pretty vague request you've put out.
That's a pretty vague request you've put out.
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The word 'azimuth' is kind of a giveaway that you're asking about a phono cartridge. :-) I use the Wally Analog Shop to do this, and it is a great tool, but kinda pricey. Michael Fremer covers how to do this in the .PDF document that comes with his video, which I haven't seen. But in a nutshell... You need a voltmeter and a test record with a band that plays a 1kHz tone into the Left channel and a band playing the tone into the Right channel. I use the Cardas Frequency Sweep test record - you can buy this wherever fine test records are sold. Set the meter to low AC volts, 5V or less. Place the meter probes into your amp's left channel output terminals. Play the Left channel tone with the volume up enough to register around 2V. Get an average reading and write it down. Next, swap the probes to the amp's Right output terminals. Play the same Left channel tone and take an average reading and write it down - this is the 'bleedthrough' channel, the crosstalk. Next, repeat the above procedure, but using the Right channel test tone. You've got 4 readings in Volts. Convert the volts to decibels. The Wally tool includes a conversion chart to make this simple, or you can google for the formula. I believe the chart is available with the documentation that Wally has on his Web site. Look for Analog Shop and a .PDF file. Once you've converted to dB, take the difference between the readings made with the Left channel test tone to give a number, then the difference for the Right channel test tone readings to give a number. Now you have two numbers. Adjust your cartridge's azimuth to get these two numbers within ... Here the relative difference depends on who you listen to, and how close you want your channel balance to be. I vaguely recall Fremer says within 10%. Wally says within 2-3dB is good, under 1.0dB is very good. I shoot for under 1.0dB because proper azimuth makes a big difference with my cartridge. Basically you're aligning the stylus to maximize channel separation or minimize crosstalk. Keep an eye on the alignment of the stylus/cartridge. To get the proper numbers if it looks like the cartridge is really tilted, then something is wrong with the readings or the cartridge itself. It also helps to equalize the output of your preamp before taking the crosstalk measurements. I probably shoulda written this first. You need a track with the 1kHz tone playing in *both* channels at the same time. (Cardas record has this.) Put the meter probes in the amp's left terminals, playing the 'both channels' track, and take a reading. Do the same for the right channel terminals. Then, adjust your preamp's balance control to get the same reading from both L and R amp terminals. No doubt some golden-eared folks will come along and say you (they) can set azimuth by ear. Listen to a female vocalist who sings center stage. Adjust azimuth to get her mouth/voice as small/narrow as you can. Incorrect azimuth tends to splay sounds horizontally, making instruments and voices larger (spread wider) than they will be when azimuth is correct. This method can work too, though you need good sonic memory to make fine adjustments. I prefer the measured approach, if for no other reason that it is repeatable with accuracy. The Wally Tool includes some low and high pass filters to smooth out the meter readings which tend to jump around as the needle traverses the groove. Hope this makes sense. There are probably other methods, but this is the one I'm familiar with. Good Luck - proper azimuth can make a huge difference especially on more sensitive cartridges. Tim |
> The word 'azimuth' is kind of a giveaway that you're asking about a phono cartridge. :-) Perhaps your experience is limited to phono cartridges, but tapes heads in particular have an azimuth adjustment. And antennas also have that adjustment, though perhaps not as common a concern in the audio world. I guess it is only a "giveaway" if you haven't dealt with the others. |
Great explanation by Tim. One addition: you need a notch filter to reduce frequencies above/below the test tone. Otherwise, at the tiny levels we're trying to adjust for, background surface noise from the vinyl will swamp the results at the meter. Wally's device includes this, or you could DIY your own. |
I can't stress Doug's suggestion enough (even Fremer left this out in his instructions) - if you measure without a bandpass at 1kHz, your azimuth measurements will be close to meaningless. Alternatively you could use an oscilloscope or spectrum analyzer, but a 1KHz bandpass filter with a multimeter will do. |
Sorry guys, you've confused me. Dougdeacon calls for a notch filter above/below the test tone. Restock agrees, but suggests a 1KHz bandpass filter. I'm showing my electronics ignorance here but what filtering point(s) is/are needed for a 1K test tone? Is there a source for plans to build this filter? Thanx. |
Pryso: Doug and I meant the same thing, but notch filter is wrong and does actually the opposite. The correct one needed here is a bandpass that passes only frequencies in a narrow band around 1KHz. Here is a link to some info about bandpass filters: Band-pass filters Band-pass filter on Wikipedia I hope this clarifies things. Rene |
Sorry for the inaccurate term. My electronics skills are easily a match for yours, Pryso. ;-) At least I knew what I meant, and fortunately Rene did too! Doug P.S. Paul and I are among those annoying guys that Tim mentioned in his excellent post. After using the Wally Analog Shop (which works great) to adjust azimuth on several cartridges, we learned we could get just about as close by listening. Our main cartridge goes below the resolution of our multi-meter, which worked out to < 0.1db crosstalk. When azimuth's correct L/R images are so tight they're almost invisible. ;-) Less fiddling time and more music time works for us now, but it was useful to be able to measure and confirm what we were hearing. |
A different question for Doug and others who set azimuth by ear - can this be done by one person while listening off center? My tt is on a side wall, well outside the nearest speaker. I've never tried listening to a test tone for azimuth since it would mean running back and forth between the tt and my listening seat. Also, thanks Rene and Doug for your quick clarification. |
Pryso, You have to be in the sweet spot to fine tune azimuth by ear. That's the only place you can hear your sytem's L/R imaging at its best. Don't use test tones to set azimuth by ear. They wouldn't help. Use music, preferably higher pitched instruments and/or vocals. Our ears are more sensitive to directional cues at high frequencies. Don't use rock, use well recorded acoustic jazz or classical. (Who cares about azimuth for rock anyway? Oops! There I go!!) It's best to rough azimuth in by eye first by making your stylus as close to vertical as possible. No matter what your meter or ears tell you, you don't want your stylus significantly off vertical - for the sake of your records and your stylus. If you have to angle it more than 1-2 degrees something's wrong (probably with the cartridge, few are perfect). Before attempting to fine tune azimuth any more closely, make sure all of the following have been done: 1. your cartridge is well broken in 2. VTF is optimal (set by ear, not just by what some scale reads; if you can't set VTF by ear you certainly won't be able to do so with azimuth) 3. Antiskating is optimal (set by ear, not by what some dial reads; ditto for needing to be able to do this by ear before attempting azimuth) 4. the system and cartridge are warmed up, play 2-3 sides before you begin. I can't describe what to listen for any better than Jtimothya did: Listen to a female vocalist who sings center stage. Adjust azimuth to get her mouth/voice as small/narrow as you can. Incorrect azimuth tends to splay sounds horizontally, making instruments and voices larger (spread wider) than they will be when azimuth is correct.When you think about what crosstalk does to a stereo image, you realize that's a perfect description. |
Doug, good stuff, very helpful. I always assumed judging azimuth correction would require listening from the sweet spot but never tried it. My cartridge set ups have been limited to a close visual check for front vertical alignment of the stylus. This whole series of posts has been informative so thanks too to Jsman for starting it off. |