The importance of VTA, SRA and Azimuth - pics

[ack]

For all interested - I have been astounded by the improvement of properly setting SRA around the optimal 92 degrees, and perfect azimuth as shown below... The geometry of the arm-cartridge is anything but appealing now, but the results are well worth it.

1) Proper SRA has dramatically reduced intermodulation distortion, which can be easily verified with large scale choral music - grainy choruses now sound extremely smooth:



If you were to look at the stylus with a 10x loupe, you'd see the end result, which unfortunately I cannot photograph.

2) Perfect Azimuth has expanded the soundstage and improved channel separation:



After setting azimuth correctly, the results can be verified by playing a 1kHz mono tone:



After these adjustments, I went ahead and realigned the cartridge with my Mint LP tractor again. The overall improvement is phenomenal. One of the more important decisions I made last year when I got back into analog was to get an arm that supports all these adjustments. I would now not be able to go back to any ordinary arm!

 

[Gregadd]

Those of you who have read Neil (NSGARCH) on other forums(Audiogon, Audio Asylum) know this is his forte. Maybe he can post some links to some of his discussions. His knowledge of azimuth alone is worth the price of admission. In this day of fixed head shells it is frequently overlooked

 

[MylesBAstor]

Those of you who have read Neil (NSGARCH) on other forums(Audiogon, Audio Asylum) know this is his forte. Maybe he can post some links to some of his discussions. His knowledge of azimuth alone is worth the price of admission. In this day of fixed head shells it is frequently overlooked

Another person who had great data on the effects of VTA and azimuth was Bruce Thigpen. In his owners manual for the ET (See pg. 51+ of manualhttp://www.eminent-tech.com/main.html), Bruce showed the sideband distortions resulting from improper alignment.

OK noticed that link is to front page--and for some reason can't link to the right file. So go under ET2.5 and scroll down to the pdf for pg. 45-65. You'll want to start with page 51.

 

[jadis]

Another person who had great data on the effects of VTA and azimuth was Bruce Thigpen. In his owners manual for the ET (See pg. 51+ of manualhttp://www.eminent-tech.com/main.html), Bruce showed the sideband distortions resulting from improper alignment.

That's why I've always loved this arm's flexibility for on-the-fly VTA adjustment and easy azimuth adjustment as well.

 

[MylesBAstor]

What does everyone use to set cartridge azimuth? As Peter has shown, it can make or break todays cartridges with their exotic stylus shapes.

Peter, I'm curious how you got the grid on your digital pic? Did you download and then add the grid? I also like the way you used the tape deck meters to measure the channels.

Personally, I was lucky enough to snag one of the last 100 or so AT cartridge analyzers years ago from AT. They were around $300 but worth every cent! Setting azimuth on the AT is done by measuring crosstalk.

 

[ack]

Ahhh, the grids... I have a Canon 40D and their software has an option to put a grid on; that's not the difficult part. The difficult part is how to grab that picture as is with the grids and save it, 'cause the software won't let you save with the grids, nor will a Copy operation grab it with the grids. For that, you need to get a screen dump, like ?lt-PrtScreen on the PC keyboard, which puts it in the clipboard. Then GIMP has to be employed, which lets you create a new picture with a simple Paste, so long as the raw picture you are creating has the right dimensions of what you are about to paste (otherwise it will be chopped off, or too big). To do this, you need to know the pixel size your camera takes as configured - in my case, Canon's software has an Info button that dumps all kinds of info about a picture (frankly, too much, like the body's own serial number!), so given the picture's XY size, I provide that to GIMP and then I paste, and from then on I can crop it and save it. These particular pictures were also sharpened with Canon's software.

The Revox's meters (and the deck itself) are a life saver in situations like these - it certainly saves me having to buy a Fozgometer or similar; and I first calibrated them with a 1kHz tone from the CD player. BTW, I also used the following technique for the azimuth which also sets the speed accurately (with the help of the SDS). Using a voltmeter, first I play a 1kHz tone with the CD player and measure the frequency at the amp's output, to figure out the meter's error - in my case, it records a 1002Hz tone; then I play a 1kHz mono tone on the turntable (Analogue Productions Test LP) to set the speed accurately, tuning the SDS until I get a 1002Hz reading, and verify again with a KAB strobe (no drift). When the channels' azimuth is perfectly set, one expects to get the same 1002Hz tone at exactly the same amplitude from both channels (I measure the voltage); they turned out to be exactly the same (this assumes of course your phono preamp, amplifier(s) and especially the line preamp's volume control are not factors in this, and they produce the same level output for a given fixed and equal level of input on both channels).

 

[Gregadd]

SRA By NSGARCH

Here are some picture.

 

[Steve williams]

what's the third picture?

 

[Gregadd]

It is an electron microscope picture of cantilever and stylus.

 

[MylesBAstor]

It is an electron microscope picture of cantilever and stylus.

Are you setting azimuth using mirrors?

If so, that assumes that the stylus is correctly mounted in the cantilever, unfortunately not always a given with a cartridge

 

[Gregadd]

I think you are right Myles that is for SRA.

 

[MylesBAstor]

I think you are right Myles that is for SRA.

Thanks and probably zenith too. Great if you still have good eyesight too eg. those of us older folks or far sighted individuals go blind using a mirror

 

[Gregadd]

That's what grand kids are for.

 

[nsgarch]

OK, before this all gets totally out of hand

1. You can read the thread that goes with the pictures here:
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1140840022
The first picture in the series was NOT shot through an electron microscope Trust me; if I could afford an electron microscope, I'd buy a more expensive cartridge instead!! No, it was shot with my Nikon digital camera through a 50x pocket microscope. It shows what a line-contact stylus (Transfiguration Temper W cartridge) looks like (side view) at zero degrees, or perpendicular to the record surface. The stylus sits on a front surface mirror, and when perfectly vertical, forms an hourglass shape with its own reflection. The other two pictures show the set up with my Goldmund TT/ SME TA.

2. I have zero tolerance for those who ever thought, or still think, VTA has a SHRED of utility in setting up a phono cartridge. UNLESS at the proper SRA and VTF, your cartridge has

• the exact same length cantilever,
• which makes the exact same angle to the record

as the cutter head that that cut the record. Good luck with that!!

3. The best way to set/check azimuth is with a test record. You can use a first surface mirror, looking from the front, but it's awkward and you can get more accurate results using your ears and a test record like the Cardas/Stan Ricker one. You play the white noise track that has one channel 'in phase' and the other channel 'out of phase' with your preamp switched to MONO. If your preamp doesn't have a mono switch, you can use two "Y" connectors back to back at the preamp outputs to combine the L and R signals. If the azimuth is correct and the stylus is perfectly vertical (from the front), you should hear almost no sound out of the speakers because the L and R signals will cancel each other. If you can rotate your headshell, do so in each direction until you find the point where the output from your speakers is minimum. If you can't rotate your headshell, use the test record, but unless there's more than just a 'whisper' of output, don't worry about it for God's sake! The cure would be worse than the problem.

 

[MylesBAstor]

OK, before this all gets totally out of hand

1. You can read the thread that goes with the pictures here:
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1140840022
The first picture in the series was NOT shot through an electron microscope Trust me; if I could afford an electron microscope, I'd buy a more expensive cartridge instead!! No, it was shot with my Nikon digital camera through a 50x pocket microscope. It shows what a line-contact stylus (Transfiguration Temper W cartridge) looks like (side view) at zero degrees, or perpendicular to the record surface. The stylus sits on a front surface mirror, and when perfectly vertical, forms an hourglass shape with its own reflection. The other two pictures show the set up with my Goldmund TT/ SME TA.

2. I have zero tolerance for those who ever thought, or still think, VTA has a SHRED of utility in setting up a phono cartridge. UNLESS at the proper SRA and VTF, your cartridge has

• the exact same length cantilever,
• which makes the exact same angle to the record

as the cutter head that that cut the record. Good luck with that!!

3. The best way to set/check azimuth is with a test record. You can use a first surface mirror, looking from the front, but it's awkward and you can get more accurate results using your ears and a test record like the Cardas/Stan Ricker one. You play the white noise track that has one channel 'in phase' and the other channel 'out of phase' with your preamp switched to MONO. If your preamp doesn't have a mono switch, you can use two "Y" connectors back to back at the preamp outputs to combine the L and R signals. If the azimuth is correct and the stylus is perfectly vertical (from the front), you should hear almost no sound out of the speakers because the L and R signals will cancel each other. If you can rotate your headshell, do so in each direction until you find the point where the output from your speakers is minimum. If you can't rotate your headshell, use the test record, but unless there's more than just a 'whisper' of output, don't worry about it for God's sake! The cure would be worse than the problem.

Thanks for the explanation Neil. One still could still conceivably set up the cartridge using VTA as shown in Bruce Thigpen's diagram in his ET 2 book.

But the key as you showed in your first figure is being able to see the stylus because one can't assume the manufacturer correctly mounted that diamond in the cantilever.

 

[nsgarch]

Thanks for the explanation Neil. One still could still conceivably set up the cartridge using VTA as shown in Bruce Thigpen's diagram in his ET 2 book.I'm sorry Myles, but no, one could not! First of all, SRA is a very well established number which varies only slightly within a very narrow range. VTA has no real pre-defining basis or standard. And if you think about the issue seriously, you realize the chance of having both VTA and SRA set correctly at the same time is basically zero (miracles and coincidence aside.) So which would you prefer: 1.) that your stylus fits the groove like a glove, or 2.) that the angle of your cantilever matches one of many possible cutterheads, and still having absolutely no affect on sonics? (Possible sideband distortion in the megahertz range will be of no consequence compared to what you'll lose with an incorrectly set SRA.) Sorry, but you simply can't have both correctly set at the same time, except by accident ;--)But the key as you showed in your first figure is being able to see the stylus because one can't assume the manufacturer correctly mounted that diamond in the cantilever.That was my point in posting that thread. It's all well and good to go on about how important it is to have the correct SRA (with a line contact stylus, that is) but what everyone wants to know next is: where do you start? And the answer is: find the zero point (vertical) for your stylus and set the SRA from there.

Thanks

 

[MylesBAstor]

Neil,

Please look at Bruce's diagram on pg 51 of his owners manual. VTA and I understand what you're saying about the cantilever, as defined by Bruce has nothing to do with the cantilever as I'm seeing it.

 

[MylesBAstor]

Neil:

Think this might be the next analog set up tweak?

http://www.nytimes.com/2008/05/25/technology/25novel.html

 

[nsgarch]

Myles, I can find no diagrams on page 51 of any of the two owner's manuals listed: ET-1, and the ET-2 (part 1, 2). only text. There is a diagram and text on pg. 31 of the ET-1 manual which if you read the text, it's very clear the author believes VTA and SRA to be one and the same thing -- right! On page 51 in part 2 of the ET-2 manual, (text only, no diagram) again he lumps VTA and SRA together. So I can only conclude he understands neither one of them.

Here are a couple of links that might amuse you. First the disassembly and repair of a Westrex cutter head, which should make it abundantly clear why any attempt to match the angle of a playback cartridge's cantilever to a cutter-head's cantilever would not only be an exercise in futility, but begs the question: which manufacturers cutter-head//lathe operator's settings are you gonna match? http://aardvarkmastering.com/westrex.htm
This page has a great diagram at the bottom: http://aardvarkmastering.com/history.htm

And what about the Decca cartridges with a vertical "cantilever" and zero VTA. They shouldn't even make music, and yet they are considered by some to be the tracking champs!

SRA is the setting to nail, and it can vary slightly from record to record due to record thickness. It can also vary due to lathe operator preferences. If you're lucky enough to own a Graham or Tri-planar or other TA with on-the-fly tonearm height adjustment, you can twiddle and diddle above and below your mean setting to see if you might dial the sound in even better. Set the SRA the very best you are able, and let the VTA wind up where it may; if you do the reverse, you will never get the best sound possible out of your cartridge.

 

[nsgarch]

Neil: Think this might be the next analog set up tweak? http://www.nytimes.com/2008/05/25/technology/25novel.html

With some partners, I am currently looking into creating some new analog accessories. There is a kids digital microscope that you plug into a PC that might work to look at stylus alignment. Also thinking of ressurecting the Decca 2+2 record brush (with a built-in ground wire ;--), Panda Paws, and a resonance absorber more audio oriented than Stillpoints (which were designed to carry 300 lbs each!)

It would be nice if there were a way to visually calibrate a stylus quickly and easily to true vertical. However, I'm also looking into finding optimum SRA electronically using common test record tracks. We'll see ;--)