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I own a scope and I know how to use it for the normal sorts of things, but up until now I've never tried to use it for aligning either the zenith or the azimuth of a cartridge. I know a DVM could be used for azimuth, but based on what I've read so far it looks like I should be able to do both on a scope. The problem is that I've found conflicting information online for what sorts of signals to use - and how to set up the scope for them. Here's what I think needs to be done for each:
For azimuth it seems like there are two approaches. I could use single channel sine wave tracks (like on the Ultimate test record) and set up the scope so that Channel 1 is looking at one signal channel and Channel 2 the other. In this scenario scope Ch.1 will be maximized and Ch.2 will be near zero (hopefully) for one test track, and the opposite for the other. The idea would be to adjust cart azimuth to try and get them to be about the same, with the goal being to keep the non-signal channel as close to zero Vrms as possible. A voltage to decibel conversion chart would be used to put the channel balance result in terms of dB.
The second way for azimuth is apparently to use a L-R track, but it's not clear to me if I do it that way, what to do with the scope. Do I add the two channels together and adjust the azimuth until it goes to zero? Not sure.
For zenith, it seems like the way to do that is to use a L+R equal amplitude (mono) track and look at both signals on the scope. The goal for this is to adjust zenith so that the two signal are time aligned.
If anyone has done this using a scope, I'd appreciate any confirmations or corrections.
Follow Ups:
Given the extremely imperfect medium of the vinyl LP, with its inevitable warps, however minute, I just wonder how many times perfect stylus azimuth is achieved in practice. People sound like they're just looking for one more excuse to play with their test gear in this quest for perfect stylus orientation.
I have to use my eyes when I use an alignment protractor. I don't see the point of using more precise instruments to establish azimuth. The turntable and the LP have distinctly limited potential as playback technology, and this imposes practical limits on stylus adjustment as well.
People knew this when I was in college. I wonder what the heck happened.
----------------------------
"Use adjectives instead of numbers, and you'll never be wrong again." ~ The Wizard of Audio Oz
Please lend me some of your magical thoughts so I can think vintage is wonderful, too.
It's not possible to align zenith using an oscilloscope. For that you need a good arc protractor to get the most accurate results. However, it is possible to set azimuth using an oscilloscope. Check out my previous post on the subject at the link below.
Another excellent tool for azimuth adjustment is the Fozgometer .
Okay. It looks like I was on the right track for azimuth. I do have a storage scope so that will help. I thought zenith could be done. IIUC, zenith is the measure of the rotation of the stylus with respect to the groove, when looking straight down from the top of the cartridge body.
http://www.theanalogdept.com/2_pt_align.htm
I thought that if zenith were perfectly set, when looking at the Left and Right channel traces from a monophonic sine wave signal you'd see them perfectly in phase. If the zenith was off you'd see the sine wave from one channel leading or trailing the other.
I normally use either a DB Systems alignment tool or the Hoffman DIY arc alignment tool, but I've been curious to see whether I could do better using a scope.
Whilst in principle, using phase measurement of a mono signal could be used to determine zenith, and indeed I have toyed with this idea myself...Unless you had a tangential tracking arm and was confident in a perfect tangential relationship, with a pivoted arm checking zenith would require a considerable number of repeat measurements to determine reliably, given the possibility of cantilever skew either dynamically during play due to the effect of reaction forces on the cantilever due to eccentric grooves/off-centred records or a fixed skew due to a manufacturing defect. Secondly, the wow induced frequency shifts would result in a degree of uncertainty on the measured phase error.
It is my understanding from reading about Soundsmith (who take great pride in only providing the highest quality of alignment, that zenith errors are rather more common than one would like to think!
Certainly this is the point behind square or rectangular shanks for the stylus in aiding consistency in alignment.
Thereafter, the mounting method either results in precise SRA alignment at the expense of tip azimuth accuracy, or the other way around according to an article I read interviewing J Carr of Lyra.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
I haven't tried this, but it should be easy to determine whether or not interchannel phase shift can even be detected when altering zenith on-the-fly while observing the oscilloscope phase measurement. This would be fairly easy to do with an SME V tonearm because overhang can be changed on-the-fly while playing a test record. As I said, I haven't tried this, but maybe I will try it one of these days just to find out if it's possible.
Best regards,
John Elison
You'd probably want two locked grooves for zenith, one at each null point. Otherwise, I suppose you could digitize the output of a test record as is passes through the null point. Either way, you'd probably need a special record with a HF tone at those two points.
I'll be interested to find out what you discover regarding using an oscilloscope for zenith alignment. My experiments didn't reveal any correlation between zenith alignment and inter-channel phase, but I didn't spend a lot of time on it. Therefore, it will be interesting to see what you come up with.
Thanks,
John Elison
I would agree given the difficulty in separating the effect of zenith errors from cantilever skew.
As for tip azimuth, the audibility very much depends on the tip design (especially bearing radius / contact design) and the magnitude of the error.
One of my Denon DL301/II cartridges has a tip azimuth of 1.4 degrees. This is not (of itself) audible given the tip profile. We've speculated on this in the past, and I agree that it is probably a variation on a "hyperelliptical" or somesuch line contact tip. Getting the electrical azimuth correct is more important and is what I focus on with this cartridge and my DL304.
However, for other simpler tips such as a conventional elliptical, tip azimuth is very audible to me and results in noticeable increase in sibilance and image smear.
Same with radical line contact tips with very large bearing radii eg Soundsmith OLC or VdH. There is a limit with these as to how much you can rotate them before they touch a portion of the groove that results in them not fitting in the groove as intended! The OLC sounds absolutely awful if you have a gross azimuth error with terrible sibilance and distortion. Once correctly aligned it is a superb sounding tip.
If one considers a simple elliptical cut (front and back face cuts), then the resultant footprint on the groove wall is an inverted pear shape. If the tip is rotated, then the contact area will gradually increase in one wall with the net effect that the scanning loss will increase in the channel with the larger scanning radius.
For a parabolic line contact stylus utilising a cut such that the bearing radius is in line with the shank/tip axis, small errors are less detectable since the line may be sufficiently long that the (possible change in the length of the contact line) does not audibly affect the frequency response or frictional force. However, it will be apparent from a thought-experiment that the contact area will gradually decrease on one wall resulting in possible differences in wear. On the other hand, a parabolic cut such as a Shibata cut results in a curved contact line which is forward of the central shank/tip azis and it will be readily seen that tip azimuth will have a profound effect on IMD given the change in effective SRA on each wall and the induced zenith error.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
my problem is the displays on an o'scope aren't stable due to the test record being off center, minor record warps, etc. so there's somewhat limited resolution. Do you have a storage scope?Useful for VTF & anti-skating to see mis-tracking on each channel. For azimuth & VTA you could also use in XY mode to compare the channels for amplitude and phase and make your adjustments to align for symmetry. For measuring cross-talk drive channel A and measure output in B and vice versa and adjust to minimize both as you have noted.
I'm thinking Adjust + is easier and more accurate but haven't tried it. Let's see what others say.
Edits: 11/29/15
Edits: 12/01/15
Here are a few of my previous posts relative to my experience with azimuth. One thing I discovered is that no two test records will provide the same azimuth adjustment results regardless of whether you use crosstalk phase or crosstalk amplitude to adjust azimuth. The bottom line from my experience is that setting the cartridge level with the record playing surface is probably just as good as using a test record to painstakingly adjust azimuth. Of course, as always, YMMV. It's certainly possible your ears are better than mine.
Edits: 11/30/15
Went back and looked at ALL of these. Some really great stuff here including your HW inquiries. A lot of work too. The part about the different test record results is perplexing.
Many Thanks.
> The part about the different test record results is perplexing.
I think this shows that different cutting lathes have slightly different azimuth. That's why I think it might be just as prudent to set your cartridge level with the playing surface and be done with it. That's what I do, anyway.
Good luck,
John Elison
My Tektronix TDS-2002 digital oscilloscope has a feature that compensates for the unstable display when looking at phono cartridge signals. Firstly, it is important to use AC coupling instead of DC coupling. Secondly, you can engage the "sweep averaging" function to eliminate random noise. This will stabilize the display that would otherwise bounce around from record warps.
Here are some screen shots showing how stable the signals are when using the "sweep averaging" function. I was measuring azimuth.
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