CD-4 adjustement

[Quadro-Action]

Hwllo - here I am again. Sometimes I like more to read as to write - especially by themes of opinions.
For CD-4 I would say, that I know quit a lot about technic and handling (unrestrained self-o+praise). So all sai , that my CD-4 reproduction is absolut clear and without distortion and big channel separation. Why more? After a few monthes I have new built in my Technics oscilloscope. So one can see also well the channel separation on the cross in the show-field by playing the warble-ton. Best results for a well or perfect channel separation are given of course, when (for example for rigt-front) the bar graph goes from the center of the show-field far to the right (front) edge. The other graph ( for rear)should not to see ( stay in the center-point or only a very little in direction behind this. For left by my demodulator (SH-400 - beneth others) it shows such a perfect situation. The situation for right shows a (only) less satisfying situation. The graph for right back shows a little idea outside the center point. And the needle in the adjustment field in the SH-400 shows not 30 dB, but around 28. This is alltogether very well, but for right not ideal.
So I think, the reason may be the needle of the pick up. I think, that it is very important, that the both "corners" of the special cuts must be perfect crossways in the groove. If not, one should turn the pick up a little. But the controling of the exactly crossway mounting of the tip needs a microscope.
As I said, I am in practice very satisfying with my CD-4 reproduction, but one likes to have the absolute perfection. So I ask other connoisseurs of CD-4 tracking here, if they can agree or have further advices.
Because it is a technical theme, it is sometimes a little hard for non americans to find the right words, but I think, you will understand, what I mean.

 

[Quadro-Action]

Because there is no an answer, it seems, that most of our worker with CD-4 don't go in those details, as I sometimes do. My mail was therfore only an attempt, to find those freaks here, which may have experiences with such adjustemens themes of the pick up and the needle. But as I said before, I have very well results with my CD-4 reproduction and when I find time enough, I may inquire self the rest. If this may relevant for other CD-4 fans, I can mail about theme that again.
Dietrich

 

[sspsandy]

My belief is that you are referring to needle azimuth alignment. This invilves adjustments to get the needle to track exactly in the center of the groove. Some turntables allow you to adjust this, on others you need to use shims on the screws holding the cartridge to the head. There was a tool called the geodisc which came with mobile Fidelity box sets, that I think measured the azimuth alignment. I'm sure that other tools exist, you need to check out high end suppliers like Music Direct. I never bothered with the tool. I have a Harman Kardon ST-7 linear turntable that allows you to adjust the alignment. I just hold a magnifier up to the needle and keep moving it side to side until it looks exactly centered. Then check it on the audio scope. Good luck.

 

[Quadro-Action]

Hello Sandy, thank you for your message to the adjustment problem. The error of a correct position of the needle in vertical hinsight is also known by me. I have seen in the past also difficult divergences and a record player as you have named is well for an easy working to correct this problem. But I mean especially a mistake by mounting the needle looking from the grooves ground up to the needel or above to the tip. Than the cut must be exactly crossways. Also there is seen often a some incorrect, because diagonal mounting. This means, that both sides of the grooves are not "scanned" in the same time, which is need for a correct or high fidelity reproduction. For CD-4 and the demodulator this can mean varying results by the channel sepration left or right.
Because I have already a microscope, I will mount soon - when I find time enough - two lights left and right. Than I can see exactly the needle from top and if the mounting is correct with 90° crossways to the cantilever. When there would be differences in hinsight of diagonal, then I will test, if a corresponding little turn of the whole pick up will have results for a perfect trecking and adjustement of CD-4 demodulators for equal channel separation left and right. So far my remarks to the problem by a non correct mounting of the diamant needle and the removal of this mistake or fault. May be later more about this.

Dietrich

 

[sspsandy]

Deitrich, certain turntables have better alignment with regards to the needle and cartridge. I have an H.H. Scott PS59 straight arm turntable that takes a P mount cartridge. It tracks CD-4 albums perfectly, in fact after I got it I used it exclusively for CD-4 for this reason. They are quite inexpensive when they show up on eBay, there is a PS69 that is higher end, they also made a tangential linear tracking turntable. They are also all belt drive units, which I prefer. They have the strobe tuning for speed, and it is one of the most accurate I have ever found, set it once and it stays right on without any variation.

By the way, on eBay US is a Pioneer PL1000 new in the box. It is currently $200.00, but what a nice unit, comes with all the original goodies:

http://cgi.ebay.com/PIONEER-PL-L100...ryZ48649QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[Quadro-Action]

Sandy, tips are always wellcome and you are so kindly to do that. But at first - I have an audible perfect CD-4 reproduction and second I have 3 turntables: The Pioneer PL-L 1000 and 800 with linear or tangential tracking and the demodulators JVC 10 S, 1000 and Technics SH-400. But there are only 1 or 2 % for an absolute measurable perfection. So far I know, no turntable in the world has a set-up for an turning adjustement of the pick up in the horizontally direction. But before the turning begins, one must see through a microscope, if or how much the needle is mounted twisty or screwy on the cantilever. I was only interested, if one here was already
searching in this hinsight. I think no (is by a well CD-4 reproduction generally also not necessary). But I am interested, if an analog measurement (on the display by demodulator or oscilloscope) can be made in such perfection, as it will be true by digital . So I must do now the "dangerous" self-experiment by working with my microscope in the next time. If the result is interesting, I may write another message about this.

Dietrich

 

[sspsandy]

Here is the Mobile Fidelity Geodisc I mentioned, they still make them:

http://www.musicdirect.com/products/detail.asp?sku=AMFSLGEO-DISC

Just for laughs I posted this cartridge alignment tool, it is only for pivoted arms and is pricey, but cool looking:

http://www.musicdirect.com/products/detail.asp?sku=ACLAAG

And this protractor is supposed to do the job:

http://www.musicdirect.com/products/detail.asp?sku=ADBSPROT

These items are all from Music Direct.

Here's a cheaper tool I found on the web, looks like it will work (this appears to be the most accepted tool for the job):

http://www.turntablebasics.com/align.html

And another high end model (cool to look at):

http://www.needledoctor.com/Pro-Ject-Allign-it-Cartridge-Allignment-Tool?sc=7&category=951

And here is a primer on doing the tweaks:

http://www.audiophilia.com/features/cartridge_setup.htm

 

[Quadro-Action]

Well to look to all the helping stencils. Those are already wellknown for me. But all this stencils will only help to find the right position of the needle (and the cartridge too), but with this it is not possible to find out something about a correct mounting of the needle and their cut directions on the cantilever. Therefore one must look through a microscope or test with special test tones. So I am working in this ways - beneth the other points of a correct justage of the whole cartridge.

Dietrich

 

[sspsandy]

In the adjustment tips that I linked to it talks about using a mono lp and a special cable hookup to determine the balace between the two side of the record groove that the needle is tracking. Also the mirror with the calibration marks with help in determining the correct alignment of the needle.

 

[The Quadfather]

Hey Sandy:
The vector misalignment you speak of will affect the left/right separation. For CD-4 use, it is important to get good left to right separation to avoid one subcarrier from influencing the other channel's demodulator. Also you want to decrease abnormal record wear. Of course, perfection is not a bad thing in audio. You do the best you can with the mechanics of the turntable, but there is cartridge crosstalk to contend with also. The SH400 has a crosstalk cancellor to contend with these irregularities. With it, there came a test record which should have some tracks that have signal one channel only. I do not have one, so I do not know if the signal consists of subcarrier, audio or both. I have just aquired an SH400 and as a result I will be looking for the record. It seems to me that the record could be used not only to set up the demod's cancellation circuits but also to test how the turntable and cartridge are performing as well. (oops, I just made the ebay price on the record go up) Connect the turntable to a dual trace oscilloscope and watch both channels at once. Play the crosstalk cancellor setup tracks. you should see a signal in one channel only. Which one depends on the track being played. Any signal in the other channel represents either crosstalk or vector alignment error. After the vector mis-alignment is minimized as much as possible, the rest is crosstalk. That should be handled with the crosstalk cancellation circuits in the SH400 demod. Note that vector misalignment could be handled by the crosstalk cancellor circuit, but you will do a better job if you minimize it to begin with at the turntable. Also, if you have an Audionics Space and Image Composer, the phono tilt circuits are the same thing as the crosstalk cancellor in the demod. so if you use the demod as a preamp for SQ play, turn off the phono tilt circuit. The demod is already doing that job. Happy listening!

The Quadfather