Tracking error distortion audibility

Dear Feathed: I can't understand your last post and maybe I'm wrong but making a quick revision on my original tonearm jigs to mount the tonearm in a TT in all cases that distance determine the exactly position of the tonearm in the TT. Am I missing something here?, please explain about.

Regards and enjoy the music.
Raul.

For this discussion ignore the arc protractors. Universal protractors work for various spindle to mounting hole distances correct. If you have slotted headshell mounting holes you can adjust cartridge angle and overhang correct. If you drill your mounting board hole further from the spindle than manufacturers specs, simpling slide the cartridge closer to the end of the tonearm and adjust angle accordingly. You get the exact equivalent of a longer effective length tonearm. You obviously need to allow for slight differences in mounting hole to stylus geo in case you change cartridges but they vary only slightly. Brooks Burdan (sp) explained this to me 20 some years ago. It's so simple I just assumed everyone did this. I've never given it a second thought.

Gosh Feathed,

You initiated this thread asking if any of us find substantially improved tracing in the area around the null points. Well, for me, the answer is no. Distortion does not noticeably increase as the stylus departs from the null points.

So, let me get this straight. You very possibly have a sub-optimal setup, or at a minimum should find a means of eliminating this from consideration. Still, you have categorically decided that debating the choice of tools to verify this is not a topic for conversation.

No one drills the arm board where the tonearm maker specifies do they?

Why would a dealer not mount the arm according to the manufacturer's spec? I can think of two reasons: (a) Incompetence, and (b) a conscious decision based on selection of an alternate alignment.

As an example of (b), I mount both the Dynavector DV-507 as well as the Artisan tonearm to Baerwaald and not to the manufacturer's specified alignment. Of course, I communicate this to my customers as well as my reasons for doing so. Now, with a Galibier, this pivot to spindle distance is easily changed at any time due to the articulated armboard, but I do this for individuals with fixed mount turntables as well.

My reasons are that most people do not have a protractor for other than Baerwaald or Loefgren, so I derive the Baerwaald (typically) pivot to spindle distance appropriate to the effective length of the tonearm.

If you have slotted mounting holes one should always mount your arm further from the spindle so as the maximize effective length and minimize tracking error. I've not read about this but I just assumed everyone did that.

Not so ...

(a) the increase in effective length is trivial as is the reduction in distortion. You can verify this by plugging the numbers into the Ellison spreadsheet

(b) even if there were a reduction in distortion, you run the risk of compromising cartridge mounting surface's contact with the headshell and have problems with energy transfer - not a good tradeoff.

(c) assuming a fixed mount turntable/armboard, why paint yourself into a corner the next time you mount a cartridge with a "short" cantilever one whose stylus is closer to the cartridge bolts (yielding a shorter effective length) that might not allow you to achieve the alignment you intend?

You are technically correct, - that you can establish your favorite geometry around any effective length (and therefore pivot to spindle distance) as long as you have enough headshell slot length to achieve the geometry you're after. Of course, with a fixed mount turntable you've hopefully selected a pivot to spindle distance that will allow you to achieve this.

I suspect you misunderstood Brooks Berdan's intent when he explained this to you. I'm sure he was arguing that small mounting errors could be compensated for at the headshell, which is of course true. I'd have great difficulty believing that someone with his fine reputation would argue in favor of stretching the effective length of a tonearm by some 3-4 mm to reduce distortion (see points above).

Regarding alignment tools that require input of pivot to spindle length, I can't accurately measure that because of my arm's pivot design.

The MMT was made by Jelco - a company I'm quite familiar with. The bearing tower's center is fairly easy to find on these arms: http://www.vinylengine.com/library/sumiko/premier-mmt.shtml.

Assuming you want to draw an arc protractor for your arm (I maintain faith that I can "reach" you), you can back your way into your effective length using the p-s that you measured. Using the Ellison spreadsheet - set your precision level to 3 or 4 decimal places and plug in effective lengths until you arrive at the pivot to spindle distance you're after.

Again, if you play with an arc protractor printed on paper, you can make up protractors that bracket around this effective length - to compensate for a measuring error on your part. One of them will be "right". Given the opportunity to produce an arc protractor on a laser printer for any effective length, why would you not go through the exercise of trying this?

What about alignment of the stylus to the cantilever? A misaligned stylus renders all methods discussed above (except maybe listening) null and void. They are utterly and completely useless.

Bingo! You have made yet a further argument in favor of an arc protractor. With a two point protractor, you're trying to line up the cantilever at the two null points. If you try to deviate from a lined up cantilever with slight clockwise and counterclockwise rotations, you'll go crazy trying to keep it straight in your head.

With an arc protractor you can vary your offset angle in both directions, knowing that you've maintained the correct effective length because you have the arc for verification. In other words, you can separate the variable of offset angle from overhang.

You have just (again) argued in favor of using an arc protractor.

Cheers,
Thom @ Galibier

Thom @ Galibier,
WOW!
I'm sure any competent person would not make the errors you cite above as reasons to not deviate from manufacturers set-up, certainly not Brooks. I understood him to mean increasing effective arm length with slotted head shell models is a trick he uses with no downside. I assumed it was commonly used by experience turntable techs. I am sorry if I misunderstood but it seemed pretty clear to me what he meant. You might have understood something different but I don't recall you being present during our conversation although I might be mistaken as you indicate you heard it with great clarity "I'm sure he was arguing.....".
I am glad even happy that you like your protractor. What is your reference that verifies your protractor's set-up? What do you use to verify the stylus is perfectly aligned to the cantilever? Your protractor?

Hi Feathed,

I'm sure any competent person would not make the errors you cite above

Well, that leaves the other possibility - that they are misinformed. It's no crime, and I surely have a lot to learn as well as the next fellow. Frankly, this is one reason I post on this forum. No one can know everything, and collectively, we are all better for the exchange.

OK, I'll do some work for you and for Brooks. Based on the Ellison spreadsheet, here are the distortion numbers for 239mm and 243 effective lengths:

Effective length = 239mm:

at 57mm = 1.16%
at 146mm = .62%

Effective length = 243mm:

at 57mm = 1.14%
at 146mm = .61%

As far as references are concerned, I primarily use the two appendages on the side of my head along with all of the other individuals who,like myself thought that years of working with two point protractors yielded as good results as you could reasonably expect to achieve. I don't know of a single individual in my listening circle who still has this opinion.

I'm going to be in So. Cal in a couple of weeks' time, and had planned on visiting Brooks. This thread gives me one more topic of conversation. Brooks is someone I've admired for quite some time. If indeed your memory of your conversation with him is accurate, then I'll take the opportunity to set him straight.

Cheers,
Thom @ Galibier