[WGH]

I was inspired to check out the calculated distortion numbers of the arm on my harman/kardon T55C turntable using the Baerwald/Loefgren "B" Excel curve generator that Wayner mentioned in the Rega thread and discovered some interesting numbers.

I have always set up the table based on the information in the owners manual:
Effective Length: 216mm
Offset Angle: 25.5°
Stylus Overhang: 18mm

The Baerwald graph using these numbers looks like this:




Changing the overhang to 19mm results in this graph with null points at 64.7mm and 121.3mm:




So did harman/kardon get it wrong?
I realigned the cartridge using the 19mm overhang and will give it a listen over the next week.

wgh

[Wayner]

I had a T25 that I thought had a weird tonearm length. I don't know what they were thinking either. I go with your later version as it's obviously better numbers.

Wayner

[WGH]

The 19 mm overhang is working out very nicely and some interesting things happened.

When I installed the FT-3 teflon caps in the Cornet2 there was a nice jump in detail but along with that came accented ticks and record noise. The added detail did not balance well with the bass so the overall result was a slightly tipped up sound, which could be corrected with a slight tweak of the bass tone control. I figured it was the nature of the Russian caps, but I was wrong.

A cartridge re-alignment after changing the overhang changed the overall presentation completely. Gone is the hyper detail and the bass is back. The highs are still present, the cartridge's sound is more balanced, bass is tight and tuneful, and the music has a more relaxed presentation like I'm back a few rows back instead of front row right in front of the trumpet section.

Another benefit of the adjustment is the background noise went down to zero. No record noise, nada. I'm listening for it, you know, that background noise that lets you know you are playing vinyl, it's just gone. Perhaps the needle is not as worn where it is contacting the record, or I happened to align the Fritz Gyger S line contact stylus perfectly but my turntable is now in harmony with the universe and music has never sounded better.

It is amazing how such a slight adjustment can change the nature of what's heard and may account for the wide differences in opinion regarding cartridges and phono pre-amps.

Wayne   

[Wayner]

Good deal, Wayne.

I think cartridge alignment is one of the most important set ups in vinyl. Improper postions and offset angles will have the stylus sounding like fingernails on the chalk board. It's kind of like going down the shoot crooked, if you will ( I was going to use a farm analogy). If you play with the offset angle on the Excel program, you will find the distortion curves go wild with even slight amounts. That is really funny because the offset angle is the hardest to set, correctly and accurately.

Wayner

[Wayner]

Wayne,

Recheck your math. I think you may have made a slight error. If you add 1mm to the overhang, you will have to add 1mm to the effective overall lenght, as you did not move your pivot 1mm closer to the table spindle. The good news is, the curve is even better!

Effective tonearm length: 217mm
Offset angle: 25.5 degrees
overhang: 19mm

Wayner

[WGH]

Thanks for the tip Wayner but I'm ahead of you on this one and have been using the new arm length in my calculations. I have gone one better and physically measured the spindle to pivot distance and with the 19mm overhang the total arm length is 219mm or exactly 8 5/8".

Entering the 219mm arm length into the spreadsheet results in a perfect Baerwald alignment.



I just had an optometrist do an exam because I busted up my glasses and he said I have better than 20/20 vision close up without my glasses and setting the offset angle is still mostly just guessing.

I'm surprised no one has invented a jig to put the cartridge in, adjust overhang and offset angle with repeatable micrometer settings, tighten the headshell screws and call it done.

Wayne

[Blackmore]

I've always wondered the same thing about a jig.  Shure had one for the V15 Type V and it worked great.  Just pop out the stylus, drop the body into the jig and align it a two points and you were done.  I've asked other cartridge reps about that and they didn't seem to know about the Shure system and didn't seem to think it would work out.  I know it would be rather arm specific, but the Shure even let you see the amount of error on one of the two alignment points if your arm geometry didn't match their alignment scheme.  Pretty slick system that did work well for the V15. 

[Wayner]

WGH,

This is exactly the direction you needed to go (confirm spindle to platter spindle spacing). And I checked the alignment card I made for my T25 and it is 8 5/8", too. Now, as I've seen you do with the Excel calculator, you can "play with the numbers" and zero in on a good curve. That's what it is all about.

Blackmore,

Yes, I wish there was a one jig, fits all tool, but as you can probably surmise, there are many, many different tonearm/spindle/offset angle designs between manufactureres and even between models. Believe me, I'm working on it. I've got CAD software and have been doing some designing. I'm not there yet.

Wayner

[get.amped]

I'm a complete newb here, but my turntable (salvaged from divorce) is my original T25 from about 1983. It's got a new belt and I replaced the Ortofon OM 5E cartridge. Everything works well but the cartridge is *obviously* not positioned correctly. I don't have the tracking angle gauge that came with it, so any help or advice you may have about how to properly set the overhang and tracking angle is greatly appreciated.

When you mention 8 5/8" total length, what are the endpoints - the tip of the stylus and the pivot of the arm?

And how is the 25.5 degree angle measured? The head has a fixed angle with respect to the arm and the cartridge is somewhat adjustable within the head. Am I looking at the intersection of the two lines that bisect the arm and the cartridge?

Thanks again for any suggestions.

Jim

[WGH]

Hi get.amped,

I'll get you started to audio nirvana with a link:

The Vinyl Engine library has the manuals for your T25 table. That will get you started.
http://www.vinylengine.com

The Tracking Angle Gauge is not included with the T25 owner's manual but it is included with the T35 owner's manual so download that one too. Print it out full scale.

You will notice an arrow pointing to the stylus tip flap line, the line is 18mm from the center of the spindle, if you want to try the 19mm overhang cut the flap line 1mm further from the spindle.

Don't try to cut an accurate spindle hole, with a very fine sharp blade cut two lines that just touch the outside edges of the spindle as shown below.

This image should print out full scale too.

When the cartridge lines up with both the 66mm and 120mm parallel lines on the gauge you will be at 25.258 degrees. I am deviating ever so slightly from the 25.5 degrees, but I have no way to measure .242 degrees to be sure.

Set the overhang with the flap first then rotate the rotate the gauge 180 degrees and align the cartridge. The owner's manual has pictures. Yes, the stylus tip to the center of the pivot with a 19mm overhang is 8 5/8".

W.

[Wayner]

The sad thing is that the offset angle is the most critical and the hardest to set. Off by .2 degrees and the baerwald curve starts to go to hell in a hurry. I'm still trying to design a system that will improve the accuracy of this, but, well, it's a bi-ch. Unfortunately, Wayne's protractor's 2 sets of lines haven't taken into account the 1mm increase in overhang so those lines in those positions will not match the new 19 mm position.

Wayner

[orthobiz]

Is it possible to accurately use these protractors to within 1mm accuracy? Seems almost impossible!

Paul

[get.amped]

Wayne,

Just wanted to express my gratitude for your help. I was able to get the tracking gauge, print it on some heavy stock and cut it out with the tab for measuring the overhang. Got to say it is a supreme pain trying to get the cartridge properly lined up but well worth the effort. Amazing how good my 30 year old vinyl sounds! And who knew my T25 would stand the test of time?

I guess now it's time to check out the other (cheap) tweaks I can make to the table. Certainly makes some sense to plasticlay it and I like the hockey puck as record clamp idea (nice one Wayner!).

Now it's time to rock on!

Jim

[WGH]

get.amped,

Glad to help out. It looks like your table does not have any suspension so the more plasticlay you can pack in the better.

The biggest improvement I have found was removing the transformer and making an outboard power supply.
Here is some info about the ps mod I did on my table:
http://www.wghwoodworking.com/harman_kardon/h-k.htm

Wayne

[WGH]

Here is the Mouser parts list for the Harman/Kardon power supply mod, I picked up the fuse and fuse holder at Radio Shack: