Fosgometer???

[Grainger49]

Edit: I am not taking a bad attitude about this, just a cheap and technical outlook.

I have seen ads and some information on the Fosgometer.  According to one seller, for $250 it "perfectly aligns your cartridge's azimuth for optimum sound! It measures channel separation, channel balance, and signal direction quickly and accurately."

I'm pretty sure it doesn't set the azimuth (being picky here) but tells you if you set it right.  The channel separation and channel balance are a result of proper azimuth.  Channel balance is also a function of the cartridge itself as well as being affected by azimuth.

I don't know what they mean by "...and signal direction...."  Does anyone know?

Does anyone have any first hand information on this device?  I am interested in the principles it works on.

Thanks in advance.

 

[johnsonad]

Look at some of the posts over on vinyl asylum.  There are quite a few threads on it if you haven't read them already.  I'm awaiting the Soundsmith Cartright...

 

[Grainger49]

Actually the Vinyl Engine gave no information about the Fozgometer other than a couple of posters saying they used it.

What I am looking for is to determine how it is used.  What is played through the cartridge and how does it allow for a better setup of your cartridge.

 

[johnsonad]

Vinyl Asylum, not vinyl engine.  They have a decent search function too.

 

[Grainger49]

D'Oh!

 

[Grainger49]

I finally got the Vinyl Asylum to load.  No one there seems to know the theory of operation for the Fozgometer.  Many say it works, my buddy has one and it is magic, and much to that effect.

So I posted asking for how it works and got, "it works," "my buddy has one and it is awesome!"

I downloaded the (poorly written) manual from the importer.  It seems that the meter will measure output in a range of 40 dB (or db as according to the manual, but with no reference to the voltage level for 0dB, completely necessary for evaluating).  If you feed it a right channel only input it measures the cartridge output and indicates right channel.  You do the same with the left and it measures the cartridge output and indicates left channel.  Then you rotate the cartridge CW or CCW depending on which was a higher output, repeat the measurements, you either match levels or minimize the difference between the levels.

This assumes that the cartridge has perfectly matched channel outputs.  It also assumes the tracks that are mono left and mono right are perfectly matched.

I think my oscilloscope test would be faster and more direct.  Swap the wires on one channel of your cartridge and sum the two outputs with a Y-Adapter.  Feed that into a single oscilloscope channel.  If the two channels are balanced then you get nothing.  Adjust azimuth and read again.  This method matches the outputs or minimizes the differences between them.

The drawback with my method versus the Fozgometer is that you don't know which way to adjust azimuth.  But I'm convinced it is faster than the Fozgometer.  Don't forget to swap the cartridge leads back after adjusting the cartridge.

 

[johnsonad]

Didn't Fremer write something about it in Stereophile?  I'm pretty sure John Ellison wrote something as to how it works on the asylum at one point.  There has been quite a few threads on the thing.  People say it works but for the price, doesn't offer me enough to purchase it. 

 

[Grainger49]

Edited:

Yes, Fremer raved over it.

I contacted John Elison through the Asylum as well as reading all his posts about the Fozgometer.  John has a method of adjusting azimuth that compares full range crosstalk using a digital recorder and computer analysis of the output of each channel.  When the right and left channels' crosstalk are closest in magnitude the azimuth is optimized.  My earlier suggested method using an oscilloscope doesn't measure crosstalk, just balance.

The Fozgometer manual describes putting in a mono (lateral) signal to both inputs and a zero reading indicating a perfect balance.  This means that the Fozgometer inverts one input and then adds them together (exactly what I suggested with the oscilloscope).  So when the azimuth measurements are made an imbalance from channel to channel affects the measurement.  

The same can be said for my oscilloscope method described above.  But . . .   I could use both channels, uncalibrate the highest level channel and match the magnitudes then invert and add to determine a perfect match for adjusting azimuth.

Yup, that will work and save over $300 - Fozgometer +LP +Shipping +Tax.

 

[johnsonad]

Too much of a pain.  I've considered doing what John does but find it a pain in the butt.  The Adjust + system will do what he does automatic but is expensive.  I hope the Cartright will do more but is still expensive.

 

[Grainger49]

If you have a scope the above method, needs some fleshing out, will do the exact job as the Fozgometer but in one step.  I already have a Hi-Fi News test LP and bought a Cardas test LP just because it has Stan Ricker on the cover, nice guy!  The Cardas LP has captive grooves (they don't spiral to the next cut) that can be used to perform these tests.  The captive grooves are handy, you don't run out of groove when adjusting.

 

[johnsonad]

Have fun with that!   More effort than I want to put into setting up a cart.  I'm willing to pay for convenience as long as it does an outstanding job.

 

[Grainger49]

I used to sell stereos from the late 60s to the late 70s.  I set up hundreds of cartridges.  In those days no one ever set azimuth with more than visual accuracy.  However, in those days only a few cartridge shells had side to side adjustments.  The goal was to align the bottom of a cartridge parallel to the album.  With all other arms, what you got from your cartridge manufacturer was what you ended up with.

One thing that is not clear is how a correct azimuth can be measured (excepting the digital photograph and special software used by M. Fremer).  The Fozgometer measures channel balance only.  That much is obvious from the instructions.  So does my scope method.  There is another theory, John Elison's below, that crosstalk is the key to proper azimuth.

I have been emailing back and forth with John Elison on the Vinyl Asylum and have become convinced the invert and add method will not give crosstalk, it indicates the cartridge's balance.  John's method assumes that the best azimuth is achieved with minimum crosstalk, it is much harder to measure and I can't figure a way to do it on my scope.

The" invert and add" scope method using one scope channel is ideal for setting anti-skate.  When you get the minimum output (best channel to channel balance) you have anti-skate optimized.  

I guess I will live with my failing eyes and physical measurements for adjusting azimuth now.  

A close reading of the Fozgometer instructions will reveal that their azimuth adjustment gives as close to a balanced output of both channels through adjusting azimuth.  This is exactly what my invert and add method does without my spending $300.  

 

[Paul Joppa]

Do I understand this correctly? You can adjust channel balance by changing azimuth or by changing anti-skate? So it is possible (indeed probable) that both can be far off and still produce apparent channel balance. Not to mention that channel imbalance can be due to a small difference in the magnet strength between the two sides, so that even if (for example) azimuth is perfect, adjusting anti-skate to produce balance would not give optimum anti-skate.

 

[Grainger49]

Yes to all.  That is from my readings (not the internet, you find anything there).  The Fozgometer manual indicates balanced output is indicative of proper azimuth:

Fozgometer Manual at Musical Surroundings

The Vinyl Engine is where I read that anti-skate affects the balance, I will research that and post a link.

Do you have any facts or help?

Do you know of an easy way to measure crosstalk?

 

[Paul Joppa]

I can't think of a good crosstalk measurement that does not involve a special recording. Easy way is one channel only. More fun is uncorrelated noise in each channel, and run a cross-correlation (or better, coherence) calculation between the channels. Most FFT machines can do cross-correlations. That should give you crosstalk as a function of frequency.

No, I don't have an FFT machine. Well, I do have an ancient Nicolet 660A that may or may not still work but I've never found a manual for it ...

 

[Grainger49]

Paul,

Thanks for entering the fray with some scientific information.

I'm not dissatisfied with the sound of my cartridge/arm/table.  I was just looking for better and more scientific methods for setting up any cartridge.  The $300 for the Fozgometer and $900 for the Cartright (does a lot more for 3 times the price) doesn't fit my famous Cheapskate reputation.  I got the scope as salvage.  It works perfectly.  I learned how to use one in school and remember at least 60% of what I learned.  I was hoping that I could use it for this.  As I said above I will rely on my failing eyes and measuring the headshell.  My arm allows me to make pretty good measurements to see that the headshell/cartridge is level.

What do you do?  I'll bet not to worry about it and enjoy the music.

 

[Paul Joppa]

...
What do you do?  I'll bet not worry about it and enjoy the music.

Yes, that's pretty much my approach. Doc B is much more careful. I do fuss with VTA, since I seem to hear big differences, and many cartridges have excess VTA when they are level to the record surface.

 

[Grainger49]

So you suggest dropping the back of the cartridge?  Any clues except the sound to tweaking it in?

 

[Paul Joppa]

I start with the shaft 15 degrees to the record surface (if it can get that low), then experiment. You really want the diamond tip to the fulcrum at 15 degrees, but that's just too hard to see. Usually you need a compromise - a greater angle if you have any records that are not completely and perfectly flat!

 

[Grainger49]

Paul,

I can take a picture of the stylus/cantilever but measuring is out of the question with the clearances I have with my arm.

My records are pretty flat with the VPI record clamp but I have varying thicknesses.  I have a James Taylor that is so thin I thought I could see through it (it plays very well) and of course have a smattering of the 180g and 200g LPs that are like putting on thick pancakes.  That changes the VTA.  And maybe one of the reasons that the 200g LPs sound good is the back of the cartridge is dropped changing the VTA?