Didn't reliaze azimuth is that important - pics

[Sambob2]

Would this Fozgometer be analogous to where you use both left and right outputs from a tape machine and plug them into a oscilloscope and adjust the head until the tone in each channel is in phase? (showing a closed diagonal line across the scope screen). An out of phase adjusted head would show an open loop on the scope...more open the more out of phase the head is. I'm thinking the answer is no, because you can't really adjust phase on a cartridge as you would on a tape machine head, but you can adjust the balance of the playback signal off the record groove. So how does this Fozgometer work, what's the theory? I can imagine that if the cartridge is severly off (in azimuth) that one channel will be favored and the other not. In other words, one set of coils within the cartridge would receive a different excursion than the other set...someone educate me on this.

If I playback a 1KHz. mono signal off the record and plug the turntable outputs into the scope, will this be the same as what the Fozgometer is doing? I've already got all I need to do that, but the extra cost of $250.00 for the Fozgometer is an "on-the-fence" purchase unless all I have to do is configure the oscilloscope with a few wires.

Still need to update the test record though, mine is about 35 years old!

Anxious to read the review Jeff.

Sam

 

[spectral]

If I playback a 1KHz. mono signal off the record and plug the turntable outputs into the scope, will this be the same as what the Fozgometer is doing?

Wouldn't it be adequate to play a left-channel-only tone and measure the amplitude of the right channel (crosstalk) in the 'scope and repeat for the right channel, until the crosstalk is the same for both and minimized? That's essentially what I did with the Revox. The only problem with my approach is that one assumes the phono preamp produces the same output in both channels for the same input, the preamp's tape loop preserves this and so does the Revox.

 

[Bernard]

The only problem with my approach is that one assumes the phono preamp produces the same output in both channels for the same input....

You are not supposed to feed it through the preamp; it is supposed to go directly from TT to the 'scope.

BTW where do you get a Fozgometer? The usual sources seem to be out of stock.

 

[spectral]

My point was that there were too many other variables in my approach, and yes there should be no need for a phono preamp when a 'scope is available, just like one isn't with the Foz - therefore the 'scope and Foz should be more accurate.

It looks like one has to wait a couple of weeks to get a Foz.

 

[Bernard]

I finally managed to locate a piece of unobtainium - a Fozgometer, for $225, on audiogon. All the major sellers seem to be out of it. I should have it in about 3 weeks. Looking forward to seeing how it works with my undamped unipivot.

 

[Satch]

Did you have to bulldoze the sacred tree of life to get it?

Let us know how it works out for you.

 

[Bernard]

I finally got the Fozgometer a week ago, then got the Analog Productions "Ultimate Test Disc", and tried it all out. You first play a 1kHz test tone through the left channel and note the reading on the meter, then do the same with the right channel. If they are not the same you have to rotate the cartridge till they are the same, or very close.

I did what the instructions said, and got EXACTLY the same reading on the meter for both channels, i.e. the azimuth was dead on without the use of the Fozgometer (I have a VPI JMW 10). I could have saved some money, but at least I know that my cartridge is aligned correctly.

On one of the sites that sells this thing I saw a note saying that they are not allowed to ship it out of the U.S. I wonder why.

 

[Bernard]

I was discussing with Justin (Mr. 211) my post above, and he told me that I gave the impression that I thought the Fozgometer was a waste of money. That was not my intent at all. What I was getting at was that in my case it showed that my tonearm and cartridge were manufactured so that they were perfectly square, hence azimuth was dead on, hence the Fozgometer was not needed. In almost circular logic I needed the Fozgometer to show that I did not need the Fozgometer.

Of course, I'm not going to now muck around with the azimuth just to see the Fozgometer at work.

I'm looking forward to taking it over to radicalsteve's place to see how it works out on his turntable.

 

[User211]

Perhaps more accurately I implied that is what people may have thought, via the following statement:

"Not surprised no one replied, though... I guess most thought you were writing it off as a waste of dosh?"

Here's a cheapskate thought. Download the free Theodolite app from the iTunes app store. I'm not claiming 100% accuracy using this method but it does seem very sensitive. You'll get the idea immediately you run it, but as I type this I admit I haven't actually tried it for this purpose yet. But it looks good against a pack of fags close up.

I've been using Audiotools from the App Store to take in-room frequency response tests. If you RTFM, you can get what seem like respectable results from the iPhone's internal mic. The author of the s/w has calibrated the mic using compensation tables, presumably using his iPhone. The accuracy depends therefore on mic consistency between phones, but if you have a calibrated SPL meter, you can use it to gain confidence you're closer to the mark. Or you can buy the dedicated microphone but that costs money (EDIT: this mic only works with an iPod Touch as it is the only one that accepts analogue line in as it turns out).

You must use the recommended settings to get sensible looking FR plots using the FFT app.

http://www.studiosixdigital.com/

Please be aware that it is a tall order to expect the iPhone's internal mic to be great.

 

[Victor]

Hi Spectral,
First of all a very Happy New Year to all the Analog enthusiasts in MLC!

Sorry to revive the thread after so many months have elapsed but I acquired a USB microscope during the hols and took some pix which brought to my attention the possibility of "believable off-axis viewing angle". In the pix you've posted here, have a look again at the cantilever's "transmission tunnel" : more of the interior is visible on the right of the cantilever than the left. True the stylus is virtually vertical against the grid but if by chance the camera is offset to the left (?) then it's possible that the true position of the stylus is toed to the left of its current position (which would be good news and meant the cart azimuth may possibly be restored slightly towards true vertical?).
Reason I ask this is because I have pictures which create an optical illusion not dissimilar to your images - but I know for a fact that in my case it is an optical illusion.

You'll see this as stating the obvious but may I ask when your stylus is off the record does it show the same attitude after it touches down as it's quite possible something has inadvertently knocked your cantilever askew e.g. cleaning, persistent antiskate torsion of the suspension etc).
If it is the case that quality cartridges are only 1 or 2 degrees off this is not an extreme angle and quite difficult to judge depending on how on-axis the cameras are (virtually impossible with any given cartridge would be my guess)?
Hope this proves to be of help but if not it was worth considering.
Kind regards....................Victor.

 

[spectral]

In the pix you've posted here, have a look again at the cantilever's "transmission tunnel" : more of the interior is visible on the right of the cantilever than the left. True the stylus is virtually vertical against the grid

You are right about the off location of the camera in the horizontal plane, but it was sitting on a tripod, so what really matters is two things: a) first and foremost, it's what I measure with the VU meters - that's the real proof; b) the stylus being vertical to the grid - that's the only relevant visual feedback.

The pictures are meant to convey the overall look and feel of the arm as one would see it if in person. Therefore, whether the camera is off in the horizontal plane or not is kind of unimportant - I only meant to show the overall impression as an interesting observation.

You'll see this as stating the obvious but may I ask when your stylus is off the record does it show the same attitude after it touches down as it's quite possible something has inadvertently knocked your cantilever askew e.g. cleaning, persistent antiskate torsion of the suspension etc).

The cartridge isn't damaged in any way. What you see is really construction "irregularities", and in most cases, the cantilever will never be parallel to the body as viewed from the front, the diamond won't be exactly perpendicular to the record as also viewed from the front, etc. The first issue is addressed by proper alignment with the various tools (protractors, etc); the second by adjusting azimuth. Since my original post, I have also adjusted SRA to +2 degrees off vertical (which I think is the right definition of SRA) or +92 degrees off horizontal (which is what's shown in some literature). BTW, after setting the weight and performing alignment, the stylus's SRA, as viewed from the side, may be off 0 degrees (or 90 if you wish), and may require radical SRA adjustment. In my case, to get to +2 degrees off vertical, I had to adjust it really +3 degrees (because it was -1 off vertical after alignment), thus the "severe" downward look of the arm from the side (see below).

See more pictures here and notice how crooked the arm now looks, but the visual aspect isn't important, it's just an interesting observation.

 

[Victor]

Apologies for the late revival ;^)

If minimal crosstalk is your goal and you don't have either a mono switch or special test gear, and you don't want to accidentally break your cartridge tags by trying to invert one channel, try this technique for fun.

Use ONE of the -20db pink noise test tracks from the HFNRR disc (or a 1KHz Xtalk track from the Ultimate Analogue Disc).

Play that track but first disconnect the I/C for the "active" channel so that you are only listening to the "crosstalk channel".
One of the good things about your ears is that unlike test gear they can easily discriminate between random noise, surface noise & pink noise so gauging the level of the crosstalk signal is not a problem.
Crank up the volume of the silent channel until you can hear the crosstalk clearly then progressively adjust by ear for minimum cross-channel bleed.
You may notice that surface noise reduces when you get closer to correct azimuth.

For comparison, not having a mono switch any of my amps, and despite the potential for inaccuracy, I obtained a cheap stereo-mono converter and used this in conjunction with the HFNRR anti-phase track. What emerges is that although both of the above methods get you in close there is still benefit to be had by fine-tuning using music.

I suspect the Fozgometer could be the same i.e. microscopic adjustments of azimuth may make a further audible difference(?)
Rumour has it the Foz works with one channel at a time for crosstalk minimisation but it's unclear whether it's looking for equal crosstalk or unbalanced. Carts will not boast either perfect channel balance or relative crosstalk so checking the results with music would seem to be imperative.

Bernard has already shown that adjustment by ear gets you into the same zone as the Foz so it seems possible that further incremental improvement could be possible?
If you own (or have reviewed) a Foz and have the capability of making miniscule azimuth adjustments it would be interesting to hear your feedback on this?

 

[Victor]

Feedback on the Foz from the "LencoHeaven" Forum...
Sounds as if it could be worryingly true and seems to confirm my suspicions.....


"....If you use a "main" or have favorite tonearm you like,I would suggest the Mint LP Best Tractor for protractor.These are made special for your arm/turntable and are probably the most accurate protractor made.Cost $100.00 or so I believe.

About the azimuth setting device, I would use my eyes and ears before relying on a Fozgometer. I have no experience with the device,but I read that this thing isn't very sensitive. You can adjust azimuth a couple degrees off and the Fozgometer reads its on. Just read a couple comments from guys who paid $250.00 for one and it didn't help them dial in the azimuth. ..."

Oh well...back to the drawing board....