IMO, correct observation, wrong analysis. Bias level modifies the HF recording response, introducing a phase shift; that is what you see. The theory about the "virtual gap" moving with bias level is moot.Biasrocks said:I've observed it myself while monitoring on a scope.
Don't take my word for it, try it on a 2 track and you'll see the azimuth going nuts as you adjust the bias.
Really easy to see on a scope running a Lissajous pattern.
abbey road d enfer said:That is why Lissajous is not a correct method. Azimuth should be set primarily by finding maximum HF level.
IMO, correct observation, wrong analysis. Bias level modifies the HF recording response, introducing a phase shift; that is what you see. The theory about the "virtual gap" moving with bias level is moot.
I agree that precise azimuth setting using the phase (Lissajous or dual-trace) method involves starting with a lower frequency in order to avoid the 2.pi aliasing, but phase measurements are affected by equalization; in contrast, setting at maximum amplitude is totally unambiguous and do not require starting with a lower frequency.Biasrocks said:abbey road d enfer said:That is why Lissajous is not a correct method. Azimuth should be set primarily by finding maximum HF level.
The reason that method was suggested is that it's easy to get the wrong phase alignment (180 degrees out) on a scope when you monitor azimuth using a high frequency tone. Which I concur.
By using wide band white noise for your initial azimuth adjustment, followed by a high frequency tone you avoid this problem entirely.
The test tapes and the record side tones that I use here include wide band white noise for accurate azimuth alignment.
Yes, I did check Bob Katz's post; I respect him very much when it comes to the essence of his activity, but I think he sometimes wander in terra incognita regarding hard theory.IMO, correct observation, wrong analysis. Bias level modifies the HF recording response, introducing a phase shift; that is what you see. The theory about the "virtual gap" moving with bias level is moot.
Did you check the discussion thread I posted, there's some heavy weights chiming in about the virtual gap phenomenon.
I am far from a heavy weight on the theory of analog recording. 8)
Mark
Yes, I did check Bob Katz's post; I respect him very much when it comes to the essence of his activity, but I think he sometimes wander in terra incognita regarding hard theory.
Yes, I read the thread.Biasrocks said:Yes, I did check Bob Katz's post; I respect him very much when it comes to the essence of his activity, but I think he sometimes wander in terra incognita regarding hard theory.
Here's one from Bob Ohlsson and one from John Klett, confirming what Bob asserted
http://repforums.prosoundweb.com/index.php/topic,6193.msg62069.html#msg62069
http://repforums.prosoundweb.com/index.php/topic,6193.msg62203.html#msg62203
Really not trying to beat a dead horse.
Mark
abbey road d enfer said:Yes, I read the thread.
And again, with all due respect, these people are not physicists.
I was a member of the REP forum for some time but I quit when I saw that faith was more important than facts, particularly when supported by a guru. I'm not a guru, just a scientist; I'm also human, I make mistakessometimesoften. If someone can prove me wrong with sustainable arguments, I'm ready to incline. I don't make it a personal matter (read my sig) but I hate to see hazy theories bandied as gospel.
It makes sense since your machine is regularly maintained and aligned, and thus there is no phase deviation in the electronics. This makes perfect sense; looking for peak level is essential in the procedure.Gold said:I only play tapes recorded elsewhere. My method for checking azimuth is to look for peak level with the provided calibration tone(s) on the VU meters and then to look at the lissajou on the scope to fine tune.
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