Topic: Mono monitoring for azimuth adjustment?!

[sunjan]

Hi all,

Maybe this is common knowledge here, but I wonder if anyone can verify the efficiency of this:

It's best to listen in mono (both channels added together, not just one channel!) when adjusting the azimuth. The correct point will be far more obvious. ... The out of phase signal components from a badly adjusted deck will cancel out when summed to mono. Unless your ears are wired in mono (unlikely!) slightly out of phase component will just sound strange when listening in stereo via headphones - and the region of "correct" azimuth appears far larger than it really is.

Summing to mono make the audibly "correct" region much smaller, helping you hit the actual correct adjustment more easily.
Taken from http://www.hydrogenaudio.org/forums/index.php?s=&showtopic=63914&view=findpost&p=571884

Mono monitoring was also mentioned by Greg Orton in a previous thread here, while discussing studio reels:

It uses the summing of the audio output of the individual tracks to mono then measures the voltage like an RMS voltmeter.  When playing back a high frequency signal (usually 10 to 20 Khz range) the sum of the channels will show a dramatic peak output voltage while adjusting the azimuth and the in phase condition is reached.  It is wise to set the azimuth at the highest frequency you have on the alignment tape then check the next lowest frequency to make sure you weren't 360 degrees out of phase when setting azimuth at the highest frequency.
 
Studios simply sum all the channel of a tape recorder to one bus and monitor the signal output of that bus with the VU meter.  The levels of each channel on the consol should be relatively the same and make sure the individual channel EQ's are turned off.  This is really the only way you can accurately adjust the azimuth for a 16 or 24 track head.
From http://taperssection.com/index.php/topic,97785.msg1314402.html#msg1314402

My understanding of all this, translated into home taping terms: if your deck doesn't have a stereo/mono switch, feed the signal to an amplifier that does, and monitor the mono signal thru the amp while adjusting the azimuth. Is that correct?

[tilomagnet]

My understanding of all this, translated into home taping terms: if your deck doesn't have a stereo/mono switch, feed the signal to an amplifier that does, and monitor the mono signal thru the amp while adjusting the azimuth. Is that correct?

Yes. I have an amp with a stereo/mono switch and once tried setting the azimuth in mono. It didn't work at all, although I was clearly hearing what I thought was the "sweet spot" for correct azimuth, that spot was very different from the setting I made with stereo monitoring and it turns out it wasn't the correct adjustemnt at all, but clearly misaligned.

Don't know, maybe my amp doesn't really output a summed mono signal of both channels, but rather two channel mono of the left or right channel only.     

The best advice for accurate azimuth adjustment that I've never seen mentioned is to monitor through your speakers instead of headphones. The difference becomes much more obvious and it's far easier to adjust for correct settings. 

[live2496]

My understanding of all this, translated into home taping terms: if your deck doesn't have a stereo/mono switch, feed the signal to an amplifier that does, and monitor the mono signal thru the amp while adjusting the azimuth. Is that correct?

I don't have experience with this, but one suggestion would be to capture the left and right to a computer soundcard and check the phase alignment in an audio editor. Having the audio captured to a file you could measure the RMS level and peak levels.