On "setting azimuth with a voltmeter".
You need a high quality voltmeter and a test LP that has bands with signal in R channel, only, and in L channel, only, respectively. Preferably the frequency of the signal is 1kHz, but you will get slightly different results at different frequencies. For accuracy in reading the meter, you will probably need to measure voltage at the output of the phono section vs the output of the cartridge, which would be more ideal. Then you play, let's say, the R channel 1kHz signal and measure its amplitude in terms of signal AC voltage in the R channel. Take note. Play the R channel signal again and measure any AC voltage that appears in the L channel. Take note. Then do likewise with the L channel 1kHz test band; measure voltage in the L channel, and ideally at this point you need to set it to be equal to the voltage you saw for the R channel signal in the R channel, perhaps by use of a balance control. Once that is done, play the L channel signal again and measure VAC in the R channel. The voltage in the L channel when playing the R channel, and the voltage in the R channel when playing the L channel, represent "crosstalk". Some people like to adjust crosstalk so it is equal in both channels. Others like to adjust crosstalk to obtain the minimum values possible. (The two goals will not be arrived at at the same azimuth angle.) There are good arguments, either way. Also, keep in mind that azimuth has very very little effect on channel balance (a difference in output between R and L). Don't use azimuth to correct channel imbalance.
You need a high quality voltmeter and a test LP that has bands with signal in R channel, only, and in L channel, only, respectively. Preferably the frequency of the signal is 1kHz, but you will get slightly different results at different frequencies. For accuracy in reading the meter, you will probably need to measure voltage at the output of the phono section vs the output of the cartridge, which would be more ideal. Then you play, let's say, the R channel 1kHz signal and measure its amplitude in terms of signal AC voltage in the R channel. Take note. Play the R channel signal again and measure any AC voltage that appears in the L channel. Take note. Then do likewise with the L channel 1kHz test band; measure voltage in the L channel, and ideally at this point you need to set it to be equal to the voltage you saw for the R channel signal in the R channel, perhaps by use of a balance control. Once that is done, play the L channel signal again and measure VAC in the R channel. The voltage in the L channel when playing the R channel, and the voltage in the R channel when playing the L channel, represent "crosstalk". Some people like to adjust crosstalk so it is equal in both channels. Others like to adjust crosstalk to obtain the minimum values possible. (The two goals will not be arrived at at the same azimuth angle.) There are good arguments, either way. Also, keep in mind that azimuth has very very little effect on channel balance (a difference in output between R and L). Don't use azimuth to correct channel imbalance.