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In Reply to: RE: Phono Cartridge Setup posted by John Elison on November 14, 2014 at 21:25:15
Thanks for your thoughtful reply, Jon. Besides giving me a lot to chew on, it gives me the chance to say how much I have enjoyed your posts over the years. You are a wonderful contributor to the forum
I understand now that "The phase angle associated with azimuth and crosstalk is completely different than phase response related to frequency response." But I still don't understand where phase response comes from.
I'm beginning to gather that phase angle and crosstalk are things built into the cartridge. In setting up dozens of cartridges using the Feickert system, I have found only one cartridge that met the ideal setup parameters. The ZU, a modified Denon, measured close to 36dB each channel (R-L, L-R) and a phase angle close to 90 degrees with only minor differences between channels. With my own much more expensive cartridge, I could get equal crosstalk (at 30db) or equal phase angle (at 55 degrees) but not both at the same time. Either the crosstalk was off by 6 dB, or the phase angle was off by 40 degrees).
I'm wondering if my cartridge is defective. It sounds good compared to other cartridges, but could it sound even better if more care were taken in its manufacture?
Just a question.
Follow Ups:
> But I still don't understand where phase response comes from.
Well, you can find just about anything on the internet these days.
Thanks, Jon; but I guess I did not ask my question right. I hope you'll indulge me as I try again. Please understand that I am not in the audio business, nor am I an electrical engineer. My last EE course was in 1967.
Let’s take a mono cartridge. As the stylus traces the groove of a test record it produces a voltage. But this voltage comes about through (in an MC cartridge) the mechanical action of coils moving through a magnetic field. It seems to me that this has to result in a phase lag, however small.
Now let’s take a stereo cartridge. Now each channel could have its own phase lag. In a well-engineered cartridge, mounted optimally, these phase lags should be equal.
So my questions are:
1. Is this what is meant by phase response?
2. What does azimuth have to do with it?
3. If phase response cannot be equalized to within X degrees, is the cartridge likely defective?
Anyone?
> 1. Is this what is meant by phase response?
Yes and no! There are different phase relationships in an audio system. There is inter-channel phase, crosstalk phase, and phase shift with respect to frequency. What you are describing with the mono cartridge is more of a time lag rather than a phase lag. In other words, if the time lag is the same at all frequencies, this does not constitute phase shift. With the stereo cartridge, there can certainly be a phase difference between channels and this would constitute a defective cartridge in my opinion.
Phase response refers to phase shifts at different frequencies relative to the original signal. In other words, all musical instruments produce fundamental tones with a specific harmonic structure that goes up in frequency. That harmonic structure exhibits an amplitude and phase relationship with the fundamental frequency. This is the reason that a piano and trumpet sound different when playing the same note. They have totally different harmonic structures attached to the same fundamental frequency.
In order to maintain the proper amplitude of an instrument's harmonic structure, an audio reproduction system must have a flat frequency response. We all pretty much understand this aspect. However, in order to maintain the proper phase relationships of an instrument's harmonic structure, an audio reproduction system must also have a linear phase response. However, phase response does not seem to impact sound quality as significantly as frequency response. On the other hand, when you achieve linear phase, especially in a loudspeaker's acoustic response, the realism becomes addicting.
Most electronic components have a very linear phase response, but transducers such as phono cartridges and speakers can have significant phase shifts with respect to frequency.
> 2. What does azimuth have to do with it?
Azimuth has nothing to do with the phase response described above. Azimuth affects only the phase of the crosstalk signal with respect to the opposite channel signal. In my opinion, it has no impact on sound quality whatsoever. However, it can be used as an indicator of correct azimuth. Of and in itself you can't hear it. What you do hear is the improvement in crosstalk performance when azimuth is set correctly. In other words, minimum crosstalk occurs at the point where crosstalk phase transitions from zero to 180-degrees.
> 3. If phase response cannot be equalized to within X degrees, is the cartridge likely defective?
I take it you are referring to crosstalk phase. In my opinion, the answer is no. Remember, all you have to do is use a different test record and you will get a different measurement and a different azimuth position. Perhaps all test records are defective! Perhaps all records are slightly different. Well, there's no question in my mind that all records are slightly different with respect to VTA, SRA, and azimuth. Therefore, I believe you can achieve just as good performance from setting your cartridge level with zero azimuth compared to adjusting it to any specific test record.
I hope this helps. This is just my opinion based on my experience of making measurements and listening. You can form your own opinion if you have the desire to spend lots of time making tedious measurements and strenuous listening comparisons. You might come to a different conclusion. Who knows?
Good luck,
John Elison
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