Stringreen, you shouldn't have to adjust VTF or VTA/SRA or alignment when adjusting azimuth. All of those parameters should be been set and locked in before you adjust azimuth.
If you have a tonearm that uses a set screw to adjust azimuth then yes, you could be affecting tonearm length if the arm tube is somehow pushed or pulled in or out of the tube sleeve. But all you have to do is put a very small drop of "White Out" on the arm tube right at the edge of the sleeve. That provides a reference marking to make sure you aren't moving the arm tube in/out as you tilt it to adjust for azimuth.
Regards,
Tom |
Tom...I'm using a VPI 3D arm, and can tell you that when moving either counterweight or CounterIntuitive around the arm tube..even slightly, I can't prevent it from moving front/back..even a miniscule amount which changes VTF. I must check and check again all the parameters. ...and when adjusting the vtf, I must again check the Foz for its indication. When I'm doing this, it seems endless, but I eventually zero it in. White out indications et al, are way too broad and inexact for me. |
Stringreen, you're description of setting azimuth on a VPI uni-pivot doesn't motivate me to try one out. If VTF is directly coupled with azimuth adjustments and is that fidgety, I think I'll stay with gimbal-pivot tonearms. :-)
So to clarify that there shouldn't be a need to adjust VTA/SRA and VTF when setting azimuth: IF arm length and VTF are stable while adjusting azimuth, having to tilt the cartridge even 1 to 2 degrees will only change height by ~0.05mm to ~0.10mm from a reference vertical stylus setting. I've measured record thickness differences greater than that on a single LP, let alone the differences in thickness between LPs.
Enjoy the music!
Tom |
Ooops, that's "your" description. I had started with a different train of thought and then changed everything but "you're". 8-) |
There are two schools of thought with regard to the endpoint of azimuth adjustment. One says to go for the least amount of crosstalk, in which case I have found over many years (using the Signet Cartridge Analyzer which reads out in "db") that the amount of crosstalk will not be equal in both channels. The other says to go for equal amounts of crosstalk in both channels, even if in doing so you have to sacrifice the absolute best values for crosstalk, which is nearly always the case. There is no right or wrong in choosing either endpoint.
I presume the Foz reads crosstalk at 1kHz. Yes? If so, what do the numbers "17" and "19" mean? If the readout is in db, then it is usually a negative number indicating the level of crosstalk below 0 db, when the channel being measured is set to 0 db. In that case, one typically sees better than -20db at 1kHz (meaning a number more negative than -20). |
Lew, the manual states that channel separation is what's being measured. Also: "The readings are virtually independent of overall signal levels, and can be made with a wide range of input signals without effecting accuracy."
So your comment about what correct azimuth entails is consistent with using the Fozgometer for alignment. Try to get both the best balance between channels and the highest separation in each channel. As you also mention, the two are probably synonymous in a perfect world, but I've found that sometimes it's a compromise between the best separation and the best balance. But which should have priority is not clear to me and I've biased the alignment in favor of trying to get channel separation in better balance while maintaining the best separation value in the lower of the two channels. Does that seem reasonable? (Reasonable or not, it sounds mighty fine. :-)
It would be helpful if Mr. Fosgate and Musical Surroundings were a bit more thorough in describing what the goals are and how to get there.
Regards,
Tom |
Tom...actually its very rewarding when you listen to the final results and how each of the parameters effect the overall sound. ...and you really only have to do the whole job once (until the next cartridge comes along..) |
Stingreen, I may try a uni-pivot tonearm some day. But for now, it's gimbals, man.
Best,
Tom |
Turns out Peter Ledermann has already used my "fun" method but without disconnecting the distracting active channel first. See last paragraph -
http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=840188&highlight=
Cheers, |
... the manual states that channel separation is what's being measured. "Channel separation" is just a derivative statistic. The only way to quantify it is to measure how much information intended to be in channel A is bleeding into channel B, and vice-versa; i.e., crosstalk. If you measure crosstalk in each direction, average the results and subtract from a notional maximum signal level, the resulting statistic is called "channel separation". The less crosstalk, the greater the channel separation. They're exactly and inversely proportional. A statement that one is measuring channel separation but not crosstalk would be nonsense. They're two sides of the same coin. |
I have to agree with Doug. Moreover, crosstalk, it seems to me as a layman, cannot be discussed without reference to a level of signal. The Signet Cartridge Analyzer guide advises one to use (any of several possible test LPs) with a 1kHz steady state tone on one channel and nothing on the other. Then you set the Analyzer to receive the recorded signal and set that value to "0db" on its meter. You then set the Analyzer to receive the signal on the ideally negative channel, and the meter shows a value on the negative side of its 0db marking. Thus you can say you have negative X db of crosstalk into the channel that is receiving no intentional signal. Then you repeat the process using another band on the test LP that has signal encoded in the opposite channel. Because you have referenced your result to 0db in both cases, you can say that the level of crosstalk in both channels is equal, or not. And you can discuss magnitude in a meaningful way. Also, as Doug inferred, the results will be very different at different test frequencies. It's usually best around 1kHz and worst at the frequency extremes.
So, I don't know what the quoted part of the Foz manual means exactly, except I guess it would be acceptable to not know the reference level, so long as one did not change the level when comparing crosstalk into channel A with crosstalk into channel B. The signal level, whatever it may be, HAS to remain constant it seems to me, when doing that, if you really want to be able to say you have equal amounts of crosstalk in both channels.
TKetcham, The only other thing in your last post that I would mention is the business about "balance". If you are talking about achieving equal amounts of crosstalk in each channel, then I understand, and I do think that's what you meant. But if you are talking about "channel balance", as in equal gain in both channels, adjusting azimuth is not a way to get there. |
Doug, thank you for the clarification regarding channel separation as a surrogate (derivative statistic) for crosstalk. I had used the term crosstalk in the past when describing the Fozgometer but wanted to be consistent with the manual. If you read the manual it does not discuss crosstalk, probably to avoid confusion.
Lew, the test record recommended by Musical Surroundings is produced by Analogue Productions and utilizes a 1kHz tone for the two channels. (They also state that any 1kHz test tone track, one for each channel, can be used.) I have to assume that the two tracks are accurate and equal in output. I have read suggestions to purchase as many as three versions of test LPs to compare tracks and ensure consistency.
I have been curious to use other test tone frequencies to see how the optimum alignment for the 1kHz frequency compares to lower and higher frequencies.
And yes, when I said balanced I was talking about trying to equalize channel separation (crosstalk) between channels. The Fozgometer does have a test for channel output balance as well.
Regards,
Tom |
"The Fozgometer does have a test for channel output balance as well."
It would be nice to be able to compare the outputs of the two channels, but do Fosgate imply that it can be equalized via azimuth adjustment? |
Lew, no, they do not imply that channel imbalances can be fixed by adjusting azimuth. However, the manual would be much more useful if it included information on how to deal with channel imbalances when adjusting azimuth for optimum channel separation (crosstalk). There are discussions on this topic at several forums but no clear answers as how to best handle it.
Regards,
Tom |
Many years ago on Vinyl Asylum, two very knowledgeable guys wrote long treatises on azimuth. At least one of them was an advocate of adjusting for "least crosstalk", rather than "equal crosstalk" (into both channels). Along the way, both stated that one should not attempt to correct for inequality in gain between channels by adjusting azimuth. First of all, even the most extreme differences in azimuth make a very small difference in relative gain between channels. I tried it with my Triplanar and Signet Analyzer; a difference from about +15 degrees to -15 degrees off the 90 degree starting point made barely a 1 db difference in channel balance, and by the way music sounded awful at either extreme. And second, you can't have it both ways; correcting azimuth for crosstalk, as one should do, will not lead also to any significant correction in channel imbalance. So, I guess you're referring to how channel imbalance might contribute to errors in adjusting azimuth for crosstalk. (Yes?) To me, that is no problem if you reference the adjustment to a "0db" point with respect to the channel that is receiving the signal, as I noted above. Don't know about the Foz, but the Signet allows you to do this. You'll still have a channel imbalance, maybe, but crosstalk will be as low as you can get it. The point is that referencing both channels to 0db for the driven channel removes the inequality in gain from the equation, as much as is possible and IMO. |
In a couple of years of adjusting azimuth on multiple cartridgess using the Wally Analog Shop tool, I don't remember ever seeing much change in output (ie, channel balance), but differences in crosstalk (ie, channel separation) were immense.
About 10 years ago I dropped the instrumentation after realizing that I can adjust by ear just about as accurately and far more quickly. As with the instruments, I've never heard a difference in channel balance when tweaking azimuth within reasonable limits (ie, within a degree or so from vertical), but changes in crosstalk from even the tiniest possible adjustment are readily audible.
YMMV, of course...
|
Dougdeacon,
Can you recommend a currently available test disc that facilitates the listening method? Interestingly enough many years ago I found that the listening method was easier, faster, and better than all the instrumentation just as you suggest. Back then I used a Shure test record that is no longer available. BTW, in those days, while in college, I worked in high end hifi retail and was the go to guy for setting up turntables. So I had a lot of practice.
Thanks,
Bill |
