Fozgometer

If you use the Fozgometer, you should heed Fremer's latest blog and also the bulletins from the distributor. Turns out the Foz is very dependent for accuracy upon the exact DC voltage being put out by its "9V" battery. 9V batteries never put out exactly 9V. Thus every Foz, new or old, needs to be calibrated prior to use. There are instructions how to do that at both sites. This revelation probably accounts for the wildly different opinions I have read here and elsewhere regarding the accuracy of the Foz.

I think "767400" is pointing out this same issue.

IMO, Fosgate should make available at least an optional external 9V regulated power supply that plugs into the Foz. Get rid of that battery.

How do you define "whack" and whether your Foz is in or out of it? It's based on a subjective impression, is it not? Unless the azimuth is so askew as to be impossible.

Thanks. I had the impression from the other posts that the Foz could be calibrated with the test tones and then still give incorrect readings when used to set azimuth. If that were the case, one would have no way to be sure whether there was error and precisely how much error.

Tketcham, As I understood Fremer's review and the comments of others "in the know", it seemed that the absolute voltage produced by the battery makes a difference. Thus installing a new battery is not a panacea; it seems that doing so would require re-calibration of the Foz. Brand new "9V" batteries will vary from about 9.1V to 9.6V in their actual output voltage. (I had to buy several for another project, and I measured about a dozen "new" ones. No two were exactly alike in voltage.) So, if the Foz is sensitive to differences in battery voltage of 0.1V, which I am led to believe is true, then it's not so simple as to say that you need to use a fresh battery every time. Seems it's better to say you should re-calibrate the Foz every time you use it, which is a burden on the user. Probably does not make much difference to change the battery in that case, so long as it is still making 9V or more. I am more in Don's camp on this issue; the Foz should be more dependable, and it could be if Fosgate would make an outboard 9V PS for it. But maybe PS noise, even very low level, is inimical to its function. Hence the battery. But also, I don't doubt that what you said is true; a lot of the reported problems may be due to end-user and/or dealer ignorance of how to use it.

Stringreen, Shame on you for comparing an Alfa Romeo to a Fozgometer. I drove a 1967 Alfa Duetto (with Weber carburetors) for six years as my only car, living in NYC with no garage, and it never ever let me down once, not even in snowstorms. In the end, a dishonest and unskilled mechanic "killed" it. (He later went to jail for fraud and theft in connection with his Ferrari repairs.) The post-1968 Alfas did have a rather unreliable fuel injection system that was necessitated by emissions requirements. That fuel injection system may have contributed to the reputation for unreliability. Many cars were converted back to use Webers in those days. Also, many troglodytes don't know the difference between an Alfa and a Fiat. The 60s and 70s Fiats were indeed problematic.

Personally, I bought a Signet Cartridge Analyzer about 25 years ago. All you need is a proper test LP, and it reads out crosstalk. Also has other uses. But I also think setting azimuth is a bit over-rated. Most cartridges sound fine if you set azimuth for 90 degrees. (I hate to say this; I used to argue quite the opposite.)

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).

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.

"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?

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.