Axiom Home Page Forums General Discussion Technical Questions s/n ratio???????????

could someone please explain the whole signal to noise ratio rating on amps thing to me in the form of-SIGNAL TO NOISE RATIO FOR DUMMIES -i tried to read a couple of articles and got even more confused
is a higher db better or worse?
thanks......ron

It's the ratio of signal to noise.

Higher is better. Assuming the testing is done at the same power rating (some rate at maximum power, some at 1W, or somewhere between). If not, you'll have to work out the difference and apply to the ratio. (10*LOG(A/B) in dB)

Bren R.

signal being the material the amplifier is amplifying

noise being anything the amplifier outputs that wasn't in the original material.

rcvecc:

What you are probably looking at is the signal plus noise devided by noise ratio defined in decibels. A higher (larger) number is better. But, you have to be very careful that all the amps are rated in the same way. Typically, they aren't. Bren has a valid point. Make sure that they are compared the same. Best would be at higher powers where the components (power supplies, etc) may be stressed.

Makers have been playing games with these numbers from the get-go.

The Rat.

Hi,

As Bren and others explained, manufacturers play with these numbers a lot, to enhance the alleged performance claims.

There's another way to think of it or describe it. You can say, for example, "the noise is 80 dB down," which means that the noise floor (analog tape hiss plus thermal noise from transistors) is essentially inaudible if the signal level is at 0 dB. Or you could phrase it this way: "Noise measured -80 dB," which is saying the noise was 80 dB below the signal level, which is great since noise that far "down" is considered essentially inaudible in the presence of music programming.

Going back to analog days, it's amazing how much tape hiss and grunge we'd put up with. In fact, some misguided fans of vinyl actually prefer noise (groove swish + tape hiss) along with their signals. They do so because they don't understand some of the peculiar psycho-acoustic effects of noise when it accompanies music. But I'll save further explanations of that for a newletter!

Regards,

In reply to:

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Going back to analog days, it's amazing how much tape hiss and grunge we'd put up with.

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Because the cure was often worse than the disease. Case in point - Dolby NR. Though Dolby S did a pretty good job... if I remember correctly, Dolby A was the one that sounded like a low pass filter and Dolby B was a high-freq compressor.

I remember feeling like a tool because I was looking for a dual deck with Dolby S and auto-reverse, which apparently was against the Dolby S spec, being that the head running backwards degraded the sound quality and could never be as precisely calibrated as an immovable head.

Bren R.

Hi,

Yep, Dolby A was the pro studio version. I know lots of recording engineers didn't like it. Dolby B was the consumer version but was very sensitive to tape calibration and mostly mistracked, so, like you say, it would often roll off the highs.

If the deck was calibrated correctly (usually not), Dolby C worked quite well. And I did have Dolby S on a Sony deck, but Dolby S never became popular. It seemed to work very well and wasn't as sensitive to calibration errors (if memory serves).

What drove me crazy about a lot of consumer cassette decks was the audible flutter. Of course, even some old pro tape decks and record cutters introduced audible flutter and you can still hear it on some of the transfers to CD (in particular an otherwise great Oscar Peterson CD called "We Get Requests"). On that CD the piano sounds like it was recorded on a dictation machine. But I digress. . .

Regards,

In reply to:

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Yep, Dolby A was the pro studio version. I know lots of recording engineers didn't like it. Dolby B was the consumer version but was very sensitive to tape calibration and mostly mistracked, so, like you say, it would often roll off the highs.

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Gee, you mean that little hole in the front of the cassette compartment wasn't just a place to hang a paperclip with the cassette J-card? Ohhh, a jewelers screwdriver goes in there... got it!

In reply to:

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If the deck was calibrated correctly (usually not), Dolby C worked quite well. And I did have Dolby S on a Sony deck, but Dolby S never became popular. It seemed to work very well and wasn't as sensitive to calibration errors (if memory serves).

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I've had two Aiwa decks (and it's amazing how much of these memories have faded away - I think they both recorded in B and C, not A & B as I thought) - one single deck and one dual deck with the dreaded Hi-Speed Dubbing - which I have never once in my life used. Even as a teen, I recognized there is no free ride. My Dolby S deck was a Sony as well, had it only briefly before someone else took an interest in it and I took an interest in this new Compact Disc technology... they're like records but they don't skip!

Though bro's deck was the first one I'd ever seen that would sense the tape composition and adjust bias from the shape of the shell (open space inboard of the record inhibit tabs was for metal, and CrO2 had an open "tab" in the middle of the top of the shell I think?)

Bren R.