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Can someone explain properly what these specs mean.

post #1 of 18
Thread Starter 
Well I understand what they mean but I am having difficulty explaining...guess Im having a writers block today. This is for a portable cd player.

Signal/noise Ratio: 84db (is this good or bad?)

Earphones Output: 305mV (RMS)
Line Out Output: 290mV (RMS)

how does one convert the Earphones output and Line out output ratings from mV to mW?

All help will be appreciated.

Im doing a review on a new mp3 cd player by Creative.

Obviously credit will be given to those who help me out
post #2 of 18
Don't know about the others, but with signal-to-noise ratio, you want as high as possible. It's just what it sounds like, implies a noise "floor". E.G. Krell amps have a SNR of anywhere between 100-120 db. One old Yamaha MD player I looked up claimed a SNR of 105 db.
post #3 of 18
I asked a similar question awhile back. You might find a partial answer here. If not, you might find it slightly interesting.
post #4 of 18
Thread Starter 
Thank you...partly helps my query and the S/N ratio did make me suspect what is wrong with the player. Now that im sure about it. Thanks
post #5 of 18
84db is not good! 95-120 is good!
post #6 of 18
oh, it is 95-100db!
post #7 of 18
As for translating the output ratings from mV to mW, well, you can't Ratings in mW would give you the output power, while ratings in mV would only give you the voltage swing.

So for the same mW rating, you can have an amp with a low voltage swing and good current capability, or one with a high voltage swing and bad current capability. You'd want the former one for low-impedance phones and the latter one for high-impedance ones.

And given the mV rating, you have no idea what its current capability is. And since Power = current * voltage and you don't have (current), you don't get the power rating.
post #8 of 18
SNR of 84 db is considered poor today. 20 years ago, it would have been kinda of the norm because the electronics were primitive and clunky. I remember reading specs of really old CD players with a SNR less than 84 db.

Joe Bloggs is right. I was about to right the exact same thing before, but my knowledge of circuits is horrible.

Anyone know if its possible to quantitively determine if the amplifier prefers wider voltage swings or higher current with a multi-meter?
post #9 of 18
Quote:
And given the mV rating, you have no idea what its current capability is. And since Power = current * voltage and you don't have (current), you don't get the power rating.
Yes, but if you manipulate Ohm's law (Voltage = Current * Resistance) a little bit more, you get:

Power = (Voltage)^2 / Resistance

And since you do know the AC resistance, impedance, of the headphone, you can figure out the power delivered at that impedance.

So you're looking at a ~30mW @ 32ohm output...

Bam!

(correct me if I am wrong of course)
post #10 of 18
I think a 84dB S/N ratio is not that poor, although it is noway to be excellent as a digital product. Those high-end Marklevinson Monoblock amplifier has only 80dB S/N, but they are still highend both in sound and in price So IMOP, 84dB is quiet enough for no annoying to most entertainment.

Regarding the headphone output capability, I did found 2 kind of calibration in those pdcp,cdrom. one is XXmW/Xohm,the other is XXmV/Xohm, there is no much difference because when it marked with XXmV/Xohm, it alway mean that one can get a nonedistortion output voltage as high as XXmV with a Xohm headphone. i.e. on my LG cdrw, it was marked 0.6V/32ohm,actually,it is no much difference with a 10mW/32ohm marking.
post #11 of 18
Chych nailed it. I just learned those formulas two weeks ago. Ahh, gotta love AP Physics B....
post #12 of 18
Ah physics, fun class, took AP Physics BC Junior year, pulled a 4 on the exam both sections, Kinetics and E&M (I only started studying the night before )
post #13 of 18
Quote:
Originally posted by alfaudio
I think a 84dB S/N ratio is not that poor, although it is noway to be excellent as a digital product. Those high-end Marklevinson Monoblock amplifier has only 80dB S/N, but they are still highend both in sound and in price So IMOP, 84dB is quiet enough for no annoying to most entertainment.
Yeah, 80db SNR is not that bad. Most people won't notice the difference between 80 db and 100 db SNR (or even aware such a concept exists). However, I am not surprised that marklevinson would publish lower SNR values because they are probably publishing realistic numbers or conservative numbers. I remember reading an article from some audio magazine that accused the bigger electronic companies of exagerrating their SNR with a simple analysis that ignores many environmental factors.
post #14 of 18
Quote:
So you're looking at a ~30mW @ 32ohm output...
I think that should probably be ~3 mW @ 32 ohms (for the earphones output).
post #15 of 18
Quote:
I think that should probably be ~3 mW @ 32 ohms (for the earphones output).
Hm, yeah that's right... silly me...
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