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Signal-to-Noise Ratio on preamps

PuX

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#1
while reading the specs of a Naim preamp one of the numbers caught my attention:
Signal-to-Noise Ratio 67dB at 0.775V
https://www.naimaudio.com/product/nac-152-xs

the strange thing is the matching power amp has decent performance judging from the specs:
Signal-to-Noise Ratio 100dB
https://www.naimaudio.com/product/nap-155-xs

what does this mean? shouldn't SNR be around 100dB on a decent device? or does this metric work differently on preamps?

is this a very low number and they are acknowledging their amp performs badly or not?
or am I misunderstanding this metric and SNR falls with lower volume/voltage?

can't find any other preamps specs with SNR numbers to compare to.
 

sergeauckland

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#2
I suspect that S/N ratio refers to the phono input. If so, it's a perfectly respectable number. If it's for a line input, then yes, rather poor, which is why I think it'll refer to phono which has a lot more gain, hence more noise.

S
 

PuX

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#4
I suspect that S/N ratio refers to the phono input. If so, it's a perfectly respectable number. If it's for a line input, then yes, rather poor, which is why I think it'll refer to phono which has a lot more gain, hence more noise.

S
it's listed under Audio Outputs.

You actually can't tell much from that spec the way it's written.
does this tell us anything? THD 0.042% [email protected], 2Vin, 0.0775V out
 

PuX

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#6
I am guessing the 2V in is from a CD player or other source and 0.0775V out is what is being sent to the power amp.
 

sergeauckland

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#7
it's listed under Audio Outputs.


does this tell us anything? THD 0.042% [email protected], 2Vin, 0.0775V out
Yes, but the output has to be switched to an input. A phono input has more gain than a line input, so that's a sort of worse case. However, as SIY has mentioned, specs like these tell you very little, better than nothing I suppose, but incomplete. For example, the THD spec above is fine hardly great, but OK, but tells you nothing about what happens at other frequencies than 1kHz. If it had said THD x% at any frequency between 20Hz and 20kHz with an input of 2v and output of 0.775v into any load over Y ohms, and with a maximum output of Zv at less than 0.1% THD that would be rather more informative.

However, specs are usually written by the marketing department, not engineering.
S
 

SIY

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#8
I am guessing the 2V in is from a CD player or other source and 0.0775V out is what is being sent to the power amp.
I'll still vote for typo. The number makes no sense. 1 or 2V out is much more typical.
 

Blumlein 88

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#12
The manual lists all inputs as having 35 db of overload margin. And 130 mv input giving .775 volts output. Assuming the output doesn't overload you might think at higher than 0 dbu (.775 v) the unit has 102 db SNR. Or something like that. Which is more reasonable, and yet maybe not great. Like SIY why have a preamp. Then again Naim does lots of odd things.
 

Sal1950

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#13
However, specs are usually written by the marketing department, not engineering.
They just throw something out to look impressive.
Since 99.99% of the readers can't attach anything meaningful to them they don't worry about it.

I'm still in the passive camp when at all possible. If you can assemble a string of components whose i/o impedance's and gain levels work together in the correct manner, nothing can sound as invisible as "nothing". ;)
JMHO
 

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