# NDX2 / NAC282 voltages question

I’m sure this is a very stupid question, but I’ll ask it anyway. If the output voltage of the NDX2 is 2Vrms, and the gain of the 282 is 10, how come the output voltage from the 282 is 775mVrms? Many thanks in advance!

No such things as stupid questions, I wonder where you found the ‘10’ since it does not appear on the Naim product website.

Preamplifier design is more complicated than multiplying and has for example to do with the ability to drive an output current to the power amplifier.

The 282 documentation says the input sensitivity is 75mv and the output is 775mv, so I assume a voltage gain of 10.

Voltage gain is usually expressed in dB, but one cannot compare the figures like you do. Sensitivity is usually the input voltage needed to drive to maximum rated output voltage.

I suggest you do a quick google search …

I’d imagine that with volume set to full then an input of 75mv gives an output of 775mv. If you apply 2v full range input from a source then at full volume it will give approx 20v. Cant imagine the power amp being happy in the situation though, hence the need for the volume control.

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The NDX2 is also very unlikely to ever output 2V, either. In the real world it will always be much less than that.

Ah ok, I see. The 10x gain is specified at a nominal input level (75mV in this case) and presumably 775mV is matched to the power amp in some way. That being the case then, why have a 2V output from the NDX2?

Yes, OK. I assumed that we can all do the conversion to dB so no need for me to do that. I also did a search prior to posting on the forum but couldn’t find the answer, which is why I’m asking for help.

2V was the max output level specified for CD redbook standard. It has since become something of an overall standard for digital kit, although some items from other brands go much higher, no doubt hoping that the “louder” item will be favoured in a casual side by side demo.

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Because the pre amp will gladly accept an input of more then 75mv. Dont forget its not 2v regardless, 2v will be a full scale max output, if the music isn’t Brickwall white noise at 0dbfs (or possibly +6dbfs) then the output will be less than 2v.

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Thanks. I found something online where someone had measured distortion as a function of output voltage on a 552, and it seems that minimum distortion is designed to occur at 75mV input (and hence 775mV output.) One could put a larger signal in, and obtain a larger signal out up until clipping occurs, but the distortion is higher.

On the NDX2, are the DIN and RCA outputs at the same level?

FWIW I recall JV saying that the Naim preamps could take up to a 7V input without overload.

The NDX2 has the same 2V max output whether RCA phono or DIN. It can be attenuated (variable output) with the latest platform but this mainly to comply with other partner requirements and optimum performance is from fixed output.

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