Signal to (what) noise????

[salad 419]

I'm not sure exactly what I'm asking. But hopefully the following questions will get me closer.
What is the "noise" in signal to noise ratio of CD inputs in a reciever? Is this the 60hz buzz between processors, grounding issues, etc?

For two similar models but having say 106db and 100db signal to noise ratio: Would the input of the 106db be louder?

I think what I'm trying to understand is if the noise is the floor and the signal is the level in? OR, is the Signal is the ceiling (because most components and recievers use the same input and output voltages) and that the signal to noise ratio is just a measure of the quality or cleanliness of the signal.

How well (on a good system) do you notice the difference between a 106 and 100db signal to noise ratio on the inputs of recievers? Very Noticable? Slighty?

[Dusty Chalk]

No, it's a ratio. So the noise is the floor, yes, but if you have two different CD players with different Signal-to-Noise ratios, then the noise floor on the quieter one will be lower. Theoretically.

[JoeE SP9]

I'm not sure exactly what I'm asking. But hopefully the following questions will get me closer.
What is the "noise" in signal to noise ratio of CD inputs in a reciever? Is this the 60hz buzz between processors, grounding issues, etc?

For two similar models but having say 106db and 100db signal to noise ratio: Would the input of the 106db be louder?

I think what I'm trying to understand is if the noise is the floor and the signal is the level in? OR, is the Signal is the ceiling (because most components and recievers use the same input and output voltages) and that the signal to noise ratio is just a measure of the quality or cleanliness of the signal.

How well (on a good system) do you notice the difference between a 106 and 100db signal to noise ratio on the inputs of recievers? Very Noticable? Slighty?

60hz hum is a usually a product of different ground potentials. SN ratio has no relationship to volume. All electronic devices (amps, preamps, reveivers etc) produce noise. If you feed any signal through a given device noise is always produced as part of the operation of the device. In your example the signal with a SN ratio of 106db would be "quieter" than the one with a SN ratio of 100db.
All it means is that the noise is that many db's lower in level than the signal. I doubt anyone could hear the difference between 100db SN ratio and 106db SN ratio. It can however be measured.

[hermanv]

Ah specsmanship, it is a wonderful thing. Two amps with an identical noise floor, one is rated at 100 Watts the other at 200 Watts. The 200 Watt amp will have 6 dB better signal to noise ratio. This is only true at full volume, if you listen at 50 watts, the signal to noise ratio will be the identical for these two amps.

The power amp is rarely the noisiest component in a quality system, pre-amps and source devices usually limit the noise floor, rarely do these devices list a noise floor specification. (capitalism too, is a wonderful thing).