What am I missing? Pre/power gain and input sensitivity.

@cat_doorman, in the case of the example you cited you are not missing anything. The main effect of different preamp gains would simply be that the volume control would be set to different positions for a given SPL.

Preamp gain can often be a significant consideration, though, in the case of phono sources (or tuners, tape decks, and other sources which typically have much lower output voltages than CD players and DACs).

For example, using some typical numbers, if a phono stage provides 40 db of gain for MM cartridges and 60 db of gain for LOMC cartridges, and the cartridges are rated to produce 5 mv (MM) or 0.5 mv (LOMC) under the standard test conditions, in each of those cases the phono stage will output only 0.5 volts when a recording is causing the cartridge to provide its rated output (which corresponds to a volume that is quite high). If substantial additional gain is not provided by a preamp in that situation much of the power capability of many power amps will not be able to be utilized on many recordings, even with the volume control at max.

Regards,
-- Al

The funny thing is, most digital sources due to Redbook standards put out too much voltage for most amps- IOW connecting them to a power amp will cause the amp to run at or near overload!


So the signal has to be knocked down, which is dumb IMO/IME. This requires a volume control and is why passive volume controls have become common. The problem is that most passive controls have an artifact which is to decrease impact at all frequencies if less than full volume. This problem is eliminated by buffering the control. So you'll need active circuitry in any event; it would have made more sense if the Redbook standard was set to 1 volt like tuners and consumer tape machines had been prior to digital.


I've noticed some confusion around this topic over the years so here are two things that are related to it:

the volume control **does not** say how loud you are playing the system. The signal level does.
Amplifier gain is different from amplifier power. Two amps can put out the same amount of power but one can have 25dB of gain and the other 35dB; obviously the one with the higher gain will play louder with the same signal level, but in the end both amps will only get as loud as their power allows.

See, here’s the thing about the internet: zero editorial standards

Some people need to prove this every day.

Think of gain as a voltage multiplier. 26 dB of amp gain ~ 20x the input voltage.

16 dB ~ 6x the input voltage.

Of course, every device has a fixed output voltage, set by the voltage rails of the power supply. This is one of the amp watt limits.

To drive an amplifier with 16 dB gain to the same level, you must provide 20/6 more volts, or 3.33 x the voltage.

This will require your pre to put out more voltage than normal, and also more noise.

Another way to think about this is that 1 Watt into 8 Ohms is 2.83 Volts.

At 26 dB, the input required is 0.141 Volts to create a 1 watt signal.

At 16 dB the input required is 0.47 Volts to create a 1 watt signal.

Best,
E

Thanks for the confirmation, guys. No matter how much I read and think things are obvious, I start to doubt myself.

With standard digital outputs being so high it almost makes sense to use a lower gain amp so you don't need to attenuate the signal so much (all other things being equal).

I guess what I was missing is how different things are with analog. I didn't fully appreciate just how much gain MC phono stages need just to get some of those low output cartridges amplified to 300mV. So with an analog system of course you would need some gain in the preamp. While at typical listening levels you may not need it, it would be a shame if your system was limited to only what you absolutely needed.

I do know I have a big blind spot when it comes to vinyl. As a kid, once I got a Walkman, I switched to cassettes over 45s on a Fisher Price record player. I started collecting CDs in college and am now streaming more than I ever thought I would. Couldn't bear to listen to a cassette the last time I even bothered connecting my tape deck. My main objection to vinyl is the ticks, pops, and noise. I'm easily distracted. The nicer systems with well cared for records may sound incredible (haven't had the pleasure), but the price of entry to get to that level is quite a barrier (as well as not owning any records).

Right now I'm using a Schiit Saga+ (unity gain) as an inexpensive interim preamp while I explore some different power amp and speaker types. I think as long as I don't try any really inefficient speakers or go for face melting SPL I should be okay. For now. 

Remember that preamps tend to have fixed gain stages internally.