Preamp gain ???

i would say this: i think it unnecessarily complicates the problem is you are trying to solve amplifer-speaker interface problems at the preamplifer. it is more manageable to decompose the problem; with regard to the preamplifier the focus should be on the input signal levels from the sources. you can then focus on the output signal from the preamplifier but most reasonable preamplifiers should be able to drive a power amplifer into clipping at maximum output voltage (such that in reality you would likely never get anywehere near the maximum output voltage). then you deal with issues of speaker sensitivity sepearately but that is more concerned with whether the power amplifier is up to snuff to drive the speaker load.

so the issue at the preamplifier is the input sensitivity of the preamplifier and the input signal levels from the soruces. i would expect that the input sensitivity of a preamplifier is going to be around 500mv, which is the line voltage signal level that you tend to get from many sources. cd players tend to be a bit higher. where you really need to watch out is when using phono sources. here you have to make sure that the phono stage provides sufficient gain for the given cartridge. ideally you want the output signal level from the phono stage to come in at around the input sensitivity of the preamplifier.

so once you have managed the input signal levels from the sources then you want to make sure that the preamplifier can drive the output voltage to the power amplifier. as i stated, the voltage amplitude should be sufficient but you probably want to check the preamplifier manual to find out what is the minimum input impedance that the preamplifier expects to see at the power amplifier, then check the input impedance of the power amplifier to make sure that the specified input impedance is considerably higher than the minimum needed by the preamplifier.

that's the analysis that you should do at the preamplifier. what you want to determine is whether the sources are providing adequate signal levels to the preamplifier and that the preamplifier is providing an adequate signal level to the amplifier. a side benefit of this analysis is that the signal being provided to the power amplifier will likely have a better signal to noise ratio, which, if the amplifier is up to snuff, will result in a better sounding system. issues related to the interface between the power amplifier and the speakers should be addressed in an analysis of the capabilities of the power amplifier.

Paperw*- Nothing that you have said is incorrect but you have neglected the attenuation/gain (if active) provided by the pre-amp, which then is added to the gain of the amp. That can result in excessive overall system gain which results in the user having to operate his pre-amp w excessive attenuation which can have negative effects on the sound. The speaker/amp interface is not usually a decision based on max gain provided by the amp vs. speaker sensitivity, and room size, source output and volume preference all vary. Therefore, god in her infinite wisdom invented the pre-amplifier. Some have adjustable gain for each input. Some do not. Some are passive and provide attenuation only. some are active and have varying amounts of gain. Some of have stepped attenuators and some do not. Some have tape loops and some do not. Some have line and phono stages. some of those w phono stages can accommodate LO MC carts, some only MM or MI carts. Not all line level sources have the same output voltage (some CD players can deliver 2V!) The ability to alter the overall gain/attentuation of a pre-amp may be vital under some circumstances. IN fact some manufacturers have recognized this by incorporating separate gain controls via front or rear panel toggle switches (e.g., Supratek); front panel rotary controls (e.g., Joule), internal dip switches/jumpers (e.g., Nagra) or internal resistors that are designed to be switched out or bypassed (some ARC).

I for one cannot imagine that sensitivity would be the primary criterion I would use to pick a speaker. Of course, that does not mean that you don't need to make sure that you don't get a serious mismatch between speaker and amp but I don't think that you are going to go w a 84 db/w/m speaker instead of a 92 dB/w/m just to provide proper volume control.

Again, this also assumes that you have a reasonable match btwn amp and pre-amp based on impedance and input sensitivity. Just my opinion; worth the proverbial $0.02. IME, YMMV, do not try at home, professional driver on closed course, LSMFT, etc, etc. ;~)

02-21-11: Swampwalker
Paperw*- Nothing that you have said is incorrect but you have neglected the attenuation/gain (if active) provided by the pre-amp, which then is added to the gain of the amp. That can result in excessive overall system gain which results in the user having to operate his pre-amp w excessive attenuation which can have negative effects on the sound. The speaker/amp interface is not usually a decision based on max gain provided by the amp vs. speaker sensitivity, and room size, source output and volume preference all vary. Therefore, god in her infinite wisdom invented the pre-amplifier. Some have adjustable gain for each input.

what i am stating is that if you manage the signal levels at the input of the preamplifier, the gain of the preamplifier is largely irrelevant [i appreciate that there is a gain relationship between the input sensitivity level and the maximum output level from the preamplifier]. that is why i am stating that you should look at the signal levels from the sources and the input sensitivity of the preamplifier and manage the problem at the input of the preamplifier. in the case of a phono source, you want to adjust the gain of the phono stage so that the phono preamplifier provides an input voltage level that hits the input sensitivity level for the preamplifier. on the other hand, if you have a source that produces a "hot" signal (like the CD that you mentioned) that is way above the input sensitivity, then the adjustment is to reduce the signal level at the input of the preamplifier. that's what an attenuator would do. some preamplifiers have trimming resistors that allow you to accomplish the same thing on a per-input basis. for my own part, i have never made use of an attenuator but YMMV.

the problem with the focus on gain as a selection criteria for a preamplifier (and, btw, i would expect that the input sensitivity of the preamplifier would vary according to the gain) is that if you select a gain level based on a "hot" signal, then the other signal levels are likely to be below the input sensitivity level for the preamplifier. in that case you are more likely to experience degraded signal to noise ratio for those weaker signals.

as i stated, you also want to make sure that you know what the minimum input impedance the preamplifier needs to see in the amplifier, which is something that you should be able to get if the manufacturer supplies good product specifications. but, in practice, i think impedance matching is rarely an issue. yeah, i suppose you should check the input sensitivity of the amplifier for completeness, but power amplifier input sensitivities tend to run between 1v and 2v, so i would rarely expect that to be an issue either. but, of course, it is always a good idea to check this stuff just in case...

the point is, if you ensure that you provide appropriate input signal levels to the preamplifier from the sources, you are not likely to have a problem in providing an appropriate input signal level to the power amplifier from the preamplifier. then the task becomes one of whether the amplifier is up to the task of driving the speakers. but if you have to take on the amplifier-speaker interface issues from the preamplifier, then you've probably got some problems in your system in general.

what if the gain in the pre-amp section is too high and, as a result, generating excessive hiss or residual noise? I have this problem and even the manufacturer states it is coming from the pre-amp section on my integrated. What else can one do if not reduce the gain?

if your integrated has pre out and main in jacks or a tape/processor loop, you could insert attenuators in the loop.