What is the role of a preamp?

[Asit]

Very nice answer, Sridhar. I was thinking of writing very similar stuff, but you beat me to it.

Regards.

 

[edjamesx]

I am not more technical ... and I couldnt understand the real pupose of preamp. Can anyone explain in simple terms who need to use preamp in what circumstances ?.

Is preamp similar to AVR?.
Is preamp better than AVR or preamp need to be used along with AVR for further enhancements?.
Does it increase the RMS wattage of AVR ..so that there's very less distortion?.

 

[audiodelic]

In my case i have a beresford caiman which can be used as a preamp with its variable outputs connected directly to a power amplifier.

How much real world benefit would i have if i add a dedicated preamp, will i be able to actually hear the difference or is it a more in theory difference?

 

[edjamesx]

I am not more technical ... and I couldnt understand the real pupose of preamp. Can anyone explain in simple terms who need to use preamp in what circumstances ?.

Is preamp similar to AVR?.
Is preamp better than AVR or preamp need to be used along with AVR for further enhancements?.
Does it increase the RMS wattage of AVR ..so that there's very less distortion?.

It seems to be AVR is a combination of preamp and power amp. Am i right

And power AMP gives the power to drive speakers. (It gives the real RMS power)
And preamp does the source selection and some sound processing ??

 

[marsilians]

I know we are going a bit OT here but there are additional reasons for using log scale vs. linear. Primarily if the relationship between the comparatives are exponential or you want to represent proportions then log scale is the preferred method. As you have correctly indicated, human hearing responds to proportional changes and it makes it easier to quantise this through the logarthmic representation.

Also technically speaking, gain is a ratio, so its just a no. and unitless. I do agree that power units do indeed have to be represented in dbW etc.

Log and Linear are simply two different ways of expressing the same thing. The voltage of the input signal is measured in linear Volt scale. The output signal is also measured in the same linear scale. Volt is an absolute scale and needs no reference. The ratio of these two numbers is a linear number. Gain is nothing but 20 x log(Output Voltage/Input Voltage). dB is a relative scale, and must be formally expressed as dBW (with reference to 1 Watt), dBmW (with reference to 1 milliwatt), etc.

Why use log scale? First, when a set of measurements involve a large range, log is helpful to compress that range to manageable numbers. In our example, output voltage is very large compared to the input voltage. Second, our ears hear in logarithmic fashion. Hence audio loudness, gain, etc are expressed in log scale.

Signal to noise ratio of an amplifier is a measure of the noise floor of an amp as a whole. If an amp has a low noise floor, it will be more sensitive to lower level input signal, and hence will be considered more resolving of details. By extension, it will give the amp a higher dynamic range (allows the signal to swing from very quiet passages to very loud passages, without obliterating the low passages). Again, S to N ratio can very well be expressed in linear scale (amplitude of desired signal/amplitude of noise) but the more conventional expression is to express it in logs.

 

[kaushik]

one thing here , if you setup sounds good dont buy preamp if you can
if you must just try if it id matching.

Specially tube pre may degrade sound if not matched, many time solid state pre
gives better SQ.

 

[BLASTO]

It seems to be AVR is a combination of preamp and power amp. Am i right

And power AMP gives the power to drive speakers. (It gives the real RMS power)
And preamp does the source selection and some sound processing ??

AVR is like integrated amp in stereo.

There are dedicated 7.1 channel processors also. These need to be connected to 7.1 channel power amps. Those are like pre-power combo of the stereo world.

 

[atozguy]

A good preamp is like Lingerie. It makes the content and playback more revealing, allowing the man a deeper insight into the source material, and paints a vivid seductive picture of the artists original intent, and keeps him thirsting for more ... A good preamp titillates the listeners senses hyeah:

I hope this post explains things as it really matters, in a format more understandable to the lay audience than all the previous needlessly technical and geeky explanations

--G0bble

If a good preamp can be equated to Lingerie, then what would you equate to a good power amp? Like me, hopefully, other members too, who thanked your post will have this vivid and seductive question reeling in their heads.

atozguy

 

[ukjeyaraj]

It seems to be AVR is a combination of preamp and power amp. Am i right

And power AMP gives the power to drive speakers. (It gives the real RMS power)
And preamp does the source selection and some sound processing ??

AVR has pre+power and also process video signals. It may have tuner(i.e., radio) too.

 

[reubensm]

There is an argument that preamps are ment for impedance matching and equalization. Tone controls and other sonic controls are purely for catering to user requirements. High end preamps dont use these as they attempt propagate a pure-signal path.