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What is pre-amp for?

 

Anonymous
 
What is the usage of pre-amp in av-receivers? As far as I know, pre-amp are used to amplify the signal. How does it work. Aren't av-receivers good enough that they need amplification?

 

Bronze Member
Username: Kano

Post Number: 17
Registered: Oct-04
Not for speakers that can suck up a lot of juice, such as ones that contain large drivers that rival many subwoofers.

Some speakers can handle as much as 600W or more. These would be in any normal sound stage be used as front loudspeakers with less powerful speakers used for the centre and surround channels. To buy a receiver that can output 600W over all channels would be rediculously expensive.

Even the Sunfire Ultimate Receiver http://www.sunfire.com/ultimatereceiver.htm has 200W per channel and that is far excessive for any normal room.

So you buy a 2 channel pre-amp that can power the front loudspeakers or a passive subwoofer (no included pre-amp). Pre-Amps can produce exactly the kind of power you need to power different speakers, like the Crown Amps used to power the SVS SS subwoofer system. http://www.svsubwoofers.com/ampeq_crown_k1.htm

Therefore a pre-amp works INSTEAD of a reciever's channel output to offer more flexibility in the sound your system can produce.
 

J. Vigne
Unregistered guest

Kano - Don't take this wrong; but, you have none of that answer correct. I would direct both of you to this thread:

https://www.ecoustics.com/electronics/forum/home-audio/56618.html

You will find some straight information on that site. If you have further questions, please ask after reading these posts.



 

Bronze Member
Username: Frank_abela

Berkshire UK

Post Number: 100
Registered: Sep-04
Anonymous,

The preamp stage in any amplifier (be it receiver, integrated two channel amp or pre/power) is mainly there to switch between sources and to control volume. The preamp may also contain a tape loop to give you the ability to record without being affected by the volume control. In some cases, the preamp also contains boost controls such as treble and bass, but this is not usually the case in higher end equipment, mainly because these controls are usually detrimental to sound quality. In the casde of home theatre, the preamp stage also contains the processing to give you DTS/Dolby-AC3/Prologic etc.

If the preamp contains a phono stage for a record deck, this initial stage of amplification is used to bring the output of a record deck up to a similar amount as that provided by line level sources such as CD players and tuners. Line level sources are not amplified at all. The real amplifaction of those sources happens in the power amp.

Regards,
Frank.
 

Silver Member
Username: Bleustar

Pensacola, Florida

Post Number: 134
Registered: Jul-04
Pre amp means exactly that Pre(before)Amp(amplification). Except for phono application(as stated above) the components in the pre/amp or processor are just to control input switching, volume level, sound contouring(bass/treble/balance)etc....

The quality of the pre/amp or processor can affect the sound, but the amplification is from the power amp, whether it is a integrated amp (power amplifier and processor), receiver (power amplifier, processor and tuner, or power amp(no processor or tuner).
 

Bronze Member
Username: Kano

Post Number: 19
Registered: Oct-04
"Kano - Don't take this wrong; but, you have none of that answer correct."

Oops, I was thinking of pre-out, not pre amp. So what's the difference between a pre-amp and an equalizer then?
 

J. Vigne
Unregistered guest


Bass and treble controls can be considered a very basic equalizer. In essence what you think of as an eqaulizer is just a more sophisticated version of bass and treble with more points in between to adjust. It normally goes in a tape or proccessing loop of the pre amp. It can be placed between the pre and power amp but this is a less desirable location within the playback chain. There is a misconception that adjusting the gain on an equalizer raises the power of the amp or changes the pre amp in some way. It does not, it merely raises or lowers the voltage coming from the EQ and passes that voltage level on to the next gain section of the system.



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