What does an Amp do and why get one?

Discussion in 'AV Receivers' started by MarshallSlate, Aug 23, 2003.

  1. MarshallSlate

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    i read the primer that didnt really say naything useful on amps
     
  2. Jason GT

    Jason GT Second Unit

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    A loooooong time ago (before my time) apparently everyone bought multiple boxes to put together a stereo system:

    one box for a tuner
    one box as a preamp (selects input, volume control)
    one box for a power amplifier (amplifies the signal from the preamp to drive loudspeakers)
    and usually a source device (turntable, back in the day)

    The signal from the source device is very low level - insufficient to drive speakers. The amplifier's job is to strengthen this signal such you get sound.

    A receiver combines a tuner, preamp and power amp all in one box. If you hvae a receiver you may not need another amplifier.

    If you DO have a receiver, though, you may want to add an amplifier to increase the amount or quality of amplification.
     
  3. MarshallSlate

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    thank you very much
     
  4. Andrew Pratt

    Andrew Pratt Producer

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    Basically an amplifier takes an incoming signal and boosts its level. Now the amplifier always runs wide open meaning that there's not way to control the volume on the amp so its the pre amplifier’s job is to control how much signal gets to the amplifier and thus how loud the speakers play. Now in most cases today we need more then just something to control the volume we also need post processing to decode things like DTS and Dolby Digital as well as offer video switching for all the devices we want to connect to the system so in today’s market you're more likely to find a pre-pro which basically means a pre amplifier and processor all in one box. It also might have a tuner in it as well for the radio. A receiver is simply a pre pro, tuner and amp all in one box (note if its just a pre pro and amp without the tuner its technically an integrated amp) So why bother going separates if you can get them all in one nice neat box with a receiver? Well there's a number of issues to consider that may or may not prove to be that important to you. The biggest reason for separating the pre pro section from the amp is that pre pro's tend to generate noise that can add to the noise floor of the amp if they're placed to close together or there isn't adequate shielding between the two. For example the Rotel 1055 receiver is for the most part just a Rotel 1066 pre amp with 5 75 watts amps onboard. The specs for both are very similar but the noise on the receiver is a few dB's higher then for the separate pre amp. In the real world you may never really notice the differences but they are there. Another reason to consider going with separate box's is that upgrades can be easier since you tend to loose a lot on depreciation on the pre pro section since technology advances so quickly there while power amps tend to keep their value longer. Most of us would agree that a quality amp will have a longer lifespan then today’s pre pro's. (I have a power amp that's at least 5 years old and is still a nice little amp while the matching pre amp for it now long since retired for the latest flavor of the month). With high priced receivers since the pre pro sections are tied to the amp's they tend to depreciate as quickly as true pre pro's and thus loose their value very quickly. This quickly becomes a numbers game though and there are arguments on both sides on which is the better buy since others will argue receivers are easier to sell then pre pro's which is likely true if you can ignore the fact you're selling it for far less then you paid for it. More often then not though the amps found in most receivers aren't all that great and certainly not as clean as a true dedicated power amp. There's exceptions to the rule but given the choice between a power amp or receivers amp most will pick a power amp. In fact a common upgrade path for people is to first buy a receiver that has pre out jacks to connecting a power amp then later on adding a nice power amp to take the load off the receiver. This can work very well with some receivers making very fine pre amps (Rotel 1055 for example) as the cost is usually a little less then pre amp equivalent due to market share. Again though the noise floor is usually better on true pre amps...at least on the bench[​IMG]
     

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