Why amplify?

Discussion in 'Archived Threads 2001-2004' started by Anthony GT, Dec 7, 2001.

  1. Anthony GT

    Anthony GT Stunt Coordinator

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    I'm starting to think about upgrading some of my equipment. One thing I don't have now but have read a lot of posts about is an amplifier.

    My question is why do you need one? I know they just don't add volume, so what are the benefits of having one?

    Also, what is the difference between a pre-amp and an amp? How these things fit together?

    I will be upgrading my receiver to eitherthe Denon 3802 or the Onkyo 787 (as of now anyway) if that is important.

    Any help would appreciated!

    Anthony
     
  2. Jeffrey_Jones

    Jeffrey_Jones Second Unit

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    Hello,

    A good quality amp can do a lot for a systems overall sound quality. This depends a lot on the other components you have in your system. Some speakers are very demanding and require a lot of good, clean power to make them sing. This can be due to their size, sensitive, impedance, etc.

    Both the Denon and Onkyo receivers you are looking at have very nice built in amps that will be capable of driving most speaker systems. I would start there and then decide if you need to upgrade to a separate amp. If you need more power, or find that the overall sound is not what you expect, I would first look at what speakers you have and then consider an amp.

    A Pre-amp is the processor that would send a signal to an amplifier. A receiver has both a pre-amp and an amp built in.

    Thanks,

    Jeff
     
  3. Bob McElfresh

    Bob McElfresh Producer

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    I can answer some of the questions:
    Your receiver is really 2 different things:
    - A pre-processor
    - An amplifer
    The job of the pre-processor is to take several different kinds of signals and convert them to individual "channels" of sound, one for each speaker.
    The job of the amplifier is to take line-level sound signals and amplify them with power so they can drive a motor - your speakers.
    The pre-processor does some very interesting things. It can take a L/R stereo signal and simply pass it along, or it can detect and decode a ProLogic signal and break it into 4 channels of sound.
    It can also take a Dolby Digital signal and break this into 6 channels of sound. It can often do the same with a DTS digital signal.
    It can take a Dolby Digital EX signal and break this into 7 channels of sound (the extra one being for a rear-center speakers).
    It can also take any of the above signals and do interesting Digital Signal Processing things to the sound.
    It also allows you to hook up 2/3/4/5 different sources and switch between them.
    It also does one very important thing: it controls the volume.
    The connection between the PreProcessor and the Amplifier are simple coaxial cables, usually with RCA plugs.
    The Amplifier is a fairly "dumb" device. It takes a signal from a rca cable, amplify's it and sends the results to some speaker terminals.
    Why go with an external Amp?
    The general consensus is that the good quality models of A/V receivers give you fairly good amplification and pre-processor functions in a single box. Many great sounding systems use only these, or one of these and a self-powered sub-woofer.
    But an amplifier is a brute-force device. Unlike transistor/IC devices, one thing that makes one amplifier better than another is the shear size of it's transformer, the quality of the materials and the size of the capacitors.
    Go to your local stereo store and look into the top of both a 5-channel amp and a A/V receiver. You should be able to see a large transformer through the vent slots.
    The Transformer & capacitors take up a large part of the A/V receiver. But the one in the dedicated amplifier - it takes up ALL the room. It's usually a large toroid (doughnut) of metal covered with wires. It look (and is) dangerous.
    The sheer size of the parts in a dedicated amp means it can produce more power for longer time and run cooler. For Music, which usually drives 2 large speakers with sound 100% of the time, an external amp can often cause the sound to be tighter and more detailed because the amp has lots of reserve power for the more subtile sounds.
    An HT system has 3 more speakers, but unlike music, it is not pushing them all with sound all the time. So in many cases it has pleanty of reserve power for the center and L/R speakers.
    But there are some chapters of some movies (Opening of Saving Private Ryan, or the lobby shoot-out scene of The Matrix) where there are many minutes of all 5 speakers pumping both loud and subitle sounds. For these very demanding scenes, an external amp can usually do a better job.
    Does this help?
    If you are looking at a new receiver, one feature to try and get is something called "Pre Outs". This is a set of RCA jacks for each speaker. You DONT hook the speakers to these, but it allows the receiver to do it's magic (decoding, DSP, volume, etc) and have the results appear at these jacks. You then add a 2/3/4/5/6 channel amplifier to these jacks and hook the speakers to the amp and now your receiver does the pre-processor functions and the power comes from the amp.
     
  4. Kevin. W

    Kevin. W Screenwriter

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  5. Andrew Pratt

    Andrew Pratt Producer

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    to be more accurate a receiver must contain a pre amp, tuner and amplifers for 2 or more channels. Most modern receivers also do processing of the incoming signal into pro logic, DD and DTS.

    A receiver without a tuner is actually just an integrated amp ie pre amp and amp in one box

    basically the amps job its to amplify the signal that the processor generates and the pre amp's job it to control the volume.
     
  6. Anthony GT

    Anthony GT Stunt Coordinator

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    Thanks guys. I think I'm starting to get it. At least the amplifier. But why would I want a pre-amp?

    Bob listed a lot of things a pre-amp can do, but my receiver can already do all of those things. I understand how a dedicated amplifier is superior to the amplifier in my receiver(bigger is better in this case), but what makes a separate per-amp better? Better circuitry to decode signals?

    Anthony
     
  7. Andrew Pratt

    Andrew Pratt Producer

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    since your receiver consists of a tuner, pre amp, amp and processing chips there's a lot of interfence going on inside that box. They also all share the same power supply which likely hurts the amps demand for current etc. The idea behind seperate components is to allow each to opperate as a seperate entity..and it allows you to pick the model that suits your needs best rather then an all in one package the receiver offers.
     
  8. Anthony GT

    Anthony GT Stunt Coordinator

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    Thanks Andrew. I'm definitely leaning towards getting an amp but may hold off on the pre-amp for now.

    My final questions on amps is how do the channels work? Meaning, I see a lot of 2 channel amps. Does this mean that I can amplify only my front speakers? Are those the only 2 speakers worth amplifying?

    When I add a SVS passive subwoofer I need another channel right? So I should look for a 3 channel amp?

    I've also seen posts where people use old receivers as amps. How does that work? Do you just run the sound from the pre-outs on your main receiver to a line-in on the old receiver? Why is that better than just using your currect receiver's built in amplifier? I'm guessing that it's because then the the current receiver's amp can direct more power to the remaining channels. Am I right?

    Thanks!

    Anthony
     
  9. Greg Rowe

    Greg Rowe Stunt Coordinator

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    Real Name:
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  10. David J Wang

    David J Wang Agent

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    How much better can a separates system sound over a flagship receiver? Will it blow me away or is it subtle?

    Also, is it inconvenient to operate a separates system? Do I have to manually control the volume on the amp or would the prepro be able to control the volume?

    Lastly, how much do equalizers help for a separates system?
     
  11. AjayM

    AjayM Screenwriter

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    When you start getting into the Flagship reciever prices ($3000+) seperates become a real option. However, for $3000 you are still pretty much in the lower end of the seperates area, so you won't get nearly as many options as you would with the reciever. You'll have less inputs (for video/audio sources, digital inputs, etc), less "fluff" features (sound fields, etc). If you have a fairly simple system, then those extra inputs don't matter and most people don't use all the extra "fluff" options, so it may be the way to go. From that you'll get an easier upgrade path (but not cheaper), most likely you will get better sound, probably more power, etc.

    Andrew
     
  12. Nick G

    Nick G Stunt Coordinator

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    David, as long as your "flagship" receiver is well designed and has enough power to drive your speakers I doubt you could hear the difference between it and seperates. In fact there is no reason that the receiver could not be superior to the seperates. Remember a receiver is just an amp, pre amp and tuner in one box instead of three seperate boxes. It is the design and quality of all the individual parts that are importent, not whether or not they are in one box or three boxes. One thing some folks like about seperates is that they can change to a different tuner for example without have to change amp and preamp. They like that flexibility and are willing to pay extra to have it. IMO though, for 95% of us the receiver is the a better solution.

    Regards, Nick
     
  13. PaulHeroy

    PaulHeroy Stunt Coordinator

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    They can potentially help a great deal depending on your room, speakers and preferences. The single biggest problem area for most folks is the interaction between bass and the room; a parametric EQ is a popular way to help tame bass peaks. But be careful about too much EQ; most people will tend to start raising levels and pretty quickly start to effectively increase the overall volume by a fair bit, potentially straining your amps esp. in a receiver.
     

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