receivers as pre/pro's...

Discussion in 'Archived Threads 2001-2004' started by John Doran, Mar 20, 2002.

  1. John Doran

    John Doran Screenwriter

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    if one were to use a 140wpc receiver as a pre/pro for much more powerful separate amps - say 400wpc - how does the volume control of the receiver work with those separates?
    i mean, assume the volume goes from -60 to +20 at increments of 1db, what happens when you get to +20? won't there still be all kinds of power left in reserve in the separate amps that you will be unable to access?
    what's happening here? would the increments between positions of the volume control simply become greater? say, from 1db to 2db? or what?
    also, what happens if you use a separate amp for the mains, and use the receiver's amps to drive the other channels?
    my (perhaps mistaken) understanding of pre/pros is that the volume control doesn't have a fixed range like the volume control of a receiver.
    can someone help me? [​IMG]
    thanks,
    - jd
     
  2. Marc_E

    Marc_E Supporting Actor

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    This is purely my opinion:

    The db increments are based on the receivers internal amp output. When you hook up a power amp externally to the pre outs, the volume up/down is just a vultage increase/decrease going out the pre-outs. If you were to power the mains, you would first calibrate them to all the other speakers so everything would be balanced.

    Hope that helps

    Marc
     
  3. Kevin. W

    Kevin. W Screenwriter

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    Calibration is the name of the game. Once everything is hooked up calibrate to 75db at which ever position on the knob you want.

    Kevin
     
  4. John Doran

    John Doran Screenwriter

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    i don't think i've managed to be clear, since i'm not sure i understand the responses.
    what i'm wondering is what happens when you want to go louder than the +20 on the dial of the receiver? I mean, i assume that it would be entirely possible to use the receiver as a pre/pro for an amp that is more than capable of going higher than +20, no? for instance, what if you use a 100wpc receiver as a pre/pro for a 1000wpc boulder monoblock? surely if the volume stops at +20, you're just not using all of the juice in the amp...
    again, my assumption is that the volume on pre/pro's isn't fixed like it is on receivers. is this right? does the volume on the anthem or outlaw or lexicon only operate between two extremes (e.g. -60 and +20)? or does it just keep increasing indefinitely (that is, until the actual limits of the amps and or speakers are reached and you have to lower it)?
    thanks again for the help.
    - jd
     
  5. Michael Mohrmann

    Michael Mohrmann Screenwriter

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    John,
    "again, my assumption is that the volume on pre/pro's isn't fixed like it is on receivers. is this right?"
    Actually, the volume control in a receiver is similar to that in a prepro. The receiver with preamp outputs operates the same as a prepro. The term "preamp" means exactly as it sounds, "before the amps". And as has been mentioned before, if your system is calibrated at 75dB, you will be at the same (or nearly the same) volume level whether using the receiver's internal amps or an external amp through the receiver's preamp outputs.
    The +20 setting you keep mentioning is sort of an upper limit. I do not believe anyone with their hearing intact listens to anything approaching that limit. [​IMG]
    Michael
     
  6. John Doran

    John Doran Screenwriter

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    ok. thanks, michael.

    so the numbers associated with the volume are in turn associated with SPL's and reference level. thus, assuming for instance that 0 on the dial is reference level, if the volume is at +20, then the SPL is reference plus 20db (or plus some amount, anyway, and if the amps and speakers are capable of producing that level...), no matter what the amplifier may be.

    right?

    i suspected that might have been the case.

    thanks.

    - jd
     
  7. Bill Kane

    Bill Kane Screenwriter

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    John, I've seen that you are a real theoretical guy for the basis of electronics; more power to you[​IMG]
    For one real-life application installing an Anthem 200x5 amp onto Yamaha/Paradigms, I discovered an immediate +10dB increase in sonic output. To keep my effect spkrs in a balanced level-setting range, I had to use Yamaha's feature to CUT -10dB to the Mains. Then I recalibrated and am quite close to the ref level I had before w/ AVIA.
     
  8. Kevin. W

    Kevin. W Screenwriter

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  9. John Doran

    John Doran Screenwriter

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    kevin,
    i think you're right - none other than john kotches made that same observation not too long ago in response to the same post of mine over at AVS Forum.
    now i need to know how to determine if a receiver, when used as a pre/pro, will output the necessary voltage to the amp stage to get maximum power from the amp...
    the thing is, i'm going to be upgrading my system and want to make sure that if i use my denon 5800 as a pre/pro for amps such as the bryston 14b st (500wpc), that when the volume on the 5800 gets up to, or at least close to, its maximum (+18), that the bryston (for instance) is also at or close to its maximum output.
    in other words, since the 5800 is rated at 170wpc (in fact closer to 140wpc), i would hate to use it to drive 300-500wpc separates if it is only capable of using 140w of that available power. you know?
    - jd
     
  10. BruceD

    BruceD Screenwriter

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    John,

    HT volume controls are "relative position" devices. That means they only change relative to their calibration setting. Not all of them use a zero "0" calibartion position.

    If you set the volume control's "0" zero reference bar at 75dB during calibration, a volume control setting of "0" will equal 105dB (DVD calibration tones are -30dB below reference) no matter what amp you are using (unless the amp clips first). Here a +20 volume control position would equal 125dB.

    If you set the volume control's "0" zero reference bar at 65dB during calibration, a volume control setting of "0" will equal 95dB (DVD calibration tones are -30dB below reference) no matter what amp you are using (unless the amp clips first). Here a +20 volume control position would equal 115dB.

    Most volume controls work on a logarithmic curve just like our hearing and the octave level frequency chart.
     
  11. John Doran

    John Doran Screenwriter

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    bruce,
    i think i understand what you're saying, but in the case of my 5800, the volume controls seem to be set along something like an absolute scale.
    for example, the volume on the 5800 goes from -60 to +18. however, that maximum of +18 varies directly by the amount by which i either increase or decrease the level of even one channel. so, if i increase the level of the center channel by 2db, then, when i turn up the receiver's volume control, it will only go to +16. see what i mean?
    which is what makes me fear that i might be able to get the volume to +18 while driving a bryston 14b st, but only actually be getting about 140wpc RMS out of the amp. you know?
    - jd
     
  12. BruceD

    BruceD Screenwriter

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    John,

    Your talking about volume trim with the +16 and +18. Volume trim has nothing to do with volume calibration.

    If you start the calibration process with an external amp andf internal amps and set the zero calibration levels this shouldn't be a problem.

    When you initially calibrate your Denon, don't you set the master volume to zero?
     
  13. Kevin Deacon

    Kevin Deacon Second Unit

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    Remember, when/if calibrating with AVIA the test tones should be set at "85db" for reference level.
     
  14. John Doran

    John Doran Screenwriter

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    i think i've got it, guys.

    thanks for all the help - i'm grateful.

    - jd
     

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