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why preamp?

Discussion in 'Sound Science' started by oqvist, Jun 2, 2010.
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  1. pcf
    Don't forget that  input switching is another important function of a preamp.. Even in this digital age, a lot of people still have more than one source- cd player, computer, streaming etc..If you have a vinyl source, you will also need a separate or built-in phono stage to bring the signal to line level.
     
  2. Lavcat


    Quote:


    Thing is I have the preamp, a Threshold FET 10/HL, and I would never be able to afford a dedicated headphone amp of the same class.  And the FET 10 is probably the only piece of Nelson Pass equipment that I will ever have.  I believe the rated output impedance is 100 ohms.
     
    I never tried the FET 10 with headphones till two days ago, but so far it sure sounds good.  Someone on diyAudio suggested adding an additional current buffer, but I'm not yet convinced that it is needed.
     
  3. plonter
    thanks for the explanations all of you guys.   it is not that i am taking this "double amping" thing too seriously,but hey..we are on the sound science forum and we are talking about theoretically geting the purest signal to our headphones, and that's legitimate.  I also learn a lot while i am at it [​IMG]
    while i maybe not able to distinguish between a 3 metet cable and a 1 meter soundwise..i am still getting the shortest possible interconnects i can.  same thing with lossless vs. lossy, all related to get the best signal we can,hoping that by combining a few several factors together (lossless+short cables+"pure" amping+good power supplies etc.) will give us an audible improvement. 
     
    i am now interested to know more about the dac's own "amplification" stage.  what component exactly is lying in there and amplify the sound to a line level output..how does it called?
    and,why is it necessary?  i mean..can't we bypass that "dac amplification" in some way?
    the only way i can think of ,is if the analog signal that produced by the dac (before its amplification stage) will be directly amplified.  am i missing something here?  what's the importance of the dac amplification stage?
     
  4. ipm
    I am contemplating taking my GS-1 and using it as a preamp for my Cambridge audio 55x series so that the GS-1 acts a pre/head amp. Any thoughts on this?
     
  5. SP Wild


    Quote:

    If it is an integrated with separate pre-amp inputs - it may be worth trying, I'd imagine the GS-1 as a pre would be even better than the built-in preamplifier.  However you would lose switching capabilities and worse of all you would lose the use of the remote.
     
    It wouldn't be really worth it from an audio quality perspective if you try to pipe the pre into an existing aux input that doesn't by-pass the volume on the Cambridge.  Unless this Cambridge of yours is in fact a power amp only.
     
  6. ipm
    my idea is cd--->GS1-->Cambridge amp via loop out on GS1 and CD in on Cambridge 550A
     
    the rmote will control each component individually
     
  7. SP Wild
    No.
     
    You're better of with a Y adapter, solid one piece.  Coming from your CD split to your Head-amp and Integrated.  You may need to power up your integrated if you hear distortion with your headamp in this setup.  There is negligible quality loss in this setup - it is the method I use.
     
    Even if the headamp has a dedicated pass through (as oppose to pre-amp) function, I still recommend splitting at the source.
     
  8. Marcus_C

    Quote:

    Ok, i'll have a go. In a dac, in the signal path, there are quite often three parts, a reciever from s/pdif/usb, the dac itself, and the line stage. There are also capacitors/resistors everywhere too. The line stage is the part you're asking about here. There are effectively two types available, active and passive.
     
    An active line stage uses a gain device as amplification (opamp, tube, etc). A passive line stage doesn't do any amplification and as such, it often doesn't have a buffer, it's simpler that way. The buffer is the important part of the stage, it takes a source with high input impedance and outputs one with a low impedance, useful for component matching. The problem with a high impedance output is what happens when that signal travels down the wires and comes across the capacitance in the wire, which means the signal path after needs to be as short as possible. With that being the case you might notice the highs aren't quite as high as they used to be. A few people note less depth and drive from passive pre-amps and they are harder to build a system around.
     
    Don't quote me on this, most of it is second hand from reading diy audio and from my somewhat limited experience.
     
  9. plonter


    Quote:


    thanks for the explanation.
     
  10. ipm
    "You're better of with a Y adapter, solid one piece."
     
    I am skeptical about that my self but i will try both; however, I have never done this.
     
    i imagine that the y connector is used on each of the RCA outs from the CD (one red one white) ? one output of the y connecor goes to headamp the other goes to integrated amp?
     
    they say in my GS-1 manual that Y-connectors are not needed with loop out or with preamp out capability.
     
    can you provide a link to getting a Y-connector?
     
  11. SP Wild
    Just use the loop out.
     
  12. ipm
    the loop out is the prescribed way, I agree and that’s my first choice.
     
    my concern is that the RCA in on the power amp will be overloaded with the headlamp output (1 Watt).
     
    as stupid as that sounds, I am wondering about it because the Cambridge Audio Azur 550A does have a volume control and it can be used as a preamp itself.
     
    if the CD player itself produces much less than 1 Watt then it could be trouble.
     
    I have no idea if this is too much for a CD in circuit.
     
    by all accounts, it should be OK if the 550A is any knid of 'power amp' worthy of the title. :)
     
  13. SP Wild
    The manual should be able to clarify.  I don't have a gs1 so cannot comment.
     
  14. ipm
    i agree. :) its an experiment. fun, no? i will try soon.
     
  15. Sumflow
    When we have multiple volume controls in the path.  How should each pot be set?
     
    Example one.
    Apple computer> IEM
    In this case the only volume control is on the computer.
     
    800px-McIntosh_MA6800.jpg
     
    Example #2
    Apple computer > Receiver > IEM
    When you have more than one volume control should one of these be set wide open?
     
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