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why preamp?

Discussion in 'Sound Science' started by oqvist, Jun 2, 2010.
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  1. plonter


    Quote:


    don't you agree that amping the signal only once should be preferred to double amping soundwise?
     
  2. SP Wild


    Quote:

    Yes.  However It may suffice in your situation, but not Ideal.  You now have the problem of the sound needing to pass  through not one, but two potentiometers.  This is not Ideal as it is fundamentally being pre-amped twice over, once actively, and once passively (attenuation) and the actual amplification is another third kind of amplifying.
     
  3. Kees


    Quote:
    We're not talking about that. A power amp does something completely different than a preamp.
    You alway need a power amp when you use speakers, sometimes the poweramp is integrated with the preamp, then we call it an integrated amp (duh).
    What he is doing here is chaining two preamps (a headphone amp is practically the same as a preamp, that's why a lot of headphone amps can double as preamp), which is counter productive.
     
     
  4. plonter


    Quote:


    just for the record..I am not actually doing this,i was just curious about this[​IMG]
    so connecting a pre-amp into a power amp for using with speakers is not double amping?
     
  5. Kees


    Quote:
    No, that is what they are meant for. You alway need a preamp before your power amp, because your power amp does not have a volume control.....
     
     
  6. xxbaker
    Remember, just because there's more things in the signal path doesn't necessarily mean it's worse.  A beta22 has more parts in the signal path than a cmoy, who thinks the cmoy is better?  Having excessive parts can be detrimental if you're stacking parts for no reason, but if there's a purpose then it might not be bad.  Having an active pre and a power amp is "technically" amping twice, but in a poweramp one normally has 3 amping stages so really you're sextuple amping? And your DAC has an I/V stage?? Don't get too caught up in how many things there are.  If it sounds good, then it sounds good.  While more is many times less, there are many other factors to consider.
     
  7. plonter


    Quote:


    yeah,,but even thogh the power amp don't have a volume control,it is still amping.
    so like xxbaker said...it is technically amping twice.    but there is no other choice.
     
    so headphones systems are the only systems that you don't have to amp twice? (considering that you use power amp for speakers).  and is a reciecer is a power amp also?
     
    my third (and probably last) question regarding this is:  the dac output..is it also can count as some sort of amping?  so in this case double amping cannot be avoided anyway.
     
  8. SP Wild
    I give up.
     
  9. fishski13


    Quote:

    [​IMG].
     
  10. xxbaker


    Quote:

    If you want to think of it that way then sure, headphones are the only systems you don't have to amp twice.  That is unless you consider an integrated amp a single amp, then you can amp speakers once according to that definition. A receiver is a combination of a poweramp, a preamp, a tuner, a DAC, an equalizer etc.  Modern receivers do many things.
     
    It gets kinda technical about DAC output stage.  Technically there is an amp stage at the output of most DACs, but it might be different than what you're thinking.
     
    My main point was that trying to avoid double amping is a silly way to think about it because a single amp is made up of many different stages which could all be separated into separate "amps" in a way.  That being said, running your headphones from an amp that's running off the preamp out of your amp/DAC probably isn't the best way to go about it.  It might be though.  Try to experiment yourself and see if you can come to a conclusion.
     
  11. 9pintube
    They CONTROL........That's even what they were originally called "Control Amplifier" ....They control your sources, amp/s volume, etc.etc. One of your most important pieces in your audio chain after your source component.
     
  12. JamesL
    An active preamp is typically a attenuator followed by a buffer, which presents your source with a higher impedance to drive, attenuates the signal, and sometimes has a voltage gain.
     
    Most active monitors/pc speakers and integrated amps/receivers I know of have a "preamp" built inside them, and since obviously a preamp can't drive speakers directly, its followed by a power amp.
     
  13. Kees


    Quote:
    No, it is not amping twice, the amping is done in two stages that are meant to be in this order. They are different. The power amp is to power speakers (not headphones, although some headphones can be treated like speakers and run from power amps).
     
    Headphones just don't need the boost of a power amp, so there is no power amp in headphone setups. 
     
    A receiver is a tuner (tv tuner and/or radio tuner) and integrated amp all in one. So it has all functionality of a tuner, preamp and power amp in one.
     
    A DAC is typically a source and outputs an analog line signal that is input for a preamp or headphone amp (or integrated amp).
     
    A lot of stand-alone DACs that have a built-in headphone amp. Like there are a lot of headphone amps that have a built-in DAC.

     
     
  14. Lavcat


    Quote:

    For what it's worth I am currently driving my headphones from my preamp output directly.

     
     
  15. JaZZ Contributor


    If it has low enough output impedance, this may be a good solution in the sense of minimized signal corruption. A dedicated headphone amp of the same class would probably still sound better, primarily due to its even lower output impedance.
     
    Some amps use complex designs, some are simpler – there are many ways to achieve a good sound. The only thing that matters is if there's a superfluous amplification stage in the signal path. Such cases of double or triple amplification represent a less than optimal solution in that the signal is less accurate and pure than it could be by renouncing one stage. Take into account that the perfect amp doesn't exist. Out of curiosity I once tried two headphone amps in series – also to find out how and how much they alter the signal. The result was a considerable loss of transparency compared to just one amp.
     
    A preamp is a normal component in a speaker setup if it implies a power amp without an integrated preamp stage or at least an input volume control. In this case it nevertheless represents a superfluous amplification stage, since the line-level signal from a CD player is strong enough and needs no further amplification for driving a power amp. The only justification for the use of a preamp is volume control, thus signal attenuation. But instead of an active preamp you could use a simple voltage-dividing attenuator in the form of a potentiometer or stepped attenuator – provided that the source's output impedance and the cable's capacitance are low enough. In this case one could speak of an avoided double amplification as well, since the signal will remain purer compared to the configuration with the active preamp. My own experience with active and passive preamps has confirmed this – the passive variants sound(ed) purer to my ears.
    .
     
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