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AVR300 stereo mode without DSP ?

Discussion in 'Arcam Owners' Forum' started by clauser, Jul 13, 2005.

  1. clauser

    clauser
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    Hi,

    Is it possible with the AVR300 to route an incoming stereo PCM signal (from the digital output of a CD or DVD player) straight to the internal DAC without going through the DSP ?
    The reason I ask this is because the DSP slightly degrades the sound and I thought that for plain stereo no DSP is needed if the speakers are set to large.

    Kind regards,
    Erwin
     
  2. Hifi addict

    Hifi addict
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    I believe that if you set the DSP settings to "stereo" the DSP is not really doing anything with it.

    the best way to bypass the DSP is to connect your CD/DVD through an analogue connection to your AVR300 and set it to "direct"
     
  3. tvh3ad

    tvh3ad
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    I'm sure someone will correct me if I get this wrong, but I believe this is easily accomplished by pressing the "Direct" button on the front panel. According to the manual, "Direct" mode shuts off all digital processing and bass management, which sounds like what you want to do.
     
  4. clauser

    clauser
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    Hi,

    The direct button only works for analog connections, not for digital.

    Kind regards,
    Erwin
     
  5. clauser

    clauser
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    Hi,

    According to the manual, all stereo settings go through the DSP.
    I agree with you that using the analogue connections is the best way to go, but then the DACS in the cd player have to be of better quality than the DACs in the AVR300. Which is not the case in my situation (Philips DVD963SA).

    Kind regards,
    Erwin
     
  6. tvh3ad

    tvh3ad
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    Oops, yes -- you are correct. And, upon further close reading, it appears that what you want to do is not possible. From the manual page re subwoofer settings: "Note that the above three Stereo Mode settings pass the audio through the DSP, which may degrade the sound quality slightly. This can be avoided for the ‘Large’ setting by pressing the DIRECT button to bypass the DSP processing."

    Ergo, the only way to completely disable the DSP is to use DIRECT, but this mode is only available for analog sources and yours is digital.

    Sorry about that.
     
  7. Jim_R

    Jim_R
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    So the large and small speaker size settings on the AVR300 do not work in Direct mode?
     
  8. clauser

    clauser
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    Indeed.

    Erwin
     
  9. Designer

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    Folks,
    I think people are getting a little confused here.

    If you have an ANALOGUE stereo connection into the AVR300, putting it through the 'ADC - DSP - DAC' route is undoubtedly worse than "Stereo Direct", which keeps the audio entirely in the analogue domain without conversions.

    The original question referred to a PCM stereo input. The fact that the PCM data passes through a DSP before going to a DAC does not necessarily mean that it will be degraded. In the case of the AVR300, the DSP and DAC data are all sychronously clocked (obviously) and are each fed from their own individually buffered master clock, not one shared line. In PCM stereo mode, data into DSP = data out of DSP (provided that bass management isn't required for small speakers etc).

    So, to answer the original question: No, there isn't a physically direct data path from the PCM input to the DAC, but actually there isn't really any need for one.

    Cheers, Mark
     
  10. clauser

    clauser
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    Hi,

    I completely agree with this statement. The reason for my question was that they state in the manual that even with the speakers set to large, the stereo mode through the DSP may slightly reduce the quality (see above quote from tvh3ad from the manual). I find that strange when the speakers are set to large.

    Kind regards,
    Erwin
     
  11. clauser

    clauser
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    Hi Mark,

    Again i agree with this statement ;) but i think the quality loss in this case is more due to the ADC than going through the DSP. In the manual they say that it is due to the DSP that the sound may slighlty degrade so i thought they were talking about digital stereo PCM.

    Kind regards,
    Erwin
     
  12. Designer

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    Right ho.
    I have just armed myself with a sample copy of the AVR300 manual that was lying about the place.

    You are correct with the quote, however the manual fails to make it clear that the statement refers only to an ANALOGUE input. It would have been technically more correct (and clearer) if it said 'ADC-DSP-DAC' path instead of "through the DSP".

    The DSP isn't the cause of degredation it is the additional ADC and DAC conversions that are.

    I didn't do much proof reading on the AVR300 manual due to other project comitments. I guess it passed the others too.

    With a PCM input the "degrade through the DSP" issue is not valid as it avoids the ADC stage.

    Cheers, Mark
     
  13. clauser

    clauser
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    Hi Marc,

    Thanks a lot for this clarification.

    Kind regards,
    Erwin
     
  14. Hifi addict

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    technically you are correct, but I think that the majority of people will not understand the abbreviations ADC/DAC and therefore it does make sence to only mention DSP.

    only the few hifi experts would question this statement, like just happened :D
     

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