Posted by UK Dave (A) on October 19, 2007 at 04:19:16

Hi

First post here. I was drawn to this forum by the prospect of the RAKK DAC.

I've recently purchased a SB3 and am already looking at upgrades. I've read various forums and one upgrade path suggested is to take the audio outputs direct from the DAC, bypassing the op amps and capacitors. I'm not to keen on this approach, but it got me thinking.

I've looked into the data sheets for the two DACs (PCM 1743 and 1794) and both appear to output similar voltages (3.1V P-P and 2v RMS). I'm looking to use the passive output stage from the RAKK DAC as an output stage for the SB3, directly from the output of the PCM1748. This would be done in conjunction with a XO-3 clock upgrade. The idea being that all parts can then be used in the RAKK DAC at a later stage.

I realise this will not provide the same results as the RAKK DAC but it may be a cost effective solution.

A few questions -

Does anybody know if this has been tried before.
Any problems foreseen
Will K&K sell the passive output seperately from the rest of the DAC

Dave

• RE: SB3 - KevinC 05:38:33 10/19/07 (2)
  In Reply to: RE: SB3 posted by UK Dave on October 19, 2007 at 04:19:16

  The PCM1748 is a single-ended, voltage output DAC, whereas the PCM1794 is a differential current output DAC, so the Passive Output Stage is not compatible with the PCM1748. If you want to eliminate the op amps from the signal path following the PCM1748, you will have to use a coupling capacitor (to eliminate the considerable DC bias) and then either use this output directly or run it through a 1:1 transformer. The PCM1748 is a low cost DAC, so it doesn't provide the higher end flexibility of the PCM1794 in terms of audio interface.
  
  To ease your way into the RAKK dac world you might want to hang around here until a Mk I comes up for sale by an upgrader to Mk II. It happens from time-to-time.
  
  Kevin Carter
  K&K Audio
  www.kandkaudio.com
  
  

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  • RE: SB3 - UK Dave 08:05:44 10/19/07 (0)
    In Reply to: RE: SB3 posted by KevinC on October 19, 2007 at 05:38:33

    Thanks for the quick response Kevin
    
    The exercise was more out of interest than saving money, although money does come into it. I think I'll probably go straight into a RAKK DAC Mk 2 unless any bargins appear soon.
    
    Dave
    
    

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  • RE: SB3 - AnandR 07:41:42 10/19/07 (0)
    In Reply to: RE: SB3 posted by KevinC on October 19, 2007 at 05:38:33

    I have one for sale, see my post below. You can e-mail me off line.
    
    Best,
    Anand.
    
    

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