Monday, 23 January 2012

Mission PCM7000

The Mission PCM7000 is a player I've already mentioned in this blog; it's the direct predecessor to the Mission PCM2.  The main difference between the two is the player that they are based upon, for the Mission PCM2 it is the Philips CD670, while for the Mission PCM7000 it is the Philips CD650.  Electrically the two players are almost identical, but physically they don't share a chassis, loader or laser mechanism.

The PCM7000 uses the same rather unhelpful variable volume output stage.  It's a resistor attenuator using CMOS switches, which isn't too bad, but it has no non-volatile memory and resets to maximum volume each time the player is power cycled.

As it stands this player is rather lacklustre, similar to the PCM2.  However, it doesn't have the same drawback the PCM2 does; there is actually space for extensive modifications inside the PCM7000.

I intended to remove the variable volume output stage and replace it with a new PCB.  At this stage it'll incorporate the following:
  • A digital filter, probably a SAA7220, there aren't many alternatives.
  • A DAC, probably still the TDA1541A, as I want to maintain some of the original flavour of the player, but I'm also thinking about using a SM5803 / PCM1701 combination.
  • A discrete output, based on either the Pass D1 or EVUL's CEN / SEN.
  • Power supplies for all of the above.
I'll write more on this post as I make progress, but it's still in the early stages right now.