CD player has noise at low signal levels

[ittaly]

I have acquired over two dozen CDPs from the 80s, all multibit.

 Most perform well right out of the thrift store. The classic 1st-4th gen sound, played on OEM equip on spinning disc, on a CDP in good mechanical and electrical cond,  is my first choice for 16/44.1. playback.

Recently I acquired a thrift store Technics cd magazine changer from 1987. It uses a single PCM56 and SM5807 4x df.

On low level signals (fade in's, fade out's, long pauses in piano sonatas, etc) considerable distortion can be heard. When signal (playback) level gets higher, it completely cleans up and sounds v. good.

I have other CDPs with the PCM56 and there is no low-level distortion.

The PCM56 is a trimmable device -- pin 14 allows MSB adjust. But the low-level distortion is a LSB issue ... yes?

I haven't yet 'scoped out the eye pattern or other performed other SM tests.

And I have not changed any of the electro caps.

Any quick ideas before I lab the unit?

 

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