Distortion at start of the first track

[skeptic Mike]

(06-02-2017 15:54)bbill Wrote:  

(04-02-2017 11:36)simoncn Wrote:  Is 'flac:wav24;' better than 'flac:wav24', or it is worse, or is there no difference?

no difference...
the actual stream.transcode is : flac:wav24;, dsf:wav24;88
from time to time, I still have the problem and only at the very start of a flac track

Am I missing something here? Why not remove the flac transcoding altogether? The Classé 2200I is supposed to support flac natively. If converting from flac to wav24 outside the Classé 2200I produces a better sound, then there's something wrong with it.
You also say that you are using BubbleUpnpServer. Presumably this is to provide an OpenHome renderer, so that you can use Lumin. On the basis of simplifying everything you could try to use a control point that worked directly with your Classé 2200I. I have no experience of IOS, so can't suggest anything, as I use BubbleUpnp on Android. Classé suggest that Plugplay works. I'm sure that others could recommend an IOS app.