I have just taken delivery of Marklin 37321 (Re620 058-8) - which comes with "in-house" MFX decoder. Lovely model with great detailing...

Unfortunately, this 620 makes really buzzy noise (especially at low speed) - which coupled with the usual DCM soundtrack easily takes the model to the No.1 spot for "Noisiest" Award - beating the runner up - a BR103 - by a significant margin.

My Re4/4 IIs - which shares the same drivetrain and motor does not produce the same sort of noise - the only difference is the decoder. The Re4/4 got ESU decoders, Re6/6 doesn't.

It was probably the decoder's load regulation values. IMO, Marklin should've got it right - especially considering DCM powers more than half of the current line-ups.
Another problem: parameter setting values of the current "in-house" decoders produce different results as opposed to the settings in the older ESU-quiped model; so I'll be having a hard time finding the right values.

Long story short, rather than tinkering with the settings - I decided to opt for the simple way out.
Ditch the "in-house" decoder and plug in a spare ESU M4 decoder - and the buzzing noise is gone!

I have to admit that I haven't bought a single brand new DCM model in a very long time... all of my DCM models are from the ESU days or older; and this Re620 will likely be the last one I ever bought!

My usual cup of tea are SDS models - these models don't actually use load regulation from the decoder - hence I never encounter any problem since the introduction of Marklin "in-house" decoders.

I wonder whether my Re6/6 is an exception, or is this the norm since they began introducing their own version of decoder?

In any case, I will unlikely to buy any of those upcoming Markin "in-house" multi-protocol decoders. I'd stick to ESU, thank you very much!