In article .com,
Robert wrote:
There is indeed a compress/expand switch on the back of the tuner
(Cambridge Audio Azur 640T. At least, I think that's what it is; the
manual is very vague about what it actually does describing it as
"warm/lively". It does not have a very powerful effect, certainly not
enough for what I need.

I don't think this has anything to do with compression. As you say, the
effect is very subtle, but it seems to be a filter of some kind, a bit
like the "mellow" and "bright" tone switches they used to fit to those
old mahogany radiograms full of thermionic valves. I've left mine in the
"off" setting, and it sounds fine on FM.

Rod.