I’m dragging this almost two-year-old thread up as a way to thank the posters for all the great info provided.
Following sKIZo’s lead (post #5), I picked up a used Directed Car Connect HD tuner last week. My motivation was that I mostly listen to a classical station out of Boston, but am far enough away/behind a hill such that I can’t pull in stereo without an objectionable level of hiss. I did all I could with an indoor antenna, and am unwilling to go with an outdoor one. But, as others have noted, the car pulls in the HD version of what I want to listen to, and it seems to sound quite good (realizing a car cabin doesn’t provide an ideal environment for critical listening). So I’ve been left wondering if I can I do better inside.
I’ve tried free streaming sources, and it is not bad, but due to compression (at least what I get from SimpleRadio which I can cast to a CCA), is less enjoyable than OTA, even in mono. I was concerned that given the comments above about similar compression being common in HD broadcasts, I would find no or little improvement for the effort of setting one up, but for the $35 it cost to get the Directed unit, I decided to give it a go. I also bought a pre-made Motorola-to-F connector cable ($8; spendy, I know) so it would not be a total kluge job to splice this into the antenna (rabbit ears).
I’ve only had it running for a day, but so far I am impressed. This unit does pull in and lock on to HD stations better than regular OTA broadcasts on any tuner or receiver I have, there is no FM stereo hiss, and it is very stable. Tonally, it does seem just slightly brighter than regular OTA; said another way, the OTA sounds somewhat veiled in comparison. It is early days, but the slightly brighter profile has not shown me any harshness, even on strings, so I am thinking the latter is true. On the LF end, the sound is very similar to OTA (this was not my experience for streaming). So I have not heard anything to tell me that HD-delivered content I’ve been hearing so far has been objectionably compressed. It is possible that the classical station is more mindful of signal quality and does not overdo compression, knowing its audience, or alternatively, I need more listening time to detect the deficiencies.
Lastly, even though it is not a sound quality issue, I greatly prefer to be able to just "turn on the radio" and listen to clean FM rather than set up a stream, even if the latter only takes a minute or so. Some combination of lazy and old, I guess.
Again, I would like to thank the earlier posters here for sharing their insights, both positive and negative, on HD Radio. All of it has been great guidance for me, and has helped me increase my listening enjoyment.