FWIW, I thought I perceived a noticeable decline in Dish audio quality a few years back just before and during the big all 8PSK roll-out for the WA when Dish was having, to my perception at the time, declining video quality, as well. I felt pretty sure that Dish was squeezing audio quality--along with video luminance and chrominance data and whatever else--to be able to fit all those video channels on the WA, and I could hear it with my ears and see it with my eyes.
But that was a few years ago, and I have to say that, overall, the video PQ and audio quality has improved since then, especially on certain channels like Disney HD who seem to be granted the royal treatment (Ergen and Iger have been cozy for a while), but Dish still following what I observe as the pecking order of PQ: premiums getting the best with certain general interest channels getting good, talking head channels getting fair to bad, and kids channels (except for Disney HD) getting by far the worst PQ and, presumably, audio treatment. But can one really detect lousy audio with talking heads? Well, not if it is done properly, and I suspect the Dish engineers at encoding are taking great care to make it sound as good as they can afford on their bandwidth diet, and part of this is assigning certain channels grouped on the same transponder so that at an average, no channel looks great at the expense of another channel on the same transponder looking horrible. So, on Dish, I think, it depends upon which channel and what the content is for that channel, along with each show having its own quality issues as provided by the producers of that show for broadcast for both video and audio.
Now, as for the audio: I have to say that in general, on Dish it sounds pretty good (using Yamaha AX-2010 with good speakers and good placement and good listening levels) for being the "old" LOSSY AC-3 format of DD 5.1 at 48kHz, 384kbps, the default standard bit rate, it seems, for all broadcast types such as ATSC, DBS, cable TV, etc. I actually observed AC-3 DD5.1 for CNN on Dish at a 448kbps rate! What??? I've never seen any DD5.1 channel on Dish over 384kbps. But I suspect that premium channels are not going to be greatly starved of audio data while other channels according to content may sound worse than others. Of course, DD5.1 is still offered on DVD's and Blu-rays for legacy, and at a higher bit rate. But after hearing a lot of Dolby True HD and DTS Master Audio, AC-3 may not sound so good.
AFAIK, no streaming service is using the bandwidth hogging--by streaming standards--AC-3 DD5.1 used by ATSC, cable TV, and DBS, etc. Streaming services like Netflix are, instead, using E-AC-3 also known as DD+ designed to operate best at low data rates for its best audio content such as action movies etc. Other inferior codecs are used for the remaining content by streamers. Although DD+ specs are superior to AC-3 with potential for bit rates up to 6.1Mbps for up to 15 full fidelity channels, don't bet on the streaming services sending out such jaw dropping superior audio quality than that "old" AC-3 because going full or high spec or high bit rate DD+ can be bandwidth hogging and can limit the number of viewers accessing the data for streaming to the home or could cause drop-outs or buffering for many customers, or (even worse?), reduce PQ for the sake of higher AQ. And Netflix PQ is already bad enough as it is (even worse than Dish linear channels at times).
Instead, streaming services can choose to send out DD+ as low as 32kbps (the very bottom of E-AC-3 bit rates) or any bit rate lower than AC-3/384kbps--the standard for OTA, Dish, etc. (highest bit rate for AC-3 is 640kbps), but such an inferior DD+ could still sound subjectively better to us because DD+ uses A LOT of psychoacoustics to make up for situations of lower audio quality/bit rates often plaguing internet streaming, especially if the streaming service wants to be certain of high video quality in its stream. The understanding of how people perceive sound and its location and its psychological and physiological effects and the other tricks that make the audio sound more "interesting" are old tools in audio to make it seem as if it is superior audio without actually providing any more data as far as the soundtrack itself.
While DD+ does have advantages and can provide superior audio quality--at the higher bit rates--than AC-3, I highly doubt that broadcasters (maybe as part of ATSC 3.0? I don't know), Cable TV, DBS, etc. are going to ever implement DD+ because it is not backward compatible with older DD5.1 AVR's/systems (I believe it is a hardware matter for compatibility) in the customer's home, and it would mean that broadcasters, cable and DBS would have to provide streams for BOTH AC-3 and DD+ for every channel to support ALL their subscribers audio equipment, and that would eat up MORE of the current bandwidth when OTA, cable, and DBS are trying to use LESS bandwidth or at least use the bandwidth they have most efficiently.
Let's keep in mind that a lot of content in DD5.1 isn't necessarily using the format to its fullest. For one thing, in a well produced DD5.1 soundtrack, the rear speakers aren't often very active throughout a show or movie, especially if it is not action content. They are there for occasional effects of placement or location and sometimes for enhancement of audio in the front. A lot of DD5.1 can sound "flat" or not very "interesting" to many people, even with action movie content. This is why many AVR's have those gimmick sound-stage settings such as Sci-Fi, Adventure, Movie House, or whatever because it can take a boring "straight" DD5.1 (often at a higher bit rate than for cable, DBS, OTA, etc. if from a DVD or Blu-ray) for that big, action movie and make it sound "better" or at least get all those speakers pumping at the same moment, and we are surrounded by all that sound all the time and isn't that why we dropped a lot of dough on those fancy AVR's?
Of course, this (those electronic sound-stage settings on our AVR's) is not what the sound mixer at the studio intended for us to hear, and yet this is how DD+ is often implemented by streaming services: appropriately low bit rates--not necessarily higher than found on AC-3 users such as Dish--with LOTS of the latest and most effective DD+ psychoacoustics that have been gleaned from decades of knowledge and experiment. "Better" or "Superior" sound for some is the more "interesting" audio, not necessarily the technically or measurably superior implementation. I have to say that I have watched action content streaming material with DD+ and was surprised at how good it sounded, and then there were other action content DD+ streams that sounded absolutely AWFUL compared to AC-3 on Dish. I think streaming services quality of DD+ varies from movie to movie and content to content and how late you may be in requesting that stream compared to those early birds who may be getting higher bit rates for their DD+ audio stream.
One major factor in audio that can make all the difference in the world: how the audio was mastered. I've seen (like many of you here) a lot of content on TV OTA and via Dish and OTT, and while I am not a regular viewer of the new Hawaii Five-0 (dear old mom and dear old aunt and uncle are), I have to say that of all the TV content I have heard on all these formats and audio codecs, that new Hawaii Five-0 is among the BEST audio I have ever heard, and yet it is served to us on the old and technically inferior AC-3 from an OTA source (at the station's studios via fiber, most likely), transmitted to a Dish spot-beam uplink via fiber, re-encoded, then sent up to the satellite, and then run though a transceiver to the down-link frequency, then received at our home and decoded by the box, and that Hawaii Five-O can kick some Dolby True HD and DTS Master Audio butt sound tracks I've experienced. H50 is one of the most visually beautiful (and I mean technically, not just Hawaii natural beauty) shows I've seen with some of the best USE of sound I've ever heard for a TV show. It beats a number of action content I've viewed from Netflix sent in DD+
H50 knows exactly how to USE sound to create one of the most compelling TV shows to experience as far as the senses and creating an emotional response that it is much more like a cinema on TV experience, like popping in a Blu-ray. Superior audio codecs can mean next to nothing if a sound mixer does not know his ART or if the streaming service implements an inferior example of a superior audio codec such as DD+. I don't think there is a streaming service out there today giving DD+ its full due, which is why it can often sound, to may ears, inferior to AC-3. Of course, streaming services often use other audio codecs (the DD 2.0 stereo implementations of AC-3) such as AAC or Ogg or whatever else, and I can tell you the audio on those streams is absolutely difficult and fatiguing for me to hear well, most often due to the streaming service being more concerned about the PQ going out, and the audio be dammed. I've ended up having to watch the content on Dish's superior AC-3 implementation of DD 2.0. However, DD+ seems to be the codec most used by streaming services for best audio especially for multi-channel action movies content. All my references were to streaming using a Roku or Fire TV, NOT via Dish boxes, so I can't say if Dish boxes down-convert a decent DD+ audio stream to something inferior, be it a different codec or reduction of data.
Further, there is a lot of video content produced with lousy sound, and there aint much Dish can do about that. Has anyone else heard the lousy audio for "The Frank Buckley Interviews" on Channel 5, KTLA? Yes, it is produced for radio (that should mean it is supposed to sound SUPERIOR), but the audio is so SHOCKINGLY BAD! The noise, the thuds, the lousy voice quality. It is an audio disaster!
Just because AC-3 is "old" does not mean that a newer codec will provide for a superior experience, especially if they are implementing that superior codec in its inferior form. But the newer psychoacoustics of the newer codec are designed to compensate for that inferior implementation, and we may believe that the more "interesting" sound is superior to that "old" AC-3 lacking the processing and psychoacoustics of the "new" codec. But in the end, it is whatever you like, even if that means turning on those AVR sound-stage processors. It's just that "better" is a relative term. And, yes, I do find that considering AC-3 is an old lossy format, the sound for content where sound really matters, is good, and best on the premium movie channels, and VOD of a show or movie can sound better )I'll rate very good) than the linear Dish channel were the bandwidth is tight.