Originally Posted by catapult
Hey John, have you (or anyone else) tested for the so-called PCM bass bug yet? Does the 775 boost the .1 LFE channel of a 5.1 PCM signal by 10dB like it should? To test, you need a player that can convert a 5.1 DD signal to 5.1 PCM. Play it both ways and see if the bass sounds the same.
hmm, interesting question. I was not aware of this, but it makes sense. I can answer this a couple of ways...
first, I have not noticed much appreciable difference between the bass levels of the bitstream DD track and LPCM track of the same movie. I can think of 4 possible reasons for this: 1.) because the player (in my case a PS3) passes the LFE channel of the LPCM track with the appropriate boost applied; 2.) The NAD is applying a boost to LPCM LFE; 3.) The Audyssey equalizer processes the signal in real-time and applies an appropriate level to the LFE, regardless of input level and lastly, 4.) the original LPCM soundtrack has a natively higher gain on the LFE channel. (#4 is pure speculation as I don't know if it is even possible to pass an LPCM signal with differing levels on each digital channel.)
Now, I know I said there is not much
difference. In my case I have always felt that the bass is stronger with LPCM, not the other way around. I feel it is most likely the PS3 compensating here, because I noticed when I had my previous processor, a B&K Reference 30 (which of course could not process LPCM, but could process a LPCM stereo down-mix over coax or toslink), that the bass was always stronger when switching from
a DD bitstream to
a LPCM stereo down-mix. The LPCM mix was always deeper, tighter, louder, and more clarified. That same impression holds today. Of course, the audyssey clouds things a little bit. I could do a better A/B comparison with my old processor, actually, because it made no equalization or room-compensation. The proof in the case of the Reference 30 was very simple -- when switching back and forth, the LPCM stereo downmix rattled my projector screen frame where it made contact with the wall screws, the DD bitstream did not. The only constant in all of this is my PS3, so as I said, I suspect it is a compensation being performed in software on the PS3.
I'll put it another way: to me, although comparing the different versions of a soundtrack is a very subjective thing, I always feel that a LPCM or Dolby TrueHD soundtrack sounds far superior to DD or DTS tracks. Is the bass level of the LFE channel actually higher when I'm listening to LPCM, or is it just the deeper, more well-defined bass of LPCM that I'm noticing? I don't really know, to be perfectly honest. I don't care, though, because to my ears it is still far superior. Will you be happy if you're sitting there with a SPL meter? I can't say, but I can
tell you that to me there is very little lacking in the performance of the 775, and that goes for the entire audible range.