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Discussion Starter · #1 ·
I have an RCA DTC-100 receiver and it has audio output options of Dolby Digital, PCM and Analog. Is there any programming that the DTC-100 can tune that can be output as PCM?


What is PCM?


My Denon AVR-5800 receiver will let me use DTS Neo:6 to enhance Dolby Surround sources but only if the input signal is Analog or PCM (not Dolby Digital). I want to understand if the DTC-100 can output PCM and what PCM is.


Thanks in advance!
 

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Pulse Code Modulation. It is just a different type of digital bitstream than Dolby Digital, and only supports 2-channel stereo sound. This is the form of audio stored on an audio CD. Since the DTC-100 has PCM as one of its options, give it a try. I will try it on mine later and see if my receiver changes to the Linear PCM icon instead of the DD icon. I don't know for sure, but it may be that if the station is broadcasting DD, you may only be able to output DD.
 

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Quote:
Originally posted by agtiny:
Pulse Code Modulation.


I don't know for sure, but it may be that if the station is broadcasting DD, you may only be able to output DD.
A STB (dtc100 included) should be able to (down) mix DD 5.1 to PCM to its digital out. Also, a lot audio receivers can not put DSP effect on the DD signal, sorta like the lock-in-widescreen on 480p on some HDTVs. So, if the DD sound is not satisfactory to you, many (H)DTV sound is 2 channel DD really, set your stb to output PCM then try one of your receiver's sound effects. I have an old Denon (3300), w/o DDPL II or DTS Neo, I am very happy with its 5 channel stereo mode in most case.


Hal
 

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Discussion Starter · #5 ·
Does anyone know if PCM would normally sound better than the analog output when downmixing an OTA HDTV or DSS Dolby Surround signal?


It's my understanding I have the following options
  • Output Dolby Digital 2.0 (matrixed Dolby Surround) which my AVR-5800 cannot engage DTS Neo:6 on
  • PCM (via the optical digital output of the DTC-100) which my AVR-5800 can engage DTS Neo:6 on
  • Analog (via the analog RCA outputs of the DTC-100) which my AVR-5800 can engage DTS Neo:6 on
 

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Try it out for yourself. http://www.avsforum.com/ubb/cool.gif


It depends on which DAC is better, the one in dtc100 or the one in Denon.


Generally speaking, analog pass has two more AD/DA conversion than digital pass. (DA in stb then AD in receiver then DA again in receiver vs. only one DA in receiver)
 

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Discussion Starter · #7 ·
I will try it but I'm trying to understand technically what the differences are with how these things are passed and what processing happens. Thanks for the info.


The bottom line is a Matrixed Dolby Surround signal is being passed among all of the different ways of passing it, right? If you look from a pure signal point of view passing via Dolby Digital would be best followed by PCM then analog, right?


The reason I'm ruling out passing the matrixed Dolby Surround signal in Dolby Digital is because my AVR-5800 won't let me engage DTS Neo:6 on it.


I'll do some comparisons of PCM vs. analog and find out if I can hear any differences.
 

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all non dolby digital output from the DTC100 is PCM (44.1 KHz sampled digital audio at 16 bit resolution)

or so called CD quality sound. Basically the same audio that is generated by a CD then passed to a digital-to-analog converter for amplification in a receiver.
 

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WW98,


All audio via DBS is digitally encoded, with the vast majority in 2-channel PCM format. If you select analog audio out on your STB then the STB will convert the digital signal to analog and output it via the RCA jacks only. If you select PCM, you will still get the analog signal out of the RCA jacks, but you should also get the unaltered digital bitstream from the optical or coax output of the STB. If you select Dolby Digital, you'll get DD out of the STB optical or coax if the DD signal is present, otherwise it will continue to send PCM on that output, plus you'll still get analog out of the RCA jacks.


That explained, it's usually best to keep the audio in the digital format as long as possible and then let the device with the best digital-to-analog circuitry do the final conversion. In this case, that's likely to be your Denon receiver. If you really must have the additional signal processing that the Denon provides on Pro-Logic material, you may want to leave your STB in PCM all of the time. If, however, you like to have DD 5.1 when it's available, I would leave the STB in DD mode, as most of the material you'll receive will be in PCM mode anyway. Most DD encoded movies are in 5.1 with only older movies in 2.0, so you'll still hear things the way you want to the vast majority of the time. If this is your DVD player that we're talking about, then you'll probably have to switch back a forth as necessary.


So, in summary, you want to avoid any unnecessary D-to-A or A-to-D conversions between the various components in your system and let the best component do the work if at all possible. Can your ears actually perceive the difference? In reality, that's hard to say. Some people are able to detect differences, though most probably couldn't. But, fortunately, we're free to choose what works and sounds best to us!


P.S. I just realized that we're referring to the DTC-100 here, so DD is the standard encoding format for all HD transmissions. Currently, most OTA broadcast stations do not appear equipped to pass on a 5.1 signal so the vast majority of this material is, indeed, DD 2.0. This being the case, you'll probably want to leave the STB set to PCM most of the time and only change it to DD when you know the material you'll be watching is indeed in 5.1.


[This message has been edited by Bandito (edited 10-05-2001).]
 

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I have exactly the same setup as you do, and the inability to force the Denon into Neo6 mode when it detects 2-channel Dolby digital is a major annoyance. If you prefer Neo6 Cinema matrix decoding to Dolby Surround (which I do), then I believe that it's worth the irritation to switch the DTC100 output mode to PCM, permitting the use of Neo6.


The only time you would ever need to switch the DTC100 out of PCM is for those few sources that are actually true Dolby Digital 5.1.


As far as arcane quality differences between 44.1kHz/16bit PCM and Dolby Digital go, these are COMPLETELY swamped by the subjective differences between Dolby Surround and Neo6 decoding. The PCM bitstream uses the MPEG1 Layer 2 (MP2) codec; I presume that the Dolby stream uses the Dolby AC3 codec even in two-channel mode. If anyone on this forum knows if DTV bothers to duplicate the digital audio (once in MP2 and once in AC3) for 2-channel program material, or if the DTC100 does some sort of internal conversion, I'd like to know the answer.
 

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Discussion Starter · #12 ·
Robert2413: the new Denon AVR-4802 lets you engage DTS Neo:6 on a Dolby Digital 2.0 signal. I wonder if the rumored AVR-5800 upgrade will incorporate this change into the AVR-5800 which seems likely considering the upgrade introduces DPL II which likely can be engaged on a DD 2.0 signal as it can be in the AVR-4802.
 
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