AVS Forum banner
Status
Not open for further replies.
1 - 12 of 12 Posts

·
Registered
Joined
·
111 Posts
Discussion Starter · #1 ·
A lot of new receivers are offering 192/24 DACs and 192/24 A/D converters.


1. What do each of these do?

2. What do I really need in a receiver if I have both a SACD and DVD-audio player plugged in through my receiver's analog inputs?


Thanks.
 

·
Registered
Joined
·
7,335 Posts
DAC is a digital/analog convertor. It takes in 1s and 0s and outputs an analog signal suitable for amplification.


ADC = Analog to digital convertor. Takes in an analog signal and converts to 1s and 0s for digital signal processing (applying bass management and time alignment as examples).


If you watch DVD-Videos, and the receiver has more flexibility than the DVD player (which is likely for DD and DTS), then you would want to push DD/DTS off to the receiver. As an FYI, the output of DD and DTS decoders is Linear PCM.


Regards,
 

·
Registered
Joined
·
4,720 Posts
Quote:
Originally posted by hifialan
Does this mean the converters have no relevance when listening to DVD-A or SACD through an analog direct input?
Hifialan,


When you are listening to DVD-A or SACD through the analog direct input - you are using the DACS in your DVD/CD player.


The information on DVDs and CDs is digital - "1"s and "0"s. At some point, these have to be changed to analog signals to

be amplified to drive your speakers.


Your DVD player has DACs in it - so that it can output the analog signal that you are inputting to your receiver.


In all likelihood, your DVD/CD player also has a digital output, so that you can use it not as a DVD "player" but as

as DVD "transport". In this case, you would feed the digital

data from the DVD to your receiver using the digital output on the DVD player, thus bypassing the DACs in the player.


The receiver, would use its DACs to convert the signal to analog, for amplification for the speakers.


Some receivers have the capability to do digital "effects" - they can process the digital data to make it sound like you're

in a small club, or a big arena. This processing has to be done on the digital signal. If you feed an analog signal

to such a processor, it will use ADCs - analog to digital converters - to turn the signal back into digital. If you

have a digital source like a DVD player - and you use this capability, you don't want to use analog inputs. The

receiver is going to take the analog input and convert it back to digital - the receiver's ADCs will undo what the

player's DAC did, and then after processing the receiver will process the signal with it's own DACs.


If you are not using digital signal processing in the receiver, then the question is - which one has the better

DACs - the player or the receiver. If the player has better DACs - use the analog inputs.


However, if you have a medium quality DVD player, and a high-end receiver, then you should use a digital connection;

so that you will be using the DACs in the high-end receiver.


Greg
 

·
Registered
Joined
·
111 Posts
Discussion Starter · #5 ·
OK. I get it. Now, if my receiver has a 192/24 dac and I feed it a signal from my standard cd player's digital out, is the receiver also performing "upsampling" or is that an additional step?
 

·
Registered
Joined
·
7,335 Posts
Upsampling is a seperate issue altogether. This is usually handled by a seperate chip like an Analog Devices AD1853.


Regards,
 

·
Registered
Joined
·
523 Posts
Quote:
Originally posted by hifialan
OK. I get it. Now, if my receiver has a 192/24 dac and I feed it a signal from my standard cd player's digital out, is the receiver also performing "upsampling" or is that an additional step?
Any digital data inside the receiver must get converted back to analog at the 'end' to go out to the speakers. If the input is CD which is 44.1/16 then the receiver will just convert that to analog most likely. There's no advantage to multiplying the digital bits up.
 

·
Registered
Joined
·
7,335 Posts
Actually there is an advantage, you can install a gentler output filter on the DAC to remove conversion artifacts.


Regards,
 

·
Registered
Joined
·
4,720 Posts
Quote:
Originally posted by hifialan
OK. I get it. Now, if my receiver has a 192/24 dac and I feed it a signal from my standard cd player's digital out, is the receiver also performing "upsampling" or is that an additional step?
hifialan,


It depends. Although the receiver has 192/24 dacs, it probably also has 44/16 or 44/20 dacs. If it sees a 44/16

signal from the CD player - it may just process this with the 44/16 dacs.


Or it may upsample to 192 so that the effect of the low-pass filter is mitigated. Or this may be selectable as an option.


It depends on the design of the receiver.


Dr. Gregory Greenman

Physicist
 

·
Registered
Joined
·
7,335 Posts
Greg,


It would be highly unusual to have multiple DACs to handle the various sampling rates. It would be one DAC capable of syncing to N number of bit depths and sampling rates, with 32, 44.1, 48 and multiples of these base frequencies to the limit of 192K. It would also support sampling depths of from 16 to 24 bits, usually with word lengths of 16,20,22 and 24 bits.


There are implementations of multiple DACs, but that's to reach the appropriate number of channels, or to go into a differential configuration, not specifically to handle various input sampling rates and depths.


Perhaps I misread the post?


Regards,
 

·
Registered
Joined
·
111 Posts
Discussion Starter · #11 ·
This begs a further question. Why do some receivers have multiple DACs per channel, and others a single DAC. Does having more really make a difference that you can actually hear?
 

·
Registered
Joined
·
7,335 Posts
hifialan,


There are a couple of options here.


One, is an 6 or 8 channel DAC vs. multiple stereo DACs, with the stereo DACs having a marginal improvement over the 6 or 8 channel DAC.


Then there's running differential, or dual differential, which increases the number of DACs in use per channel, which again gives a marginal improvement in performance.


Audibility is another issue altogether, as you are always listening to more than just the DAC.


Regards,
 
1 - 12 of 12 Posts
Status
Not open for further replies.
Top