Digital to analog converter, what does that get me. I notcied some preamps have and some don't. For instances I believe the dc-2 does not have it and the Parasound AVC-2500u has it. Can anyone explain?
A digital to analogue converter (DAC) does exactly what it says on the tin, it converts digital data to an analogue output which can then be amplified and sent to your speakers. The Lexicon DC-2 does have DACs, 8 of them in fact for the 7 main speakers and the subwoofer. Dolby Digital, DTS and PCM (CD audio) are all digital formats and can't be sent directly to a speaker, they have to be decoded and converted to analogue somewhere along the line, whether this is in the CD/DVD player or in the decoder/pre-amp.
Maybe you're confusing this with direct analogue inputs? The DC-2 in common with many home theatre processors and recievers doesn't pass analogue audio straight though, it is first converted to digital (with an ADC, analogue to digital converter), and then back to analogue. These extra steps do affect the signal, but the digital stage has the benefit that processing like bass management, time alignment and/or surround modes can be applied. I believe the Parasound AVC-2500 doesn't convert it's analogue inputs to digital.
All modern receivers, integrated amps or processors have D/A converters. Basically, anything with digital inputs needs D/A converters.
Here's an example of where they are used. Let's say you have your DVD player hooked up via it's digital output into one of your processor's digital input. It doesn't matter whether it's optical or coax. The audio data that comes in through that digital input is digitally encoded. It might be Dolby Digital or DTS or PCM. '
If it's DD or DTS your processor decodes the data, turning it into PCM; if it was already PCM then nothing need be done (although Dolby Pro Logic or DPLII or other DSP modes could be applied here).
The PCM data then passes through the D/A converters before being sent to the speakers. This is how the digital data becomes the analog data your speakers require.
What separates one D/A converter from another is it's resolution and it's rate. If the device doesn't say then it's likely a 16 bit, 48kH D/A converter. Newer, more expensive D/A converters could be 24 bit, 96 kHz or even 192 kHz.
The number of bits describes the size of a digital sample. The larger the sample size, the more discrete values can be represented making things sound smoother. The sampling rate says how often samples will be output. Again, more frequent samples being better. You want your D/A converters to be at least as good as the source material.
Your statement is true in the Home Theater world, but there are still components being made for the stereo world which are strictly analog -- and there probably will be for the next few years. After that, I suspect that stereo only pieces will be relegated to niche status in the high-end.
Great "Reader's Digest" condensed explanation of DACs BTW.
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