• 11-29-2004, 09:43 PM
    spuppy517
    Digital receivers vs DAC receivers
    Ok - I asked this question over in the Home Theater discussion group and got nowhere so maybe the good people here in Digital Domain will have more thoughts. I am looking to upgrade my home theater receiver and I am seriously considering Harman Kardons DPR (Digital path receivers). I just recently got into this stuff and had no clue that most A/V receivers convert all sources into analog via DAC before amplifiying it out to your speakers. How can this TRUELY be called doldy DIGITAL?!?!?! So apparently H/K has a line that has a true digital path with true digital amplification. It seems like a no brainer right? So I feel like I am missing something, does anyone know anything more about this technology, or have one of these receivers??? It's just that I don't have tons of money and if I'm going to spend 1000+ on a receiver it better be awesome, and I don't wanna feel like in two years that I missed the boat on something. Is this digital path receiver the next big thing? HELP!
  • 12-03-2004, 08:19 AM
    Feanor
    I think so!
    Quote:

    Originally Posted by spuppy517
    ...
    How can this TRUELY be called doldy DIGITAL?!?!?! So apparently H/K has a line that has a true digital path with true digital amplification. It seems like a no brainer right? So I feel like I am missing something, does anyone know anything more about this technology, or have one of these receivers??? ... Is this digital path receiver the next big thing? HELP!

    Receivers and amps that aren't "all-digital" (or "digital path") must convert from digital to analog before the final amplification stage in order to work.

    But back before the final amplification stage, some receivers convert analog signals to digital in order to do "digital signal processing" (DSP), that is, bass management and all the various "effects" they offer. If the unit is not "all-digital", the processed signals are then converted back to analog to be amplified. In some cases, the user has a "direct" option, i.e. to by pass DSP, so that the signal, if analog, remains analog throughout.

    "All-digital" receivers, such as some Harmon Kardon models and Panasonic SA-XRxx models, not only can but must convert all analog signals to digital, (whether or not the users wants DSP). That's because these receivers have digital amplification stages that don't need and can't use analog input.

    Remember: most CD and DVD players offer you the option to feed the receiver by way of both stereo analog outputs or digital (coxial or Toslink optical) outputs. Fed by analog, the receivers will do conversions I described above; fed by digital, the receiver doesn't have to do the pre-DPS, analog to digital conversion.
  • 12-03-2004, 08:54 AM
    htfan14
    All speakers are analoge, therfore ANY digital signal must go through DAC's before output to your speakers.
  • 12-03-2004, 10:00 AM
    Feanor
    Not actually
    Quote:

    Originally Posted by htfan14
    All speakers are analoge, therfore ANY digital signal must go through DAC's before output to your speakers.

    If by "DAC" you mean electrical circuitry, this isn't the case. The digital amplifier creates a signal, which though switched, appears continuous to the speaker due the extremely short switching intervals. If you like, the speaker itself is the DAC.
  • 12-04-2004, 12:57 PM
    Jace
    DAC stands for Digital to Analog Converter. it is needed regardless of technology before your speaker sees it. speakers are totally analog devices and cannot do any sort of conversions itself.

    here is the short and skinny of both methods described. for a system that is not fully digital (ie. the sigal goes to analog amps before going to your speakers) you get your input signal in either digital or analog, depending on which method you use from your source. if it is an analog input, an ADC (analog to digital converter) is used to turn the signal into digital for processing (bass adjustments, eq's, surround sound decoding etc.). this digital signal is then converted to analog by the DAC's and sent to the amplifier stage. after that, the amplified, analog signal goes to your speakers.

    in the case of an all digital system, you get your input, the same as described above. you process the data the same as above. now this is where the difference is. instead of converting the signal back to analog to amplify it, you keep it digital and send it through a digital amplifier. the output of your digital amplifier signal is still gonna be digital and therefore is not suitable for your speakers since it is all in binary code (1's and 0's, or in other words, high voltages and low voltages that make up a code that represents your analog information. this is done using whats known as pulsewidth modulation). so at this point, it goes through a filter (final stage of the amplifier) to convert the already amplified signal back to something a speaker can recognize and then it goes to your speakers.

    -Jace
  • 01-01-2005, 07:22 AM
    J*E*Cole
    H/K owner
    If you look at the specs closely between their DPR's and the AVR's, you will find them to be relatively identical except for one, which is THD. This figure is lower on their AVR line than on the Digital Path line. If DPR tech is so great, then why isn't the reverse of this true. The DPR's cost more but the AVR's have slightly better specs. I don't think DPR is a gimmick, in fact I believe anything H/K claims about their products. As most enthusiasts know, H/K rates their components power ratings differently, and I for one think, more accurately then other manufacturers. What I can tell you after owning my AVR now for about 4 months is that I continue to be pleased with this product the longer I have it. It's performance and striking appearance make it one of my better buys in this category. I had the option to buy a DPR at the time but because of the store's meaningless audition room, could not actually hear it, so I bought the AVR and like I said, am most happy. It also has some degree of future-proof-ness. It has ultrawide bandwidth, wide frequency response, and low THD which should make it a good contender for SACD. But to sum up, I don't think you could go wrong with any Harman/Kardon product they currently make.

    Good luck.
  • 01-02-2005, 11:58 AM
    hermanv
    There are two possible ways of making "digital" ouput stages. One divides the signal into a set of finite width steps the other divides the signal into a infinitely variable number of widths. Even though both systems employ rail to rail switching the second process is really an analog ouput process that uses a comparator to "slice" the signal then drives saturating output devices

    The big problem with using your speakers as the integrator for a switched output stage is that no one designed their crossovers to deal with very fast and powerful switching edges. I'm guessing that you'll find most digital ouput stages include at least a rudimentary LC filter to stop these edges from getting out.

    The technology has been around for many years, for early efforts, reviewers agreed that they sounded awfull. As the switching frequencies go up and up they will probably sound better and better. What they really do is save money on amplifier power stages and amplifier power supplies. If these savings are passed on to you with no sound penalty, fine. It is doubfull to me that these techniques will ever sound truly better that a well designed analog approach but they might make a hunderd watt stereo amplifier the size of a pack of cigarettes or even smaller.

    The reason I think they will forever have limitations is that until someone invents a true digital speaker the signal driving the speaker must be made analog at some point in the chain. It is easier to do a good job of this function at low levels and small components than it is at high powers with large inductors and capacitors that carry high currents and voltages.
  • 01-03-2005, 12:45 PM
    Feanor
    Well stated, but ...
    I think great sounding "digital" amps have arrived.

    Quote:

    Originally Posted by hermanv
    There are two possible ways of making "digital" ouput stages. One divides the signal into a set of finite width steps the other divides the signal into a infinitely variable number of widths. Even though both systems employ rail to rail switching the second process is really an analog ouput process that uses a comparator to "slice" the signal then drives saturating output devices
    ... I'm guessing that you'll find most digital ouput stages include at least a rudimentary LC filter to stop these edges from getting out.
    ...

    The first way you describe is, I'm guessing, PWM, (pulse width modulation), a.k.a. "Class D". The second is a method such as used by Tripath processors, a.k.a. "Class T". And yes, I believe that essentially all "digital" power amps call for a low-pass filter after the output stage; as I understand it, this can be a simple, passive filter such as used in a speaker cross-over network. As a result, the signal appears continuous to the speaker -- directly analogous to movie frames seeming continuous to our eyes.

    If you believe that "digital" amps must have inherent sound quality limitations, have a listen to one of the Bel Canto eVo Gen II series, ("Class T"): you might just change your mind.
  • 01-13-2005, 04:04 AM
    Rob H
    Digital Amps
    NewForm Research, manufacturer of high end loudspeakers, is a strong proponent of digital
    amplifiers. Their newsletter (update) of August 03 is devoted to this topic:

    http://www.newformresearch.com/whats-newfr.htm

    Having gone from Denon's top of the line 2-channel receiver (DRA685), to a Panasonic XR25 digital receiver, I am sold on the benefits of digital amplifiers. The specs, on paper, may not be as good as an analog amp, but the proof is in the sound. The little Panasonics, at least in 2-channel mode, are amazing.

    Rob