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Why aren't class-D amps, digital amplifiers?

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  • #16
    Originally posted by JRT View Post

    Class D because D is the next letter after class C, sequentially.
    That is what I thought but then I saw class-F, G, and H which seem to be derivatives of A/B and maybe came before D, so I wasn't sure.

    I can't find anything definitive about classes and when they were first proposed and by whom.

    A lot of you guys have engineering backgrounds and probably know a lot of this stuff just from reading published materials.

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    • #17
      The closest I will ever be to an engineer is having paid for my kid to an engineering college. I am a total lay person when it comes to the details of audio. But I love music, how it sounds on a good system, and I love DIY. I don't really care if one calls it Class D, digital, switching or whatever. I know, just like other types of amps, Class D can sound very, very good, and it can also like crap. What happens when we get to class Z?

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      • #18
        Originally posted by dst View Post
        What happens when we get to class Z?
        The veil will finally be lifted.

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        • #19
          Helped me.

          https://en.wikipedia.org/wiki/Power_amplifier_classes

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          • #20
            Follow-up Q: I recall my first exposure to digitally recorded material referring to PWM on the cover of the albums.

            Was PWM the method used that would allow them to store digital data in analog tape?

            It would seem that to get from analog to digital, you would need to encode, and PWM would be one method of encoding. What are other methods?

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            • #21
              Originally posted by philthien View Post
              Follow-up Q: I recall my first exposure to digitally recorded material referring to PWM on the cover of the albums.

              Was PWM the method used that would allow them to store digital data in analog tape?

              It would seem that to get from analog to digital, you would need to encode, and PWM would be one method of encoding. What are other methods?

              I very much doubt that it was "PWM" - more likely "PCM".

              We are talking about modulation, quantization, bit depth and encoding/decoding.

              Wiki has the answer, history, and variations.

              https://en.wikipedia.org/wiki/Pulse-code_modulation

              Interesting - many of the same techniques were used for digital data storage and transmission in the early years of conversion
              from dedicated T1 lines and muxes to shared mediums.

              I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
              "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

              High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
              SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
              My Voxel min sub Yet-another-Voxel-build

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              • #22
                Thanks Don, it was certainly PCM I'm sure.

                I'm getting to the point where I sort of need a book or two, to explain all of this in context.

                The Wikipedia articles are very good but it wouldn't hurt to have an organized text.

                Any suggestions, or should I just keep digesting the wiki articles?

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                • #23
                  since I don't have a heavy math or physics background, I just learn what I can when I need it.

                  Some of the encoding techniques, like NRZ and 1's density were used in early digital data transmission.
                  Cisco has some articles on PCM, LPCM and other encodings that were used in their Voice over IP prootocols.

                  Hope this helps.

                  I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                  "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                  High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                  SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                  My Voxel min sub Yet-another-Voxel-build

                  Tangband W6-sub

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                  • #24
                    Elliot Sound Products' website has a very good description of the various classes of amplification.

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                    • #25
                      Originally posted by donradick View Post
                      I very much doubt that it was "PWM" - more likely "PCM".
                      It was PCM. Sony used it for Betamax VCR audio tracks, so many recording studios mixed down masters to stereo on Betamax decks, which had better S/N than analog tape.

                      www.billfitzmaurice.com
                      www.billfitzmaurice.info/forum

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                      • #26
                        Originally posted by donradick View Post
                        since I don't have a heavy math or physics background, I just learn what I can when I need it.

                        Some of the encoding techniques, like NRZ and 1's density were used in early digital data transmission.
                        Cisco has some articles on PCM, LPCM and other encodings that were used in their Voice over IP prootocols.

                        Hope this helps.
                        One's density was a requirement in the serial bit stream to allow tracking of a signal's timing so it could extracted from an incoming line and provide clock to a device. Used to implement synchronous networks.

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