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Yung SD100-6 Review--Part 2 (DOTD)

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  • Yung SD100-6 Review--Part 2 (DOTD)

    I started reviewing this amp a while back:

    http://techtalk.parts-express.com/sh...ght=Yung+SD100

    I thought it was very well built and after tracing out most of the preamp board, it was clear that the amp has much more circuit flexibility than most, and that the preamp section is well thought out.

    I was going to do a part 3 review with some tests for output and distortion, but never got around to it. I started part 2, which was a description of the power amp and switching regulator circuitry. However, I didn't see what I was hoping for, and gave up. But since this amp is today's DOTD item going for $69, I thought it would be helpful to provide some more information on what I found.

    First off, this amp is only rated at 100W, but it uses plus and minus 53V rails. So there is plenty of voltage swing to provide 100W at 8ohms--you don't need a low impedance driver to get the full rated power from this amp. I was impressed by the generous supply voltage.

    The amp provides plus and minus 15V standby voltage for the activity detection logic. There is an activity signal that goes to a delay circuit controlled by C32, a 100uF capacitor. The "output" of the activity circuit goes from -14V to +15V, with +15V being "on".

    I was hoping that the amp would use a high performance controller chip like the IRS2092, because I was considering modifying this amp for full-range operation. But it doesn't use that design--it is based on an older topology. It's probably a good, stable design, but it wasn't what I was looking for, so I didn't do any more investigation to draw out the circuit. I just reassembled it and decided to use it without the risk of breaking it through testing.

    The amp would probably be difficult to trace out anyway, because they ground off the part numbers from some of the IC's. You can see the sanded ID's in the attachment.
    Click image for larger version

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    Anyway, it's a good amp for the price, and it's built well and has some modding potential. At the DOTD price it's a very good deal. I'd be interested to see some real measurements on power and distortion, but not interested enough to do them myself :rolleyes:
    Attached Files
    Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

  • #2
    Re: Yung SD100-6 Review--Part 2 (DOTD)

    Thanks for the heads up. Don't really have a need or place to use one though

    Comment


    • #3
      Re: Yung SD100-6 Review--Part 2 (DOTD)

      Just bought two... GREAT DEAL!!
      "We are just statistics, born to consume resources."
      ~Horace~, 65-8 BC

      Comment


      • #4
        Re: Yung SD100-6 Review--Part 2 (DOTD)

        Originally posted by neildavis View Post
        The amp would probably be difficult to trace out anyway, because they ground off the part numbers from some of the IC's.
        Ugh. So they obtained the IC's through an illegal channel, or they're using copy-cat IC's. Maybe it's a good deal, but my respect for Yung just went way down.
        DARPA Jr - 2015 InDIYana Winner - RS180-8 + RS100P-8 + ND25FA
        The Aria's - RS150-4 (or RS150-8) + XT25SC90
        The Mariposa's - TEBM65C20F-8 + ND16FA
        The Canzonetta's - RS100P-8 and ND16FA
        AudioSource AMP-100 Mods OR Pyle PAMP1000 Mods

        Comment


        • #5
          Re: Yung SD100-6 Review--Part 2 (DOTD)

          Originally posted by tyger23 View Post
          Ugh. So they obtained the IC's through an illegal channel, or they're using copy-cat IC's. Maybe it's a good deal, but my respect for Yung just went way down.
          I hadn't considered those possibilities. Since they were obviously rough sanded, with no attempt to remark them, I assumed they were trying to prevent others from copying their circuitry.

          The IC's are buried on the bottom of the board--you can't see them without breaking at least 5 strong glue joints. The sanded IC's are in the power supply section.
          Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

          Comment


          • #6
            Re: Yung SD100-6 Review--Part 2 (DOTD)

            Originally posted by neildavis View Post
            I hadn't considered those possibilities. Since they were obviously rough sanded, with no attempt to remark them, I assumed they were trying to prevent others from copying their circuitry.

            The IC's are buried on the bottom of the board--you can't see them without breaking at least 5 strong glue joints. The sanded IC's are in the power supply section.
            Unfortunately, sanded ic's are only common when the chips were obtained through unofficial channels. You can see those type chips available for sale in the tech markets and streets of Shenzhen/Shanghai, etc.

            Most of those chips are legit IC's from the real companies, but the street vendors will remove the chips from reclaimed or non-working boards. They'll unsolder them (usually with a hair dryer), clean them up, scuff the top to get rid of the manufacturer and lot numbers (which prevents tracking) and sell them as a used IC.

            It's a lot like buying a used car with no warranty. Sure, it's a Ford, but you have no idea where it's been, how it was treated, what it's been exposed to, or how long it might last.
            DARPA Jr - 2015 InDIYana Winner - RS180-8 + RS100P-8 + ND25FA
            The Aria's - RS150-4 (or RS150-8) + XT25SC90
            The Mariposa's - TEBM65C20F-8 + ND16FA
            The Canzonetta's - RS100P-8 and ND16FA
            AudioSource AMP-100 Mods OR Pyle PAMP1000 Mods

            Comment


            • #7
              Re: Yung SD100-6 Review--Part 2 (DOTD)

              I have no doubt regarding the existence of used chips in the Asian market. However, I fail to see how their mass-scale purchase and testing is efficient for a major manufacturer. I strongly suspect Neil had it right to begin with... just corporate protection of design. Mass-produced cloned chips are a different story though.
              "We are just statistics, born to consume resources."
              ~Horace~, 65-8 BC

              Comment


              • #8
                Yung SD100-6 Review--Part 2 (DOTD)

                You're welcome to believe that if you wish, but if a reputable company wants to protect their design, they work with the silicon vendor to create a custom part number that's not publicly documented. (Apple, dell, hp, and many others do this.)

                A reputable vendor would NEVER scratch off the part or lot number from a part because they loose the ability to track issues and failures and they can no longer return the chips for failure analysis or demand a refund on a failed chip.
                DARPA Jr - 2015 InDIYana Winner - RS180-8 + RS100P-8 + ND25FA
                The Aria's - RS150-4 (or RS150-8) + XT25SC90
                The Mariposa's - TEBM65C20F-8 + ND16FA
                The Canzonetta's - RS100P-8 and ND16FA
                AudioSource AMP-100 Mods OR Pyle PAMP1000 Mods

                Comment


                • #9
                  Re: Yung SD100-6 Review--Part 2 (DOTD)

                  Originally posted by tyger23 View Post
                  You're welcome to believe that if you wish, but if a reputable company wants to protect their design, they work with the silicon vendor to create a custom part number that's not publicly documented. (Apple, dell, hp, and many others do this.)

                  A reputable vendor would NEVER scratch off the part or lot number from a part because they loose the ability to track issues and failures and they can no longer return the chips for failure analysis or demand a refund on a failed chip.
                  Regarding their corporate dealings... I have little respect for Dell, Apple or HP... and many others. Extreme corporate control is governed by the "billions" they possess.
                  "We are just statistics, born to consume resources."
                  ~Horace~, 65-8 BC

                  Comment


                  • #10
                    Re: Yung SD100-6 Review--Part 2 (DOTD)

                    Originally posted by tyger23 View Post
                    You're welcome to believe that if you wish, but if a reputable company wants to protect their design, they work with the silicon vendor to create a custom part number that's not publicly documented. (Apple, dell, hp, and many others do this.)

                    A reputable vendor would NEVER scratch off the part or lot number from a part because they loose the ability to track issues and failures and they can no longer return the chips for failure analysis or demand a refund on a failed chip.
                    Although my experience is in a different industry, I believe you have likely hit the nail on the head.
                    Click here for Jeff Bagby's Loudspeaker Design Software

                    Comment


                    • #11
                      Re: Yung SD100-6 Review--Part 2 (DOTD)

                      I source obsolete, rare and proprietary I.C.s for a living and have seen many automotive companies relabel parts or have them custom labeled but NEVER ground off or even "re-topped"
                      Loosing the ability to repair or modify a amp is why I did not buy one of these yesterday.

                      Comment


                      • #12
                        Re: Yung SD100-6 Review--Part 2 (DOTD)

                        That's going to be a costly process, having custom packaged parts... and impractical economically unless you are on the scale of one of the Big Boys. Someone selling stuff in the hundreds or thousands a month I wouldn't expect to. I'd say far more likely copy protection. Unfortunately it likely means no schematics on demand.

                        Sometimes, one can make out the markings, with angled light, wetting with solvent, under a microscope.
                        Too bad this was yesterday, might have picked up a couple....

                        Comment


                        • #13
                          Re: Yung SD100-6 Review--Part 2 (DOTD)

                          Originally posted by jonpike View Post
                          That's going to be a costly process, having custom packaged parts... and impractical economically unless you are on the scale of one of the Big Boys. Someone selling stuff in the hundreds or thousands a month I wouldn't expect to. I'd say far more likely copy protection. Unfortunately it likely means no schematics on demand.
                          That's what I had assumed, and if you look up "IC marking obfuscation" or "sanded IC protection" you'll find plenty of examples where this has been done (see the attachment). Tyger may be right, also. The repair argument is weak because these low-voltage parts are not the ones that usually fail in a switching power supply, but the "shady supplier" argument makes sense. I have no idea why those chips were sanded, but if they were that way to deter reverse engineering, it sort of worked on me, because I didn't feel any interest in tracing the circuit, as I did for the preamp section.

                          At any rate, I'm still impressed at the amount of circuitry in the preamp section and the overall quality of the construction. It's not a cheaply built amp--the boards, the shock mounting and sealing is much better than most plate amps that I have seen. Again, I haven't tried to characterize the output power or distortion, or see how well the protection circuitry worked, so maybe this amp has issues that I don't know about. But from what I've seen so far, this amp is a good choice if you need a small amp that is powerful and lightweight--especially if the price is $69.

                          Click image for larger version

Name:	IC_obfuscation.JPG
Views:	1
Size:	63.5 KB
ID:	1165686
                          Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                          Comment

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