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  • Amp, Bookshelf & miniDSP Project

    I have been kicking around the idea for a while to build an amplifier to power a set of bookshelf speakers. The purpose is to have a space where I can just listen to music without the involvement of my HT system. I really wanted to design a passive speaker from the ground up but after some research decided I would like to try a DSP solution. Since PE now carries miniDSP, I thought this might be a good opportunity to give it a try. I will start with the amp as that will dictate what speakers I will build.

    Amplifier:
    Sure 4x100 Watt Amplifier AA-AB33182
    Mean Well MW NES-200-24 24 VDC 8.8A 200W Regulated Switching Power Supply

    Speakers: Dayton Audio RS150P-4A 6" Reference Paper Woofer 4 Ohm
    Dayton Audio RS28A-4 1-1/8" Aluminum Dome Tweeter

    EQ/Crossover: Will use an Omni Mic for measurements
    miniDSP 2x4 Kit Digital Signal Processor Assembled Board

    I have a pretty good idea about what I want to do. With that said, I have a few questions:These are the basics and I know just enough to get into trouble. I am hoping to get feedback from the community in order not to go to far off the rails. Any and all advice is greatly appreciated.

    Gordy
    "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

    The Madeleine
    The Roxster
    Swopes 5.0
    Acoustic Panels
    Living Room Make Over

  • #2
    You'll get a nominal 36w per channel into 8 Ohms @ 24v. That translates to 3a @ 24v. You'll get 56w into 8 ohms at 30v. That translates to ~4a. The extra headroom might come in handy.

    What size are the PS caps on the 4x100 Sure amp? I see 11 of them.

    Comment


    • #3
      1) AFAIK, the best match would be the nes350-24. If it's the tk2050, about 40 clean watts is all it will do. Tried powering the minidsp with the 24v power supply, but it was too noisy. Much quieter with it's own wall wart. Is there a way to filter the 24v supply before the mini? You get a coupon for software with the mini from PE, didn't get that when ordering directly from minidsp.

      2) Don't know about the BT board, but the mini has a nice level meter to dial back input to a usable range. Output is .9v on the basic 2x4.

      3) IMO, yes.

      4) Post the amp enclosure after you get everything mounted. I'd like to see it. May supply me with some ideas.

      5) A question I'd like to ask. IMO, the rs150 and rs28 are nice performers, is the BT connection up to their level? Does it have optional inputs?

      YMMV, just my $.02, and objects in the rear-view mirror are closer than they appear.
      http://techtalk.parts-express.com/fo...khanspires-but
      http://techtalk.parts-express.com/fo...pico-neo-build
      http://techtalk.parts-express.com/fo...ensation-build

      Comment


      • #4
        I don't have the amp yet unfortunately. But From what I can tell, they look like 50v 220uf caps. I will be driving 4ohm speakers.
        "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

        The Madeleine
        The Roxster
        Swopes 5.0
        Acoustic Panels
        Living Room Make Over

        Comment


        • #5
          Originally posted by Kornbread View Post
          1) AFAIK, the best match would be the nes350-24. If it's the tk2050, about 40 clean watts is all it will do. Tried powering the minidsp with the 24v power supply, but it was too noisy. Much quieter with it's own wall wart. Is there a way to filter the 24v supply before the mini? You get a coupon for software with the mini from PE, didn't get that when ordering directly from minidsp.

          2) Don't know about the BT board, but the mini has a nice level meter to dial back input to a usable range. Output is .9v on the basic 2x4.

          3) IMO, yes.

          4) Post the amp enclosure after you get everything mounted. I'd like to see it. May supply me with some ideas.

          5) A question I'd like to ask. IMO, the rs150 and rs28 are nice performers, is the BT connection up to their level? Does it have optional inputs?

          YMMV, just my $.02, and objects in the rear-view mirror are closer than they appear.
          I will knock down the voltage of the DSP to 12v with a switching regulator.

          I will be able to switch to 3 different inputs BT being one of them. Will probably fill the other two with two pairs of RCAs
          "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

          The Madeleine
          The Roxster
          Swopes 5.0
          Acoustic Panels
          Living Room Make Over

          Comment


          • #6
            Originally posted by Gordy View Post

            I will knock down the voltage of the DSP to 12v with a switching regulator.

            I will be able to switch to 3 different inputs BT being one of them. Will probably fill the other two with two pairs of RCAs
            So you will be using the 2x4HD, IIRC, it's 2v output.
            http://techtalk.parts-express.com/fo...khanspires-but
            http://techtalk.parts-express.com/fo...pico-neo-build
            http://techtalk.parts-express.com/fo...ensation-build

            Comment


            • #7
              I will be using the 2x4 not the HD. My concern is the amplified signal output of the 4.0 Sure BT module. The 2x4 has a selectable input of 0.9 and 2.0. I don't want to overdrive the DSP. 0.9 for the output should be more than adequate. If I had digital sources for the HD I would love to use it but I will be streaming via BT or analog line. I don't ever remember the last time I listened to a CD, I would not even know where mine were stored.
              "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

              The Madeleine
              The Roxster
              Swopes 5.0
              Acoustic Panels
              Living Room Make Over

              Comment


              • #8
                Originally posted by Gordy View Post
                I don't have the amp yet unfortunately. But From what I can tell, they look like 50v 220uf caps. I will be driving 4ohm speakers.

                I got one of those a couple of months ago - yep - those are 50V 220uF caps

                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

                Comment


                • #9
                  Originally posted by Millstonemike View Post
                  ... The extra headroom might come in handy..
                  Couldn't hurt
                  "Not a Speaker Designer - Not even on the Internet"
                  “Pride is your greatest enemy, humility is your greatest friend.”
                  "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

                  Comment


                  • #10
                    Originally posted by donradick View Post


                    I got one of those a couple of months ago - yep - those are 50V 220uF caps
                    How did it end up working out for your application?
                    "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

                    The Madeleine
                    The Roxster
                    Swopes 5.0
                    Acoustic Panels
                    Living Room Make Over

                    Comment


                    • #11
                      Originally posted by Gordy View Post
                      I will be driving 4ohm speakers.
                      Sorry, I missed that. You'll have plenty of power @ 24v; ~70w. Too many PS amps is never a problem. You could always save a couple bucks and a bit of size going down to the 6.5 amp unit.

                      Will you be doing the dual BT - Wired input like on the Madeline? It would be interesting if you can hear a difference in quality given the driver selection.

                      Comment


                      • #12
                        Originally posted by Gordy View Post
                        I will be driving 4ohm speakers.
                        Sorry, I missed that. You'll have plenty of power @ 24v; ~70w. Too many PS amps is never a problem. You could always save a couple bucks and a bit of size going down to the 6.5 amp unit.

                        Will you be doing the dual BT - Wired input like on the Madeline? It would be interesting if you can hear a difference in quality given the driver selection.

                        Comment


                        • #13
                          I took a quick look at the amp's manual - it has a gain of 32 dB (voltage gain of 40) and gives full output (with Vcc = 30V, load = 4 ohm, 10% THD, 108 W) with an input of 520 mV. To stay at 1% THD reduces the input value to 400 mV. A PS of 24V will reduce both of those numbers. Something to keep in mind when setting up your miniDSP.

                          Originally posted by Gordy View Post
                          I will be using the 2x4 not the HD. My concern is the amplified signal output of the 4.0 Sure BT module. The 2x4 has a selectable input of 0.9 and 2.0. I don't want to overdrive the DSP. 0.9 for the output should be more than adequate. If I had digital sources for the HD I would love to use it but I will be streaming via BT or analog line. I don't ever remember the last time I listened to a CD, I would not even know where mine were stored.
                          "Everything is nothing without a high sound quality." (Sure Electronics)

                          Comment


                          • #14
                            Now that I think about, you could probably use a laptop brick (Dell 19v at 4.57a) - 45W into 4 ohms. That would save a fair amount of space. Perhaps a couple of additional PS bypass caps near the off-board near the power inputs would manage any current draw from dynamic peaks. Maybe a couple of 6,200uf caps - may be overkill, but easy enough to try.

                            Comment


                            • #15
                              Originally posted by Millstonemike View Post
                              Now that I think about, you could probably use a laptop brick (Dell 19v at 4.57a) - 45W into 4 ohms. That would save a fair amount of space. Perhaps a couple of additional PS bypass caps near the off-board near the power inputs would manage any current draw from dynamic peaks. Maybe a couple of 6,200uf caps - may be overkill, but easy enough to try.
                              I have thought about it. Space I don't think is going to be an issue. Once I have the component list finalized I will bring it into SketchUp to see how everything fits. I am still on the fence in regards to the chassis. I might go with a hardwood enclosure of some sort.
                              "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

                              The Madeleine
                              The Roxster
                              Swopes 5.0
                              Acoustic Panels
                              Living Room Make Over

                              Comment

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