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Adding subwoofer to a stereo amp and speaker in/out plate amp question

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  • Adding subwoofer to a stereo amp and speaker in/out plate amp question

    I am building speakers for my son and was also going to build a DIY amplifier. I was going to build two boxes...(1) a pre-amplifier with an input selector and potentiometer (also with a Sure bluetooth receiver and later a DIY phono pre-amp) with line-level outputs via RCA cables to the amplifier, and (2) a TDA7492 amplifier board in a box by itself with the RCA cables in and speakers out.

    However, I am also building a subwoofer and trying to figure out how to get the low frequencies to the SW. I was thinking of using a plate amplifier with speaker level inputs. For the Dayton Audio plate amp I see how to do this, speaker cables in and back out. But the BASH plate amp has speaker level inputs but no speaker outputs.

    So...(1) How does the BASH plate amp get the output to the speakers? (2) Is running the speakers through a plate amp my best option or is there a better way?

    (I realize a better way may be just to buy a cheap used 5.1 amp off eBay and may do that if that is the consensus.)

  • #2
    This. Preamp out to sub in, satellites out to amp. read up about it. Watch the video. I have 2. Or, a 2.1 chip amp that powers all 3.

    Dayton Audio SPA250DSP 250W Subwoofer Plate Amplifier with DSP

    New 2.1 - Techtalk Speaker Building, Audio, Video Discussion Forum

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    • #3
      I like djg's suggestion with the DSP plate amp. This way you can control the high-pass filter. Another option, which is a new product that I plan on trying in the future, is this DSP board you can program but comes preconfigured for 2.1 use. It uses the ADAU1701 chip that has been around a while.
      My Builds - Vigor (Nola Brio Knockoff) - Overnight Sensations w/ Voxel - Speedsters in surplus boxes - Zaph B3N's in bamboo - Classix II in BR-1 cabinets - Dual TPA3116 D2 amp in an old music box - Mariposas

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      • #4
        The bash plate amp only "outputs" to the subwoofer, it does not have any kind of a high pass filter for the satellites. It hooks up in parallel the satellite amp either at line level or speaker level. This means your satellite speakers run full range. For integration with the subwoofer and protection they should probably have some kind of a high pass crossover. A simple first order crossover should do the trick.

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        • #5
          Originally posted by devnull View Post
          The bash plate amp only "outputs" to the subwoofer, it does not have any kind of a high pass filter for the satellites. It hooks up in parallel the satellite amp either at line level or speaker level. This means your satellite speakers run full range. For integration with the subwoofer and protection they should probably have some kind of a high pass crossover. A simple first order crossover should do the trick.
          Ah, I did not realize that! The Dayton does high-pass at 125Hz using the high-level inputs and outputs so that may rule out the BASH.

          I like the other options, but am trying to keep this on the cheap side for now so the DSP plate amp is out, but the little DSP board may work.

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          • #6
            This is the cheapest. 3 channels of amp, and unlike many 2.1 chip amps, the satellites do have a fixed 100hz pass. Chip amp watts are a bit inflated. Depends how big and loud you want it.

            Lepai LP210PA 2x30W + 60W 2.1 Channel Mini Plate Amplifier TPA3118 with Power Supply

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            • #7
              These are on clearance. I paid a lot more for 2 earlier model units. Used them for years with PC and bedroom. Real watts, Recommended. AC in, no dangling power brick.

              Dayton Audio MCA2250E 2x22W + 50W 2.1 Channel Class D Plate Amplifier

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              • #8
                Restocked. This needs a powered sub, only two amp channels. Johnny Richards used an earlier model for his Tiny Tyms, a well received Project Gallery design, IIRC.Available new also.

                RESTOCKED Dayton Audio WF60PA 60W Class D Full Range 2.1 Plate Amplifier with Wi-Fi and Bluetooth

                Tiny Tym | Parts Express Project Gallery

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                • #9
                  Thanks djg, I should have provided more info in the original post. The mains will be Paul Carmody's Hitmakers and the sub is an Infinity Reference 1020w 12" that can handle 300w.

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                  • #10
                    If you can put an extra set of jack outs in the sub, wire a 100-150uF cap between the ins and new outs. That's the cheap way.
                    Wolf
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                    • #11
                      Well, I have a couple of SMSL SA50 chip amps using that TDA7492 chip. With 24V bricks. They're OK, the Hitmakers will take a lot more than that chip will put out. I see overdrive and distortion in your future if your son is typical. Maybe not. Millstonemike has explained here several times how the chip amp watt ratings are produced.

                      Silver D's little board looks like the way to go. Sounds like you want to make it yourself. Good luck.

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                      • #12
                        So I remembered I bought some higher powered Sure amplifier boards about 2 years ago for a different project but there were no easy crossover solutions so I assumed I would just rely on plate amplifiers and I put the Sure boards in a closet. (1 x 500w board which I think is realistically 300w low distortion with a 48v power supply.) But now looking at this $29 DSP board that SilverD linked to I wonder if that was all I am missing. Below is a diagram of what I am thinking, but I don't know the electronics well. A few questions:

                        Pre-amp:
                        • Can I run 12v into the enclosure and split it to the Sure Bluetooth board and to a 12v to 5v step-down converter to power the DSP board? (Not only "can I", but is this in fact what I "need" to do?)
                        • I have an Alps potentiometer - would I put that before the DSP board so that it attenuates the stereo signal before getting to the DSP board and being split to the mains and sub?
                        Subwoofer:
                        • Do I need anything more than the RCA in, on-off switch, power supply and amp board?
                        • Is there an advantage to putting the power supply and sub-amp in the sub and running line-level signal to it; or build a sub-amplifier to sit with the preamp and amp, and run speaker-level signal to the passive sub box?
                        Click image for larger version

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                        • #13
                          Originally posted by djg View Post
                          These are on clearance. I paid a lot more for 2 earlier model units. Used them for years with PC and bedroom. Real watts, Recommended. AC in, no dangling power brick.

                          Dayton Audio MCA2250E 2x22W + 50W 2.1 Channel Class D Plate Amplifier
                          I've been looking at that amp. There seems to be different opinions on the high-pass for the mains. Do you know the slope, and -6dB point for it? I think 150hz is too high for my use, but if it's 6dB slope, and -3dB at 150hz, that might make it usable. If it's -6dB at 150hz, then it's not a good option for me..One user review stated that the sub amp rolls off at 35hz. That's a deal breaker too, if it's true.

                          For the sub portion of the amp, is the 50w legit? I have a 10" sub, and that might just be enough power. I think it just reaches x-max with 50w. The whole package looks like it could be fun to play around with if the bass management is usable for more capable speakers.

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                          • #14
                            rpb,

                            Someone somewhere on the internet posted a test of these 2.1 amps showing the claimed high pass was way off. I have an older version, and I don't know that my units had any high pass. I can say I used them with a ported TB W8-740C sub design for years. Several different small 2 way satellites, very nice sound. The pots got scratchy but responded to deoxit.

                            These are class D amps with AC power input. The specs aren't too rigorous, but nowhere near as bad as 10% distortion into 2 ohms, which is typical for power brick chip amp specs.

                            I got the chip amp bug and abandoned these. That was short lived when I "discovered" the Dayton DSP plate amps. The DSP amps do everything I ever wanted. A 2.1 DSP plate amp powering all 3 channels would be enticing, but it's more flexible to use any stereo amp.

                            Bottom line, for $65 clearance, a real bargain for a PC or bedroom 2.1.

                            Edit: maybe Dayton is clearing these out because they're going to introduce something better.

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                            • #15
                              Thread hijack over.

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