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  • Active Xover and Bi-amps

    Hopefully I'm not posting something that's already been posted.
    Any thughts on these cross overs and bi-amps?

    https://www.xkitz.com/collections

    Thanks,
    Mike
    "We're speaker geeks, not speaker nerds. Nerds make money!" Marty H
    Bismarck, North Dakota
    My Current System: Jolida SJ502A, Squeezebox Touch, and Carmody Sunflowers
    My Garage System:Marantz 2238B and Nano-Neos

  • #2
    Just me, but I tend to prefer the 'sound' of the Tri-Path based amps boards. They sound smoother.

    The minidsp 2x4 kit is $80 but you can find some good information on the ADAU1701 ($17?) dsp board on Neil's website http://www.audiodevelopers.com/
    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


    • #3
      Those are nice, with a high quality amp and a variable 4th-order crossover. The prices are reasonable.

      However, if you want more crossover flexibility and other signal conditioning options, the Sure amps with the ADAU1701 DSP are even more attractive. I started to work on the code to control the ADAU1701 from a local display, but my amp didn't like the abuse from premature software and died the other night. I've got another amp on order, but it will be a while before I post some info, since I need the hardware to test the code. But in the short time it was working, it looked very promising.

      ​The XKits are going to need better heatsinking to achieve the rated output.
      Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

      Comment


      • #4
        This might be tough to answer, but how user friendly are these types of things? Do they use a GUI interface? I'd like to try something of this sort, but I don't want to wind up with something that just sits on a shelf.
        Thanks,
        Mike
        "We're speaker geeks, not speaker nerds. Nerds make money!" Marty H
        Bismarck, North Dakota
        My Current System: Jolida SJ502A, Squeezebox Touch, and Carmody Sunflowers
        My Garage System:Marantz 2238B and Nano-Neos

        Comment


        • #5
          No GUI, you have to change the entire bank of resistors to change the Xover frequency (their site sells the "modules" for $5 each). You get a electrical 4th order LR at the specified frequency. Op-amp based crossovers. In the "old" days Audio Control used the same setup in their car audio crossovers.
          "Everything is nothing without a high sound quality." (Sure Electronics)

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          • #6
            Neil is a whizz with things electronic. I'm the exact opposite, but find the minidsp software easy to use. Not saying my speakers are at their utmost potential with my minidsp skills, but it was relatively easy to get them running, measuring, and sounding pretty good. There's no way my skills could have built a passive crossover that sounded as good.

            Here's the minidsp software download page https://www.minidsp.com/products/plugins/2x4-plug-ins
            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 don't have any pictures yet of the GUI for the Sure JAB3 amps, but they use the Nextion display that is described in this thread: http://techtalk.parts-express.com/fo...isplay-for-dsp

              ​This project uses the teensy3.2 CPU to control the ADAU1701 on the amp board and to receive commands from the Nextion touch screen display. Those displays are about $16, which is reasonable for the amount of interaction they provide. I've got another version of the code that uses Bluetooth and an Android app to control the DSP, but for the Sure amps I wanted to stick with the Nextion display. This project is using two of the Dayton WiFi modules, one in each speaker, and Bluetooth gets "difficult" with two destinations (it's designed to pair with a single client). If I move on to designing networked cell phone apps (using WiFi), the amps could be controlled using a smart phone app, without needing a local GUI.

              ​This approach is much different from the miniDSP, as the teensy3.2 controller does the Bilinear Transform​ to calculate the filter coefficients from the GUI. So, no PC is needed. You just use the GUI to select whether you want a 2-pole, 4-pole or 8-pole LR filter and select the frequency, and all of the number crunching and DSP control is done with the teensy CPU.

              ​I'll be writing up this project in gory detail later on...as I said, my one amp died and that put the project on hold until I get a replacement. I've got one coming via economy shipping and the other via "express"
              Click image for larger version

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              Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

              Comment


              • #8
                Regarding those xkitz amps: I had posted something very similar back in 2007. You could change the crossover frequency by plugging in different resistor packs (the blue components on the right). The LM4766 is an excellent amp, and the approach still makes sense for people who insist on a quality class AB amp. My wife's computer speakers use these amp boards.

                Click image for larger version

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                Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                Comment


                • #9
                  I noticed on the 100 watt kits something unusual, maybe something got reversed. It gives the power output as 53 W RMS into 8 ohms, and 36 into 4 ohms. This is the reverse of what is usually seen. Why would this be?

                  Comment


                  • #10
                    Originally posted by skatz View Post
                    I noticed on the 100 watt kits something unusual, maybe something got reversed. It gives the power output as 53 W RMS into 8 ohms, and 36 into 4 ohms. This is the reverse of what is usually seen. Why would this be?
                    I noticed that too, presuming it's an error and they reversed the power based on the other channel specs. The only way the power would go down that severely into 4 ohms would be if it had a terribly high output impedance. Sent from my SM-G920P using Tapatalk
                    Electronics engineer, woofer enthusiast, and musician.
                    Wogg Music

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                    • #11
                      Can't link there but take a look at the T1 and T4 (hotrod versions of Sure's T-amps?) at hifimediy dot com. Both have less power into 4 ohm than 8 ohm.
                      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


                      • #12
                        Originally posted by neildavis View Post
                        I don't have any pictures yet of the GUI for the Sure JAB3 amps, but they use the Nextion display that is described in this thread: http://techtalk.parts-express.com/fo...isplay-for-dsp
                        It's a bit confusing from the Sure documentation - do these store the parameters, or do they need to have them reloaded at startup?

                        Comment


                        • #13
                          Originally posted by skatz View Post
                          I noticed on the 100 watt kits something unusual, maybe something got reversed. It gives the power output as 53 W RMS into 8 ohms, and 36 into 4 ohms. This is the reverse of what is usually seen. Why would this be?
                          ​Amps can be current-limited (they can provide enough voltage swing into the load, but not enough current), voltage limited (they can provide plenty of current, but the supply voltage isn't sufficient to achieve full output), or package/thermally limited (they shut down or go into self-protection mode when they get too hot). A lot of chip amps are "package-limited", which means you need to get the heat out in order to achieve full output. For a package-limited device, you need to operate it in its most efficient range, as that's when there will be the least heat generated. Apparently, the LM4766 is most efficient when driven into a 6 ohm load. See figure 17 in the datasheet:

                          Click image for larger version

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                          Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                          Comment


                          • #14
                            Originally posted by spasticteapot View Post

                            It's a bit confusing from the Sure documentation - do these store the parameters, or do they need to have them reloaded at startup?
                            ​The JAB3 uses self-boot mode, which boots the program and parameters from an on-board EEPROM. Their "user interface" is four pots that are connected to the Aux inputs of the ADAU1701. The program that Sure puts in the EEPROM makes the pots do something, but I don't know what that is, and I don't really care. As far as I know, Sure isn't making their SigmaStudio layout available, so if you want to change the default program, you will need to "write" your own program using SigmaStudio. Sure has a programmer and connector that you can use to put the complied program into the EEPROM.

                            ​My approach to using the JAB3 is to disable the self-boot mode and have the CPU load my own program and parameters into the ADAU1701. That way, I know where all of the DSP cells are located, and I can change them using the LCD GUI. On startup, the CPU programs the ADAU1701, initializes the parameters, and then changes the parameters in response to the GUI.. This is a much more flexible approach, and it is consistent with how Analog Devices expected the device to be used.
                            Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

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                            • #15
                              neil

                              When you get the component blocks finalized, let us know, and I for one will buy the boards and beta test the rig.
                              These Sure boards came out at the right time, I've been thinking about taking the MindDSP route, but kept putting off the purchase.
                              This solution looks very flexible and with low cost entry.

                              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

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