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Hardware Review: 41hz.com Amplifier Kit

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  • Hardware Review: 41hz.com Amplifier Kit

    As some of you may know I was looking to find a good solution for an 'in dash' amp that wasn't built into a headunit (I've got nowhere to put one since the screen is going there!)
    I considered trying to get one of the mondeo amps but had a hard time finding one and wasn't sure if it would fit behind the dash anyway!
    So.. new plan, a few people suggested the amps from 41hz.com so I checked out their site and ended up buying the AMP9 12v Kit.
    http://www.41hz.com/main.aspx?pageID=130

    This amp is 4x60w and its pretty damn small (50mm x 160mm)
    Two days after ordering my kit arrived from Sweden, I was pretty impressed with the delivery speed and couldn't wait to get stuck in building up the kit!

    I opened up the package to find all the components neatly packed and then it dawned on me... what have I let myself in for, I'm no master solderer by any means.. but I was willing to give it a shot!



    After a quick breakfast and a good study of the bill of materials to make sure everything was there I got stuck in soldering the components onto the bottom of the board... this is around 1 hour in, a long way to go yet!



    Soldering these components definatley gets easier as you go along, but if you've not but much component soldering before then I'd recommend you get the SMT solder kit thats available from 41hz, this is simply a dummy board with components to help you hone your skills
    Here we are at around 3 hours in, bottom side is now finished and I'm around half way through the top of the board..



    One you get past soldering the Tripath chip, which I found a little tricky due to the closeness of the contacts the rest of the top is fairly plain sailing... that is until you reach the Toroid Inductors!
    The Toroid Inductors are the 8 Rings you see on the top of the board that are wound with wire, when the kit arrives you get the 8 rings on their own and 8 strips of wire.. you know whats coming next
    You have to wind each toroid with 52 turns of wire.. it took me around 25 minutes per toroid, so that was done while watching some evening tv.
    One thing I will say is that if you keep the center of the ring tight with your winds you do get exactly 52 winds before you are back at the beginning, makes life much easier when trying to count them!
    You may want to put a plaster or something over your working fingers while winding the toroids as after winding 8 rings you fingers get rather sore!!

    After another hour or so I finish up the top of the board.

    In my haste to test out my work I decided to hook the power up via croc clips onto the board via my bench PSU.. BAD IDEA!!
    I hadn't realised that all along the edges of the board (between the layers when you look side on) there are copper tracks exposed, this must be connected to ground since when I fired up the amp for the first test it shorted with the positive croc clip

    Once I realised my mistake I soldered up an ISO connector for the power and audio outputs since this is what I'd be using in the car anyway..
    I got quite disheartened on the second test of the amp when I didn't get any output.. fearing I had burnt something out with my earlier escapades I started checking for damage.
    Not finding anything obvious I double checked the online troubleshooting guides at 41hz.com and realised that by default the amp is muted, you are required to jump two pins to bring it out of mute I tested this with a peice of wire and there was life!

    I've now mounted the amp into a case which will also house my steering wheel control interface for the carpc.
    Here is a shot of my test setup using my trusty Zune as a source;



    So far I'm extremely impressed with the output of this little amp, it stays cool, sounds great.. and its really pretty loud!
    Just need to get the rest of the install finished now

  • #2
    Thanks for the review. I'm sure some will find this very helpful.

    Cheers
    System always under construction


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    • #3
      Congrats! I am doing pretty much the same as you. My goal, a complete in-dash solution, completely HU less.

      I also purchased the Amp9, and although constructed, isn't tested yet. In the process, I did manage to lift ONE trace, and decided that repeatedly heating to solder connections on and off the amp was a bad idea, so I am currently awaiting some terminal blocks to solder to the board, so I can use screw terminals and a single 16pin idc connector for the inputs/logic.

      Some pointers:

      The onboard bridge rectifier isn't really needed if your going to power it from a DC source. If you power it from a regulated DC source, you can do away with all three of the large bulk caps as well. I only mention this because if at some point space gets to a premium, you have some options of shortening the board.

      Also I found that "GC" makes some really good 2 part epoxy that I used to secure the toroids, so they don't move when it finally gets planted into the car.

      Looks Good!

      -Alan

      PS What are your going to do about an AM/FM tuner? I have a thread and think a company in my industry maybe releasing a product that fits my needs for a tuner, but I always like to read what other people are doing...

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      • #4
        Thanks for the comments guys - Interesting stuff about cutting the board size down!!
        I'm going to do without AM/FM tuner since I don't really listen much to radio, however I guess I may add a USB tuner to the CarPC if I miss it too much

        Alan, you may be interested to watch the development of this thread; http://www.mp3car.com/vbulletin/car-...kit-amp-2.html
        Its regarding auto-unmuting the amp via the Serial port of the CarPC.. not going too great at the moment but I've got a member on here helping out who really seems to know his stuff!

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        • #5
          Will do! Oh, and on the subject of shortening the board, here is a thread you might be interested in (look towards the bottom):

          http://www.41hz.com/Forums/topic.asp?TOPIC_ID=1289

          -Alan

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          • #6
            Anyone know the SNR or the THD?

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            • #7
              Damn which I could find something prefabbed like this, I don't have the dexterity to solder all of this stuff nor do I have the time.. but I'd prefer something small to your standard 4 channel amp which is huge.

              Comment


              • #8
                AcuraTLFan; Here is some info from the datasheet for the Tripath chip used on this amp, hope it helps you:



                Rbsx; I'd say get a small basic kit (one of the Velleman style ones) from Radioshack for making a flashing LED circuit or something... then use that to practice your skills on. I'm no soldering expert by any means, but if you take your time and practice first its not too hard.. the guide that comes with the amp steps you through the whole assembly process.

                Comment


                • #9
                  Originally posted by swift_gti View Post
                  AcuraTLFan; Here is some info from the datasheet for the Tripath chip used on this amp, hope it helps you:



                  Rbsx; I'd say get a small basic kit (one of the Velleman style ones) from Radioshack for making a flashing LED circuit or something... then use that to practice your skills on. I'm no soldering expert by any means, but if you take your time and practice first its not too hard.. the guide that comes with the amp steps you through the whole assembly process.
                  Might I also ask how much it set you back?

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                  • #10
                    Originally posted by rbsx View Post
                    Might I also ask how much it set you back?
                    Sure, I meant to put it into the review but forgot..

                    It cost me 65 Euro / 44 Sterling, that converts to around $88 USD Delivered.

                    Definatley worth the money in my opinion

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                    • #11
                      Originally posted by swift_gti View Post
                      Sure, I meant to put it into the review but forgot..

                      It cost me 65 Euro / 44 Sterling, that converts to around $88 USD Delivered.

                      Definatley worth the money in my opinion
                      I suppose, but I can pick up a preassembled 4ch amp for around $100-120 up here, though it won't be able to fit under the deck, it might just be easier for me to do.

                      Comment


                      • #12
                        I just wanted to add to Swift_GTI's review of the 41Hz kit/support.

                        I have built 2 of the amp9's from 41Hz. I ran into some issues both times; none of which were the fault of 41Hz. A couple were my own stupid boneheaded mistakes. I also had some deep technical support questions as well when constructing the first amp as it pertains to AM radio and automobile use.

                        Anyway, both times, Jan at 41Hz went above and beyond the call of duty! All my technical questions were answered fully and timely.

                        As far as kit quality, both amps worked on the first try. They are very easy to build, and the instructions are quite good. The amp9 assembly instructions do need a revision though as there are 2 parts I believe that aren't labeled as to where they go, but with the datasheet from Tripath and process of elimination its very obvious where they go, but really should be documented in the assembly instructions.

                        Overall, If your looking for a 4 channel amp that is small and powerful enough to replace a headunit or for integration into a carPC, I don't think you will be dissapointed with the kits from 41Hz.

                        -Alan

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                        • #13
                          Can you get these from anywhere, pre assembled?

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                          • #14
                            Sometimes members will offer them for sale in the classified section over at the 41hz forums. Or a member might build on for you, but otherwise not that I know of.

                            -Alan

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                            • #15

                              The onboard bridge rectifier isn't really needed if your going to power it from a DC source.


                              You will lose reverse-polarity protection by doing this. Could be valuable if someone ever hooks up the battery backwards. I've had this happen and it blew my amps...


                              If you power it from a regulated DC source, you can do away with all three of the large bulk caps as well. I only mention this because if at some point space gets to a premium, you have some options of shortening the board.


                              You might want to be cautious removing the caps completely. Removing the caps will likely result in a reduction in low-frequency response and overall dynamic range. The caps are there for two reasons, one is to help filter noise and ripple, but the other is to provide a low-impedance high-current power source for the moments when a lot of power is necessary such as during heavy bass notes or drum beats. If you take out the caps, you will have to ensure you have heavy guage wiring all the way to the battery, and even then, the amp will probably still suffer.

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