Question On Building A 4 x 50 watt Audio System

Discussion in 'General Electronics Chat' started by ajm113, Jul 10, 2013.

  1. ajm113

    Thread Starter Member

    Feb 19, 2011
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    Hey everyone long time no see, I finally got back some of my equipment I had gone for a while and now I'm thinking of starting a little side project of building a audio receiver for my room and had some questions. Some parts of how I'm makign this I already figured out, I just had some little questions here and there to fill up the gaps.

    1. I know a lot of amp projects that use no more then say 20 amps use ICs to do all the work, in this case I'm guesting I'm having to use MOSFETS or transistors to deal with the amplification of the stereo input. Can anyone recommend me a good parts that could accommodate this task and maybe some reference material on creating a basic amp with these?

    2. I plan on adding a Sub too on the side. How can I kinda ... get the 'bass' from a audio input to the sub correctly?

    3. Also is there a cheap or in expensive approach to adjust say volume using a microcontroller and some resistors connected to some pins in parallel to a MOSFET?

    Any other reference material in accomplishing making a little audio system would be great just so I get the backbone of the system figured out. I kinda want to make a receiver I can connect my PC, Ipod, and TV to in my room basically. lol
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
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    I don't know when EPE comes out in AZ, but you are in luck,

    Look at a new project starting August 2013, p46

    "superb four channel amplifier on the cheap"

    This article may have been written just for you.
     
  3. ajm113

    Thread Starter Member

    Feb 19, 2011
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    I'm sorry I'm not aware of what EPE is. I've been out of touch for a while. lol
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Everyday Practical Electronics magazine in the UK.

    PM me if you don't have access to this
     
  5. wayneh

    Expert

    Sep 9, 2010
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    Is it really worth your time when you can go buy something like this or this or this or this or a million other used amps looking for a good home?
     
  6. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    No it certainly is not worth the time..... but I built a few "time sink" projects back in the day just for the fun of it. It's good for learning.

    I never did build a home brew audio amp for in house because my speakers are very expensive and I was never sure enough the protection circuits would keep them from harm. Built some for cars because the speakers are cheaper.

    The problem is: if you want an amp that can deliver 4X50 watts of continuous power, that takes a healthy power transformer and heat sinks. The mechanical deswign and power supply will be the major time sink.

    The store bought units use a lightweight switching power supply to save size and weight.
     
  7. ajm113

    Thread Starter Member

    Feb 19, 2011
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    @wayneh: To me yes... I kinda want to get the habit of building circuits in areas I don't usually touch, since I plan on getting a Associates in Electronics Tech and thought something like this would be a good warm up project and do on the side while I'm not programming, working or going to school.



    @bountyhunter: I'm willing to drop watts for the cost of loudness. The max loudness more then likely I usually will be using would be around 50-70db. I'm somewhat also trying to achieve getting this thing small as possible too.

    I found this schematic on the net and it seems like something I can mod using.
    http://www.aaroncake.net/circuits/amp20w.asp
     
    Last edited: Jul 10, 2013
  8. wayneh

    Expert

    Sep 9, 2010
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    Fair enough. We see a lot of noobs around here that underestimate the time and effort of a DIY project, totally on the wrong side of make versus buy, so please excuse the question.

    Since you want small, look into using a SMPS. As noted, that's where the market is now and there are good reasons for that.
     
  9. ajm113

    Thread Starter Member

    Feb 19, 2011
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    Understandable, I know my limitations and I know I'm not planning on getting to crazy with this project as you can tell I'm willing to lower my wattage a little just to have something that works decently. ;)

    Defiantly already on that! They are great at reducing noise if filtered properly in audio equipment, I've been searching for some examples, but not many break down how parts of the circuits work. Unless I need to recap some things I may have forgotten.
     
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Loudness is an interesting characteristic.

    A 500mW to 1500mW transistor radio can sound louder than a high quality 100W amp.
     
  11. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    The good reasons are doing it on the cheap. Switchers are now so cheap they own everything, but a lot of audiophiles think the old transformer power supplies sound better because switchers have almost no stored energy. They do very poorly when asked for large peak currents to accommodate audio transients. I have a 2 x 60 Akai receiver made in 1973 and it probably weighs 50 pounds due to transformer weight.
     
  12. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    There are some really high quality integrated amplifier power ICs available. That's what I used to build the amps for the TV speakers I built. They sound great and are much easier to build.
     
  13. wayneh

    Expert

    Sep 9, 2010
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    Anybody can make something nice if cost is no object. But getting the job done for less money (and more efficiently in power usage) is the essence of good engineering design. You make it sound so dirty! Audiophiles might pay more for a heavy big transformer design, but the larger market segments are happy to get other features and pay less. Heck, you can't even convince people to reject those modern mixes that have almost no dynamic range, the "sausage" approach to music mixing.
     
  14. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I spent about 15 years designing switchers. They are efficient and lately they are really cheap in watts/dollar, but they work great until they go pop and all is DEAD. IMHO, linear supplies were more reliable... as evidenced my that 40 year old Akai receiver I have that still works fine. Never had a single part replaced. Just my opinion.

    Yeah, I laugh too when the audiophiles pay hundreds of dollars for giant toroidal cores and wind there own transformers. But linears still give me a better feeling than switchers. And switchers crank out noise like a small radio station.
     
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