help noob wanting to build 8 channel 16 watt audio amplifier

Discussion in 'The Projects Forum' started by facehead, Nov 13, 2009.

  1. facehead

    Thread Starter New Member

    Nov 13, 2009
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    hello all im new to circuit building but have been doing alot of research.

    I have found pcb designs for mono 2watt audio amplifiers but my problem is that this is not for a normal home stereo project. im working on an audio art installation and what i need to do is design 3 units (all the same design) that are 8 inputs 8 outputs all with a volume control and each individual channel is 2 watts amplified. I feel confident that i can figure the rest out if someone could point me towards info that will help me figure out how to use a single ac to dc adapter plugged into the wall to power each of these channels individually. the idea is to have each speaker have its own input and output but all be amplified by the same power source so i dont have to use batteries or and armada of power strips in the design.

    thanks

    :chuck:
     
  2. facehead

    Thread Starter New Member

    Nov 13, 2009
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    the speakers are 2 watt 8 ohm if that helps
     
  3. facehead

    Thread Starter New Member

    Nov 13, 2009
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    my logic says (perhaps faulty logic) that i should just build a 16 watt amp and running wires to each of the 8 channels would divide the 16 watts into 2 watt sections. However im really not sure what im doing here.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    You should use eight separate audio amps like a TDA2030, TDA2003 or similar and run one for each channel. Their data sheets show how to set them up. You would need to have power supply voltages to run them.
     
  5. facehead

    Thread Starter New Member

    Nov 13, 2009
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    but then can i make them (the amplifiers) all powered by one initial power source like a wall adapter? or do they (the amplifierss) all have to be individually powered?

    p.s. thanks for the reply :)
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Yes, you can use the same supply for all of them, provided that it has sufficient voltage and current.

    You might consider the LM1877 2W stereo audio amplifier, which you could use as a dual mono amplifier.

    You can use up to a 24v supply with that amplifier.
    MPJA.com has a 24v 4.2A power supply on sale for $10:
    http://www.mpja.com/email/11-10-09a.asp?r=%%ref%%&s=4

    I'd suggest adjusting the supply down to 22v or so before connecting it up; it has a 10% adjustment range.
     
  7. facehead

    Thread Starter New Member

    Nov 13, 2009
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    thanks also :)

    im gonna take this info and get started thanks for your help im sure ill have another question or 2 as i go

    should i go with the inverted or non-inverted amp?

    :chuck:
     
    Last edited: Nov 13, 2009
  8. SgtWookie

    Expert

    Jul 17, 2007
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    I'd go with non-inverting.
     
  9. facehead

    Thread Starter New Member

    Nov 13, 2009
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    So going through ive found out what everything on the diagram is :)

    MY first question is i see there are two large triangles indicating 2 amps in one one for left one for right. are those part of a component? Do i buy the lm1877 and that is the amplifier? do i need to buy two lm1877 chips? Is the dotted line around the amps in the diagram saying that they are both contained within the one chip?

    the other problem im having is figuring out where the input or inputs are on the non-inverting diagram. is it marked vL and vR? i only say that because it appears to be the same place as the inputs on the non-inverting one.

    I can identify capacitors, resistors, ground, and amplifier im not sure about the dotted lines especially on the resistors on the left side of the diagram (the slanted dotted line box). also the arrows coming from 6 and 9 pointing to the 100k resistors on the left.

    Sorry for extensive noobisms im from the music and art side of things. MY technical knowledge is just bits of internet knowledge waiting to be tied to gether in an understanding.

    thanks

    :chuck:
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    If you are looking at the top diagram on page 7 of the National Semiconductor datasheet for the LM1877, then yes.

    The LM1877 contains two 2W amplifiers.
    One LM1877 will provide two audio outputs.

    If you want 16 audio channels output, you will need 16/2=8 LM1877 ICs, plus the associated components.
    Yes.

    If you're looking at the bottom left schematic on page 7 in the above referenced datasheet, yes.
    The upper schematic is also noninverting.
    The basic difference between the two is that the upper schematic is using a single voltage supply (+V and ground only), and the lower one is using a split power supply (+V, -V, and GND).

    That indicates the pots (potentiometers) are mechanically connected; they are "ganged".
    The resistor with an arrow pointing to the middle indicates that they are potentiometers; variable resistors. This project would require "audio taper" potentiometers.

    Understood. That's what this site is all about. :)
     
  11. facehead

    Thread Starter New Member

    Nov 13, 2009
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    ok almost there :)

    so my component list per unit is this for the split supply diagram lower left of page 7...

    2-2.7ohm fixed resistors
    2-100k fixed resistors
    2-2k fixed resistors
    2-5µf electrolytic capacitors
    3-.1µf fixed capacitors
    2-2k audio potentiometers

    1-24v dc 4.2a power supply(which is capable of powering 4 of the above circuits in the same piece of equipment)

    ALSO: then there are two more fixed capacitors that are just labeled as 0.1 on the left connected to vl and vr i imagine this just means two more 0.1µf fixed capacitors

    this list look about right?


    and then the power supply you mentioned above would be running to the v+ and v- of each of 4 stereo amps? and also to the pos terminals of the input components themselves? meaning v+ goes to vL (positive terminal) on the rca jack) and v- goes to vR (positive terminal on RCA)

    thanks again i feel like i have very few things left to ask before getting my hands dirty.
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    OK, it's time for a reality check.

    This is in the best interest of your project ending successfully.

    Have you ever assembled electronics projects before, and had them work successfully?

    Do you know how to solder?

    Do you know how to lay out circuit boards, and get them made, or make them yourself?
    (you'll need to be able to do all of these things in order to have a chance of building this thing successfully.)

    If you have never assembled an electronic circuit before, you need to do several of them before you go any further with this project.

    This particular project is not terribly difficult for someone with a moderate amount of experience, but it will involve a lot of components and a lot of time.

    In your best interests, I most strongly urge you to purchase several electronic kits one at a time, build them, and report back on your success or failure with the kits.

    I am not trying to "put you off" - I'm attempting to help you gain the skills that you must have, in order to attempt something that is really beyond a complete newbie to electronics.

    I don't know what your "must have" timeline is. However, the sooner you start/complete the kits and establish your track record, the more likely that this project will reach a speedy and successful conclusion.

    I really want this project to be successful for you. If you follow my suggestions; taking on smaller projects to build experience and a successful track record, you will have far more confidence and experience than you have right now.

    I have worn your shoes. I worked very hard on my 1st transistorized project many years ago, and it was a complete failure.

    I hope you will take my advice.
     
  13. facehead

    Thread Starter New Member

    Nov 13, 2009
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    my experience is minimal i have done a couple circuit bending projects and repaired an old bass amp and made my own audio cables so my soldering isnt great but i think its good enough. i have not ever put together a circuit from components and blank board. Ive looked up several tutorials on the etching process with blank pcb boards but was going to try this first one on a bread board then move onto the PCB laser print transfer method once i know this will work. I have not layed out a circuit board before but didnt want to research that apect untill i knew i had all the components right and that i made them function together.

    I was considering buying kits but money is more of an issue than time. I assumed that this would be simple enough to be my kit project. This particular circuit diagram just isnt as common sense to me in some areas as others i looked at previously with numbered component lists to reference.

    Are you saying that my questions will be answered if i am able to complete a couple kits prior? Meaning i will know the answers im looking for by learning them through kits. I guess i didnt intend on milking a forum for answers but this just ended up being so rapidly helpful. I can go back to plan a which is read a books and tear apart some computer speakers.

    thanks for the shortcut though :)

    im gonna guess i can figure it out from here.

    :chuck:
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    I'm not trying to "blow you off" or discourage you from attempting this project. However, this is not what I would consider to be a project at a beginner's level.

    The individual circuits themselves are not very complex. However, you will basically need to build eight duplicates of the same circuit, and have them function together.

    What started this off is that you did not understand the difference between a single supply and a split supply.

    I see. Well, kits are designed with success in mind. The instructions for assembly are usually rather complete, and there is little left to chance.

    Making your own PCBs is somewhat of a quantum leap upwards in the level of skills required. If it can't be done on a single layer board, your chances of success are not good.

    No. My point is practicing soldering, assembling, following directions to a successful conclusion. I have very little idea what your capabilities and experience levels are. However, some things you've said have lead me to believe that you are at a basic novice level.

    I just want to try to make sure that this project will be successful. Neither of us will be happy if it is not successful.

    I simply do not have the time to devote untold hours towards training you every step of the way on how to complete your project.

    That might seem unfair, but that is just the way it is. Why should you deserve more help than other people?

    There are plenty of useful pages to read right here on AAC; they're only a click away at the top of your screen.
     
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