Help me with my electronics project.

[BoomAM]

Hi.
Ive been told that i need to design, research and build something electronic, for a project;
Im planning on a switching Amplifier. I am aloud to buy pre-made parts and modify them bty.
To allow me to have my headphones and speakers plugged into my PC at the same time. The switch will be on a "extenter cord", the amp is to help out with the volume. Cos ive heard that splitting a audio signal can reduce the volume by upto 50%.
Heres the Amp im planning on buying;
http://www.maplin.co.uk/products/module.asp?CartID=031105135102558&moduleno=32295&Products=1

Ive concluded that i`ll need the following parts;
An amp.
Parts for the switch(not sure on exact parts)
3 female phono connectors. (one input, 2 output)
1 male/male phono lead (to connect to PC)

Will the AMP need connecting to the mains to work, or can it draw its power from the PC? Prehaps from a 12v connector? As my PSU (antec 480W), has a external 4 pin connector.

Are there any circuit diagrams that you can point me to?


Thanks in advance.

 

[Matthias99]

It's a very simple circuit, and I would be amazed if a search for "amplified splitter circuit diagram" didn't turn it up.

Here's one such result -- I'm sure you can find something there:

http://www.epanorama.net/links/audiocircuits.html

Drawing power from the PC is probably easiest, as you'll need +/-12 and +5V DC.

 

[BoomAM]

What power amp would i need?
I suppose the external 12v power connector on my PSU would be the best place to draw power from?

 

[BoomAM]

I cant find any proper schematics on google. And the website that you provided has some ok drawings, but they are hand drawn and are hard to make out some of the components and their values.

 

[BoomAM]

Here are my two theories/ideas/quetions.

----------------------
1)
Would i have a significant volume drop if i was to have the AMP before the split?
Cos ive found this splitter cable;
http://www.maplin.co.uk/products/module.asp?CartID=031105152634776&moduleno=28112&Products=1
Using the right amp, that could add +100% volume (making 200% original volume), then it splits (which removes 50% volume), which then makes the volume 100% again. Correct?
So all i`d need is an amp that could to an exact doubling of the volume, with the computer plugged into that, then the output of the amp, plugs into the splitter. Correct?

----------------------
2) Have the splitter build into the AMP, with an external manually operated switch to switch between the outputs.
----------------------

Which would be better as far as audio quality goes?

 

[Matthias99]

What power amp would i need?

Depends what you're driving! Headphones can be driven at line level (ie, the level you get out of a headphone jack), but you'll need to crank up the voltage for speakers, unless you're running it from your splitter box to an external amplifier (it sounds like you wanted to build a combo splitter and amp, though). How much depends on the impedance (and thus size) of the speakers you're driving.

I advise doing some reading, and looking at amplifier cirucit diagrams.

You'll need +12V, -12V, and +5V for an opamp-based circuit, all of which should be available from your computer's power supply. You can also buy an external power supply, which might be more convenient for testing. However, the amp you had above sounds like it takes AC power -- looks like it already has some extra filters and stuff built into it.

This is the datasheet for the solid state IC in that amp -- you could just buy one of those and wire it up yourself (don't forget a heatsink!), as it will only require DC power (it can take +12/-12 or +12/+6 volts):

http://www.semiconductors.philips.com/acrobat/datasheets/TDA1521_Q_CNV_2.pdf

That would simplify your wiring and be a smaller (and cheaper) circuit, although theirs will probably sound better.

 

[Matthias99]

I thought you wanted to build a switching amp? Why all the splitter cables all of a sudden?

 

[BoomAM]

Makes it easyier. Its a "B" option at the moment. If i can have two designs done, with theory, advantages and disadvantages for each, and then build one of them, i get more points than just doing one.

For final usage, the Power will come from my PCs PSU. For testing/building, a seperate PSU will be used.
So the amp i suggested in my first post will suit my needs?

The speakers being used are; Creative Inspire5300 5.1 ; Just the Front L/R will be going into the amp/being split.
The Headphones are some philips wireless ones, which i can provide the specs if nesissary.

 

[BoomAM]

The amp i suggested says that its an audio amp, but it doesnt look like it has any type of audio connectors on it?!
The schematics of it in that PDF you found seems to suggest that its a mono circuit as well. I need it to be stereo.

 

[Matthias99]

It's a stereo amp -- it has two mono inputs and two mono outputs. You'd have to wire it into a circuit and connect the audio jacks to it to do anything useful with it, obviously.

I'm getting confused now on what exactly it is you want to build. I *thought* you wanted to take your computer's stereo audio output and split it to drive headphones and speakers simultaneously at the appropriate power levels. If you're using powered speakers and headphones, though, you don't need to amplify the signal at all. But looking at your first post again, it looks like maybe you want to have a switch that will power *either* the headphones or speakers. Which one is it?

Both of those are very simple circuits, and neither requires that sort of amplifier (which was what was throwing me off). You'd only need one of those to power a set of speakers directly. A splitter (driving both at once) is absurdly simple -- just take your stereo input and run it to two dual op-amp chips (total cost: about $2) wired as 1:1 amps. That will split the signal without causing any drop in volume. Adding a switch (so it drives just one or the other) isn't much harder. If you're doing that, you can also skip the first two op-amps (since you're not "splitting" the signal anymore, it won't drop in volume).

 

[sao123]

Build something more exciting...such as your own wireless speakers, a homemade telephone, a digital clock which could fit in a 5.25 CDROM bay and run off your computers power supply.
Be imaginative...
look here for inspiration....

Think Geek PC Cigarette Lighter

 

[BoomAM]

Originally posted by: Matthias99
But looking at your first post again, it looks like maybe you want to have a switch that will power *either* the headphones or speakers.

This one. The inclusion of an amplifier is to make it "more electronic" and suitable for the project.

Originally posted by: sao123
Build something more exciting...such as your own wireless speakers, a homemade telephone, a digital clock which could fit in a 5.25 CDROM bay and run off your computers power supply.
Be imaginative...
look here for inspiration....

Think Geek PC Cigarette Lighter

All good ideas, but i dont need wireless speakers. I have wireless headphones, i have a telephone. Theres a clock on the PC screen and on my wrist. A cigarette lighter, i dont smoke, and even if i did, i wouldnt as the smoke fumes can cause all kinds of gunk to clog up fans and stuff.

 

[blahblah99]

Oh man, when I first read this post I thought the guy wanted to build a SWITCHING amplifier and was about to chime in on the details....


I would first recommend reading up on basic electronics because by the sound of your posts, it doesn't seem like electronics is your strong point.

If your speakers are self-powered, then it will use low level signals. Your headphone uses low level signals. If you just want a circuit to allow you to use headphones + speakers at the same time, then all that's required is an opamp buffer to the headphone and to the speakers.

 

[BoomAM]

Originally posted by: blahblah99
I would first recommend reading up on basic electronics because by the sound of your posts, it doesn't seem like electronics is your strong point.

Cheaky arnt you.
Ive been studying Electronics for the last year, and am half-way through the second. My problem is deciding the exact specifications of the actual project.
Im thinking of scrapping the above idea, and use the following;
Get 2 old hi-fi speakers, and make a circuit that`ll allow them to be used as stereo speakers on a PC. Cos that`ll save me buying some speakers for a second system them. I`d imagine that that`d be easyier as well. I cant be arsed doing something too hard as i dont have much time on my hands.

 

[blahblah99]

Originally posted by: BoomAM

Originally posted by: blahblah99
I would first recommend reading up on basic electronics because by the sound of your posts, it doesn't seem like electronics is your strong point.

Cheaky arnt you.
Ive been studying Electronics for the last year, and am half-way through the second. My problem is deciding the exact specifications of the actual project.
Im thinking of scrapping the above idea, and use the following;
Get 2 old hi-fi speakers, and make a circuit that`ll allow them to be used as stereo speakers on a PC. Cos that`ll save me buying some speakers for a second system them. I`d imagine that that`d be easyier as well. I cant be arsed doing something too hard as i dont have much time on my hands.

Well I apologize if I came off as an ass, but it just bothers me when people ask for help on a subject and don't phrase it properly, so lemme see if I understood your question correctly:

You want to build an amplifier so you can interface to your computer to power passive speakers. You would also like to have a line-level output off your computer so you can connect to POWERED speakers (or headphones), right?



If that's the case, you only need a couple of opamp buffers, that amplifier module in your link, and some input/output connectors. You might also need to build a switching supply converter (which you can build using a few components from maxim-ic, national, or any other IC companies) to convert the +12V to +-12V because the power supply may not be able to supply high current on the negative voltage rails.

 

[Lynx516]

BTW audio amplifiyers if made from scratch are very very poor unless you are very very good and use some very complex tequniques. I would recomend using a prebuilt amp chip such as a Philips TDA8511J, this can output 13W to a 2Ohm load when given a 15V supply. Or if you want more power the ST Microelectronics TDA7293 can provide 50W from a 45V supply with only 0.1% distortion. These chips are failry cheap and used in creative an logitech speakers

 

[BoomAM]

Originally posted by: blahblah99
Well I apologize if I came off as an ass, but it just bothers me when people ask for help on a subject and don't phrase it properly,

Dont worry about it. I did`nt.

You want to build an amplifier so you can interface to your computer to power passive speakers.

Yes. This will be easyier to do that the amp things.

You would also like to have a line-level output off your computer so you can connect to POWERED speakers (or headphones), right?

Not anymore. It`d make a good fall back project, but i think the above would be a better option.

 

[Mingon]

Have a look at a boostaroo you could take one apart and have a nose around, then perhaps implement one onto a PCI slot. they run of 2 x recharable AA battereries, but with some changing you might be able to include a potentiometer and power it from a 3 pin mobo connector and have variable amplitute. I have a boostaroo I can take apart / photo if you want.

 

[BoomAM]

Seems an alright product.
But it defeats the idea of my electronic project.
Thanks anyway.

 

[Lynx516]

that boostaro thing says that it gives no distiortion. ANYTHING THAT SAYS THAT IS LYING.

 

[pillage2001]

Originally posted by: BoomAM
What power amp would i need?
I suppose the external 12v power connector on my PSU would be the best place to draw power from?

You would need a filter if you're drawing power from the PSU. The amout of static and interference you can get is astonishing.

 

[Howard]

Originally posted by: Lynx516
that boostaro thing says that it gives no distiortion. ANYTHING THAT SAYS THAT IS LYING.

Yes. Even a short silver cable will give distortion.

 

[lameaway]

Originally posted by: blahblah99
Oh man, when I first read this post I thought the guy wanted to build a SWITCHING amplifier

Same here lol

Perhaps you could modify a circuit like this to meet your needs...

 

[BoomAM]

I`ve asked my lecturer for the exact details on what the electronics and/or mechanics project needs to include/be.
After a quick discussion i found that i can do one of the easyist projects that i could possibly do. "Improving the Cooling on a heat generation PCB Board". AKA How to add a decent HSF to a video card. Sweet or what? Ive done that loads of times to my own cards. I have a couple of old video cards spare, loads of HSF`s and plain HS`s. Nice and easy. We`ve got till march to plan, explain, built, test and conclude the project. I`ll get it done by xmas, with loads and loads of info on it.