PC amplifier

Soldato
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15 Jun 2006
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I know some people on these boards like to use Hi-Fi speakers with thier PC, but don't like the space the amplifier unit can take up. The usual suggestion is the Sonic-T, which is compact but requires and external supply (or lots of batteries). So, i've been building this for a few days (it's not for sale or anything, i'm just posting as some of you may find it interesting).

This is a stereo compact amplifier designed for PC use with power supply built in. It is rated 2x18W RMS, which may not sound like so much, but it can push that continually with low distortion (0.3%, lower at lower volumes) across the full frequency range. In PC speaker ratings it would be called around 2x40W.

I have played music through it and watched a film through it and it gives a very good account of itself in both situations (connected to my B&W DM602 speakers and PC). It has no problem with deep explosion sounds and voices come across very clearly. Music sounds good, not a huge difference between this and my Rotel RA01 in terms of clarity. Enough volume for most bedroom applications (probably not parties or big room use, though I haven't tried putting it up near full).

It cost around £35 to build (though it took far too much effort tbh). Some pics below. Could be placed horizontally or vertically (though vertically you can see fixing bolt heads on one side). Comments welcome :)







 
Soldato
OP
Joined
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Posts
3,900
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Swindon
Thanks :) ,it's built from individual components, resistors capacitors etc. The amplifiers use a pair of "chip-amps" with most of the circuitry inside the chip. I've just used the application circuit for this adding a suitable power supply and volume control etc. I don't have the facility to make PCB's, so this is assembled on stripboard :eek: . Because of the limited space to work in, the layout had to be tight and this helps ensure it is stable anyhow. The case is a hammond extruded aluminium one, I like the way they look and because they are quite thick and full aluminium construction, they take care of a lot of the heat themselves (the chips are bolted to the case and half a CPU heatsink is in there too ;) )
 
Suspended
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17 Mar 2006
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9,055
I would be interested in one of these (for a pair of B&W 601's)
:)

Our business has facilities for properly made trace PCB's. Perhaps sort out a trade, we make x PCB's for you, you build me one amplifer?
 
Soldato
OP
Joined
15 Jun 2006
Posts
3,900
Location
Swindon
Not sure that I can make and sell these on any real scale, it would be possible, but would need a lot of new equiptment and it would then take the price up too much. Part of the cost being quite low is that i've used non-ROHS components for the transformer and the audio connectors, which means that big 120VA toroid is only £3.50 :p . However, to sell these on any scale they would have to conform to the ROHS directive (it then costs £11 or so). Working by myself on it takes too long tbh, and a pillar drill is really needed (yes, those holes are drilled with a portable drill). I do intend on mabye making another, from this one i've learnt a few things:

- Use connectors between the power supply board, soldering it all together before assembly is messy and awkward.

- Use a PCB for the power supply board, most parts on it have large leads and the stripboard holes need enlraging for them. The tracks are too thin really too.

- Make some kind of holder for the amplifier boards, fixing entirely by the chip isn't very stable.

- probably the use of a lower voltage transformer. This runs at the maximum it can take, and I had to drop a bit of voltage for protection. It does mean it can produce full output though

- The heatsink probably isn't required, the case can take away the heat very fast as if it interfaced with outside air over it's entire surface.

- Use of a better volume control pot. The cheap one in this doesn't track perfectly (left is too loud at low volume on the dial)

Thats a few things, there are also ground loop issues (low level buzzing when connected to other earthed equiptment, ie, the PC).

A tutorial is a neat idea, I might try that once I have confirmed a better design.
 
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