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Old 22nd February 2010, 07:57 PM   #1
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Default Complete newbie help.

Hi,
i'm really interested in trying to build my own audio system.
Unfortunately as i'm just a teenager i don't have much cash to spend and i can only buy items off UK websites.

I have found this kit amp which seems cheep and cheerful, hopefully a good starting point.

200W Power Amplifier : Audio Amplifier Kits : Maplin
and the manufactureres website Velleman nv

is this a 2 channel or 1 channel amp?
How would i actually use this as part of a system?

EG, to run an ipod through it do i just attach the ipod to the input and a speaker on the output?
Will i need a preamp? if so will this be acceptable? Universal Stereo Pre-Amplifier : Audio Amplifier Kits : Maplin

As you can see it is a very tight budget from the parts i've listed.
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Old 22nd February 2010, 08:40 PM   #2
tomchr is offline tomchr  United States
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Don't underestimate being a teenager interested in electronics. I got my first soldering iron when I was in first grade because my dad was tired of me always using his... In my teens I built a fair amount of lab equipment (mainly power supplies) but also audio amps.

The Velleman kits are usually pretty decent. I can't vouch for the sound quality of a Velleman amp as I've never tried one. But I'd expect it to work if assembled according to the instructions.

You could also look at some of the chip amp/gain clone stuff. A lot of these circuits use an LM3886 with a few external components and a lot of them are wired point-to-point (i.e. no circuit board used). I threw together one of these amps in about 90 minutes and it performs very, very well. I just implemented the "typical application" circuit in the data sheet. See this thread for a bit more detail.

One word of caution, though. Be careful with the mains voltage. It can and will kill you if you aren't careful.

~Tom

Last edited by tomchr; 22nd February 2010 at 08:51 PM.
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Old 23rd February 2010, 01:02 AM   #3
godfrey is offline godfrey  South Africa
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Hi, and welcome to the forum!

That's a single channel amp. You'd need two of those modules to make a stereo power amp.

Yes, you can just hook an iPod to the input and speakers to the outputs (assuming the iPod has a volume control) - so you you don't have to have a preamp.

Now the bad news, given your budget: These kind of modules can be a bit deceptive in terms of cost because not everything you need is included.

In this case, you need to also buy the power supply transformer and a heatsink, which will probably cost more than the amplifier itself.

Here's a suitable transformer (the 160 VA one):
AC 230 V Toroidal Mains Transformers : Mains Transformers : Maplin

I can't find any suitable heatsinks at Maplin. Geez, they've got even worse than I remembered.

You also need a box (case) to put it in but they're stupidly expensive so it's probably best to either make your own or steal one from an old computer, broken VCR or something.

Anyway, here's the amp module on Velleman's site:
Velleman nv
and here's the assembly manual PDF:
http://www.velleman.eu/downloads/0/i...k8060_rev1.pdf

For a stereo amp, the cost (in British pounds) works out something like:

A) amp modules: 2 * 15 = 30
B) transformers: 2 * 24 = 48
C) heatsinks: 2 * 5? = 10?
D) a couple of connectors and other bits: not much
E) box: free (hopefully)

Total cost: probably about 90 pounds

You can probably save a bit if you use one bigger transformer for both channels instead of two separate ones.

btw: I'm not saying it's a bad amp or bad value for money, it's just not as much of a bargain as it looks.

Cheers - Godfrey
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Old 23rd February 2010, 01:30 AM   #4
godfrey is offline godfrey  South Africa
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Hmm... just had another look round the Maplin website - there doesn't seem to be much choice of anything there. I was wondering what other amplifier kits or transformers they had. Answer: none

Do you know of any other UK suppliers?
If not, maybe someone else here on the forum does.
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Old 23rd February 2010, 01:38 AM   #5
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There are numerous suppliers, not all in the UK, but this is not necessarily an impediment as postage from Europe is quite quick and is often acceptable from worldwide sources, e.g. China

Have a quick search on either ebay.co.uk or ebay.com for audio amplifiers. Or look here for example:- 41Hz Audio:Sounds Good to Me!

w

Last edited by wakibaki; 23rd February 2010 at 01:41 AM.
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Old 23rd February 2010, 01:41 AM   #6
mikje is online now mikje  United States
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I built a Velleman K4003 and added a Velleman K8084 and am very happy with it. It's not very powerful, but there are plenty of speakers available that work great with it (Fostex, Tang Band). The K8084 isn't needed, I just like having a volume and tone control.
If you're looking for a lot of power, this one isn't what you want. Otherwise, it's really a great little amp.
I also built one from Audiosector and am very happy with that one too.
Right now I'm building one from eBay and one from www.dukescreations.com. Duke is VERY helpful and a great guy. I don't know what the shipping would be, but the price includes everything you'll need (xformer, pots, speaker posts, etc.).
Mike
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Last edited by mikje; 23rd February 2010 at 01:49 AM.
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Old 23rd February 2010, 09:02 AM   #7
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Im in the Uk too mate and also new to all this diy stuff... but I went to audiosector, got a kit and had a go.... Its now up n running.

It wouldnt have happened if it wasnt for all the help here at the forum, so go for it mate... The help is here to see you through.

You wont regret it.
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Old 23rd February 2010, 04:20 PM   #8
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Hi tt01mamba.

That is the first amp I put together, and is how I found this forum first.

Maplin do not stock suitable heatsinks or transformers for the kits they are selling. I asked their "technical help" about this and I am still waiting for a reply 4 years later! You need heatsinks big enough to mount the full amp board to, the small transistor (top right corner of photo) is a thermal sensor. I didn't know that and used 3 small heatsinks, it resulted in a meltdown. Maplin are more of a toy shop these days.

I would second a chipamp as a first build, kits are available from trustworthy sellers on here, there's ebay too but be careful which you choose. You can just use a volume pot and a source selector switch on the input to keep your costs down. The biggest part of the cost isn't the amp parts though, the power supply, heatsinks, connectors and case will add up to far more.

If you have spare time, tools and some imagination you can rework old cases, my first chipamps are in recycled VHS video players. If you choose to buy a case there are many available out there at various prices.

What music do you listen to, how loud and what speakers will you be driving? Your room size will have a bearing on what amp power to choose also. You may need a lot less Watts than you might think.

John
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Old 23rd February 2010, 05:33 PM   #9
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Checking out the data sheets on some of these chips and reading the scope shots, charts and reviews, the ''amp'' isn't the problem, nor is it that much trouble to wire one up.
It's the power supply that is the large delivery task for supplying over what the amp expects.
I like to balance things or simply go a bit more modest with the expectations, desing the amp to accomodate the speaker, which determines the power supply needs.
Under-rating the PS for the task isn't recommended, finding out what it really requires is part of making a deal on an amp for the application. Then, perhaps another.
That's where I am @@rate, having LM3875'd a transformer/chassis I had to good result for listening at moderate levels, getting ready to torroid some lower ESR reservoirs to feed an LM3886 or two for a higher precision, higher powered build.
Heat sinks are found in many a unit of monitor boards, fortunately a nice flow of these free sinks tend to make themselves avaialable because they strictly outlast the capacitors, although they require gloves and tools to safely extract for a new application.
An old fried PA thing with large fried Xformers [2 out of 3 is pretty good], sits out there...has huge heat sinks built into heavy duty, predrilled chassis...more holes than I'll ever use on an amp.

Last edited by petemoore; 23rd February 2010 at 05:50 PM.
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Old 24th February 2010, 07:53 PM   #10
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Thank you all for the replies and welcomes.

It's probably a bit early for me to start learning how to read electronic diagrams. I'll go for the maplins as my first "kit". ill try a 2 channel system first but will need know what to put in it and how to wire the two channels together, (are they completely independant? Just use 3.5mm stereo jack to RCA? to split an ipod into 2 channels?)
http://www.cablesdirect.com/prodimages/CC399-25_LR.jpg

thanks for the warning Godfrey, ill come up with a "shopping list" over the next week. The main problem isn't buying alot of cheaper parts, it's dumping 150 at once into an amp. How will this amp sound? I've got a 5 year old cinema system linked up to my computer, but unfortunately it will only do stereo sound from external sources (will only do 5.1 from the DVD player) But even with 2x60W speakers and the sub, it has no problems with loudness.
http://images01.olx.com.pk/ui/2/07/39/35719839_1.jpg

How does the thermal sensor work? does it lower power to the chips if they're getting a bit hot?

Listen to mainly jazz, some large orchestral stuff and alot of piano. Ill be buying some of the cheap (and nasty) Hi Fi speakers from maplins, maybe the 25W tweeter and a 6.5" mid for each channel? I won't be playing it loud. Room size is small bedroom with alot of junk in it.

How would i get a better sound quality out of this amp? (only by replacing some components and not rewiring it) It says to use more powerful caps to get a better sound... etc etc,
Thanks again.
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