So bridging the two chips will draw more power than running them in stereo (which is what I did now)?

Selling them is a no no, I allready hacked them up to test it out.

Oh well. I guess I will use them in the testing phase, and the fork out the cash for a real transformer.
But it was a fun thought to power the circuit from a $2 source

BTW. I have an old PC ATX power supply laying around, it has lots of coils in it. Is there any way I can identify voltage/windings and so from the numbers printed on top of them? Or will I have to hook them up to a power source and test?

DocZ

It worked! - atleast first test worked out. I played music through the amp board with my makeshift power transformer. The wall warts did not get any hot. This was just all layed out on my work surface, I will do more test when I get this to the next stage.

What noticed was this: Treble control didn't have much effect, other than bring in RF interferance. Volume was not extremely high, but it had a lot of kick. I was also really amazed by the eight inch testing speaker I used. It cost me $10 so I was a bit scheptical but it delivered.

Next steps:

• Add mains fuse
• Add secondary fuse
• Bridge the two chips
• Build a chassis
• Build speaker / combo cabinet
• Add a preamp circuit
• More testing
• Figure out a way of measuring current while testing... I think I need to do some reading on this one.

If I find that I need more current, can I add more of these wall warts in paralell? Will two 12V 1A in paralell give me 12V 2A?

DocZ

I just built the power supply, hooking them up in series does indeed produce +12_0_-12V My main concern is the current. What will happen if the power supply cannot supply enough current? Is it just that it will not be as powerful as it can be? Or will it overload and burn up the transformers? I read somewhere that this chip needs a 40VA power supply, do I calculate that from the input or output?

DocZ

Well there are a couple of stores that sell these things online. But they are rather expensive. A toroid 30VA 2x12V costs about $50USD, I can find a 6VA for $12USD but I don't believe that is going to cope with the TDA2030. The datasheet for the TDA2030 says it needs a 40VA supply, and 60-80VA for two bridged chips, those toroids cost over $100. Why are transformers so expensive anyway? Isn't it just a chunk of iron wrapped in copper? Haven't we used those for several decades? One would think that the prices of these devices that are practically inside of everything would drop due to the demand.... oh well...I thought solid state would be cheaper than valve amps because the components are cheaper, but it seems it is the same with any amplifier, the transformers and speakers make up 80% of the cost.

I will try to hook those wall warts together and see if I get a signal. Can I use anything line-level to test it?

DocZ

Quote from: Koreth on February 14, 2010, 03:16:29 PM
Do the wall warts put out 12VDC or 12VAC? 12VAC, after being put through a full wave rectifier and a couple smoothing caps is closer to 16 or 17VDC. 12VDC has already been rectified and is just that, 12VDC. You an run a TDA2030 on 12VDC, but you won't have as much headroom or power output than if you gave it a higher supply voltage.

They are 12VDC, I thought I could wire two of them in series, with a center tap for 0V

DocZ

I do have a couple of 12V 1000mA wallwarts. I used one for B+ on the Ruby amp. Can I hook those up in series for positive, negative and ground?

I am from Norway, and the only place that sells these kinds of things I have found, charges $50 - $100++++ for transformers. The laptop chargers cost $2, but shipping is $10, my guess is that the seller ramps up the shipping charge to compensate for the low product price, this is quite common on Ebay. But it might be real bricks as you say

Thank you for your reply,

DocZ

Hello everybody, I'm new to this forum and new to this wonderful world of electronics. I got hooked after I took it upon myself to restore my dads old Teisco 10 tube amplifier from the 50s. After a lot of great help and effort I managed to fix it and restore it to it's original state. So now I got the taste for electronics. Since tube gear is extremely expensive, I started my next project which was building a Ruby Amp. It souds great! A pity it is not loud enough to work as a full band amp.

So I thought I would be able to use the LM386 as a preamp and then get something more powerful to power it. I bought a TDA2030 amplifier board on Ebay, my idea was to use it in a speaker to make it active. And see if it would be good enough to use as a surround speaker. Anyways I ended up getting three boards with a total of six TDA2030s because the first two boards got damaged from shipping.

My idea was that maybe I could bridge a couple or more of these chips to get the power I need to power a 2x12 cab and get the great sound of the Ruby out to the masses. But my first bump in the road is a power supply. This thing needs +15V and -15V as well as 0V. The only transformers I can find with 2x15V and 0V are really expensive! About the same prices as the high voltage transformers used in tube amps. My question is then, is there a cheaper solution to this? If so what can I use? Can I use two 15VDC wallwarts in series to get 15-0-15?  A 15V 4A laptop charger costs like $2 on ebay, compared to the 2x15 toroid that costs $80 it is quite tempting to try it out! But since I have no idea if this will work, I thought I'd ask you guys to see if this is a stupid thing to do.

Cheers,

DocZ