HELP with making two mono amps in to one stereo amp (with more output power)

[Nigel Goodwin]

Those aren't bridged.

 

[Hero999]

All right my last schematic contained an error shorting the +V to 0V.

Here's the corrected version:

It's not bridged, my previous incorrect schematic wasn't bridged, it's connected as two separate channels as is the corrected version.

The problem with the second schematic in the picture is that the long input return leads both go back to the power supply, rather than to the IC's 0V pin.

Do you understand both of the above statements?

 

[GooseElectro]

Yes I understand that . I have made it on strip board so I am trying to think how this applys I am going to post the diagram and picture of how I have wired it. It is all very cramped on the board will this make a diffrence ?

 

[Ghosty_Ghoul]

Cramped is good.

Is each channel on a different board with the returns going back to either the battery or just one board? That could be your problem.

 

[bountyhunter]

Your offset adjustment is in a positive only direction. What if you need a negative offset adjustment, swap the amp ICs?

No, if I remember correctly (and it's been 20 years) the DC outputs both sit at about 1/2Vsupply. I recall the TDA2003 has an internal resistive divider which always sets the output OP point to half supply. The trimmer is centered at that voltage and can swing above and below it. That means it can adjust the offset in both directions around the nominal value to get zero Volts across the speaker..

The "single ended" design centers the operating point at 1/2Vsupply, has a cap couple to the speaker whose neg side is connected to ground which means the max signal swing that the speaker can ever see is 1/2Vsupply. The bridge setup allows one output to swing up and the other to swing down at the same time, so the peak signal swing is Vsupply. However, I believe the DC bias (no signal) set point for both outputs on the bridge design is 1/2Vsupply. They can not both sit at ground because then the "negative going" side has no swing room.

 

[bountyhunter]

I will have to post my wired circuit I am making a stereo amp not a briged amp ! Bothe circuits work fine on there own. Somthing to do with connecting them.

IMHO, the problem will disappear if you do this:

1) use a "single point" power ground for the point where both load (speaker) negative lines come back and tie to the power supply ground.

2) Run a wide and short trace straight from the single point power ground to EACH of the ground pins of the 2003's and DO NOT TIE OTHER COMPONENT GROUND LEADS TO THOSE TRACES ALONG THE WAY. This gives you a separate power ground lead to each IC's ground pin from the single point ground.

3) Tie the ground leads for the other circuit components together ant then connect them to the ground pin of each 2003 (do it on each channel) right at the IC ground pin.

4) The R-C compensation on the output (R4 - C3) should tie directly to the ground pin AT THE IC.

 

[Ghosty_Ghoul]

He's building it on Veroboard so I don't think that's an option.

This circuit really needs to be built on a real PCB.

 

[GooseElectro]

Here are the wireing diagrams and photos

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there are more at: **broken link removed**

thank you for any help

 

[Ghosty_Ghoul]

You've got the inputs and outputs connected at one end of the PCB so it's no surprise it's giving you trouble.

Connect the input, output and return as close as you can to the respective IC and the problem should go away.

 

[GooseElectro]

after looking at how i have done this what do you think is the best way to go from here? it looks like strip board is not the best for amp circuits hower one works fine on its own. If a pcb is the best thing to do dose anyone know the best way to do this? is it to order online or make at home? any detales about websites or kits will be very usefull

thanks again.

 

[GooseElectro]

You've got the inputs and outputs connected at one end of the PCB so it's no surprise it's giving you trouble.

Connect the input, output and return as close as you can to the respective IC and the problem should go away.

what do you mean by return?

 

[Ghosty_Ghoul]

The 0V side of the input or output.

 

[bountyhunter]

He's building it on Veroboard so I don't think that's an option.

OK, now I understand why it won't work.

 

[audioguru]

Those tiny little heatsinks are almost useless.
But a TDA2003 with a 12V supply and feeding an 8 ohm speaker has an output power of only 1.5W at clipping so the IC will not heat much.

 

[GooseElectro]

I think I should of mentioned this erler but I an using 18v in to both amps into a 4 ohm load. Would the size of the heat sinks be causing the problem with drawing aslot of current or distorted sound ( I think it will distort but not sure about current) ?
Thank again

 

[blueroomelectronics]

Those are voltage regulator heatsinks. Audio amp heatsinks are much larger.
**broken link removed**

 

[audioguru]

The datasheet shows an output per channel at clipping into 4 ohms with a 17V supply of about 6W. Their power output graph stops at a 17V supply because 18V is the absolute max supply voltage.
At full output the heat from each IC is about 7W which is much more than your little heatsinks can cool.

 

[GooseElectro]

Those are voltage regulator heatsinks. Audio amp heatsinks are much larger.
**broken link removed**

Ok fair enought but will this be causing the poblem? Like I say bothe work fine on their own and I don't mind them gett stupidly hot any burning out . to be honest I don't think this will happen , I can see what u are saying though by the book.

I am going for a compact protable amp to run both of batteries and mains do u think I have chosen the wrong ic for this ( I chose this one as it was a simlple circuit and quite loud, someone said the quality was poor but I have found it ok)

 

[audioguru]

I hope you are not using two little 9V batteries in series. They would continuously drop the 18V to 16V then to 14V then to 12V then to nothing fairly quickly.

 

[picbits]

After reading through this thread I'm curious as well as to how you are providing the supply to the unit.

Are you currently using batteries or a plug in power supply ? What is the voltage you're using and how much current can it provide ?