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Author Topic: TDA2003 based Guitar Amp  (Read 26540 times)

n9voc

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Re: TDA2003 based Guitar Amp
« Reply #15 on: May 02, 2008, 05:05:22 AM »
Your quite welcome!

Just a thought for you - have you tied the DC ground of your system to the "earth" ground plug on the mains?

Second notion - do you have your preamp exposed to the air and not running on the same  DC supply as the amplifer (thus common ground)?  This could be the source of hum as well .  Try tying all circuit power grounds together.

With most of my FET input devices, due to the high impedance present, if I don't have the DC ground tied to earth, I get some hum - with a lot of metal at DC ground and the DC ground not tied to Earth, I get a LOT of hum when running on the mains.  I do recommend bringing all the grounds to a single point (google "star grounding") then tying that point to the earth ground.

The advantage of single point grounding for hum reduction was illustrated to me when I had two of my amplifiers daisy chained together through the "buffered output" of the first.  I had one in one room, and the second about 30 feet away in another room.  Each was plugged into the wall, but the wall circuits are on different breakers. When I had the second one plugged in, it hummed something awful.  Fortunately, it was a battery backup unit and I unplugged it from the wall, running that unit on battery - eliminating the ground loop between the signal cable and the two "earth" ground points - hum disappeared.

hope this helps! 8)

casiomax

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Re: TDA2003 based Guitar Amp
« Reply #16 on: May 03, 2008, 03:36:27 AM »
thanks again for the suggestions. a little bit of humming is fine i think, due to sometimes in a lot of places, earth ground zero-ohm is hard to achieve, so there should be something like 0.44ohm is the best thing you can get.

Now, i have read somehwere on the net, split supply for the DC source might help to overcome hum and noise problem, is this true? haven't tried it, maybe i will try it just for proof  :D

I only built half of your circuit, which mean only using 1xTDA2003 on a 4ohm speaker, not too loud but enough. For the preamp, i took a schematic of MicroAMP circuit, i have tested them, works well. But before that, i did try to make a bridge configuration from the datasheet schematic, not successful, everytime i plugged in the power, noise coming out of the speaker, couldnt figure out why.

anyway, TDA2003 is very simple amp to build...!! thanks! now i am building my seffect (distortion-compressor-reverb) in one box.

casiomax

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Re: TDA2003 based Guitar Amp
« Reply #17 on: May 04, 2008, 05:11:33 AM »
quick question, does TDA2003 or TDA2005 need a regulated powersupply?

casiomax

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Re: TDA2003 based Guitar Amp
« Reply #18 on: May 18, 2008, 12:15:24 AM »
question,  how do i make an attenuator? seems that from my guitar directly to the amp, when i crank up the volume, without an effect, the guitar sounded a bit distorted.

n9voc

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Re: TDA2003 based Guitar Amp
« Reply #19 on: May 22, 2008, 12:35:41 AM »
Casiomax,

Almost any solid state circuit can benefit from a firmly regulated supply.  Caveat - be certain regulator can deliver at least twice the expected full steady state load, and have a minimum of 1000 uF post the regulator to insure that it absorbs the fast rising currents until the regulator can catch up.

Secondly, bear in mind the circuit has a voltage gain of 100 as it is straight up.

With a 12 Volt supply, the absolute maximum producable signal by the amplifier chips is 12 volts peak to peak before the waveform distorts due to supply rail limitations. (actually a hair less than 12 V, but we'll say we have ideal amplifiers for this example)

12/100= 0.120 volts p/p maximum input before distortion.

I have measured 0.750 volts p/p out of my electric guitar.

As you can see, doesn't take much to drive the output to distortion.  The FET input of the original design maintains the high input impedance that guitars like to see in an amplifier and the 10-50k volume pot then serves as an attenuator.

lacking the front end impedance match, here is a high impedance attenuator schematic:


casiomax

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Re: TDA2003 based Guitar Amp
« Reply #20 on: May 23, 2008, 02:50:29 AM »
I am forgetting the other important key to have a good amp, speaker. I have purchased vintage 30g12 replacing the one i have, suprisingly.... sounds a lot more better! nothings wrong with the input or my guitar.

but on my amp, i did not built the buffer stage, would this affect anything?

n9voc

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Re: TDA2003 based Guitar Amp
« Reply #21 on: May 23, 2008, 05:42:19 PM »
If you talking about the buffered output - that is strictly optional, and will have no effect on the amplifier performance.  It simply allows an output that is electronically isolated "buffered" from the rest of the amplifier.  you could put a short across the buffered output to ground, and the amplifier will still run.

If you are talking about the FET guitar input buffer, then it will simply affect the input impedance of the amplifier - if you have another preamp that is between the guitar and power amp stage, don't worry about it.   Without the guitar input FET circuit, the input impedance of the amplifier is the potentiometer, in this case 50 kiloohms.




Anirvan

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Re: TDA2003 based Guitar Amp
« Reply #22 on: April 30, 2019, 06:03:13 AM »
I have two questions-

1. As shown in the diagram, the inputs are shorted to make a single input. Will it damage the ICs ?

2. If the 470 uF capacitor at the pin 2 is replaced with a 220 uF capacitor then what difference will it make in the circuit ?

n9voc

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Re: TDA2003 based Guitar Amp
« Reply #23 on: May 01, 2019, 09:15:45 PM »
Wow!  Eleven years since I last revisited this topic!

Anirvan,

The inputs are AC coupled together, but not DC coupled.  This protects the IC from damage. in the eleven years since last posting - neither or nor the current owner of the amplifier has had any issues with this arrangement.

If you are speaking of the RCA and 1/4 inch jack, Those are isolated from the IC by the FET.  Again, no problems known. :dbtu:

Regarding the 220 uF vs 470 uf in the feedback circuit - the Xc of 470uF is about 4.2 ohms at 80 Hz, and Xc of 220 uF is about 9 ohms at 80 Hz. 

Looking at the feedback resistive setup - i think that going with a 220 uF would reduce the bass amplification response of the amplifier - by how much?  I have not a clue. :cheesy:

 

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