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Author Topic: Power amp clipping  (Read 4434 times)

iTzALLgoOD

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Power amp clipping
« on: April 29, 2009, 03:03:35 PM »
I have a functional TDA2030 PCB that I made right from the datasheet but it clips with minimal input.  I am using a 12.5-0-12.5 2 amp transformer and a pair of 4700uf caps in the power supply. Here is the preamp schematic that I am currently using.



I am only using it up to the volume pot with out the extra gain stage on the breadboard.  LTSpice says that I should only have about a 400-600mv output after the BM tonestack but I can readily make the power amp distort. 

Will this lead to premature failure of the power amp chip?? From what I get out of the datasheet I should be able to get closer to 890mv input to get the maximum power output.

Enzo

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Re: Power amp clipping
« Reply #1 on: April 29, 2009, 09:57:19 PM »
You tell us that Spice says there SHOULD be 600mv after the tone stack, but you don;t tell us what you actually have.  What do you have at the output pin of the first stage?

Clipping in the signal path is not chip failure.

You didn;t show us the actual schematic of your 2030 stage.  My first thought was your feedback circuit from the speaker out was not working.

What signal level is actually getting to the power amp in?

iTzALLgoOD

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Re: Power amp clipping
« Reply #2 on: April 30, 2009, 09:32:49 AM »
I don't currently have a way to check the actual output. :'( 
Is there any free signal generator software so that I can use my PC's soundcard?  I haven't looked around to much as I only have internet access at work currently.

As far as the TDA chip goes the schematic and PCB are copied directly from the datasheet.

Quote
Clipping in the signal path is not chip failure.

I don't think that the chip is failing.  I don't worry about it in stompboxes but was a little concerned with premature failure of a power amp chip.  I actually kind of want some clipping at 90%-100% of the volume knob.  Just not so early.

I am using this for a bass amp if that makes any difference.  Thanks for any help

Enzo

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Re: Power amp clipping
« Reply #3 on: April 30, 2009, 08:14:46 PM »
A signal generator is fine and all, but you can use your guitar, or play a CD through the thing for a test signal.  Use your meter set on AC volts to check levels.

J M Fahey

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Re: Power amp clipping
« Reply #4 on: April 30, 2009, 11:49:54 PM »
Hi Itzallgood. Great advice from Enzo, and I add: download a 1KHz MP3 tone. This, played through a typical cheap MP3 player will give you a very stable and portable 100 to 200mV "signal generator", handy anywhere.
Clipping a 15W *bass* amp, with unspecified speakers, is very easy, so what you tell us is not surprising.
 The same power, with a guitar, goes a long way.
Bye.

iTzALLgoOD

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Re: Power amp clipping
« Reply #5 on: May 04, 2009, 09:32:37 AM »
Thanks for the help guys.  This is my first attempt at a simple chip amp and my seriously limited knowledge of electronics had me thinking there was a design issue.  I like the MP3 player idea.

joecool85

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Re: Power amp clipping
« Reply #6 on: May 04, 2009, 03:31:05 PM »
I built a TDA2030 for my brother a while back, it was suppose to be used as a small portable bass amp...it was awful.  Exactly the issues you're having, very hard to get a good clean sound out of it, no matter the speaker it was connected to.  It was "ok" on guitar, but I was actually more happy with the somewhat quietter but much better sounding LM386 amps I'd built in the past.

**edit**
Excuse me, it was a TDA2003, totally different animal.
« Last Edit: May 04, 2009, 03:32:28 PM by joecool85 »
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Enzo

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Re: Power amp clipping
« Reply #7 on: May 04, 2009, 10:26:10 PM »
The signal is so much larger on the bass.  100 watts is screaming loud for a guitar amp.  But 100 watts is not much for a bass.  When a player has a 1000 watt bass rig, it isn;t about how freaking loud it can be - he might not be any louder than a 200 watt rig.  But that 1000 watt capability allows a clear effortless sound to emerge from the speakers.

In a way it is like pulling a large travel trailer down the highway.  You can do it with a little Volkswagen bug or with a large powerful SUV.  One will struggle to do the job, the other won;t struggle at all.

SO when making a very low power bass amp, you must keep the limitations of the system in mind.

iTzALLgoOD

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Re: Power amp clipping
« Reply #8 on: May 05, 2009, 09:29:45 AM »
Thanks guys.  I don't mind the low output or the clipping for that matter.  I play guitar 99% of the time.  I bought a cheap Squier bass just for recording and had fun with it.  I figured that it would be a cheap and easy project to make a little practice amp for it.  Everything is ready to go I just have to build a cabinet for it.