need tda7240 guitar amp schematic

[jogina111]

I got a  tda7240 ic from a friend and Im planning to build an amp for my '59 lp..please give me a simple schematic to build using the tda7240..thanks!

[Keeb]

Well, there is one in the datasheet. Just add a 10K pot to the input for a volume control.
http://www.datasheetcatalog.org/datasheets/105/378745_DS.pdf

Then maybe throw something in front like a preamp? Maybe runoffgrooves tonemender?

Edit; I'm not familiar with this chip but I have seen a lot of TDA20X0 chips being used in this way.

[jogina111]

cant read the file.,maybe post a pic?

[waltk]

Search here for "Tiny Giant"

[jogina111]

tiny giant looks pretty interesting but can be quite a hassle for me... Any more suggestions? Im thinking of getting something like the tda2003.. 

[Nasse]

Sometimes when yo have to work on a computer with no Acrobat Reader, you can google something like "online pdf viewer google" or thereabouts

[jogina111]

does this ic requires a preamp before I can play my guitar or I can directly plug my guitar on?

[Jdansti]

tiny giant looks pretty interesting but can be quite a hassle for me... Any more suggestions? Im thinking of getting something like the tda2003.. 

I'm confused about what it is you are wanting to do. Your initial post said that you got a TDA7240, so Keeb gave you the data sheet that has the schematic on it.  It seems that you can't read pdf's.  Next, Waltk recommended the Tiny Giant and you said it's a hassle for you. Then you said you want more suggestions and you're thinking about the TDA2003.

I don't mean to be rude, but it appears that you want others to do your research for you as you throw out moving targets. Asking for help is fine, and there are a lot of people here who are very eager to help, but you need to do some of your own legwork and not have people shooting ideas at you until something grabs your fancy.

I did an image search on "TDA2003 practice amp" and found lots of schematics with minimal parts. You might want to give that search a try and then ask the forumites any questions you have about it.

My comments here are not intended to insult you, but to help you move toward being better at researching your project and knowing how to get useful help here on the forum.

[Jdansti]

jogina111,

After reviewing some of your other posts it looks like it's difficult to get parts shipped at decent prices to where you live. This may be why your posts sometimes seem scattered as you look for projects you can build with what you have on hand.

I'll send you a parts kit for a musicpcb.com Tiny Giant amp (http://musicpcb.com/wp-content/uploads/2011/02/Tiny-Giant-Build-PDF-rev2.pdf) including the PCB, heat sinks, and offboard components. No charge to you.

You will need to supply:

TDA7240 IC (which you already have)
~17-20vdc power supply
Speaker
Enclosure
Knobs
Wire, solder, and other building supplies

If you're agreeable to this, send me a personal message with your address.

[haveyouseenhim]

What a cool thing to do John

[jogina111]

is there any other way to power up the tiny giant amp except through a  laptop power supply?

[Jdansti]

The short answer is yes.  Any DC power supply that has an output of 15-32VDC and is rated at 4A or greater will work. However, the higher you go above 15V, the more heat is dissipated at the LM338T regulator.  If you need to go lower than 15V, you'll need to do some tweeking as described below.

As PRR has pointed out on another thread, most of the TDA amps are made for automobile sound systems. Voltage in a car would typically be ~14V when the engine is running, ~12V with the engine off, and ~18V with a malfunctioning voltage regulator (a bad situation as your car battery fluid begins to boil!). So the TDA amp is designed to handle this voltage range without damage.

However, the Tiny Giant was designed to operate at 14V and has a variable voltage regulator (LM338T) that is fixed at ~14V with a 1k resistor. In order to work, the regulator needs an input voltage higher than the regulated output voltage. You could go with a lower supply voltage, but you'd need to adjust the output of the LM338T by changing the 1k resistor to another value. You could substitute a 1k trim pot for the 1k fixed resistor.   If you do this, there are a few things to consider:

1) You still need a 4A supply.
2) The amp's output power (volume) will be reduced if you have <14V output at the LM338T or increased if you go higher. (See the chart below from the TDA7240 datasheet).  Be careful not to fry other components if you adjust the LM338T higher than 14V.
3) You may have some bias voltage issues if you change the LM338T output voltage. Maybe this has been covered in the Tiny Giant thread, or else someone smarter than I can educate us.

[jogina111]

I went to some stores checking out for dc adaptors but they all have a 12v max..
I'll keep on looking tomorrow..

[Jdansti]

Watch the output current. You need 4A (4000 mA).

Two alternatives:

1) Use a 12VDC, > 4A adapter and modify the Tiny Giant regulator output.

2) If you can find an AC adapter or bare transformer with an output (secondary coil) between 16-35VAC, > 4A, I can help you convert it to DC fairly cheaply.

[PRR]

With 4 ohm load, 1.2 Amps is marginal, 2 Amps should be ample.

With 8 ohm load, 0.6 Amps is marginal, 1 Amps should be ample.

The 4 Amp number comes from the fact that laptop owners expect fast re-charge, and it takes that much power to fill a large laptop battery in an hour or so; and in some places old laptop power suplies are VERY cheap. It is more than the Tiny Giant would ever demand.

[jogina111]

if paul is right, then I could get that 12v 800mA-900mA DC adaptor and modify the TG to make it run on 12volts. right?
Shop owner said when I asked him if they have a dc adaptor that can produce 14-18v 4A: "what?! Car batteries only have 12v and 24v means 2 batteries, your looking for something very complicated mister!" 

[Jdansti]

Thanks Paul for clarifying the current requirement. 

Could you please help us out with the voltage issue?  The LM338T on the TG amp cannot provide regulated output greater than approximately Vi minus 1 to 2 volts.  If jogina111 can only find a 12VDC power supply, and we change the adjustment resistor on the LM338T so that it regulates the output somewhere around 10-11V instead of 14V, would we have to change the value of any of the resistors on the TL072?

I don't think that musicpcb.com allows posting of their schematic, so here's the link:
http://musicpcb.com/wp-content/uploads/2011/02/Tiny-Giant-Build-PDF-rev2.pdf

[slacker]

No there's no changes needed to any of the resistors on the TL072. The way it is set up with the two 1Meg resistors connected to the non inverting input mean it is correctly biased to half of whatever the supply voltage is.

If you know the supply is 12 volts then you could omit the LM338T, this is there in part so you can use power supplies that would otherwise fry the 7240.

[jogina111]

No there's no changes needed to any of the resistors on the TL072. The way it is set up with the two 1Meg resistors connected to the non inverting input mean it is correctly biased to half of whatever the supply voltage is.

does that mean if I used  12volts with the lm338  stage on, i am only supplying it with 6 volts?

[anchovie]

No. Biasing the audio signal is different to powering the chip. It puts your audio halfway between ground and the PSU voltage for the best possible headroom.