simply powerful "car" amp (TDA7560?)

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Benik3

Benik3

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Joined 2013
vseumel.blog.cz
#1
Amplifier with TDA7560 + LM1036

Hi 🙂
I would like to build some simply, cheap but powerful amplifier (I know, it's hard to put these things together 😀 )
Because I want to supply it from 12V, some car amplifiers chips looks like good choice. I looked on TDA7560 which has 4x output, up to 23W/4ohm 1% THD (is it per channel?). Or do you know about some more powerful amp? (maybe use 2x stereo amp)

Also I would like to build some simple treble and bass correction. (Maybe one to front and one for rear). I saw that e.g. in Lepai amp they use somthing like this one DIY Audio Projects Forum • Simple Passive Tone-Control
Next volume control and balance F-R.
I want to use it from one stereo source.

Is also possible to put this amplifier into bridged mode? If I get it right, I would have to build phase inverter...

I will use it on some party, so the quality of sound isn't so important.

Can you help me with this? Thank you 🙂
 
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#4
No, you cannot bridge connect amp channels that are already bridged themselves, it won't work.
The only thing you can do to get more power is either use lower impedance speakers to increase current draw, or use a switch-mode power supply to generate a higher drive voltage for the amps.
Also be aware that even if you somehow manage to double the power to the speakers, it will only give you about 3dB SPL increase. To double the appearent SPL you'll need about 10 times the power to the speakers.

Mike
 
#6
Michael: OK. Because when I tried to find something about it on google, I found that it's possible with phase inverter and connecting speaker to + F-R and + R-R...

Mihkus: But for that I should have very powerful step up converter.
If you calculate the power of TDA7560, you get up to about 200W of power, right?
 
#7
I'll say it agian - No, you cannot bridge connect amp channels that are already bridged themselves, it won't work.
Looking at the data sheet (here: http://www.st.com/web/en/resource/technical/document/datasheet/CD00001962.pdf), the four channels show singe-ended inputs and differential outputs (the "+" ouput and the "-" output are both active, no ground connection,) in other words the output of each channel are already basically bridged, and you cannot bridge connect already bridged outputs.
The only way to get more power output with an amp like this is to use low impedance loads, and looking at the data sheet, it's apparent the distortion goes up dramatically around 15 - 20 watts output. If you need more power than this chip can provide, I suggest you look at other alternatives.

Mike
 
#8
Michael Bean said:
I'll say it agian - No, you cannot bridge connect amp channels that are already bridged themselves, it won't work.
Click to expand...

The point is that these are already bridge amps. You can't bridge a bridge amp.

You can build two of them for 8 channels, and drive two pairs of biamped speakers, or dual woofer/dual tweeter biamped speakers.

Your best alternative is to use more efficient speakers. 3 dB more efficiency is equivalent to twice the power form the amplifier. This is by far your most practical alternative.

With the right speakers, "23 watts x 4" is a whole lot of power.

By the way, to get that "23 watts" will require employing 4 ohm speakers.
 
#9
OK, I got it 🙂
The 23W should be enough for me, I just wanted to know this...

Now about the tone corection. The one I posted looks, that it work OK, but it' only passive, so there is 20dB lost.
But I could solve this by adding pre-amplifier. Do you have any tested tone control with preamp? I looked e.g. on schematic of cheap chinese amp Lepai 2020+...
 
#14
OK, I searched a little and people are satisfied with the LM1036, so I will use it 🙂
I want to use one for front and one for rear repro....
But I want to supply it from stereo source, so I need to connect F+R plus input together.
Must I use some "filters" or I can simply short it?

Last thing, it's better to use foil capacitors then ceramic, right?
Electrolytic's I will use Nippon Chemicon, I can buy them simply in GES in my town...

Thank you 🙂
 
#17
OK, I tried to ask one guy, who built the AMP. I hope that he will answer me.
But back to the second question.
Can I simply short the inputs to make it 2x stereo, or I must use some filter capacitors or resistors?

Now I'm working on schematic. After finish of work I will post it here 🙂

Mihkus: We already dealt with it. It's possible to bridge 4x amp to 2x with phase inverter, but the amplifier can't be already bridget inside. That's problem of the TDA7560...
 
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#18
12Vdc as the power source for an amplifier cannot allow any more than ~4Vac as the audio output. It's a law of physics.
If your bridge a pair of amps running from a 12Vdc source, then you can double the maximum voltage available to ~8Vac. Again that is a law of physics.

If you have a 1ohm speaker then the maximum power from the bridged pair of amplifiers fed with 12Vdc will be <64W into 1r0.
Each amplifier of the bridged pair will be trying to deliver 32W into 0r5 and must be capable of driving a half ohm reactive speaker load.

If you require more power and/or require to drive a higher impedance load, then you must find a way to supply more than 12Vdc. 13.8Vdc is a small improvement, but it will, at best, give a modest 32% increase in maximum power.

Don't try to defeat the physical laws.
 
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