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Old 15th February 2013, 07:55 PM   #1
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Default chip + circuit recommendation for driving4Wrated speaker/4ohm using bipolar 12v DC

Hello,
I would like to add a small full-range speakers to my synthesizer, so that I can have some fun with it easily/immediately/even without spending time connecting it to PA or studio monitors.
The speaker I would like to use are small Visaton BF 45 (90Hz - 20KHz)
4 ohm
4 watt rated power
8 watt maximum power
I assume that some chipamp would be easiest way to do that.
The synthesizer has a +12v and -12v power rails inside which i would like to use, so either some chip that can use bipolar power, or if running from a single rail, I would prefer to use the -12v rail, while that rail has the same PSU as +12, but the synth draws much less current on -12v. (if possible)
I'm thinking about using either one speaker MONO, or Dual Mono (the synth is mono).
Please, could you advice either some chip (+circuit if possible) or transistor circuit that could be used in my situation?

thanks !!
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Old 15th February 2013, 08:41 PM   #2
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TDA2050V

It will work at single 12VDC

http://www.st.com/internet/com/TECHN...CD00000131.pdf

You will have to change cap polarities for use with a negative supply...not sure if I'd do that but it can be done.

Or use an old laptop supply and add some power supply filtering and get above 16VDC so you could use a LM1875T/NOPB.

http://www.ti.com/lit/ds/symlink/lm1875.pdf
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Old 15th February 2013, 08:43 PM   #3
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LM4940
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Old 15th February 2013, 09:43 PM   #4
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I'm thinking something along the lines of a TDA1013B.
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Old 15th February 2013, 11:31 PM   #5
johnr66 is offline johnr66  United States
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How much current is available from the + and - 12 volt rails?
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Old 16th February 2013, 12:22 AM   #6
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thanks to everyone. so far, the LM4940 seems to be most close to what I'm looking for? Just mono instead of stereo would be better, but maybe i'll just use two speakers.

johnr66: it's a modular synth, so it depends on how many and what kind of modules I have mounted at the moment, but from the -12v rail most modules use only 1/2 or 2/3 of what they use from the +12v rail. For +12v I would like to keep current draw of this driver under 150mA if possible... if i could find a way how to use the -12v only, i could be much more generous...
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Old 16th February 2013, 01:23 AM   #7
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Quote:
You will have to change cap polarities for use with a negative supply...not sure if I'd do that but it can be done.
This should not be necessary. Just invert your thinking.
The TDA2050 "ground" becomes the negative supply and its positive rail becomes "ground".
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Old 16th February 2013, 01:36 AM   #8
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Quote:
Originally Posted by dnk777 View Post
Please, could you advice either some chip (+circuit if possible) or transistor circuit that could be used in my situation?
TDA8566 comfortably meets your requirements on a single 12V supply. Its available from Mouser, schematic (very simple) is on my blog (link over to the left on the number of entries).
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Old 16th February 2013, 08:03 AM   #9
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i'm bit worried about the current draw so i'm also thinking about going class-d. are there some class-d chipamps suitable for DIY? i've found some on texas instruments web, but they all seem to be SMD / impossible (for me) to solder them + unable to use on a protoboard
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Old 16th February 2013, 12:46 PM   #10
johnr66 is offline johnr66  United States
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Your not going to get it done with 150ma, so if you can get 1+ amps off the negative rail, you can run a chip amp at 4 ohms. If you you don't have this much current to spare, you can use an 8 ohm load, however, you will need 500ma or more available.
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