Can I wire a 24v amp and 12v blue tooth like this? - diyAudio
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Old 12th March 2014, 03:58 AM   #1
andysam is offline andysam  United States
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Default Can I wire a 24v amp and 12v blue tooth like this?

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I have a 24 volt DC amp (2x50watts) and a 12v DC Blue tooth board I would like to use in a portable boom box. I will be using two 12v batteries to get the 24volts. I found a way online to wire the two components so they each get their appropriate volts. However, I obviously need a on/off switch for the boom box. Would my wiring diagram be ok?

On a separate note, would a push button 12v switch that is rated for 10A be ok to use in this application? Or do I need a 24v on/off switch?
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Old 12th March 2014, 04:21 AM   #2
lexer98 is offline lexer98  Argentina
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First at all ... always in a circuit the power switch cut the positve lead and you need a double pole single throw switch ...

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Old 12th March 2014, 05:00 AM   #3
DUG is offline DUG  Canada
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Don't do it that way...Your amp will get 36V...and other bad things.

The magic smoke will probably leak out and it will not work without keeping the magic smoke in.

Use a double pole switch...one for each battery/device set in the positive connection.

Connect the negatives together at one point.
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Old 12th March 2014, 05:16 AM   #4
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Yeah but I would do it like this since there will be other cables that use common ground. You don't want to lift the main ground and have the potential for feedback and the amp using the signal cable for ground. It will smoke up.

As for the switch, the 12 will probably work but may eventually fail. You can just use one rated for 120 volts. Use a wall switch, good for 15 amps @ 120v.
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Old 12th March 2014, 05:21 AM   #5
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Quote:
Originally Posted by DUG View Post
Don't do it that way...Your amp will get 36V...and other bad things.

The magic smoke will probably leak out and it will not work without keeping the magic smoke in.

Use a double pole switch...one for each battery/device set in the positive connection.

Connect the negatives together at one point.
This would require two types of batteries and two types of chargers. The other method would use a common battery and a single 24v charger.

The way I have it pictured it would not have 36 volts or blue smoke. Besides, you can't get 36 volts out of two 12v batteries. This is common for wiring stuff in a 12/24v environment such as a tractor trailer where this amp was probably designed for use.
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Old 12th March 2014, 05:27 AM   #6
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Yes, I agree with this using the double pole switch.
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Old 12th March 2014, 06:16 AM   #7
andysam is offline andysam  United States
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Thanks everyone!
Brian/lexar, where would I connect my charger leads to? I am planing on using this PSU wired to the batteries:
24 VDC 1880mA Switching Power Supply US and EU | 120-054
Would I just wire the female 2.5mm x 5.5mm plug directly to the batteries? One of the wires to the positive side of Battery 1 and the other wire to the negative side of Battery 2?

BTW: This is the amp and the bluetooth i am going to use:
Bluetooth Audio Receiver Board v2.1+EDR 12 VDC | 320-351
2x50W TDA7492 Class-D Amplifier Board | 320-301
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Old 12th March 2014, 12:38 PM   #8
DUG is offline DUG  Canada
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Originally Posted by Brian Oshman View Post
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Yes, I agree with this using the double pole switch.
Even if they were two 12V batteries there is still the problem with having the two negatives of your BT and AMP at different potentials.
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Old 12th March 2014, 12:50 PM   #9
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The drawing by DUG is the only correct one so far. Brian's drawing will probably smoke the bluetooth module.
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Old 12th March 2014, 01:14 PM   #10
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The correct way is to either have 3 batteries. 2 in series for the amp and 1 for the bluetooth module (and possibly a mobile phone/mp3 player recharger). Or to have any number of identical 12V in parallel and use a dc-dc converter to get the 24V rail.

In the latter case you should notice that the bluetooth module and the amplifier must share ground so you do not connect the ground output of the dc-dc converter to anything but instead connect ground of the amp to the ground input of the dc-dc converter (or better still directly to the battery minus point).

In this set up you can also add a switch to shift to a 12V rail when you don't need maximum power output capacity. The amp uses about 5-6 times less power on 12V than on 24V when conversion loss in the dc-dc converter in considered.
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Last edited by Saturnus; 12th March 2014 at 01:19 PM.
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