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Old 22nd February 2010, 08:28 AM   #1
pra3718 is offline pra3718  India
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Default 6 channel power supply

As I understood, the importance of power supply distribution to each channel/CHIP, I wish to build such a power supply.

If I am using 6 TDA7294/LM3886

For my sub I need 35v +-
For front speakers I need 24v +-
And Center & Rear I need 18v +-

This can be manage with three 24-0-24, 18-0-18, 12-0-12 transformers but Is that possible to obtain three supply from single transformer ?
If I use 24-0-24 = 35v +- I need to drop the voltage

Thank you & Regards.
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Old 22nd February 2010, 12:50 PM   #2
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Why would you need 18V for the center and rear?
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Old 22nd February 2010, 03:08 PM   #3
pra3718 is offline pra3718  India
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Quote:
Why would you need 18V for the center and rear?
It's my listening test. I don't want it should equally sound with front speakers.

I found attached picture while googling, request to expert member to make 35v +- to 18v +-

Thanks & Best Regards.
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File Type: gif dc-12v-to-dc-6v-75v-9v-converter-using-2n3055.gif (3.0 KB, 575 views)
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Old 23rd February 2010, 09:01 AM   #4
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rather change the gain of the amplifier than the voltage size. crude easy way is to build the amplifiers with a variable pot at input and set them up afterward.

you are going to waste power and make your project unnecessary complicated by adding the extra circuitry.
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Old 23rd February 2010, 09:18 AM   #5
ratza is offline ratza  Romania
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Quote:
Originally Posted by pra3718 View Post
I found attached picture while googling, request to expert member to make 35v +- to 18v +-
Output voltage will be the Uz - Ube, Uz is the voltage drop across the Zener diode and Ube is the voltage drop across the base-emitter junction of the transistor. Ube is 0.6V typically. Pay attention on the power dissipation on the transistor, it will be a lot of heat there.
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Last edited by ratza; 23rd February 2010 at 09:22 AM. Reason: Missed one char
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Old 23rd February 2010, 10:52 AM   #6
pra3718 is offline pra3718  India
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Thank you ratza for technical description

Quote:
rather change the gain of the amplifier than the voltage size. crude easy way is
to build the amplifiers with a variable pot at input and set them up afterward.
I accept your solution, but consider real complexity.

My previous project and assembling problems & looking for easy solution.

Previous project 7.1 ( 7 chips=tda2030a & 1 chip=tda7294 )
It sounds very good & error-free. I build all this on the floor.
1) Transformer 2 Nos (12-0-12, 24-0-24)
2) Power supply 2 Nos ( One is for 2030 & another for 7294 )
3) Two big heat sink ( One is for 2030 & another for 7294 )
4) One big PCB & 7 Chips size 8" x 4" approx
5) PCB for 7294 size 4" x 4" approx
6) 4 channel crossover to run front amps & speakers
7) Low pass equalizer to run sub-7294.
8) lot-off wiring.
Still I could not set in subwoofer enclosure.

For this I have to reduce components. I am using two bigger & heavy transformer 5 Amp each. If I learn how to drop voltage 35vto18v I can reduce one transformer.

2nd try is to reduce transformer I build BRIDGE=tda2030a & tda2050 but it is not good as 7294 mono.

Then I decided if choose 7nos 7294/3886 I will be able to reduce components.
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Old 23rd February 2010, 11:24 AM   #7
ratza is offline ratza  Romania
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pra3718, powering the chips with different voltages won't help at all, you'll only limit the maximum power. You need to adjut gains of each amp so they match with the speaker sensitivity. The sub will have the highest gain, while rear will have lowest. This can be achieved very simple by using voltage dividers at the inputs of each channel.
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Old 23rd February 2010, 11:58 AM   #8
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That's what i said In different words

Don't remove spark plugs or only stay in 1st gear to change your speed of your car.

Just lift your foot a bit.

pra3718

Add Rin toyour circuitry and use 35 0 35 V on all your amps and set the input level afterwards.

http://diyaudioprojects.com/Chip/LM3...86-chipamp.png
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Old 23rd February 2010, 01:42 PM   #9
pra3718 is offline pra3718  India
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Ok. Accepted.

But here is lot-off threads where member manage tda2030a/tda2050/lm1875/lm3875 for surround sound and lm3886/tda7294/tda7293 mono/bridge for sub. How they manage ? Are they using 2 transformer and all this (post # 6) components. It is still difficult to keep in sub-enclosure.
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Old 23rd February 2010, 02:01 PM   #10
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Personally I believe in keeping all 5-7 channels as well as speakers identical. or as identical as the setup allows.

I would assume levels as well as delays would be set by a preamp\processor\receiver.
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