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Old 6th September 2002, 08:44 PM   #1
CryingDragon
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Arrow Need Help!!!

Ok,So i'm designing a 2 channel amp around the STK086G (70W Min,yes the data sheet says Min not Max) And:

#1 I want it to sound good,naturaly so i have deisgned the circuit card around whats called the "Application" schematic in the data sheet,Is this the proper one to use for best sound?

#2 Data sheet says reccomended voltage +- 42V with a Max collector current of 7A well if my math is right at 42 volts it should only take 2 amps to make 80 watts,So can i run these amp chips at say 30 volts at 4 amps and get the same quality sound?

Sorry for the beginner questions i just need some help.

~CryingDragon
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Old 8th September 2002, 04:40 AM   #2
CryingDragon
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Default ?

Nobody can help me?
Ummm...here are my silk and trace deisgns for it,Will running two of these same amp sections (the attched trace diagram represents one section) off of one PSU affect the sound? Mabey some unwanted feedback between the two?
http://www25.brinkster.com/cryingdragon/amp/silk.jpg
http://www25.brinkster.com/cryingdragon/amp/trace.jpg
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Old 8th September 2002, 05:07 AM   #3
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You wouldn't 'run' these chips at a specific amperage, they will draw amperage according to the voltage of the wave and the load it is run on. at 30 volt rails, the voltage amplification will be slightly under this, lets just say 27V for s**ts and giggles. This 27V into an 8 Ohm load will draw 3.375 Amps. given such, this suggest 91.125 W for an output. This all seems to be within the specs that you gave for this chip.

As for the quality of the sound, I cannot say for sure. I would suspect that it would be fine unless this chip is designed to be run at a VERY specific voltage.

-D.
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Old 8th September 2002, 06:06 PM   #4
djk is offline djk
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You guys need some help?

"#2 Data sheet says reccomended voltage +- 42V"

That means it will blow up if you use more than +/- 42V on the supply. This means a 30-0-30V transformer.

"with a Max collector current of 7A"

This means it will blow up if the load draws more than 7A. If we use the maximum rated voltage of 42V that means we cannot go below a 6R load.

If you want an amp that will put out 70W/8R X 2 you will need a transformer rated at 30-0-30V at about 280VA. If you want to drive 4R you will need to lower the voltage to 22-0-22V. The main filter caps would need to be 6,800F/50V for 8R or 15,000F/35V for 4R with a bridge rectifier rated at 10A/200V or higher.
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Old 8th September 2002, 06:56 PM   #5
CryingDragon
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Eeeeee Thankie! And will that 30-0-30 300VA run both my amps? Like i said i have the two sections (or 2 chips) or will i need 600va?
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Old 10th September 2002, 10:14 AM   #6
djk is offline djk
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300VA will run two 70W/8R amps at full power, no problem.
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Old 10th September 2002, 07:45 PM   #7
CryingDragon
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Default Yeay

Thanks!
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