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Chip Amps Amplifiers based on integrated circuits

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Old 8th April 2004, 02:19 PM   #31
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Quote:
get back to working on world peace
Hey man, world peace doesn't just happen overnight you know. You ever been to the Third World? I have. You can't even get sour apple Blow Pops, let alone world peace. Sure, Kofi, just wave the magic wand, throw some pixie dust in the air and voila-- world peace.

Hey-- we can swap jobs if you want. I'll work at the Racine Howard Johnson and you take the Secretary General of the UN gig. I've been meaning to get back into customer service anyway. Oh, and by the way, don't let Purevjav Gansukh (Deputy Permanent Representative of Mongolia to the United Nations) pull that, "here, have my chair" gag. He's done it to every new member of the UN and it gets old really fast.

Quote:
Do you mean a 24-0-24 VAC transformer?
Yes-- sorry for the confusion. Also, I have the LM3875, not the 3886. I know I said the 3886 but you have to remember that I'm a dumbass.

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I think that is within spec for voltage, whether it can handle the resulting power dissipation depends on how big your heatsink is.
Yeah, I think that's going to be the main issue here. I believe that the chip can handle the power, but I may have to heat sink again. Right now since its running with reasonably low power (18-0-18 VAC for about 26V DC), I have finned aluminum heatsinks on the chips that are about 6" by 4". They get hot, but not too hot to touch. Also, there's really no ventilation in the breadbox, so I have to open the front of the box when I'm engaged in lengthy listening.

I really have no idea how much heat is being dissipated. Frankly, I've just been using the touch-it-with-your-hand-and-see-if-its-too-hot test. Not very scientific, but it gives me some peace of mind (no world peace jokes here, please).

Will raising the DC voltage from 25V to 35V increase the heat so dramatically that I will need new heat sinks?

Also, what about the distortion I mentioned. Will raising the voltage even address the distortion issue?

Thanks in advance for any advice you can offer.

Kofi
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Old 8th April 2004, 11:47 PM   #32
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So lonely...
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Old 9th April 2004, 02:09 AM   #33
paulb is offline paulb  Canada
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Patience...
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Old 9th April 2004, 12:57 PM   #34
paulb is offline paulb  Canada
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Quote:
Originally posted by Kofi Annan
Of course, now I am concerned that the midrange and bass speakers are not being driven enough at low levels and are getting some distortion. Even at higher levels, the midrange and tweeter seem to distort at certain frequencies. Maybe its the crossover, but I am inclined to think that my power supply is too small, so I'm thinking about upgrading it.
Kofi
A higher supply may help. Depends where the distortion is coming from.
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Will raising the DC voltage from 25V to 35V increase the heat so dramatically that I will need new heat sinks?
Look at the curve "Power Dissipation vs Output Power". For 8 ohm speakers, and an output of say 20W, the device dissipation will go from 18 to 32 watts. So yes, it probably will.
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Old 9th April 2004, 01:34 PM   #35
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Thanks!

Unfortunately (or maybe fortunately), I discovered last night that the distortion I was hearing was coming from one of my midranges. I sent away for a new midrange and it should arrive on Monday.

Thanks for all the great advice. I'll try to learn about this "patience" you speak of.

Kofi
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