Junkie-
Your friend did exactly the same thing I am doing. Get rid of all the (-) voltage stuff, turn the +12V into -12V and the +5V into +12V.
The one thing I can't understand is why does only the +5V output have L-C-L-C, while every other output, including +12V have only L-L-C? I am fortunate that my supply has space for a cap right after the big yellow cross-coupled inductor-toroid. So both outputs will have a true L-C-L-C filtering.
Steve
Your friend did exactly the same thing I am doing. Get rid of all the (-) voltage stuff, turn the +12V into -12V and the +5V into +12V.
The one thing I can't understand is why does only the +5V output have L-C-L-C, while every other output, including +12V have only L-L-C? I am fortunate that my supply has space for a cap right after the big yellow cross-coupled inductor-toroid. So both outputs will have a true L-C-L-C filtering.
Steve
Isn't a PC power supply very noicy to be used in a audio amplifier? It has a high switching frequency but often not out of the hearing frequencys. As you mentioned, it got to have a good filtering on the output if it would work properly. But buying components for it? Wouldn't it be cheaper to buy a 300VA transformer and maybe build a regulated supply (maybe from parts from the computer supply)?
Putting the amp in the same box without Really good shielding from the SMPS would also introduce a lot of noice..
Putting the amp in the same box without Really good shielding from the SMPS would also introduce a lot of noice..
bose said:
Every Car amp over 25W/ch having a DC-DC converter uses a TL494 PWM IC, the same controller chip in the majority of half-bridge pc supplies. The typical switching frequency is 33-36kHz, about 10-15kHz above the highest frequencies the human ear can sense.
The weak-n-wimpy cheapy output filter 470-1000mF OEM caps are replaced with much better units, typically Panasonic HF, HFU, HFC, or the newer FC series Low-ESR 105C electrolytics, usually 1500-3300 (or higher) mF, and 35V or above.
The whole idea here is to use the pc supply and not to replace it. Since this is about modifying a Switching supply and not making a linear one, using a 300VA 50-60Hz transformer kinda' defeats the purpose. While there are many cheaply designed AT & ATX pc supplies out there, there are (were) some well-designed and well-built ones with good filtering and low noise. It's just a matter of finding one. With the glut of 250W and under supplies floating around, this shouldn't be too hard.
Any well-designed SMPS in close proximity to the amp section (same enclosure) will have low EMI and RFI, and of course be shielded from the amp.
Car amps do not suffer this problem because their DC-DC converters use a big toroid instead of the traditional E-I core ferrite for the main power transformer. Toroids, for the most part, are self-shielding by nature of their geometry: almost all the magnetic flux is contained within the core, with very little magnetic strayfields.
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