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Old 26th May 2008, 09:15 AM   #11
Dan2 is offline Dan2  South Africa
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i wouldn't say its a good amp - it was the cheapest in the shop (sansui)

the IC is kia6210ah.

i actually am going to use this in my room - its a 4 channel amp and i have a pair of AIWA bi-wired speakers that the amp will drive. only 2 channels work now - but i got hold of another amp with the same problem, so im gonna put both working stereo chips in one case.
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Old 29th May 2008, 04:51 PM   #12
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Quote:
Originally posted by EWorkshop1708
Input filters..........I don't see that many car amps with them. You must have a good amp, most amps I see have no snubbers or filters.

Glad you figured it out.

What amplifier is it? What IC's does it use to drive the speakers?
On the contrary, most car amps DO have them in the form of a bar core inductor. This amplifier, however, uses a simple E-core (laminated).

Perfect Example of a cheap Sparkomatic (looks to have been modified for use in a PC!):
Click the image to open in full size.
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Old 29th May 2008, 07:02 PM   #13
Dan2 is offline Dan2  South Africa
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yep it looks like that!

just thinking now i should also run my amp straight off the pc PSU- i don't need tons of power from the amp so it should work great.
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Old 29th May 2008, 08:30 PM   #14
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Quote:
Originally posted by Dan2
yep it looks like that!

just thinking now i should also run my amp straight off the pc PSU- i don't need tons of power from the amp so it should work great.
Dan-

Be careful using an AT or ATX psu. Regulation is achieved by loading down the +5V line. Without that, the +12V line will read only about +10.5V. I would do these three things:

1) find the resistor that senses the +12V line, and adjust it for +13.8V.
2) Find the sense resistor for the +5V line and and tweek it to let the 12V line put out the +13.8V.
3) Find the Crowbar overvoltage protection circuitry for the +5V out and disable it. This usually involves unsoldering a TO-92-cased SCR.

Measure the output voltage on the +12V line at various loads and make further adjustments to the upper sense resistor on the +5V line, until +13.8V is reached at full load (which is about 8-10A).

One other thing- you may wish to upgrade the usually low-quality low-ESR electrolytic caps in the output sections to good Panasonic FC-series or TS-series cans. Same thing for the 200VDC units on the primary side. I would go with 330mF Panasonic TSHB units.

There are several threads in the Power Supply Forum on using pc SMPSs as general power supplies and for audio use. Check them out, as there is a ton of good advice. Let us know how this works out.
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Old 30th May 2008, 07:40 AM   #15
Dan2 is offline Dan2  South Africa
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Oh wow i didn't know you could get some extra juice out of a pc psu!

well as i will be listening to my room speakers at moderately low volumes i don't think i will mess with that PSU, but i do have another project that could benifit from that! Its a car cd frontloader that i run straight off a pc PSU. i have a sub (and amp that has its own transformer) connected to it so i don't need tons of bass, but a bit of extra power would sure help.

so the resistors i have to tweak - are they variable or just normal resistors that i will have to swap with different values??
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Old 31st May 2008, 03:58 AM   #16
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On most ATs & ATXs, this is usually a 1% resistor. Stepping back a bit, the controller chip (almost always a TL494 or equivalent) senses the output(s) by a resistor ladder (upper & lower), with the NI input of the PWM chip's on-board error amp connected to the junction of these two resistors.

For sensing multiple outputs (like +5V & +12V), the single upper resistor is replaced with two resistors, each proportioned for the voltage it is sensing, and the percent regulation desired. Since the +5V is the most tightly regulated, its sense resistor will be proportionally smaller than the resistor connected to the +12V line. To determine which is which, simply follow the traces on the pc board from the output(s) back to their respective sense elements. The first component you will hit is a 1/4W 5% resistor. This is the one you will tweek.

Depending on how you want to set this up, you could either calculate the new value for the higher voltage (now +13.8V), replace it with a pot in series with a resistor, to make the output continuously adjustable.

I would be careful about feeding a moderately high-powered chip-amp from 12V, as its undervoltage lock-out might kick in. Operating from +13.8V will make the amp much happier.
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Old 31st May 2008, 06:32 PM   #17
Dan2 is offline Dan2  South Africa
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Great stuff i will definitely check that out soon!!

thanks N-Channel
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Old 31st May 2008, 07:03 PM   #18
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In the photo you can clearly see "L1" marked right by the transformer looking object. I would bet dollars to donuts that is simply an inductor. there is no SMPS in this amp, it runs straight off of 12V to power those IC's and that inductor is in there to help filter out noise!
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Old 31st May 2008, 07:05 PM   #19
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PS

PC connections would have 2 black wires in the middle. those leads are +12V Ground and the yellow is most likely remote turn on!

NOT pc connections.
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Old 31st May 2008, 07:25 PM   #20
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Quote:
Originally posted by Zero Cool
In the photo you can clearly see "L1" marked right by the transformer looking object. I would bet dollars to donuts that is simply an inductor. there is no SMPS in this amp, it runs straight off of 12V to power those IC's and that inductor is in there to help filter out noise!
I don't think anyone was claiming it was a SMPS transformer.
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