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Old 20th September 2012, 12:21 AM   #1
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Default Impulse purchase on ebay - Sure Electronics 2x250W Class D

Hi All,
Just yesterday I did a bit of an impulse purchase of the following
2 Channel 250Watt Class D Audio Amplifier Board - IRS2092 | eBay
with the manual for it here
http://www.sure-electronics.net/down..._Ver1.0_EN.pdf

My plan was to bridge the outputs to drive a 8 Ohm Subwoofer, and power it with a linear supply that should be good for ~51V.

Now I'm a little nervous - I read the manual (after impulse purchase of course) and it really only mentions a power supply of +- 65V, so my first question is whether my existing +- 52V power supply will indeed work (seeing the module apparently supports "undervoltage protection" made me more nervous still).

Secondly, can the unit have it's outputs bridged? I couldn't see a reason why not until i read in the manual
"Never connect -spk a and -spk b as they are on different nets" which as I understand it means bridging the outputs is not an option.

Any help would be appreciated! And thanks in advance.
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Old 20th September 2012, 12:30 AM   #2
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Hmm, further reading of the lower powered 2x125W units manual shows the exact same details in the manual for the power supply (+- 70V on the diagram, and +-65V in the recommended power supply table) but the text in the ebay post says +-50 to +-65 for this unit.

Being a cynical man, I can't help but wonder whether there's any difference between the modules other than a different pricing...
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Old 20th September 2012, 12:58 AM   #3
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Also, note that this amp is for 8 ohms loads. There is no 4 ohm spec. For 8 ohms loads you will be fine. There are better IRS2092 amps for 4 ohms loads, however. I don't recommend it with this unit.

-Charlie
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Old 20th September 2012, 01:00 AM   #4
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2x250W IRS2092 Class-D Amplifier Board 320-313

This would appear to be the exact same unit as I purchased (2x250W), and the text on the page states

"Note: Minimum recommended power cable size is 16 AWG. This amplifier board requires two power supplies. We recommend two of the 48 VDC, 12.5A regulated power supplies adjusted to 56 VDC of output as a minimum requirement. This amplifier board is recommended for experienced users only with the proper equipment to measure the voltage output of the power supplies. Failure to use the minimum recommended power supply voids the warranty of this amplifier board."

Which means I might be stuffed with my +-52V supply that I have here.

further research led me to http://www.inductor.com/irf/iraudamp7d.pdf which I believe is the reference design it's based off.

The relevant bits are the power supply requirements +-60V to +-80V for this unit.

Damn! If I'd got the 125W unit i would have been fine! Stupid impulse purchasing. At least it was cheap!
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Old 20th September 2012, 01:18 AM   #5
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The price of 2092 based amps has come down.
I put the cat amongst the pigeons by selling mine at £14-99 for a 300 watt version.
Nothing like a bit of competition to bring prices down.
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Old 20th September 2012, 01:22 AM   #6
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Yup, according to the reference design datasheet, it looks like I could have used the 2x125W unit bridged, for a 500W output on a 8ohm load. It's a bit confusing - i would have called that a 4 ohm load on each channel.

@CharlieLaub - yeah there does not seem to be any details on the sure site about 4 Ohm loads, but there does seem to be lots of references to 4 Ohm loads in the other links I had there. I guess I'll see how it goes... I'm looking through the datasheet to see if I can mod the unit down to the 125W spec, and thus use it as I'd planned.
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Old 20th September 2012, 01:29 AM   #7
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The original IR design only worked into 8 ohms with the mosfets they used.

I run 300 watts into 4 ohms with 45 volt supplies with irfb4019's.

For 750 watts I use irfb4227's in two pairs into 2 ohms.
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Old 20th September 2012, 01:30 AM   #8
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@nigelwright. I kind of bought because I'd been looking at the cheap designs here in this forum and realised I could buy one for significantly less than I could build one. That price you mention is pretty sharp! I can only imagine the margin must be pretty tight.
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Old 20th September 2012, 01:33 AM   #9
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I dont sell at a profit. I break even.

I was a electronics design consultant for 16 years and like to keep my hand in with hardware and software now I dont do it full time.
Even then I have to buy in pcb's from China.
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Old 20th September 2012, 01:52 AM   #10
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Apparently the mosfet's used on the module I got are IRFI4020H, and it looks like a few resistors need changed to alter the module to a 2x125W version. Sadly it's all smd parts on the underside, and not within my abilities to change. Oh well.

Well I guess I just need to bodgy up some kind of power supply ande see if it works. If I let the magic smoke out, well, at least it was cheap...

@nigelwright I hope breaking even means you at least end up with a few samples to hang on to...

Last edited by aspringv; 20th September 2012 at 01:53 AM. Reason: clarity and responding to others
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