Impulse purchase on ebay - Sure Electronics 2x250W Class D

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aspringv

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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/download/AA-AB32291_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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aspringv

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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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aspringv

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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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aspringv

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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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aspringv

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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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aspringv

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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... ;)
 
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Neil Davis

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aspringv said:
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.
Click to expand...

The IRF2902 reference amp is designed to be scalable, with tradeoffs that can be made for supply voltage and power output and load. The Sure amp is closest to the Amp7S-200, but different values have been selected for the OVP, UVP and current trip levels. The following table should help you figure out what you have and how far you can "push" the amp and what power supply you can use. Enjoy.

It looks like one possible interpretation of this data is that the amp should work fine in bridged mode for an 8 ohm load with 51V supplies (this is because the OVP, UVP, and OCSET are close to the same values as the AMP7S-150). Unfortunately, the circuitry needed to bridge the amp isn't on the board--you would have to buy the parts and add them yourself (the PCB will accept the parts, but that area of the board isn't populated--at least, mine isn't) :(.

Caution: the part values for the "Sure" column were taken from my board that I bought about 9 months ago, and they may be different on the current boards.

Sure.jpg
 
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Neil Davis

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aspringv said:
...That's amazingly helpful.
Click to expand...
Always nice to have some facts, isn't it? :D

Cheers - I'll have to do a bunch more reading and see if there's a happy point where I can bridge the module I have ordered.
Click to expand...

It's really just about keeping within the amp's Safe Operating Area (SOA). You can use higher voltages with an 8-ohm load to get max power, or you can use lower voltages with 4-ohm loads. But you can't do both, because you end up being on the wrong side of the SOA curve. And once you pick your load and supply voltages, you need to select the resistors to set the over current and over/under voltages.

That Sure amp is a great value--all of the components seem to be the same quality parts that are specified for the IR reference amps, and the board layout is identical. But it may not be set up for the load you want to use. I was hoping to bridge this amp also, but I decided it would be easier to just go with two 8-ohm subwoofers in the box.
 
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