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Class D Switching Power Amplifiers and Power D/A conversion

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Old 4th August 2012, 02:47 AM   #501
redjr is offline redjr  United States
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Originally Posted by NissanSR20Man View Post
....
I still think LJM's L25d and hien.t.nguyen's L25de is pretty cool, I just need to decide which to use. either way +/-70V and 250W is calling to me
Yeah. It's calling to me too. After reading pages of this thread I decided to order the ljm designed L25D version from zoe. I just like to have the extra headroom. I'll be driving it with a linear PSU at +-70v. Should be interesting to hear how it sounds.
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Old 4th August 2012, 12:20 PM   #502
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Originally Posted by blairfrischx View Post
Actually, I might just swap out all of the 22uF 25V caps while I am at it with Elna Silmics. There are six per board. I may also order some 22nF MKP caps to parallel across CP1 on each board.

I will have to check when I get home whether the buffer caps in the L20D are actually 470uF 100V (per reference design) or 100uF 80V (per board markings). I think I will sub them with 470uF 50V Nichicon KZ caps.

I can't seem to find a good replacement for the 1nF ceramic caps (C2,C4,C6,C7) since they are so small, so I may just leave them in place. I was trying to find a comparable WIMA cap, but they all seem to be much too large.

R2 and R7 will probably be swapped with 1% Vishay/Dale resistors of the appropriate values.
stick witht upgrading the input and buffer caps , the rest won't give you any improvement (in sound ) .

Cheers ,

Rens
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Old 4th August 2012, 06:51 PM   #503
redjr is offline redjr  United States
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I have one of these Sure Electronics class D amps that I have not fired up yet. Not trying to de-rail this thread by introducing another design, but was curious if anyone has both and done any serious comparison to the L25D by ljm. They both use the same IRS2092 chip and output devices, so was interested on any comments about it. I need to get this on my bench and see what it sounds like. I will be operating it with 65v rails.
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Old 4th August 2012, 07:27 PM   #504
exflaco is offline exflaco  Armenia
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These Sure are iraudamp7 look at google ,the same schem l25d by ljm other design.
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Old 5th August 2012, 02:44 PM   #505
redjr is offline redjr  United States
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Originally Posted by NissanSR20Man View Post
Doctordata - The comments about your speaker protection peaked my interest too. During the test after the mods, you did find the turn off time to be proper? I am not sure how fast the time really is, 1S or shorter? I have been pondering the protection scheme for some time. The bus pumping phase shifter of your is quite nice too! I planned on using cristy's BIPS module to offer the nice finished look of the jacks, and offer some line driver capabilities too.

Overall it sounds like you put your system through the ringer regarding testing. Its nice to know the ebay speaker protection circuit actually do work.

My multichannel setup would be for home theatre, driving a total of 8 full range speakers. The sub would probably be qty2 L25 bridged. Just cause I'm anal about commonality of looks and parts, I would probably use all L25 modules. My main speakers are 93db too and cannot wait to really push them hard. I have an antique onkyo reciever only "claiming" 60Wx2 in stereo mode. In multichannel it is pretty poor for my setup. My whole system is made up of athena audition series, not great but a really good speaker for little money.
Linky here
My Man Cave - Home Theater Forum and Systems - HomeTheaterShack.com
Nice. Very nice man cave you have there.
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Old 5th August 2012, 03:17 PM   #506
redjr is offline redjr  United States
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Originally Posted by momomo67890 View Post
u should replace the caps in the ps board.
Actually, the filter caps on that particular board are high quality Rubycon electrolytics. I have the identical board and the pcb along with the build quality is first rate. I seriously doubt they would fail (unless pushed beyond their 80v rating), and start a fire.
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Old 5th August 2012, 03:30 PM   #507
redjr is offline redjr  United States
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the big black ones they are fakes just random sized caps pulled out of other electronics.
Not. And what do you base this knowledge on?
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Old 5th August 2012, 04:32 PM   #508
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Originally Posted by redjr View Post
Not. And what do you base this knowledge on?
cut the tops off the caps and the real maker of each cap will be reveled . the tops being the fake plastic disk ontop.
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Old 5th August 2012, 04:37 PM   #509
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Originally Posted by momomo67890 View Post
cut the tops off the caps and the real maker of each cap will be reveled . the tops being the fake plastic disk ontop.
Nothing surprises me anymore and I would love to see a picture of those caps "without makeup"...
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Old 5th August 2012, 04:40 PM   #510
redjr is offline redjr  United States
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Originally Posted by blairfrischx View Post
Some good news and some bad news here.

Good news first - it functions at 35V +/-

Click the image to open in full size.

See that little blue light? Beautiful.

All that was necessary was swapping out the resistors as noted in the quoted post.

Click the image to open in full size.

Now, on to the bad news. After removing, modifying, and rewiring the amp board in the one amplifier, I turned power on and POOF. Smoke. I accidentally wired DC+ to the wrong terminal on the board, and it fried something on both boards. The power supply rectifier/filter board was easy enough to fix - remove burnt traces and replace with thin wires. The amp board is another story entirely. I fear I may have burned up the opamp, rendering it useless. There are no obviously burned traces on the PCB or components, and yet it does not function, and the pretty blue light does not function.

Anyway, that's a problem that is simple enough to solve by buying a new amp board, replacing the resistors, and not wiring incorrectly. This post is more to announce to everyone that it is possible to swap resistors and operate at lower voltage.

Now here's an album of the project so far: Photo Album - Imgur
Nice pics of your project so far. Excellent job!
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