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Old 6th January 2013, 09:42 AM   #241
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Recently I found 2 LM1875 and I'm interested to make a small stereo amp with them.

After a quick search for PCB layout, I landed here.

But unfortunately I found that some photos are deleted now or perhaps I missed the detailed feedback and photos of any successfully completed project following a PCB-layout posted here (with the exception of one or two) despite so much valuable information or guidance posted here by the kind and experienced members.

Earlier I looked into the datasheet of LM1875 and was utterly disappointed to see such a careless, confusing misaligned PCB-layout in an official datasheet contrary to the nice and clean TDA2030/50 PCB layout.

So,to be on the safe side, I am badly in need of a DIY ready-to-build LM1875 PCB-layout that was tested extensively by our members and built with their entire satisfaction.

Please help me choosing one.

Thank you.
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Old 8th January 2013, 12:08 AM   #242
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Quote:
Originally Posted by csom View Post
Earlier I looked into the datasheet of LM1875 and was utterly disappointed to see such a careless, confusing misaligned PCB-layout in an official datasheet contrary to the nice and clean TDA2030/50 PCB layout.

So,to be on the safe side, I am badly in need of a DIY ready-to-build LM1875 PCB-layout that was tested extensively by our members and built with their entire satisfaction.

Please help me choosing one.
The LM1875 is pin compatible with your TDA2030/50 PCB's. But if you want an LM1875 specific, just read through this thread and look for AndrewT's comments. I see some cases where he said: "I like this" which is pretty much a grade of A+.

After you select a nice PCB, you can then try out various schematics to see what results you like best. LM1875 is a general purpose power op-amp and is capable of supporting many different designs.
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Old 8th January 2013, 04:17 AM   #243
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Salut. A realizat cineva un PCB pentru alimentare asimetrica ? Sunt interesat. Am vazut ca au fost realizate numai amplificatoare cu alimentare simetrica. Multumesc.
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Old 8th January 2013, 04:23 AM   #244
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PCB Power unequally realized someone ? Are interested in such wiring. Thank you.
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Old 8th January 2013, 11:22 AM   #245
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Quote:
Originally Posted by danielwritesbac View Post
The LM1875 is pin compatible with your TDA2030/50 PCB's. But if you want an LM1875 specific, just read through this thread and look for AndrewT's comments. I see some cases where he said: "I like this" which is pretty much a grade of A+.

After you select a nice PCB, you can then try out various schematics to see what results you like best. LM1875 is a general purpose power op-amp and is capable of supporting many different designs.
Thank you so much Daniel for your answer. I will make the pcb and report you back here.
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Old 9th January 2013, 02:03 AM   #246
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Default LM1875 PCB

Here is a very compact LM1875 PCB.
Attached Images
File Type: gif LM1875-2013-PCB.gif (14.6 KB, 357 views)
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Old 9th January 2013, 12:10 PM   #247
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Originally Posted by danielwritesbac View Post
Here is a very compact LM1875 PCB.
Thank you so much Daniel. Much appreciated!
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Old 9th January 2013, 04:53 PM   #248
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I'd like you to look at the "2R" "input groundlift resistor" that has been used to create a "signal star" ground.
That groundlift resistor will help you in PCB design.
Click the image to open in full size.
I'm sure you'll want the signal star ground feature. However, depending on your application, you may wish to rearrange the small signal+ components for your design.

P.S.
To support an especially weak MP3 player so that it doesn't run into the headphone protection range which is useless to amplify, you can change the amplifier's feedback resistor to 56K, thus the MP3 player set not higher than 70% can push the amp to full blast. Setting high gain relocates the compromise to the power amp so that a modern source can be useful (but really high gain costs a tiny bit of power amp quality). The gain setting shown on that board is already high enough for a computer to push a 25w amp near max without straining the computer sound chip too much. RMAA software, which is free, can help you determine what output level a given computer can do cleanly.
This amp design contains compensation, and therefore, you might get higher quality by setting lower gain (33K feedback resistor) and then push with a preamp as needed.
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Last edited by danielwritesbac; 9th January 2013 at 05:16 PM.
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Old 10th January 2013, 03:32 AM   #249
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Wow I can't believe the 1875 is still being discussed after all these yrs. I was the apps eng who supported it back in the 80's. I've been poking around on this site to look for ideas for an active crossover and amplifier for a simple 2-way loudspeaker. The LM3886 seems to be improved over the 1875 and of course the 386. It's probably more stable and has better thermal shutdown capability. I was thinking about building a board that would be fitted to the back of a std 2-way speaker (ala plate amp that subs use). I'm thinking about 40W (6" driver) + 25W (tweeter). Feed power with an AC brick supply, would like + and - rails, on-board bridge, outputs DC coupled, Linkwitz-Riley active crossover, user adjustable, time delay compensation. I really think passive crossovers are adequate, at best. Any thoughts or references you can provide me, Daniel?
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Old 10th January 2013, 07:03 AM   #250
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I had only two thoughts on that.

LM3886 pounding out the bass, teamed up with LM1875 run from LM317&LM337 doing a pretty job with the high fidelity treble. You got all the power, none of the shout, none of the clipping.

If you use a LM317&LM337 pair per each LM1875 chip, your treble will have the bigger stereo separation of dual-mono, but with the low cost of only one transformer to run the whole thing.
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