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Class D Switching Power Amplifiers and Power D/A conversion

Experience with ebay 2.1 amps?
Experience with ebay 2.1 amps?
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Old 6th November 2017, 05:56 PM   #1
den_hr is offline den_hr  Croatia
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Default Experience with ebay 2.1 amps?

Have been searching the forum for opinions of the ebay 2.1 Class D amps, but haven't really found much... (my previous experience is only with "normal" 2.0 stereo modules).

So, a short question: does anyone have any recommendations (based on experience) for an 2.1 amp (e.g. various 2x50w + 100W amp modules) available through "usual suspects" (ebay, aliexpress, tc...)?

I'm thinking about a new project, and need a compact 2+1 amp, not necessarily too powerful - but it has to be 2+1 ("normal" stereo plus subwoofer). Planning to power it from a "laptop brick" (18-19V, perhaps 4-5A), so it definitely won't reach the declared power, anyway

I'm leaning towards this one from sanwu:
TPA3116 2x50W+100W 2.1 Channel Bluetooth Digital Subwoofer Power Amplifier Board | eBay
- since I've found a couple of positive opinions about it....

Thanks in advance for any recommendations!
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Old 6th November 2017, 06:09 PM   #2
DrewT is offline DrewT  United States
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^ I have one of those. I posted here about it. The bass output cuts off completely if one of the bass control knobs is turned more than just a little bit from full counter clockwise. I later also noticed that changing the overall volume causes one of the satellite speaker cones to move drastically. I don't know if I just got a defective unit, or if it's a bad design.
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Old 7th November 2017, 07:49 PM   #3
millstonemike is offline millstonemike  United States
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Here is a common 2.1 board. I'm using this in a 2.1 boom box. Driving an 8" woofer and two 5" full range speakers rnning at 24+ volts. Lots of power and has held up to many days on the beach at loud volumes (80 W into the sub channel plus the L-R full ranges).

I modified the ".1" LP filter to suit my needs by replacing two poly box caps in the filter circuit thus changing the filter's Fc and Q.

Note that others here have received boards where the filter components were miss-populated with parts of the wrong values. This caused the LP filter to be unusable without mod's. On the flip side, both boards I ordered worked well out of the box. No hiss. Check out this link for a analysis.

TPA3116 2.1 Amp - Step by Step Modifications - Techtalk Speaker Building, Audio, Video Discussion Forum

Last edited by millstonemike; 7th November 2017 at 07:52 PM.
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Old 7th November 2017, 08:42 PM   #4
den_hr is offline den_hr  Croatia
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Thanks for the info so far!
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Old 10th November 2017, 06:27 PM   #5
Think is offline Think  Netherlands
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Experience with ebay 2.1 amps?
Posted this here :

"Now listening for a few months to a $20 TPA3116 2.1 amp and I'm really blown away: real 2x50W+100W and the sound is so detailed, and just very NICE! And this 10oz (?) amp is more powerfull then the 25lbs Yamaha...

It runs fine with an old laptop adapter (+/- 19v >3A) The varable crossover is about 80-500hz. The solderingjob is among the best I have ever seen.
As subs are best run in mono and you can also run 2 fullrange bi-amped speakers from it.

Only 'negative' thing I've found is the noisefloor, but even with big sensitive PA speakers connected, I can hear it just a little within a foot when nothing is playing, so still good."
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Old 10th November 2017, 09:39 PM   #6
millstonemike is offline millstonemike  United States
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Think (good screen name BTW),

What is the number on the part I've highlighted from the picture in your link. Also, can you tell the potentiometers' resistances?

2.1.png

Last edited by millstonemike; 10th November 2017 at 09:42 PM.
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Old 10th November 2017, 09:50 PM   #7
HumbleDeer is offline HumbleDeer  Belgium
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The pots are nearly always 50K Logs. This is denoted by B50K. B for B Taper (Audio Taper) and the number for the resistance.

I do have to say 10K pots work better.

Quote:
Originally Posted by Think View Post
Posted this here :
Only 'negative' thing I've found is the noisefloor, but even with big sensitive PA speakers connected, I can hear it just a little within a foot when nothing is playing, so still good."
THIS video is Certainly the solution. I did it to all three of my boards and it's 100% fixed. This works on other boards too because it's a principal issue, and not chip specific.
YouTube

Last edited by HumbleDeer; 10th November 2017 at 09:52 PM.
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Old 10th November 2017, 10:53 PM   #8
millstonemike is offline millstonemike  United States
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Quote:
Originally Posted by HumbleDeer View Post
The pots are nearly always 50K Logs. This is denoted by B50K. B for B Taper (Audio Taper) and the number for the resistance.

I do have to say 10K pots work better.



THIS video is Certainly the solution. I did it to all three of my boards and it's 100% fixed. This works on other boards too because it's a principal issue, and not chip specific.
YouTube
Yes sir, almost always 50K. I've seen that video. That's (why I asked about the pots.

And he's working on the board I used in my "boombox". My contribution was in the sub channel, changing the two box poly caps to get an Fc and Q on the fixed LP to suit your needs and eliminating / reducing the sub's 34 Hz HP to reasonable levels.
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Old 11th November 2017, 09:18 PM   #9
Think is offline Think  Netherlands
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Experience with ebay 2.1 amps?
Quote:
Originally Posted by millstonemike View Post
Think (good screen name BTW),

What is the number on the part I've highlighted from the picture in your link. Also, can you tell the potentiometers' resistances?

Attachment 645092
That chip reads: 78M05 DN1718 and I measured ~ 44k Ohm on the volume and treble pots with a cheap multimeter.

btw. The little switch selects if the mains crossover or play fullrange.

I don't know much of amps, but I noticed there are a lot more smd resistors and other components on this board in comparison with simular boards.

//edit: I won't be doing any mod for the noisefloor because it's good enough. Nice to read there is a 34Hz HPF which can be altered.
I measured temperatures after playing for hours and nothing gets warm at all; max 35 celcius.
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Last edited by Think; 11th November 2017 at 09:46 PM. Reason: added info
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Old 11th November 2017, 10:15 PM   #10
millstonemike is offline millstonemike  United States
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Quote:
Originally Posted by Think View Post
That chip reads: 78M05 DN1718 and I measured ~ 44k Ohm on the volume and treble pots with a cheap multimeter.

btw. The little switch selects if the mains crossover or play fullrange.

I don't know much of amps, but I noticed there are a lot more smd resistors and other components on this board in comparison with simular boards.

//edit: I won't be doing any mod for the noisefloor because it's good enough. Nice to read there is a 34Hz HPF which can be altered.
I measured temperatures after playing for hours and nothing gets warm at all; max 35 celcius.
The guy in the video is using my board, not you. Sorry for the confusion.
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