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Class D Switching Power Amplifiers and Power D/A conversion

Small cheap amplifier to convert passive to powered speaker
Small cheap amplifier to convert passive to powered speaker
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Old 25th March 2020, 02:44 AM   #1
TomHaitch is offline TomHaitch  Australia
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Default Small cheap amplifier to convert passive to powered speaker

Hello, you were all so helpful when I was upgrading my stereo speakers a while back and I'm hoping your collective expertise can help again today!

I am hoping to make a mono 'grotbox' speaker for checking my mixes on.

I have a single driver passive speaker to do the job. At the minute I am running a Lepai Class T amp to drive it, but it keeps making loud clicking noises intermittently and scaring the life out of me.

I'm hoping to turn the speaker into an all in one unit with the amp on the inside and a power-switch attached to the outside somehow.

Part of the point is that it doesn't sound great so I'm looking for something cheap and effective rather than 'good'. Any advice is appreciated!

I've attached pics of the speaker and driver.

Audio will be coming from Protools > RME interface > Mackie Big Knob

Thanks in advance
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Old 25th March 2020, 05:33 AM   #2
horst303 is offline horst303  Australia
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Or you could have the amp on the outside with a switch and a volume control for convenience.

This one doesn't make any extraneous noises whatsoever:
Breeze Amp HIFI Class 2.0 Stereo Audio Amplifier TPA3116 Advanced GY | eBay
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Old 25th March 2020, 06:53 AM   #3
TomHaitch is offline TomHaitch  Australia
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Thanks. It looks good. The Mackie Big Knob is a huge volume knob so it's not that convenient to have one on the unit, tbh.

Alternatively, any clues on what would make the Lepai make such a wretched sound? I figure it's something PSU related.
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Old 25th March 2020, 02:07 PM   #4
Douglas Blake is offline Douglas Blake  Canada
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Quote:
Originally Posted by TomHaitch View Post
I am hoping to make a mono 'grotbox' speaker for checking my mixes on.
Something like this small mono Amplifier Board hooked up inside the speaker cabinet should do the job quite nicely. You can even add a volume control and switch by just drilling a couple of holes in the side.
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Old 25th March 2020, 02:10 PM   #5
Douglas Blake is offline Douglas Blake  Canada
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Quote:
Originally Posted by TomHaitch View Post
Alternatively, any clues on what would make the Lepai make such a wretched sound? I figure it's something PSU related.
Lepai --Lepy, Lepi, etc.-- amps all deteriorate like that. Its about crappy design and cheap volume controls. The volume controls in the original design where in the feedback loops of op-amps, the least bit of dust and you get full power pops and clicks each time you touch them.
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Old 26th March 2020, 12:56 AM   #6
TomHaitch is offline TomHaitch  Australia
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Thanks! Ok, so say I buy this amp here, I would need to run the standard speaker wires into 'audio out', the + and - from the TRS out of the Mackie Big Knob into 'audio in' and the + and - of a 12V power supply into 'power in'?

And that should run? Or is there more to it than that? I'm finding it really hard to Google tutorials, so apologies if this gets asked all the time.

Thanks for your help, Douglas. That's the kinda thing I'm looking for
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Old 26th March 2020, 02:46 AM   #7
Douglas Blake is offline Douglas Blake  Canada
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Quote:
Originally Posted by TomHaitch View Post
I would need to run the standard speaker wires into 'audio out', the + and - from the TRS out of the Mackie Big Knob into 'audio in' and the + and - of a 12V power supply into 'power in'?
Correct.

Power + and - to your supply... 19 volts is pretty common in laptop chargers and it will give you a little more oomph.

Speaker + and - simply hook up to your existing speaker.

In + and - go to microphone cable connected to a TRS plug, + goes to the tip, - goes to the sleeve.

Then ... enjoy.

The only extra I would advise is that if you find the chip running hot, you should invest in a small heat sink for it. You can get them with adhesive pre-applied so they just peel and stick on the chip. If you go with this buy the biggest one that will fit without touching anything else.


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Thanks for your help, Douglas. That's the kinda thing I'm looking for
No worries, mate.
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Old 26th March 2020, 11:39 AM   #8
Khron is offline Khron  Finland
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Or what about one of those tiny blue TPA3118 PBTL boards? Since you only need a mono amp anyway

[Shameless plug] That's essentially what I did, when I cobbled together a pair of rear / surround speakers for my living room Complete with balanced inputs, no less...

Khron's Cave: #28 Active full-range surround speaker project (BN96-12832 & TPA3118)
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