Small cheap amplifier to convert passive to powered speaker

[TomHaitch]

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 🙂

 

[horst303]

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

 

[TomHaitch]

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.

 

[Douglas Blake]

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.

 

[Douglas Blake]

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.

 

[TomHaitch]

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 🙂

 

[Douglas Blake]

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.

Thanks for your help, Douglas. That's the kinda thing I'm looking for 🙂

No worries, mate.

 

[Khron]

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)

 

[TomHaitch]

Correct.

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

Amazing, this is great advice, thanks! Someone in my area is giving these away - I’m guessing either of them would work?

Khron: thanks that link was helpful!

 

[Khron]

Stay away from those "replacement" ones, unless you have a deathwish or something.

The Asus one should be fine though, the OEM being Delta, (one of) the most reputable power supply manufacturers (it's mentioned on the lower side of the label, but the "ADP-xxx" model number is an indicator as well).

 

[bonjonno]

I use TPA3118's alot in my home studio for a variety of things. They are surprisingly great. Even run a pair of 30 y.o. 10" subwoofers with them. HP 135W laptop bricks are great for power.

 

[Douglas Blake]

Amazing, this is great advice, thanks! Someone in my area is giving these away - I’m guessing either of them would work?

Yep either one should be fine.

 

[Khron]

If we are to go strictly by what it says on the label, sure. But you can bet your rear end that "replacement" one hasn't been safety tested on any sort of level. Is it really worth the (potential health / electrocution) risk, though?

Yep either one should be fine.

 

[impuls60]

TPA3118 PBTL boards are great with very good sound and very little hiss.