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Author Topic: Black Box Amp  (Read 3324 times)

blackcorvo

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Black Box Amp
« on: August 16, 2015, 10:24:27 PM »
Recently I got a bunch of TBA820 ICs, and I thought about putting one of them to use in a mini amp project.

By their own they're not that great, but after putting a small preamp in front of it (borrowed from this post by PRR on diystompboxes), they actually sound pretty decent, specially through a proper guitar speaker.

Here's the layout I'm using and the schematic, plus a couple photos of the final build (I used a dual pot for the treble+bass control due to space limitation):




It does overdrive a little, but nothing too exciting. The LM family of chips sound much better overdriven IMO. It's more of a clean amp to be used for practice with pedals or as a bench test amp.

J M Fahey

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Re: Black Box Amp
« Reply #1 on: August 17, 2015, 03:03:42 AM »
Cool  :dbtu:

In my book, LM386 are toys, and TBA820 is the first "real" amp.
By the way, it's also the loudest one with a meager 9V battery supply, so it does not surprise me that you find it's harder to distort, it simply has more headroom than the competition..

blackcorvo

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Re: Black Box Amp
« Reply #2 on: August 17, 2015, 06:31:04 AM »
If I wanted all the power I can squeeze out of this amp without losing the portability, I could easily put together a "15v" pack out of 4x 18650-type batteries for it. A 16v laptop power supply could be used to charge it to full capacity.

Enzo

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Re: Black Box Amp
« Reply #3 on: August 17, 2015, 09:13:25 AM »
Or a 12v gel-cell running a switcher.  Then the circuit voltage is not tied to battery voltage.  Those batteries have a lot of juice.

blackcorvo

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Re: Black Box Amp
« Reply #4 on: August 17, 2015, 11:40:20 AM »
Or a 12v gel-cell running a switcher.  Then the circuit voltage is not tied to battery voltage.  Those batteries have a lot of juice.

Perhaps one of these? https://www.pololu.com/product/2571
« Last Edit: August 17, 2015, 11:54:31 AM by blackcorvo »

Enzo

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Re: Black Box Amp
« Reply #5 on: August 17, 2015, 12:06:58 PM »
That is the idea, but we'd have to study the information.  Engineer types like Juan would know more than I on that.

blackcorvo

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Re: Black Box Amp
« Reply #6 on: August 17, 2015, 12:53:49 PM »
That is the idea, but we'd have to study the information.  Engineer types like Juan would know more than I on that.

Considering the info on the TBA820's Datasheet, it can deliver 2w on 8R at 12v. That would be 500mA.
The booster circuit can deliver up to 1A with Vin of 5v and Vout of 18v.
If we think of losses and say the amp actually uses 750mA, even a 6v sealed battery would be enough to power the circuit with a good 250mA+ to spare.

Enzo

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Re: Black Box Amp
« Reply #7 on: August 17, 2015, 11:36:49 PM »
If you are committed to the TBA chip, cool.  I think in my head I was kinda thinking a more versatile power source would allow more powerful amp chips, like a TDA2030-40-50.

blackcorvo

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Re: Black Box Amp
« Reply #8 on: August 18, 2015, 01:09:57 AM »
If you are committed to the TBA chip, cool.  I think in my head I was kinda thinking a more versatile power source would allow more powerful amp chips, like a TDA2030-40-50.

Not really looking into that much output at the moment. I can barely use this amp through my 8" Vox Bulldog without getting told to turn down the volume!

Plus, I'm planning on having this amp built into that Bulldog's cab in the future (or another version of it, perhaps with a Vox stack?) with a 12v 2.3A sealed battery in it, since I would like to take it to a local trimestral event.
Last time I went to it, I used my trusty Honeytone, but next time I wanna take something I actually made by myself.

 

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