Hey folks, I'm out of my depth here and need some guidance.
I want to build the TINIEST possible audio solution that has Blueooth + One Watt Stereo Amp + Microphone input + Rechargable battery that provides at least 4 hours of usage.
When I say TINY, I mean tiny.
It can be either a single piece that is say, max dimensions of 1.5"H x 3"W x .75"D.
Or, it can be two pieces that are 1.5"H x 2"W x .75"D.
There are tons of tiny little Bluetooth modules and 1W amps out there. But I'm fairly sure there must be some "gotchas" when it comes to putting these requirements together?
As for the enclosure, since I want it as small as possible, I'm thinking I'll have to learn to fiberglass so I can make my own enclosure.
I want to build the TINIEST possible audio solution that has Blueooth + One Watt Stereo Amp + Microphone input + Rechargable battery that provides at least 4 hours of usage.
When I say TINY, I mean tiny.
It can be either a single piece that is say, max dimensions of 1.5"H x 3"W x .75"D.
Or, it can be two pieces that are 1.5"H x 2"W x .75"D.
There are tons of tiny little Bluetooth modules and 1W amps out there. But I'm fairly sure there must be some "gotchas" when it comes to putting these requirements together?
As for the enclosure, since I want it as small as possible, I'm thinking I'll have to learn to fiberglass so I can make my own enclosure.
I'd say the smallest you could get is one of those Bluetooth receivers with the built in batteries. No worries about discharging lipos too much then as they have built in cutoff circuitry.
They need amps though, and you might as well go with a 3w amp because you can get some ready made ones for not too much on the bay of e.
They need amps though, and you might as well go with a 3w amp because you can get some ready made ones for not too much on the bay of e.
Something like this looks good for charging battery using MicroUSB:
Adafruit Micro Lipo w/MicroUSB Jack - USB LiIon/LiPoly charger [v1] ID: 1904 - $6.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Adafruit Micro Lipo w/MicroUSB Jack - USB LiIon/LiPoly charger [v1] ID: 1904 - $6.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Yes, the Bluetooth receivers with built in power are all headphone only wattage ratings. I've tried this and it just didn't get loud enough.
Could you link the 3W amp you're talking about?
OH, maybe this is what you're talking about?
5V USB Power Supply Mini Digital Power Amplifier Board 3W 3W DC Amp Module Good | eBay
5V USB Power Supply Mini Digital Power Amplifier Board 3W 3W DC Amp Module Good | eBay
That's the one. Trouble is, when I've tried it in the past I recall there being a ground loop because I was running the amp off the bluetooth module's battery.
It's been a while though, and I may have been doing something wrong, so don't take my word for it.
Using the tiny amps in the Sony Ericsson speakers (made for mobiles) fixed the issue though.
Sony Ericsson portable speaker MPS-75 | eBay
You could scavenge both the amp and the (decent, for the sizes) drivers from them (though it's not quite in the spirit of what you're after, I'd imagine).
It's been a while though, and I may have been doing something wrong, so don't take my word for it.
Using the tiny amps in the Sony Ericsson speakers (made for mobiles) fixed the issue though.
Sony Ericsson portable speaker MPS-75 | eBay
You could scavenge both the amp and the (decent, for the sizes) drivers from them (though it's not quite in the spirit of what you're after, I'd imagine).
Hahah, for those prices, it doesn't matter. I bought two of those and two of these:
Mini Digital Amplifier Board Class D 2 3W USB Power PAM8403 Audio Module DC 5V | eBay
Four mini 5V digital amps for $7 shipped.
So, can a Bluetooth module and amp both share the same LiPo battery? I read somewhere the grounding can get kind of tricky.
Btw, I want the amp to be full power all the time. The volume should only be controlled by the Bluetooth transmitter, in this case, a Cellphone.
Mini Digital Amplifier Board Class D 2 3W USB Power PAM8403 Audio Module DC 5V | eBay
Four mini 5V digital amps for $7 shipped.
So, can a Bluetooth module and amp both share the same LiPo battery? I read somewhere the grounding can get kind of tricky.
Btw, I want the amp to be full power all the time. The volume should only be controlled by the Bluetooth transmitter, in this case, a Cellphone.
Pretty good little amps you know. I made a YouTube demo of them some time ago:
micro amplifier - YouTube
Granted, the speaker it was plugged in to was pretty efficient compared to the tiny ones you'll probably end up using, but you get the idea.
What materials are you thinking about using for the enclosure? Working at such a small scale does prove difficult if you want to use wood. Thought of 3D printing one?
P.S. My posts aren't going through straight away due to me having <10 posts (mods have to review them).
Do you remember what size the amp was? Or if it's smaller than 1.5"? Is it two amps, one for each speaker?
Hahah, you keep sneaking your posts in before I reply or have read your posts.
Thanks for your help.
And no, that's not just a problem with you. It was ground loop issues now that I remember.
The amps in the Ericssons are tiny, really tiny. Something like 3cm by 3cm, so just under 1.3" squared. The best thing about them is that they've been designed to work off the same battery as the source, which makes them pretty flexible for projects like this.
If only they were available separately!
You may want to look out for a set of MPS-70 speakers. The drivers are pretty much as good as it gets for the size (don't expect too much though, they're pretty small) and the in built amp isn't too hard to resolder wires to (unlike the MPS-75)
If only they were available separately!
You may want to look out for a set of MPS-70 speakers. The drivers are pretty much as good as it gets for the size (don't expect too much though, they're pretty small) and the in built amp isn't too hard to resolder wires to (unlike the MPS-75)
Usually it's a single stereo amp, but models like the MPS-80 have separate mono amps in each speaker.
You could probably find them a bit cheaper than that if you hunt around a bit I've managed to get a few for around £3 ($5.50 ish), as they're often sold off as clearance.
As for wiring them up, it's important to connect them to the battery after the lipo protection circuitry. This means that when the bluetooth module notices that the battery is approaching 3v and cuts off, the amp won't be left on drawing power.
The best way I've found to do that is use one of these units:
Wireless A2DP Bluetooth Stereo Audio Receiver for iPhone 4 5 Samsung S3 S4 HLRG | eBay
The board has two sections. One for power and its own built in (rubbish) amp, and the other for the oem bluetooth unit that they just solder to the board.
What you need to do is solder the new amp's audio input to the output of that soldered on bluetooth board. This bypasses the rubbish amp and gives pretty decent audio. I bought mine well over a year ago though, so it's possible that they've updated the circuit to include a better amp since then (I doubt it though).
As for power, you've got to do essentially the same thing. Just jack in to the power that's being fed to the bluetooth module, and the units power circuitry will cut the power to the amp when the unit is off or when the battery is almost empty (lipos can't be discharged beyond 3v).
I've managed to get a few for around £3 ($5.50 ish), as they're often sold off as clearance. As for wiring them up, it's important to connect them to the battery after the lipo protection circuitry. This means that when the bluetooth module notices that the battery is approaching 3v and cuts off, the amp won't be left on drawing power.
The best way I've found to do that is use one of these units:
Wireless A2DP Bluetooth Stereo Audio Receiver for iPhone 4 5 Samsung S3 S4 HLRG | eBay
The board has two sections. One for power and its own built in (rubbish) amp, and the other for the oem bluetooth unit that they just solder to the board.
What you need to do is solder the new amp's audio input to the output of that soldered on bluetooth board. This bypasses the rubbish amp and gives pretty decent audio. I bought mine well over a year ago though, so it's possible that they've updated the circuit to include a better amp since then (I doubt it though).
As for power, you've got to do essentially the same thing. Just jack in to the power that's being fed to the bluetooth module, and the units power circuitry will cut the power to the amp when the unit is off or when the battery is almost empty (lipos can't be discharged beyond 3v).
I think I'm going to go with one of the amps I purchased from eBay.
I'd really like to get a solution working that could work for multiple peoples.
If there are ground loop issues then I"ll try an isolation capacitor and maybe some other tricks.
LOL, but I do think I'll get these speakers you're talking about though, just so I can have a comparison to a known-working solution.
Thanks for the help, Matthew. You should post more often!
I'd really like to get a solution working that could work for multiple peoples.
If there are ground loop issues then I"ll try an isolation capacitor and maybe some other tricks.
LOL, but I do think I'll get these speakers you're talking about though, just so I can have a comparison to a known-working solution.
Thanks for the help, Matthew. You should post more often!
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