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Old 28th November 2016, 10:21 PM   #1
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Default Custom Bluetooth Speaker

A friend talked me into building a bluetooth speaker for my Dad instead of buying one. I was up for the challenge, but I have hit a road block and neither of us can figure it out. I hope this is the correct forum to post in as no others seemed appropriate.

This is my first time trying this, so please go easy on me. I am not as well versed as some of you.

I have connected this battery pack to this amp and wired the amp to these speakers.

My problem is I have no sound. I tested the speakers with a AAA battery and they produced static. I just can't figure out why I have no sound. Please tell me there is a simple solution that I am just missing.

Here are some photos just in case.
Click the image to open in full size.
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Old 28th November 2016, 10:31 PM   #2
Pano is offline Pano  United States
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Moved to Class-D amplifiers.
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Old 29th November 2016, 01:12 AM   #3
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1st question are you getting 12volts from battery pack into the amp??
You need a minimum of 8volts, maybe you only have 5volts.
It must be correct polarity into the socket in the amp. Check the documentation that you should have got with the amp.
Is there any LED's lighting on the Amp?


Almost certainly the speakers are 4Ohms. The amp you have, is not specified to work into 4 ohms. It may be that the amp is shutting down due to this. But maybe not. At low volumes I think you should have some sound.

Do you have a bluetooth signal from this device showing on your phone?
is there a beep sound when switch on?

In the meantime order some better speakers. Any Amp will be only putting about 12Watts at 12Volts battery supply, so look for something 12-25Watts, but with a SPL or Sensitivity of 90 or above.
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Old 29th November 2016, 02:19 AM   #4
gec is offline gec  United States
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I assume you have LEDs lit up on the board? Have you successfully paired with the amp?

Try changing both dip switches to off, then try with one on and then the other on. Maybe between the 4ohm speakers and the high gain setting (both switches on) the amp's protection is kicking in.
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Old 29th November 2016, 11:27 AM   #5
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Quote:
Originally Posted by whizgeek View Post
1st question are you getting 12volts from battery pack into the amp??
You need a minimum of 8volts, maybe you only have 5volts.
It must be correct polarity into the socket in the amp. Check the documentation that you should have got with the amp.
Is there any LED's lighting on the Amp?


Almost certainly the speakers are 4Ohms. The amp you have, is not specified to work into 4 ohms. It may be that the amp is shutting down due to this. But maybe not. At low volumes I think you should have some sound.

Do you have a bluetooth signal from this device showing on your phone?
is there a beep sound when switch on?

In the meantime order some better speakers. Any Amp will be only putting about 12Watts at 12Volts battery supply, so look for something 12-25Watts, but with a SPL or Sensitivity of 90 or above.
I am not sure how many volts I am getting from the battery to the amp. The amp did not come with any documentation. As for the polarity, there is an image provided on Amazon. I connected the positive/negative to the respective positive/negative terminals on the speaker.
Click the image to open in full size.

I do receive a Bluetooth signal. The amp shows up on discoverable devices and connects. My phone responds to pressing the play, prev, next and vol buttons on the amp.

Would you mind making a recommendation for something, as you stated, 12-25Watts, but with a SPL or Sensitivity of 90 or above. Please keep in mind, I am trying to make this bluetooth speaker fit on a desk or other furniture in an office.


Quote:
Originally Posted by gec View Post
I assume you have LEDs lit up on the board? Have you successfully paired with the amp?

Try changing both dip switches to off, then try with one on and then the other on. Maybe between the 4ohm speakers and the high gain setting (both switches on) the amp's protection is kicking in.
LEDs do light up on the board. The blue flashes when pairing or responding to pressing play, pause, etc on phone. I tried every possible combination with the dip switches.

Last edited by Dismantle; 29th November 2016 at 11:44 AM.
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Old 29th November 2016, 10:51 PM   #6
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I found some info on this board online. basically it needs >8v up to 24V input.
There is an instructable showing this amp with battery power bank, that uses a 5v-12v converter.
Bluetooth Speakers Powered by Power Bank - 2
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Old 29th November 2016, 11:21 PM   #7
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Quote:
Originally Posted by whizgeek View Post
I found some info on this board online. basically it needs >8v up to 24V input.
There is an instructable showing this amp with battery power bank, that uses a 5v-12v converter.
Bluetooth Speakers Powered by Power Bank - 2
It's hard to tell from the photo, but is he running the power from the battery pack's USB port to the converter, then from the converter's 5.5mm plug into the amp?

If so, I can have my battery pack's 5.5mm port open for just charging and not worry about using the splitter.

His link leads to the German store. Would either of these below work for me?

https://www.amazon.com/KUNCAN-Adjust...onverter&psc=1

https://www.amazon.com/KUNCAN-Conver...v+dc+converter
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Old 30th November 2016, 02:10 PM   #8
gec is offline gec  United States
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It sure seems like you got a bad board. A lot of the TDA7492p boards are known for turn on and turn off thumps even when they do work.

If you are willing to buy a different amp board (~$13.50) I would suggest this one instead, as several users on this site have had good luck with it (search the forums) and it does not seem to suffer from the turn on thump:

Bluetooth 4.0 TPA3116 50W+50W 2X50W Audio Receiver Amplifier Board Component | eBay

There is a modification posted on this forum to improve the noise floor but for the average user it is probably not necessary. My son uses this amp as is and it sounds great.

Just use the 12v output of your battery, it should work fine. The amp will deliver more power with higher voltage but for what you are building, you are fine. A step up converter risks adding noise.

Your speakers will work but keep in mind there are no readily available Thiele-Small parameters so you are guessing on enclosure size and type. Car audio speakers typically want a fairly large sealed enclosure (they are designed to mount on a dashboard or in a door) which may not be what you want on a desk.

IMO, the best bang for the buck for a desktop speaker right now are the 3.5" Tymphany from PE:
Peerless by Tymphany TC9FD18-08 3-1/2" Full Range Paper Cone Woofer

Build the enclosure per their specs, divided with 0.2 cu ft per driver with 1.5" ports tuned to 72hz and you will have a very nice, easy to build project that should eliminate your regret of going down this path. If you email PE, they can give you specific enclosure dimensions and port size and length (and recommend which ports to buy - flared are best). 14w x 10d x 5h (internal, and with a divider in the middle) will be in the ballpark. 1/2" thick material will keep the weight manageable. You can play around with the proportions a bit to suit your taste and to accommodate the port length required.

Good luck!

Last edited by gec; 30th November 2016 at 02:15 PM.
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Old 30th November 2016, 03:13 PM   #9
gec is offline gec  United States
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I just re-read your question about the step up converter. Keep in mind that Volts x Amps = Watts. Your 5v output is coming off of a step down converter that is limited to 2 amps. Stepping that up to 12v drops your output to less than 1 amp (or trips the internal current protection - if it has any). Just use the 12 volt, 3 amp output of the battery pack and save the 5v output for charging a phone or something. With a full charge your pack will have 12.6v and when it gets down to around 9.6v (or thereabouts) the protection board (if the battery pack has one) will shut it down until you recharge. Play time will depend on the quality / manufacturer of the cells in the pack and how close it is to 6000mah.
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Old 2nd December 2016, 11:37 PM   #10
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I went ahead and ordered the amplifier you recommended. Thank you for all the helpful information.

What are the ports for?
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