I had trouble with the Sanwu v1.1 board. It may have been flawed from the get-go, but my pushing it ended up partially killing it - bluetooth connects, but no audio. I'm pretty sure that this is the board with Chinese accented voice prompts. One advantage of the v1.1 board is thickness, the tallest component is the speaker wire socket and that can be removed. If ease is more important, XH2.54 4-Pin plugs with ~8" wires are cheap on eBay.
While I have been able to overload (causing it to reboot) the Sanwu V2.0 board at max volume, I have yet to kill it. I'm no audiophile, but this sounds as good as any other PAM8403 3 watt amplifier and the gain is just enough higher to make a difference. It pairs quickly with appropriate level audio tones (I've got another board with overly loud/distorted audio prompts) and has good reception. At less then four bucks on eBay, this is a hard to beat low power bluetooth amplifier... Which had me happy enough to forget the white noise that was noticeably gone when I switched to the KRC-86B (below). It's not much, but you can hear it in the background at minimum volume.
I got over 36hrs of runtime using a 2.5ah 18560 running through a 5v step-up. It is interesting that this is only 2hrs more than I got with the TPA3110/KRC-86B combination using the same battery running through a 9v step-up. It is also worth noting that the charger battery protection circuit was the cuttoff point (~2.5-2.6v). The TPA/KRC setup cutout at 3.25v (bluetooth minimum, not on step-up) which could mean that the TPA/KRC combo is actually more efficient. All my tests are done with the same speakers and at pretty much the same volume (relatively low).
The following includes comparisons that are likely inaccurate because I used a preexisting 8403/KRC setup that has different speakers.
...At center volume, the PAM8403/KRC-86B combination is twice as efficient (30ma) as this board (60ma). There's less relative difference at the highest volume. This board is louder, using up to 120ma, than the 8403/KRC using up to 70ma (spikes a bit higher). While the extra volume of this board is nice, the overloading/rebooting is starting to bug me (not an issue w/ the 8403/KRC).
...With a slightly different setup, running this board at 4v (directly off the battery) the draw is only 30-40ma and I can max the volume. The board will start beeping when the battery starts getting low. The trigger point depends on the volume level/load and battery voltage level. I got it to start beeping at 3/4 volume with the battery at 3.2v. The max volume is ~5db higher (79 VS 74 @ 1M from one speaker) than with the 8403/KRC. For equivalent decibel output, the 8403/KRC volume level needs to be set two (of 15) steps higher than with this board.
...After over 48hrs of running this board directly from a 2.5ah 18650 battery, beeping starts at almost maximun volume (3.25v). It looks like, at medium volume, the board consumes ~36ma (only 6ma more than the 8403/KRC). A 500mah (real capacity) battery should provide over 9hrs of runtime... The real capacity of my "500mah" Li-Po is ~332mah and it lasted 6-1/4hrs (...7:44... 7:46).
Another plus of this board is that it can be used as an alarm clock. This is possible because the amplifier shuts down when there is no audio signal... It looks like this standby mode uses ~14ma (16hrs with that 332mah battery). At ~.05w that's significantly less than most wall chargers use on standby (nothing plugged into them).
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...It appears that voltage has no noticeable effect on maximum volume. The only difference when running this setup at at 5.2v (VS 4v) is a slight decrease in current. I don't have an averaging multimeter, but it looks like ~.035 VS ~.045a at max volume (i.e. ~.18 watts for both). The maximum volume with both voltages (same song) was ~74db (1M from 1 speaker).
While I like the red board, the last ones (right) I got appear to be mistakes. I'm not sure about the caps, but the 47k ohm input resistors amount to 0 input gain (same resistance as the green board pot at its lowest setting), i.e. significantly lower amplification. Replacing the 47k ohm resistors with 10k fixed the volume level. I'd like to try something a bit smaller than 10k (e.g. 8.2k), but the next one down I had was 4.7k and that was too low.
I've been playing with more powerful amps and haven't compared the various 8403 boards, e.g. the simple green board or the one with volume control (no obvious +/-'s after brief tests of both).
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My current testing testing (of the pictured TPA3110/KRC combo) only shows that the amp is incredibly efficient, in the same ballpark as the PAM8603, over 34hrs of runtime on a 2.5ah 18650... The measured current draw is ~50ma at the testing volume. That seemed really low, but the DigiKey Battery Life Calculator says I should get 35hrs at 50ma. I have no idea how that translates to output power, but it cannot be much if it takes 1000ma to produce 7.5w.
The amp sounds good and the default gain is right where I want (just below center for everyday listening). With a full battery (~4.2v), I can crank it up without anything cutting out. However, as the battery voltage drops, cranking up the volume starves the bluetooth and it drops. Bluetooth drops permanently when the battery reaches 3.25v (exactly).
...I'm not sure why bluetooth drops when it should be getting at least 3.25v (its min), but after adding a 5v step up for the bluetooth I'm able to max the volume regardless of battery voltage. The maximum reasonable volume for the testing setup seems to be around 87db, ~8db higher than with the Sanwu 3w.... Adding the 5v step-up reduced runtime from ~34hrs to ~24hrs. Comparing the current draw I got ~100ma w/ step-up and ~70ma w/o. The two differences are consistent (~44%), but seem like an awful lot. I tried a completely different 5v step-up module and got the same result (~100ma). I also had similar losses when running the Sanwu 3w off a 5v step-up
TPA/KRC with different amp step-up boards (no KRC step-up):
At 33 x 25 x 3.5mm, it back-to-back pairs nicely with the KRC bluetooth board. Of course the audio out/in pins aren't in the same order, but two of them can line up pretty darn close. At least for my current uses, having the speaker connections at the same end is also a plus.
...The current setup replaces a 2016.5 charger/step-up with a small 9v step-up that is back to back with a 03962A charger. This setup is more compact and gains a protection circuit.
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At 30 x 25 x 2.5mm, its pretty much the same size as the TPA3110 and back-to-back paring with the KRC bluetooth works here as well (image). While I was liking this board, it has taken a back seat since I got the TPA board. The gain on this board is just too high for driving 4 ohm speakers with 9 volts. It also appears that this board is not as efficient as the TPA, at least on the low output end.
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- Re: Bluetooth and Amplifiers
- Posted by Adam on Tuesday, 22-Jan-2019
Hi Dave![ reply | link ] to this. Go to [ topic | top ]
I have a question: can I connect two 3 watts speakers, one 10 watts and one 12 watts in series to the amplifier (HW-332-C8). Each speaker has 4 ohms. And can the 3 watts speakers be in pair with the 10 or 12?
Thanks for Your advice
- Re: Bluetooth and Amplifiers
- Posted by Dave L on Tuesday, 22-Jan-2019
Theoretically, the HW-332-C8 can output 3 watts per channel with 4 ohm speakers. That's barely enough power to drive one speaker per channel. I'm pretty sure it wouldn't even work with speakers in series (2x4 ohm = 8 ohms).[ reply | link ] to this. Go to [ parent | topic | top ]