The 28mm 8 Ohm 3W speakers…
have arrived. And so are the 5-position switches, plus other stuff not relevant to this Project such as UV Glue. From past experiences, the 3W speakers I’ve had were good enough for prop sounds. The only issue is the choice of amplifiers that must be small enough to drive them. Last but not least, you will definitely need a LiPo battery of considerable discharge capacity as they are the ones which could deliver the massive current needed. One of the tell-tale signs of insufficient battery power is the clicking sound coming from the speakers during playback.
For the want of a better Bang
During the test with only the 3W speaker and the JQ6500-16P, the sound output was quite dismal. It got slightly better when I stuck the speaker into the Toy Blaster’s original sound chamber. But this was still lacking. So when I put the speaker thought a makeshift 64mm piping (from a wires pool) with an inner diameter of 20.8mm, the change was undeniably better. The sound was no longer crinkly sharp but it felt as if it has more bass to it.
So, the next thing I did was to connect a 3W Amplifier Module which uses a PAM8403 2W Class-D Stereo amplifier. The result was just… loud. However, once I repeated the test with the makeshift pipe, the sound was awesome! Bear in mind, I am feeding a 2W audio signal from the board’s 8002A 2W into a 3W amplifier. (Maybe I need to lower the volume of the original sample too as there is a lot of clipping).
About the Battery Life thing…
OK, during standby, the JQ6500-16P will last about 4 hours and that’s it. Once you link it with the PAM8403 amplifier, that battery life could not even reach one hour. This became a very worrying fact as the 280mAH Lipo was just the right size to fit into the ammo clip of the AndersFP 3D printed PKD Blaster with my Lighting System (which can go for hours). Do I want to really explore spaces for a much bigger LiPo? Actually, to be honest, getting a 3D PKD made here in Malaysia can be an issue because one, firearms of any kind is illegal and two, the print service is not exactly cheap.
Excerpt from the PAM8403 Datasheet
“In order to reduce power consumption while not in use, the PAM8403 contains shutdown circuitry to turn off the amplifier’s bias circuitry. This shutdown feature turns the amplifier off when logic low is applied to the SHDN pin. By switching the SHDN pin connected to GND, the PAM8403 supply current draw will be minimized in idle mode. The SHDN pin can be left floating due to the internal pull-up.“
Yeah, we could be looking at a standby current of less than 1μA.
There is an option to shut off both the amplifiers. Assuming the microcontroller in the JQ6500-16P shuts down the on-board 8002A amplifier, it would be great. It does this by giving Pin 1 a HIGH signal voltage. On the other hand, the PAM8403 amplifier needs a LOW signal to shutdown. Therefore, I would need to invert the output signal of the JQ6500-16P to suit the PAM8403. I can go about creating a ‘sandwich’ adaptor PCB with additional circuitry for both modules to work together, or redesign both the MP3 & Amplifier into a single PCB. I am not too familiar with the JQ6500-24SS chip alone as I suspect it needs to be pre-programmed to work. Sadly the BOM alone would never justify the cost.
That is, assuming there is a SHUTDOWN signal coming from the JQ6500-24SS chip, which I doubt.
Image courtesy of Circuits DIY.
However, coming back to reality, I need to ask myself, at WHAT CONDITION does the 8002B amplifier shuts down? I am assuming that the said amplifier shuts down when there is no audio playback. In theory, with the whole JQ6500 module on, the LiPo battery would last even longer.
The first Magic Smoke of 2026
You know what? Let’s scrap the plans of using the PAM8403 amplifier module. I’m going to just stick to the 2W amplified output and use the JQ6500-16P as is. Just soldering the SHUTDOWN link or even the LEFT/ RIGHT output from the Voice Module can be time consuming and what with the interim PCB, it can get quite expensive too.
Filename numbering
While testing the playback sounds, I did notice that the ‘arrangement’ of each sound was out. I specifically wanted the Blade Runner PKD sounds to be on the first two Pins but they ended up as the last two. There is no software that allows me to ‘view’ the contents of the JQ6500-16P’s Flash memory. After taking a look at my own list on the Windows File Explorer, I deduced that the uploaded re-arranged the files Alphabetically. Looking at the image below, it was the only explanation since the argument does not hold even if it follows on the Date Created format.
The Whatchamacallit Chamber
OK, I am not sure what is it’s correct terminology as I’ve been calling it the echo chamber or sound chamber, which, I would surmise, is wildly inaccurate. The so-called concept is to place a speaker onto one end of a short Pipe which is then used to enhance the sound. There is a proper name for it but it escapes me. However, I would delay calling it a Pipe Speaker or Pipe Enclosure which actually sound boring.
Although the speaker’s diameter is 28mm, the closest PVC pipe I got was the 1-inch. Taking out the inner diameter of about 3.0mm, I would have about 22.4mm clearance which is, as expected, crimps on to the speaker’s surround layer. I have cut three different PVC tubes of different lengths. 35.7mm is for the bullet chamber, 79.8mm is for the inner barrel of the blaster and 63.2mm which simulated the wire spool. And as expected, each length created different final sound.
