Amplifier Experiment

[wibblywobbly]

I had ordered various super cheap parts from China to see what use I could put them to in an RC tank, or with scenery, and decided to sit down and figure out how to connect them today.

I used:

Clark TK22. Already had one.
Heng Long Volume Control. Already had one.
PAM8403 mini amplifier. 5 for 99p from China.
6v (4x1.5v) battery pack. Already had one.
Adjustable Voltage Regulator. LM2596S Step Down Module. 2 for 99p.
Switch for power to TK22. Already had one.
Two Visaton FR8's. Already had them.
Two HL speakers. Already had them

The HL volume control was just plugged straight into the TK22.

Two wires come out of the speaker plug on the TK22, as it is mono sound. The amp board is stereo. I therefore hooked up the negative speaker wire to GND input on the amp, and joined the Left and right inputs on the amp together, and attached them to the single positive wire from the speaker plug.

The two speakers were attached as normal to the two speaker outputs on the amp. Fiddly soldering but it was all secure.

The amp needs to be powered ideally at 5.5v. For the test I hooked up a voltage adjuster between the battery pack and the amp, and adjusted it to 5.5v output.

That was it, job done.

I tried it first with the HL speakers in case anything was going to blow up, and heck they were super loud.
I then tried the Visaton speakers, and my eardrums hurt.

With a better quality potentiometer for the volume control it would sound even better, as would a more powerful amp, Clark uses a bigger one. The total cost to do this was 70p? . I took a video, but the sound is automatically adjusted, so it doesn't come across.

I have also received two SD card players that can be hooked up to an Arduino and an amp, next little project is to find a sound player program on the web that actually works, load that onto an Arduino, then load compatible sound files onto the SD card, and see if I can get it all working. After that it's a matter of hooking up the project to an artillery gun in the battlefield scenics, and getting it to work with the IR to generate hit and fire sounds. Wish me luck!

[Max-U52]

Hey Wibbs, first, I know exactly what you mean about sound levels not coming across well on video.

That's a 3 watt amp, right? Could you do it with a bigger amp, say 20 watt? I think the TPA for the IBU is 6 watts, and with these visaton 4 inch 4 ohm 20-30 watt speakers it really does have some serious volume, but you know me - wantmorebigger!

In fact, I'm so impressed with these 4 inch speakers I'm thinking about trying to jam one in a King Tiger or Jagdtiger.

Do you think you could use an RVC with that? Having volume control from the TX can come in handy.

Are you going to put in some kind of step down so you can run off main battery and eliminate the extra battery pack?

Think you could post the video anyway? I'd really like to hear it.

[wibblywobbly]

Just been reading up on the amp. Apparently they can deliver more power to a 4ohm speaker than an 8 ohm, which is what my Visatons are. There was a 'huge' difference using the Taigen speakers, the ones with the chrome dome on the speaker, as they are lower impedence. What you cannot do with these boards is wire both stereo outputs to one mono speaker. It will blow the board.

You could use any amp you want, as long as you can power it at optimum levels. Eg a 5v amp will lose performance at 4.5v, so a 12v one will do likewise. The voltage adjusters can take a large voltage and reduce it, but it would need an inverter to take a low voltage and increase it.

It will work on any board with a speaker socket. the original volume stays where it is. I have tried it on a TK22, a 27mhz HL, a 2.4ghz HL, and one of the new RX18's with wireless volume adjustment. They all work, though the wireless one seems to play whisper quiet or full volume, nothing in between.

The effect on an RX18 with a Taigen speaker (or any 4ohm speaker) is the most noticeable. I am going to install the Leopard based RX18 in my Chieftain ARRV as I have stacks of room for the electronics in there, and it suits the tank.

I'll post up the vid, it takes a while on You Tube....

[wibblywobbly]

phpBB [video]

[Saracen]

Be very careful with these cheap LM2596S step down modules, as they are not overload or short circuit protected, and usually seem to fail in a pass-through mode, hence taking out whatever is connected to them

BTDT

Adrian.

[wibblywobbly]

You missed the logic.

The only thing connected to it is the PAM8403 amplifier, 20p each, and I have 5 of them for 99p. If it does any damage it is 20p max. It is connected to a 6v battery pack, the PAM8403 runs on 5.5v, so even with fully charged AA batteries it can only push through 6v maximum. The AA's will drop to 5.5v very quickly, so the voltage adjuster isn't handling any excess current at all, hence nothing can blow up.

I could run the voltage adjuster from the tank battery, which is 8.4v max, in which case it would need to step down from 8.4v to 5.5v, though tank batteries drop to 7.5v pretty quickly. It would cost a couple of pennies to put a resistor on the output from the voltage adjuster to ensure that the forward voltage was never more than 5.5v. Thinking about it, the super cheap way of doing it would be to simply run the PAM8403 straight off the tank battery with an inline resistor, doing away with the voltage adjuster altogether. It is only there because it is a way of adjusting the voltage correctly without faffing about with resistors while testing.

[Saracen]

> hence nothing can blow up.

If only that were true

Maybe I'm more sensitive because I've been using them to step down from the 24V main batteries in 1/6th models. Lot more possibilities for letting the magic smoke out.

I moved over to the KIM055L replacement circuits, which seem bomb proof. The first thing I do now is wire the outputs together and power them up to 24V.

If they survive that, they go in the drawer. Call it Basic Training .

Adrian.

[wibblywobbly]

Be very careful with these cheap LM2596S step down modules, as they are not overload or short circuit protected, and usually seem to fail in a pass-through mode, hence taking out whatever is connected to them

BTDT

Adrian.

You must be psychic, lol, I have just been tinkering and the damned thing is not allowing me to adjust the voltage at all. I am stuck on 5.5v from a 6v battery pack. I managed to get an Arduino hooked up to an SD card, loaded a gun fire sound on, and it plays. Snag is that when I add an amplifier into the mix I am getting huge interference that starts after the sound has played and doesn't stop, and I have no idea what is causing it...

[Jussek]

good work mate!

you minimalists!

why not use something like this?



we will do in the Panzodrom to play our battle soundtracks...

oh! and we have the DJ included, so at night, after some night tanking, we can play some music too



best regards

[HERMAN BIX]

And you wonder why I want the world expo 1/16th there !!