The suggestion for the potentiometer between the pre-amp and the amp is mainly because my cheap amp does not have a volume control… If your amp has a volume knob then there is no need to add the pot and just connect the pre-amp directly to the amp.
Ah okay cool.
I really need to get one of those pre-amps made. Should be really simple. Wish I could see the underside of that protoboard though
Nothing too exciting to see on the underside. I used the wire leads where possible for connections and had just a few additional insulated wire connections were needed.
It is just half of an inexpensive protoboard from radioshack, so there are solder pads around the holes. Since the board is only single sided, the pads are bit wimpy, so reworking a board does not always go too well.
For fun (we all have different ideas about what is fun!), I am making a small PCB but this is a simple enough circuit that building it by hand on a protoboard is not too bad.
yea ive got a bunch of those smaller protoboards. Need to build one of these myself.
Ok, one more update.
I am now trying to look into rechargeable battery packs, 'cause right now, my pack is running on TWENTY-SIX AA’s.
8 for the Jupiter Lights,
8 for the Amp,
8 for the Pre-Amp,
2 for the Crix kit.
And as GhostGuy mentioned, the amp goes through its’ batteries like, every hour and a half. I can’t keep doing this shit. :walterpeck:
After that’s successfully tested, I’ll be finally wiring in the switches, and then I’m done!
I’m working on a regulator that will let you hook up a 12v rechargable supply and get 3.3V out, so it should theoretically be able to be used for everything. The snag I’ve hit is that the circuit I’ve made comes out with a nice clean 3.3V, until you put a load on it (like Crix’s sound chip). Then it drops a bit and I get distortion. I can’t figure out why or how to fix it.
I run everything off a single 9.6V RC vehicle rechargable battery. It only lasts a few hours, so I may change over to a larger amp-hour capacity 12V battery.
My pack has separate 5V linear regulators for the pack lights and the gun lights, a 3.3V linear regulator for the sound module, and the pre-amp and amp just connect directly to the 9.6V battery.
The connection diagram I showed above has a separate battery for the sound module because that is what most people are doing. I added a 3.3V regulator so that I would only have a single battery to re-charge/swap when the pack dies.
sponge: didnt have any issues with your regulators? Got a schematic for your 3.3V?
There have been a couple of “warnings” about using regulators, for example the replica props sound module says “Do not use a voltage regulator” then goes on to state that 5V could cause permanent damage. From the several slightly conflicting data sheets I could find on the sound module, the testing and specs are done with 4.5V. There should be no problem at all with the 3.3V, the output is just less than with the recommended 4.5V, but since we are not driving the speaker directly the lower voltage should be fine. Also many people are running with and recommend 2 or 3 AA batteries, so that could be less than the 3.3V from the regulator and works fine.
You can use any old 3.3V linear regulator - just make sure it can handle the voltage that will be applied to the board. Without a direct drive to the speaker, power dissipation for the regulator should not be an issue. I chose an LM1086-3.3 since it is bullet proof and can handle up to 30V in so will be fine with most any battery pack. I also wanted to make sure it could supply several hundred mA since I may want to hook up a speaker at least to test that things are working and do not want to overload the regulator if I do that. Design overkill, but it doesn’t really cost very much more than a minimum design.
Yea I’m trying to use a 3.3V also, but I get a ton of static when I use it. None if i swap it for 2xAA. I don’t understand why. What caps did you use, if any?
Also, I tried last night to build that pre-amp, but it appears the big bag of assorted resistors I bought a while back doesnt have any 100k or 200k resistors. Back to Frys for me…
I had to swap out the LM358 for whatever Frys name brand version is.. looked it up in the book on the shelf there. Should work, but I’ll go find the datasheet to be sure the pinout is the same.
I used a 0.1uF ceramic disk on each side (in and out), and also a 22uF electrolytic on the output (regulated side). On the pre-amp board I am waiting to get back from the manufacturer, I also added another electrolytic to the input side. Depending on the regulator used and the distance to the battery, different manufacturers recommend different things. Make sure the electrolytic on the battery side (if you use one) is rated for voltages greater than the max battery voltage, which can be a bit higher than the stated voltage of the battery.
Some linear regulators are not stable and can oscillate if you do not have any decoupling caps, so maybe that is the issue. I have always liberally applied decoupling and have not run into that problem.
Depending on what you are comparing, using separate batteries for the sound module allows the grounds for the sound module and the pre-amp to be separate. Once you use the regulator on the same battery to provide power to the sound module, the grounds will be tied together. This common ground and fewer batteries is what really drives the need for the pre-amp, unless you have an amp with differential inputs (most don’t). A simple check would be to use the separate batteries, but tie battery packs’ negative leads together (“grounds”) and see if the static returns. You should also check to see if the output voltage is near the 3.3V to make sure the regulator is hooked up properly.
The 200K values are somewhat arbitrary. If you use something significantly different, you may need to change (inversely proportionate) the 50pf filter cap (47pf is more common and close enough).
I do miss having a Frys nearby. I just have to order everything/anything and wait…
Frys is so expensive though. As long as I’m in no rush I definitely prefer to just order online.
I definitely get 3.3V out of my regulator… until I put the sound chip on it, and then it fluctuates 3.25-3.28 or so, IIRC.
I’ve been using 10uF on the input, 10uF on the output, and 0.1uF ceramic on the output (I read that electrolytic caps suck at dealing with high frequencies, so the ceramic is there to just smooth it out). I think the caps I’m using are 50V but I’ll have to double check when I get home.
Interesting thought on the grounds. I’m trying to visualize how I should hook that up to test…
Maybe I’ll also try using the same size caps as you.
I need to get that pre-amp wired up, though! In the last couple images of your protoboard, the resistors all appear to be the same value (unless my screen is playing tricks with the colors). I’ve only ever built stuff on a breadboard (VERY new to electronics) so I’m also having a difficult time visualizing how to connect the components together on the underside (that’s why I mentioned wanting to see the bottom)
Thanks for your patience, I know from a wealth of experience in another field that it can be frustrating at times helping noobs with something way over their head 
This is somewhat schizophrenic - I originally used 4.5V regulation for the sound module to get the most volume out of the sound module’s speaker driver and that was where the 100K and 200K ohm resistors were used to actually lower the gain. Then the request was for a sound module running off of 2 AAs, so I wanted more gain and decided that having all of the resistors the same value would make things easier. For a 3.3V reference on the sound module it could be somewhere in-between. The output usually goes through some volume control, so as long as we are close there should not be a problem. The 200K on the input along with the cap form a low pass filter, so those could be left alone and just the two 100K ohm resistors can be adjusted to change the gain with little affect on the filter.
The voltage changing just a little should not be a big deal - it is fairly small and differentially there should be decent common mode rejection, so hopefully very little of it would be seen differentially. Of course frequency content can also play a role, but that is hard to characterize with a voltmeter.
For caps, if you care about high frequencies, you can also use tantalums or some low ESR electrolytics if you want to skip adding the 0.1 ceramics. Those caps can cost more than just adding the ceramic and for this application either should be fine. And surface mount caps are significantly better (much lower lead inductance), but not as easy to work with for hand soldering on breadboards!
I don’t have pictures for that board, but basically I placed the parts so that I could use the leads as wires - just fewer wires to cut, strip and solder to make the connections. I looked through my build photos and I do have pictures of the thrower’s board top and bottom. This was packed, so I ended up putting some resistors and a cap on the bottom just to get it all to fit…
Here is the component side (PICs not loaded into the sockets yet):
And here is the wiring side:
The little pre-amp board has a lot less connections, so would not look as messy…
Oh my god that is a thing of beauty! I bow to you, good sir!
Thanks for the suggestions, I’ll try to work something out in the next couple days.
okay so… the regulator works great. i get a nice clean sound when the chip is connected.
But… only if the amp isnt powered using the same 12V source as the VR and chip. as soon as i connect the amp to the same battery, static. Think the pre-amp would fix that?
Yes, yes it will 
Sweet mother of God.