That’s insane.
I like how you stacked the transistors.
Seconded-- that’s some skillful work. Man, oh man.
In other news, still need to properly wire up my switches, but the sound issue is rectified. Thanks and cheers to all involved!
What are you sweet mother of god’ing? Spongeface’s amazing skillz?
Thanks to you for starting that thread, or I would have never built a pre-amp, which solved all my issues!
So weird. I wish I understood what’s going on there.
yea me too. Oh well, I’ve given up on that idea.
There’s two ways to use a potentiometer. You can use it as a voltage divider or as a variable resistor.
If you use it as a voltage divider, which is the most common setup, you need to have three wires going to it connected to the right pins. Were there three wires going to it?
The way the whole voltage divider thing works is this:
Imagine inside the pot is a semicircle of carbon. At one end you have say +5v attached. At the other end, you have 0v. The wiper… the thing that moves along the arc, is connected to whatever you want to adjust between +5v and 0v.
The carbon has a resistance of 10K ohms typically. This value isn’t terribly important however because the pot isn’t being used as a resistor. Instead, what happens is when the wiper is is moved, at one end you might have 0 ohms of resistance between it and 0v and 10K ohms between it and +5v, so the path to ground is easy for the electrons to travel and there’s not a lot of potential pushing back on them from the +5v end.
If that confuses you, all you really need to know is that the wires themselves have some resistance too, and this resistance can mess with the resistance ratios causing the voltage to be wrong. If all three wires have 1K of resistance for example, then not only are you not gonna get as much voltage through the pot, but now instead of there being infinitely less resistance at one end of the pot, there’s only maybe 10x less resistance at one end. Ratio = 10K / 1K. That may also reduce the voltage you get out of the pot.
So, if you want to diagnose the problem, the first things I’d check are:
A) What is the resistance of the pot? If it is 10K, you could try a 50K pot. That would increase the resistance ratio between the ends.
B) Are there three wires going to it? If not it may be being used as a resistor, though I doubt they’d design the amp that way.
C) What is the resistance of the wires? If you have a multimeter use it to measure that. It’s probably not very high, but if it is, I think using a larger gauge wire will help. Also this will tell you if there’s a break in the wire.
Please note I’m hardly an expert on this stuff, so I could be mistaken about some of the above.
Hm… forget what I said about the wire’s resistance. I just used an online table to determine that your standard wire is gonna have between 0.1 and 0.25 ohms of resistance every 10 feet. That’s miniscule compared to the resistance in the pot, so it should have no significant effect on the voltage division, or on the voltage reaching the pot.
Still, you should check to make sure there are no breaks in the wire using a multimeter. And I’m curious how many wires you had going to it. Full volume all the time could mean you didn’t have ground connected.
It’s the pot that was removed from the amp, wired up exactly as it was when ti was still connected to the board. So 3 wires.
Anyway, here’s my latest creation (actually, my first… first time ive ever used protoboard. Made a few mistakes, but it seems to work.
Takes 12V in, and spits out 2x 12V connections (one for the amp and one for the light kit), as well as a 3.3V connection for the sound chip. (I still need to get my screw terminals so I can actually hook it up).
Also included is the pre-amp circuit itself hardwired to the 12V. Figured I might as well throw it all on one board.
Holy shit, all from one board! Nice! See, this is ALMOST like what I was initially hoping for last halloween-- one board that does it all. Granted, this is still several individual and separate systems (light kit, sound kit, amp, preamp) but it’s getting closer to an all-in-one. What’d be awesome is if people reverse-engineered a single component with light, sound, amp and preamp (if need be, to rectify that pesky static issue) all on one board/system.
Nice looking preamp you got there, dude! I’ll be posting a video of mine soon so you can hear the magnificent difference, but in the meantime, you should let us hear yours!
Thanks man. It’s a bit of a mess especially since its my first time using it and I’m still not good at creating an efficient layout. But the VR works… I need my screw terminals to verify the pre-amp is working, but it worked great on my breadboard.
Doing all of this on two chips (since you probably want one in the gun) wouldnt be TOO difficult. Most of the components used are commodity, generally. Its a matter of programming the PICs mostly, something I have yet to try. I’m still VERY new to all of this electronics stuff!
That looks great!
The heat sink may not be necessary, but certainly won’t cause any problems. Does it even get warm to the touch?
Just for fun: DC Power = DC Voltage (Volts) * DC Current (Amps)
For the 3.3V regulator it should be supplying the sound module with 6mA if there is no speaker attached so the power dissipated in the Voltage regulator is only about 1/10 W = (12V-3.3V)*(0.006 Amp + ~0.006A Voltage regulator quiescent current).
The heat sink would be needed if you attached a speaker to the sound module since the current requirement would increase substantially.
One other note on the heat sink for the voltage regulator: many regulators put a voltage on the large tab that you screw the heat sink to. Be careful when mounting the board so that the heat sink does not come in contact with other pieces of metal, as they may be grounded and that would create a short circuit.
If needed, electrical insulaters can be used to electrically isolate the heat sink while still maintaining good thermal conductivity, but for a project like this it should not be an issue!
I tried both a 10k and 25k pot, with all three wires soldered into the same spots as the pot that came with the amp (which I removed). If the wiring is up to, say a foot long, there are no problems at all with the sound or controls. Just as iPV6 wanted to do, I was hoping to be able to wire up the pot in my gun box so I could control the volume there, but that required longer wiring, of course. As soon as I got the longer wiring going (using standard hookup wire), though, the sound was horrible and staticky, as if it was picking up interference. That’s why I was hoping the shielded wiring would fix the issue, but apparently it didn’t.
I’m not sure why the longer wire distance would/should make such a difference in the quality of the connection in this case, but it definitely does.
(Sorry to be hijacking your thread here, Ronnie).
Everything he said.
Wondering if a pot on the pre-amp instead might be do-able.
Sad to say, no luck. The regulator circuit worked fine, but I got a ton of distortion through the pre-amp. Likely I just botched it up somewhere (being my first time using a perfboard). The circuit worked just fine on my breadboard. I guess I’ll just have to build another.
Hm…
If the problem is interference then there’s a couple things you could try. One is a ferrite bead, and the other is a decoupling capacitor.
I’ve posted a message on the electronics forum I use to ask the fellows there what they think the best solution would be and how to wire it. Basically though, the ferrite bead is a donut shaped magnet you would place near the amp and wrap the wire around several times and it acts as a low-pass filter for noise. The decoupling cap is also a kind of low-pass filter, and you would wire it in parallel with the center wire on the pot I think, near the amp.
Basically, the idea here is the voltage in the wire is noisy… with spikes and high speed changes, due to electromagnetic interference from the electronics in your pack, and all around you. A low-pass filter smooths out these spikes and rapid changes, allowing only low frequencies… slow changes in voltage… to occur.
Perhaps, but it did work flawlessly when on the breadboard, which likely just means I did a poor job of building it. My soldering skills aren’t great (my iron tip is way too thick, too) and I had to run a lot of jumpers just because I haven’t done this enough to really get the hang on strategically placing components.
If I don’t need the heatsink on my regulator, do you think I could get away with a TO-92? It would take up a whole lot less room 
Still in discussions with the electronics guys. It seems the problem may be much more complicated than I thought. They’re talking about issues with impedance and capacitance.
I think what they’re saying is there’s probably an AC voltage rather than a DC voltage going through the pot, and the long leads impede the flow of the AC signal. This may have something to do with another thing they mentioned which is that long leads can have a capacitance, so they would in essence store a little bit of electricity and release it as needed like a capacitor which would tend to smooth signals out.
This is just my limited interpretation of the information they’re giving me though. I’m gonna read up on impedance and see what I can learn.
The distortion you guys are hearing… can you describe it more?
The following info would help:
Is the volume really loud all the time, or can you adjust the volume, but it SOUNDS like when you max out the volume on something with all the clipping and compression which happens to the sound?
Can you describe the distortion you’re hearing? Is it like what I just described, or is it just noise? Pops? Does it sound like the trebel or bass is turned all the way down? Is it just a mist, or does it have arms and legs?
Well, I’ll tell you how it sounded to me.
There was the audio of the SFX, which would be LOUD, but faint (as in, not a lot of clarity), and the rest of the sound was this crunching static noise. The video I posted at the start of this thread has it, to a small degree. There was a definite lack of bass or treble, I suppose, when I ran it through my piezos AND 3-way speakers.
The potentiometer itself; as someone else mentioned, the best way to describe that would be “little to no control”. When turned all the way DOWN, the sound was still blasting and staticy. When turned about HALFWAY, it’s at it’s quietest, and then when turned all the way UP, it was blasting and staticy again. Also of note, the volume would shift erratically when turning the pot from lowest to midway to highest. Like, “LOUD faint, getting louder LOUD LOUDER faint LOUD” all in the span of a few seconds, and all with that crunching static. Little to no control!
If we ever cross paths again, I can let you see this issue in person, all I have to do is open up my pack and remove the preamp from the configuration, and it’s right back to this sound.
Oh, right, one good turn deserves another.
I’ve heard every kind of sonic distortion known to man… but this beats the hell outta me. 