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Adding a volume control to some speakers

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markronz:

--- Quote from: yotsuya on September 12, 2011, 07:20:43 pm ---I've used that same pot, but I did it inline between the sound source and the amp, not between the amp and the speaker. Your diagrams and wiring seem right on, based on what I did, but I don't know if you need any resistors inbetween.

--- End quote ---

I guess I'm not sure what you guys mean when you say the amp.  Is there an amp in my machine?   There's two pictures attached to this thread.  If you want to see high res pictures, here are links to the first two:
pic 1 high res
pic 2 high res
You can see that there are two speakers on the top part of the door.   Each of these have two wires hooked up to then.  One positive (+) and one negative (-).  All four wires just go directly to the circuit board.   In the second picture you can see there is one more additional speaker on the bottom of the door.   The bottom speaker appears to be used for the lower base type sounds.  The upper ones are the normal type speakers.   It says 8Ω 10W on the two top speakers, and it says 8Ω 20W on the bottom speaker.
So I guess I don't think there's an amp in play here, is there?


--- Quote from: BadMouth on September 12, 2011, 08:14:17 pm ---alright, found my old one (used to control the volume on the center channel speaker of my car stereo back in the 90's).

It's called an L-Pad.

Do a search on fleabay for L-Pad. 
It might be just as cheap to get a new one on there, but my offer stands.

Wiring is easy.  speaker wire in...and speaker wire out.

--- End quote ---

Thank you for the generous offer!   I was initially just trying to use these pots from Radio Shack because it was something local that I could get, and didn't have to order online.   I have heard other people have used those L-pad's before, so that may end up being what I have to do.  I believe that I would have to use one per speaker?   Any idea if that's true?  If so, I would have to get three of them, in which case it wouldn't make much sense to get your one.   I might as well just order three of them at that point, but thank you anyway for the offer!


--- Quote from: capt awesome on September 12, 2011, 08:18:22 pm ---I don't have my pachislo near me but i believe they usually have a volume control hidden inside somewhere.  I think it was just a button for low middle and high volume but don't quote me on that.  I know I turned mine down before I gave it to my dad.  check what everything does before you go and install sometyhing thats already there

--- End quote ---
In my third picture attached below, there are two volume adjustors that are on the circuit board thing in my machine.   There is no volume knob in mine, just these switches.  From what I can tell the sound has three settings:  loud, super loud, and my ears are bleeding loud.   So that's the reason why I am playing with these pots to adjust the sound instead.

Anyway, I tried to hook up my pot in the fashion I showed in my picture from before.  When I do that, it doesn't appear to work right.  When the pot is turned all the way up, the sound works at 100%.  If you turn the knob down the smallest increment possible, the sound bumps down to like 1%, barely even audible.   Then stays at 1% no matter how low you turn the pot.   So that doesn't appear to work right.

So if anyone has any ideas on what I'm doing wrong, please let me know.  Or if there's an amp somewhere I need to be looking for, please let me know that too.   OR if you think I should just pay the extra money and buy three L-pads, let me know that too!   Thanks for the help so far everyone!

markronz:
This site with the L-pad has a good wiring diagram on it
http://www.parts-express.com/pe/showdetl.cfm?&DID=7&Partnumber=260-251
It appears to match my diagram I made before.  So that's good at least, that I seem to be on the right track.  However, like I mentioned, I tried out that wiring method and it didn't work.  There was only 100% and 1%, nothing in the middle.

What I don't get is what's the difference between the L-pad I linked above, and a normal potentiometer?   Anyone know what the difference is?

I have tried this pot -- this one lets you hook up two speakers to it, just like the L-Pad appears to do:
http://www.radioshack.com/product/index.jsp?productId=2062359#
also this pot:
http://www.radioshack.com/product/index.jsp?productId=2062298
Both these pots only do the 1% or 100% thing.   

So I just don't get what I'm messing up.   I could order one or two L-pads but I don't want to do that, unless I know it will work, and there is in fact some difference between that and a normal pot.   

boardjunkie:
You need an L-pad that is intended for speaker level use. A regular pot is not rated for the low impedance of the speaker or a speaker level signal. Plus, you'll be grounding the speaker line if you turn it all the way down. This can burn up the audio amps. Not a good way to go.

A stereo L-pad is what you need. But, it'll be large (2-3" in dia).

I'm betting there's a trimpot somewhere on the board near the audio amp to set output level.

BadMouth:
I'm not sure what the difference is, other than they are a lot bigger and meant to handle the power. (and they actually work, lol)

The L-pad I have is stereo and has a small board with screw-down terminals on the side of it
with speaker + - in and + - out.  It's as simple as it gets.
It looks like two of these stacked up with a circuit board on top the terminals:


That would cover your two main speakers if the sub is tolerable.
If not, you could try putting one of these in-line with the sub:
http://www.ebay.com/itm/10pcs-Ceramic-Cement-Power-Resistor-10W-8-ohm-/370484461907?pt=LH_DefaultDomain_0&hash=item5642984153
Just make sure that it isn't generating too much heat.
Radio Shack should have them, but I couldn't find them on the website.

markronz:
There is no existing pot to turn the volume down, I can tell you that much.   Only those two dip switches.   I guess volume level is a common issue with these pachislo machines.    

I thought I did buy some pots that weren't just normal pots.  Both of those I got from radio shack were listed as "audio/volume controls" so that is why I thought they might work.

I think I will just get some L-pads.    You're right though, I should test it out to see if the base speaker volume level is tolerable on its own.  Maybe I can just get away with the one L-pad to control the two top speakers, and leave the third speaker alone.  I think I have enough information to go on now.  Thanks again for the help guys!

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