Adding a volume control to some speakers

[markronz]

Hey everyone.  This is hopefully an easy question.  I recently got a pachislo machine.  The volume is too loud, as they tend to be, so I am installing a Potentiometer to use to control the volume going to the two speakers.  Attached is a picture of the speakers.   They have two wires going to each. One is clearly labeled as + and the other as -.   I am using this potentiometer, so that I can wire up both speakers to the one pot. 

I found this page here. Which shows how to wire up the pot:


So now I need to know how to use all this information to actually wire it together.   Is the negative (-) wire coming from the speaker the ground wire?  If so, is my attached wiring diagram correct how I have it set up?

[yotsuya]

Hey everyone.  This is hopefully an easy question.  I recently got a pachislo machine.  The volume is too loud, as they tend to be, so I am installing a Potentiometer to use to control the volume going to the two speakers.  Attached is a picture of the speakers.   They have two wires going to each. One is clearly labeled as + and the other as -.   I am using this potentiometer, so that I can wire up both speakers to the one pot. 

I found this page here. Which shows how to wire up the pot:


So now I need to know how to use all this information to actually wire it together.   Is the negative (-) wire coming from the speaker the ground wire?  If so, is my attached wiring diagram correct how I have it set up?

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.

[BadMouth]

Post-amp, you need something like this.....
http://www.radioshack.com/product/index.jsp?productId=3207537
You don't need one that heavy duty.

There's a name for them, but I can't remember what it is.
I have one in one of my parts bins....somewhere.
It's been there for over 10 years.  If I can find it, it's yours.

*I know nothing compared to the electronics gurus of BYOAC.  Hopefully they'll weigh in.

[BadMouth]

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.

[capt awesome]

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

[markronz]

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.

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?

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.

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!

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

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!

[BadMouth]

Both of those I got from radio shack were listed as "audio/volume controls" so that is why I thought they might work.

That just means they aren't linear in how they taper.
Never buy those as replacements for the pots in arcade controls! 

Seriously, if you are in the US, shoot me a PM with your address and I'll put this L-Pad in the mail tomorrow.

[darthpaul]

I am using L-Pads on my Pachinko machines and MAME cabinet to control volume,http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-260 they are the way to go. You may want to check out this site for any other questions you may have http://www.pachitalk.com/forums/.

[Blanka]

Aren't those L-pads getting hot? If you turn down 50watt to say 2 watt, a lot will be converted to heat.
I bet there must be an option for the line-signal too, I even expect a small screwdriver pot on the PCB. A sound amp chip is pretty easy to locate on the board. They often have a little heat dissipation unit attached.

[BadMouth]

Aren't those L-pads getting hot? If you turn down 50watt to say 2 watt, a lot will be converted to heat.

Yep, that's how they work.  The farther you turn down the L-pad, the warmer they get.
I doubt these machines have 50w amplifiers in them though.

I sent markronz the spare one I had.  It's rated for 50w per channel.
As long as he sets the sound on the machine to the lowest level first and doesn't turn the L-pad all the way down, I doubt it will get any hotter than slightly warm to the touch.

It's something to check though, before you close the machine up and forget about it.

[markronz]

Aren't those L-pads getting hot? If you turn down 50watt to say 2 watt, a lot will be converted to heat.
I bet there must be an option for the line-signal too, I even expect a small screwdriver pot on the PCB. A sound amp chip is pretty easy to locate on the board. They often have a little heat dissipation unit attached.

I swear there is no other volume control on this pachislo machine besides the two dip switches on the PCB.   But like I said, they do not lower the volume enough.  From everything I've read, this is common on these machines.

Yep, that's how they work.  The farther you turn down the L-pad, the warmer they get.
I doubt these machines have 50w amplifiers in them though.

I sent markronz the spare one I had.  It's rated for 50w per channel.
As long as he sets the sound on the machine to the lowest level first and doesn't turn the L-pad all the way down, I doubt it will get any hotter than slightly warm to the touch.

It's something to check though, before you close the machine up and forget about it.

Yeah I will definitely keep my eye on that, and won't turn down the sound all the way.  I just got back from the weekend yesterday and I did receive your L-Pad BadMouth!   Thank you so much again for sending that.   And it does look even easier to hook up than the other L-Pad's I've seen online.   + / - in and out and that's it, just like you said.  Should be a cinch!

I will hook it up soon and let you know how it works.  But before I do, I had one question.  Like I mentioned, there's three speakers.  8Ω 10W on the two top speakers, and it says 8Ω 20W on the bottom speaker.   What would happen if I wired the two 10W top speakers both up to channel 1 on your L-Pad you sent me, and then the 20W bottom speaker to the Channel 2 on the L-Pad?  Would that work?  Or would that just be bad news?   Like I said before the bottom speaker does the base sounds, and it might be ok as is without adjusting the volumes, but it might not.   So I guess I was just wondering if it was even a possibility to hook it up like that, or if I should keep it one speaker per channel?

[BadMouth]

What would happen if I wired the two 10W top speakers both up to channel 1 on your L-Pad you sent me, and then the 20W bottom speaker to the Channel 2 on the L-Pad?  Would that work?  Or would that just be bad news?   Like I said before the bottom speaker does the base sounds, and it might be ok as is without adjusting the volumes, but it might not.   So I guess I was just wondering if it was even a possibility to hook it up like that, or if I should keep it one speaker per channel?

Aren't the top speakers stereo?  Bad things could will probably happen to the amp if you ran the stero leads together!

If they are mono, or you only used the leads from one side, then it could be ok. 
If you try it that way though, wire the speakers in series (+ lead to speaker +, then - from that speaker to + on the other speaker, then - from the 2nd speaker back to the - lead).  It will put less of a load on the amp than wiring them parallel.

Personally, I'd just use the thing as it was intended.
If the sub is too loud, buy another L-Pad or see my comment above about wiring an 8ohm cement resistor in line with it.

[leapinlew]

Aren't those L-pads getting hot? If you turn down 50watt to say 2 watt, a lot will be converted to heat.
I bet there must be an option for the line-signal too, I even expect a small screwdriver pot on the PCB. A sound amp chip is pretty easy to locate on the board. They often have a little heat dissipation unit attached.

I swear there is no other volume control on this pachislo machine besides the two dip switches on the PCB.   But like I said, they do not lower the volume enough.  From everything I've read, this is common on these machines.

Thats how my machine was. The way I solved my volume problem was to sell the machine.

[markronz]

The volume knob look GREAT!  Thank you so much BadMouth!  For the time being, I think I'm going to leave the lower speaker as is.  Might have to find a resistor in the future, but we'll see. I'll cross that bridge when I get to it.  Thanks again everyone for all the help!

[venom]

Hi, from the uk   

Looks like a good forum., I  used this before for groovymame when I configured my mame/neo geo cab. Anyway I have just bought a  thunderbords 3 pachisl.  I understand that the humming noise is quite normal, but even setting the volume switch to lowest actual gameplay is too loud.  Reading this post I amgoing to try an l-pad. No radiosahck over here and also need help with the correct way to install. Hope is ok to re-open post ?

Right found what I think I need a l-pad  15 watt 8 ohm STEREO .

Does this look right

http://www.ebay.co.uk/itm/SPEAKER-L-PAD-STEREO-Part-Number-LP-200-8-/271197271977?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item3f249df7a9

I cant quite understand the way to wire it though  even from this

http://www.arnscott.com/PDF/Installation%20Sheets/L-PAD%20Stereo%20Installation.PDF

Its the top second picture I want to wire as its got two speakers in it.

I understand that I can cut the + wire to each speaker and put the wire  to  the two pin 3's. I can then run a cable from pin 2's to the + of the speakers to complete the circuit. I cant quite understand what I do with the common from the amp do I attach that to pin 1 then also put a cable from pin 1 to the - of the speaker. I.e pin 1's will have two wires soldered to it.  There are supposed to be some l-pads with screw terminals but I cant find any.

Appreciate help as never even played on the machine or know much about them before i bought it !

[Drnick]

Cut the ground lead, take a wire from Pin 1 and connect the 3 ends together.  You can use a butt connector (Halfords) or a connector strip (Poundland) to keep it neat (2 ends of ground wire in 1 side, wire from pin 1 in the other).

[venom]

cheers Drnick. Have loads of crimps from my arcade cab restore.

just for my clarity.

Cut Both grounds that currently go to the two speakers lets call them A and B

Then take one of these wires to pin 1 (A)
Insulate the other wires of e.g in terminal block (B) i.e no need to connet to the l-pad.

Then on the other pin 1 attach two wires and wire then  speaker 1 ground and speaker 2 ground.
So only using 3 wires in total.
I looked at speakers today and both have 8 ohm 10 watt wrote on them so  15 watt is more than plenty may even see if they make 10 watt ones.