How to connect an in-line volume control?

[bluelight]

Hey everyone,

I am running an audio line from my PC, to a lepai 2020a amp, and out of the amp are two positive and two negative lines running to my 2 stereo speakers for my bartop arcade.

What I am wanting to do is, connect a volume knob between the amp and the speakers. So that I can set my MAX volume that I want using the knobs on the amp, then be able to control that MAX volume and turn it down lower using a knob that will be on the outside of the cab.

I tried setting the max volume on my PC and using the amp volume to do this but it will not work as it blew another amp I bought (this is my 2nd.)  And the reason I can't setup the amp knobs to be accessible on the outside of the cabinet is my 4 year old would likely crank it to max and blow the amp again so that is the reason the max volume but be set on the amp, and be able to be turned down from there using a different knob.

Hopefully this makes sense... so the question is.. what type of knob can I use for this? I would like to be able to do this with butt connectors (same ones that hooks up to the arcade buttons and my speakers.)

I can't find anything that is inexpensive and is able to just allow the 2 channels to run through it.

There has to be a setup for this.. I would appreciate some help from anyone who may know how I can set this up easily and what I need. My goal is to do this solder free BTW.

Thanks.

[RandyT]

There are devices which act as in-line volume controls, but they aren't simple potentiometers (and usually require some soldering).  The reason you can't just use a pot is because this will change the impedance of the load , and this can make the amplifier "very angry" or even damage the outputs. 

You might be able to use a simple pot to attenuate the low level signal going into the amp.  The problem with this approach is that the noise created by the amp is a constant, so the S/N ratio goes way down.

If it's a cheap amp, the best and cheapest approach is probably to just desolder the pot and add wires so you can put the control on an external plate, but that takes some work.

[bluelight]

There are devices which act as in-line volume controls, but they aren't simple potentiometers (and usually require some soldering).  The reason you can't just use a pot is because this will change the impedance of the load , and this can make the amplifier "very angry" or even damage the outputs. 

You might be able to use a simple pot to attenuate the low level signal going into the amp.  The problem with this approach is that the noise created by the amp is a constant, so the S/N ratio goes way down.

If it's a cheap amp, the best and cheapest approach is probably to just desolder the pot and add wires so you can put the control on an external plate, but that takes some work.

Thanks but what you suggest defeats the purpose of what I want to do it for. The volume control will come after the signal comes out of the amp, between the amp and speakers. What would really be good is if they make something that speaker wires can clip into on one side and comes out of on the other side, with a pot between. There has to be something like that. But I don't think a pot being adjusted after the signal comes out of the amp would damage or effect the amp in any way but I may be wrong.

[RandyT]

I  think you are looking for something which is both simple and cheap, but in this case, neither really applies.

Something like this is what's required to do the job properly.

[bluelight]

I  think you are looking for something which is both simple and cheap, based in this case, neither really applies.

Something like this is what's required to do the job properly.

Yeah something similar to this only not in wall mount form but just in the form of a knob.even if it is a box with a knob that's OKiI can mount that. as long as the input and output is raw speaker wire I guess.

[mrclean]

https://www.radioshack.com/products/radioshack-10k-ohm-linear-taper-potentiometer?variant=5717291589

[RandyT]

https://www.radioshack.com/products/radioshack-10k-ohm-linear-taper-potentiometer?variant=5717291589

Pots are used prior to the amplifier stage in the design.  It's a cheap amp, so if it gets damaged, it's not the end of the world.  But I wouldn't use just a pot on the output side of any amp I really cared about.

[bluelight]

https://www.radioshack.com/products/radioshack-10k-ohm-linear-taper-potentiometer?variant=5717291589

Pots are used prior to the amplifier stage in the design.  It's a cheap amp, so if it gets damaged, it's not the end of the world.  But I wouldn't use just a pot on the output side of any amp I really cared about.

Why can I not use it the way I said, after the amp? And if I did,  how could that hurt the amp considering it is after the amp and one way? If what you are saying is true, fine.. Just tell me why because I don't see how the setup I described effects the amp in any way. Also, I'm not going to be careless with the amp and blow it if I can help... It was around $25 so cheap but not something I want to just flush another $25 down the toilet. I saw this pot before I posted but it doesn't seem to match what I am looking for.. Doesn't have stereo input and output sides.

[JDFan]

What cables are you using ??

Perhaps something like the Volbox ( http://gadgetunit.com/2015/07/10/review-volbox-a-simple-audio-volume-control-knob-for-anything-video/ ) if using 3.5mm connectors



OR a similar unit for RCA connections : (http://www.amazon.com/gp/product/B003FPD3IS/ref=s9_simh_gw_g422_i2_r?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=desktop-1&pf_rd_r=1SW1EMMXQCKJWXSHD5WP&pf_rd_t=36701&pf_rd_p=2079475242&pf_rd_i=desktop )

[bluelight]

What cables are you using ??

Perhaps something like the Volbox ( http://gadgetunit.com/2015/07/10/review-volbox-a-simple-audio-volume-control-knob-for-anything-video/ ) if using 3.5mm connectors

I'm using regular speaker wire. It comes out of the amp using the little holes with clips that you insert the bare wire into... Then goesto the 2 four inch car speakers and connects with butt connectors. Pretty much the bare wire but if I needed to splice or something I guess i could.

[bluelight]

What cables are you using ??

Perhaps something like the Volbox ( http://gadgetunit.com/2015/07/10/review-volbox-a-simple-audio-volume-control-knob-for-anything-video/ ) if using 3.5mm connectors



OR a similar unit for RCA connections : (http://www.amazon.com/gp/product/B003FPD3IS/ref=s9_simh_gw_g422_i2_r?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=desktop-1&pf_rd_r=1SW1EMMXQCKJWXSHD5WP&pf_rd_t=36701&pf_rd_p=2079475242&pf_rd_i=desktop )

Actually this could work.. I would just need to find maybe an adapter Cable or something.

[RandyT]

Why can I not use it the way I said, after the amp? And if I did,  how could that hurt the amp considering it is after the amp and one way? If what you are saying is true, fine.. Just tell me why because I don't see how the setup I described effects the amp in any way. Also, I'm not going to be careless with the amp and blow it if I can help... It was around $25 so cheap but not something I want to just flush another $25 down the toilet. I saw this pot before I posted but it doesn't seem to match what I am looking for.. Doesn't have stereo input and output sides.

I actually did tell you why .  Amplifiers expect a certain load on the outputs, usually 4 or 8ohms.  If you get too far away from this specification, components can overheat and die.  There's a reason why you see speaker impedance switches on some amps, as well as switches to indicate how many speakers are connected.  It's just like when using resistors (which are also loads).  If you place two 8ohm resistors in series, it's a 16ohm load.  If you place them in parallel, it's a 4ohm load.  Depending on how speakers are connected to an amp, it does essentially the same thing.  Running two 4ohm speakers in series on a single output channel of an amp designed for 8ohms is usually ok.  Doing the same with 8ohm speakers usually isn't.   

With a pot, you are adding additional load to the output, which, depending on the amp, you may (for a while) or may not get away with.  But in any event, it's not the proper way to do what you want to do.

A simple DC power supply is a good example (although not exactly the same) of how a load affects things.  It also has an "output".  If the supply is designed to power a 2amp load, but you connect 5amps worth of stuff to it without a limiting fuse, it's going to first overheat, and then start killing off components.

If you note, the RCA connector device connects at the input side, as I suggested.  One of the product questions (4th one down) is similar to what you want to do, and the answer indicates that the unit will not do it.

[JDFan]

Actually this could work.. I would just need to find maybe an adapter Cable or something.

Should be able to just attach the bare wires to a 3.5mm plug adapter ( http://www.parts-express.com/35mm-male-to-screw-terminal-connector--090-110 )

[bluelight]

Why can I not use it the way I said, after the amp? And if I did,  how could that hurt the amp considering it is after the amp and one way? If what you are saying is true, fine.. Just tell me why because I don't see how the setup I described effects the amp in any way. Also, I'm not going to be careless with the amp and blow it if I can help... It was around $25 so cheap but not something I want to just flush another $25 down the toilet. I saw this pot before I posted but it doesn't seem to match what I am looking for.. Doesn't have stereo input and output sides.

I actually did tell you why .  Amplifiers expect a certain load on the outputs, usually 4 or 8ohms.  If you get too far away from this specification, components can overheat and die.  There's a reason why you see speaker impedance switches on some amps, as well as switches to indicate how many speakers are connected.  It's just like when using resistors (whish  are also loads).  If you place two 8ohm resistors in series, it's a 16ohm load.  If you place them in parallel, it's a 4ohm load.  Depending on how speakers are connected to an amp, it does essentially the same thing.  Running two 4ohm speakers in series on a single output channel of an amp designed for 8ohms is usually ok.  Doing the same with 8ohm speakers usually isn't.   

With a pot, you are adding additional load to the output, which, depending on the amp, you may (for a while) or may not get away with.  But in any event, it's not the proper way to do what you want to do.

A simple DC power supply is a good example (although not exactly the same) of how a load affects things.  It also has an "output".  If the supply is designed to power a 2amp load, but you connect 5amps worth of stuff to it without a limiting fuse, it's going to first overheat, and then start killing off components.

If you note, the RCA connector device connects at the input side, as I suggested.  One of the product questions (4th one down) is similar to what you want to do, and the answer indicates that the unit will not do it.

Ok..  I understand what you are saying as far as pots... But just to clarify, will the 3.5 mm device that JDFan recommended not work between the amp and speaker, causing the same problem you mentioned?

The reason I am trying to do this after the amp instead of before is on my last lepai amp, I set the volume on amp and turned down the PC volume which is of course before the amp, very low. This cause something to go wrong with the amp andit stopped completely and gave me a flashing blue light from then on.. I sent it back and have a new one now. I assume it was because the signal became really weak before the amp or ssomethingso iI thought doing this after amp would be the solution. It is sounding to me there is no solution cause I want a secondary control for the amp volume (which will be set to about 50%) and that ssecondary volume will be like this.. 10 = 50% volume or max amount the amp is set to and 0 or 1 = little or no volume going to speakers.

Again, the reason this is being done is so my 4 year old can't crank the knob on the amp to 100% and mess it up.

[bluelight]

Actually this could work.. I would just need to find maybe an adapter Cable or something.

Should be able to just attach the bare wires to a 3.5mm plug adapter ( http://www.parts-express.com/35mm-male-to-screw-terminal-connector--090-110 )

Yep that's exactly what I was talking about except RandyT says it will mess up my amp so not sure now. it sounds like either this ssolution will work or nothing will to achieve my desired result. :/

[yotsuya]

I've rolled my own with an audio extension cable and a guitar pot I bought off of ebay. Works just fine.

[RandyT]

But just to clarify, will the 3.5 mm device that JDFan recommended not work between the amp and speaker, causing the same problem you mentioned?

To my eyes, the unit is simply a stacked pot with a knob in a project box, wired to a couple of 3.5mm connectors.  But I can't say for certain.  It's probably fine for the low-levels associated with devices having a 3.5mm jack.  When you start dealing with multiple watts of power, and larger amplifiers, I think the same issues (and possibly some additional ones) will present themselves.

The reason I am trying to do this after the amp instead of before is on my last lepai amp, I set the volume on amp and turned down the PC volume which is of course before the amp, very low. This cause something to go wrong with the amp andit stopped completely and gave me a flashing blue light from then on.. I sent it back and have a new one now. I assume it was because the signal became really weak before the amp or ssomethingso iI thought doing this after amp would be the solution.

That's probably not an accurate assumption.  There's no reason I can fathom that an amp would die from too low an input level.  It simply amplifies what it is given.  If the level was too high going in, possibly, but not the other way around.  Electronics die for lots of reasons, insufficient or dirty power, voltages where they shouldn't be, QC issues, poor components, whathaveyou.  You have a much better chance of messing up the amp by playing with the output side, rather than the input side.

[bluelight]

But just to clarify, will the 3.5 mm device that JDFan recommended not work between the amp and speaker, causing the same problem you mentioned?

To my eyes, the unit is simply a stacked pot with a knob in a project box, wired to a couple of 3.5mm connectors.  But I can't say for certain.  It's probably fine for the low-levels associated with devices having a 3.5mm jack.  When you start dealing with multiple watts of power, and larger amplifiers, I think the same issues (and possibly some additional ones) will present themselves.
I

The reason I am trying to do this after the amp instead of before is on my last lepai amp, I set the volume on amp and turned down the PC volume which is of course before the amp, very low. This cause something to go wrong with the amp andit stopped completely and gave me a flashing blue light from then on.. I sent it back and have a new one now. I assume it was because the signal became really weak before the amp or ssomethingso iI thought doing this after amp would be the solution.

That's probably not an accurate assumption.  There's no reason I can fathom that an amp would die from too low an input level.  It simply amplifies what it is given.  If the level was too high going in, possibly, but not the other way around.  Electronics die for lots of reasons, insufficient or dirty power, voltages where they shouldn't be, QC issues, poor components, whathaveyou.  You have a much better chance of messing up the amp by playing with the output side, rather than the input side.

Well... Maybe you are right. Maybe it was just a bad unit and I am fearing this method for no reason. I can try doing it before the amp like you said to achieve the same thing probably. I just know that I had the amp turned up to about 75% and tried to turn down the PC audio in windows and I found even with the PC volume down to like 10% it was still loud. At some point during these adjustments the amp quit and was toast. That's where my assumption came from that maybe I should do it after the amp so it wouldn't effect it. But I'm an electrical newb so I yield to you lol.

[Slippyblade]

Only time I've ever smoked an amp was when I accidentally hooked up the 12v supply to a 5v amp.  It worked GREAT for about a minute.

[Frank Drebin]

From PC

3.5mm male to RCA male




To Volume Control knob (PAC LC1)



to Amp

Male RCA to female 3.5mm, (pc amp) or male RCA to Male RCA. 





Amp can be full out or throttled for volume control, as you are throttling on the inlet side.

[keilmillerjr]

Set the amp to max volume with the computer at max volume. Then you can make adjustments with buttons. Done. You might already have a service panel mounted to your coin door.

[Phreakwars]

Don't know if you are using a newer iPac for your interface, but what I did on my son's cabinet, is set the volume on the computer to max, set the amp to where I wanted the max to be, then assigned volume up/down to 2 shift key buttons on the iPac. So when he wants to adjust the volume, all he has to do, is hold down the shift key (player 1 start), and tap fire button 4 for volume down, or 6 for volume up. It works out nicely, and no need to drill another hole for a separate volume control.

Edit: This method comes in handy for the jukebox software as well. At (PC) full blast, those Sony X-plod's rock the rec room.

[bluelight]

Don't know if you are using a newer iPac for your interface, but what I did on my son's cabinet, is set the volume on the computer to max, set the amp to where I wanted the max to be, then assigned volume up/down to 2 shift key buttons on the iPac. So when he wants to adjust the volume, all he has to do, is hold down the shift key (player 1 start), and tap fire button 4 for volume down, or 6 for volume up. It works out nicely, and no need to drill another hole for a separate volume control.

Edit: This method comes in handy for the jukebox software as well. At (PC) full blast, those Sony X-plod's rock the rec room.

to

What amp are you using?

[Phreakwars]

Don't know if you are using a newer iPac for your interface, but what I did on my son's cabinet, is set the volume on the computer to max, set the amp to where I wanted the max to be, then assigned volume up/down to 2 shift key buttons on the iPac. So when he wants to adjust the volume, all he has to do, is hold down the shift key (player 1 start), and tap fire button 4 for volume down, or 6 for volume up. It works out nicely, and no need to drill another hole for a separate volume control.

Edit: This method comes in handy for the jukebox software as well. At (PC) full blast, those Sony X-plod's rock the rec room.

to

What amp are you using?

This one:

http://www.newegg.com/Product/Product.aspx?Item=9SIA1HE2V64865

[dezmond]

If the amp has knobs on it to control volume, dissect the amp, de solder the knob, add extension wires and bob is your uncle!  Mine has volume, bass and treble. I plan to do this with mine.  Can't be too hard

[bluelight]

Don't know if you are using a newer iPac for your interface, but what I did on my son's cabinet, is set the volume on the computer to max, set the amp to where I wanted the max to be, then assigned volume up/down to 2 shift key buttons on the iPac. So when he wants to adjust the volume, all he has to do, is hold down the shift key (player 1 start), and tap fire button 4 for volume down, or 6 for volume up. It works out nicely, and no need to drill another hole for a separate volume control.

Edit: This method comes in handy for the jukebox software as well. At (PC) full blast, those Sony X-plod's rock the rec room.

to

What amp are you using?

This one:

http://www.newegg.com/Product/Product.aspx?Item=9SIA1HE2V64865

I thought I responded to this but I guess not. This is the amp I had before when I tried to turn the PC volume down, the amp quit on me. I guess it is a fluke.... you have no issues if you turn the PC volume all the way to 0? Ever had the amp stop emitting sound and then the blue LED ring around the volume just faded in and out?

I think I will try it this way again and hope for the best... the knob may be more convenient but I am using a mini-pac so I think your way will work.