Adding Head Phone Jack to System 11 Machines

I've read a number of posts regarding how you can add a headphone jack / speaker switch to the coin do using the pinovators kit (Which looks super awesome). However each time someone asks if someone has a solution for system 11 machines none of the posts seem to have any follow up. If I am understanding this correctly it should be somewhat simple right? I would need a headphone jack, some wire, and a switch to turn off power to the speakers, oh and a small amp for volume control to the headphone jack? Has anyone else does this before? I'd like to do it on my Pinbot and Bk2k just to start as it would be super nice to only have the mechanical noises as the game music is what my wife is somehow still able to hear . What I am not sure about is which wires do I need to be connected to in order to get audio to the headphone jack. It would be awesome if a kit existed for this but I can understand given how basic the sound is on system 11 that most people wouldn't really worry about it. Thanks for any help!

#2 5 years ago

DAV

wayout440

Pinside member

First off, you can't just throw an amp in there for the headphones, depending where you tap for the headphones jack. The audio is already amplified, and you can damage the amp or even the game.

#3 5 years ago

DAV

wayout440

Pinside member

#4 5 years ago

ELD

darcangeloel

Pinside member

Quoted from wayout440:
First off, you can't just throw an amp in there for the headphones, depending where you tap for the headphones jack. The audio is already amplified, and you can damage the amp or even the game.

Fair enough, so what would be the best way to tap into the audio?

#5 5 years ago

DOG

RatShack

Pinside member

I picked up a Rollergames (System 11C) recently and I want to design my own, here's what I've figured out. This may or may not apply to earlier System 11s.

On the audio board, all the signals get mixed together and fed to a buffering op-amp. The output of this is wired to one of the pins on the volume control header. The signal goes to the volume control pot next to the tilt bob on one wire then comes back on the other. This return signal is what gets fed to the speaker amplifiers.

You can tap into the pre-amplified audio signal at the volume control on the side without the resistor and audio ground from the shield of the volume control cable.

I tapped the signal and ran it through a 10uF capacitor and 1/8" audio jack, then plugged it into a headphone amplifier. Worked great.

Note: this doesn't affect the existing speakers at all. Eventually I want to add a switch that disconnects that audio return line.

#6 5 years ago

DAV

wayout440

Pinside member

That's a fair solution

#7 5 years ago

ELD

darcangeloel

Pinside member

Quoted from RatShack:
I picked up a Rollergames (System 11C) recently and I want to design my own, here's what I've figured out. This may or may not apply to earlier System 11s.
On the audio board, all the signals get mixed together and fed to a buffering op-amp. The output of this is wired to one of the pins on the volume control header. The signal goes to the volume control pot next to the tilt bob on one wire then comes back on the other. This return signal is what gets fed to the speaker amplifiers.
You can tap into the pre-amplified audio signal at the volume control on the side without the resistor and audio ground from the shield of the volume control cable.
I tapped the signal and ran it through a 10uF capacitor and 1/8" audio jack, then plugged it into a headphone amplifier. Worked great.
Note: this doesn't affect the existing speakers at all. Eventually I want to add a switch that disconnects that audio return line.

That sounds pretty similar to system 11 a and b. If memory serves the audio off the audio board and the cpu get mixed and sent to the speakers. Do you by any chance have a picture of where you tapped the volume pot? This sounds like a fairly decent way to do this. Do you know where you got the amp from? Awesome stuff!

#8 5 years ago

ELD

darcangeloel

Pinside member

Sorry you actually explained it hahaha. Help me understand what you mean by shield however? Like is it connected to the ground braid or something? Very cool this is working.

#9 5 years ago

DOG

RatShack

Pinside member

OP
Quoted from darcangeloel:
Sorry you actually explained it hahaha. Help me understand what you mean by shield however? Like is it connected to the ground braid or something? Very cool this is working.

Shield is the outer connector on the cable, usually made of wire braid. It's silver on the volume cable.

Kind of hard to see where I got audio ground, it's connected where the resistor and volume cable shield are connected at the screw lug.
20181105_190337 (resized).jpg

#10 5 years ago

ELD

darcangeloel

Pinside member

Ah got ya. So top lug to the white wire and it looks like the ground side in that audio jack is just an unshielded stranded wire? It looks like you connect at the actual screw lug the wire and resistor connect to? Sorry if it sounds like I'm repeating you just trying to understand so I don't screw it up. hahaha

Do you remember by any chance what jack you used? Or the amp? If you had links that would be awesome! If not no worries

#11 5 years ago

ELD

darcangeloel

Pinside member

For example would this work? I'd cut the male end off and connect it to the pot. Then the volume control would already be inline and I can plug head phone into the other end? https://www.amazon.com/Headphone-Extension-NEORTX-Adjustment-Earphone/dp/B076LQF5ZZ/ref=mp_s_a_1_7

Then I'd need to put in a switch to turn off the speakers. Also I'd need to think about where mount the head phone jack but that should be but so bad

#12 5 years ago

DOG

RatShack

Pinside member

OP
Quoted from darcangeloel:
Ah got ya. So top lug to the white wire and it looks like the ground side in that audio jack is just an unshielded stranded wire? It looks like you connect at the actual screw lug the wire and resistor connect to? Sorry if it sounds like I'm repeating you just trying to understand so I don't screw it up. hahaha
Do you remember by any chance what jack you used? Or the amp? If you had links that would be awesome! If not no worries

For testing I used a regular 1/8" stereo plug wired up mono, 10uF electrolytic capacitor on the signal line. Your plugs will depend on your amp.

My test amp is a powered bookshelf speaker, it has a headphone output. You're looking for a stereo headphone amplifier.

#13 5 years ago

ELD

darcangeloel

Pinside member

https://www.amazon.com/Technical-Pro-MA2020-Amplifier-Microphone/dp/B01D4TJCB6/ref=mp_s_a_1_13

Quoted from RatShack:
For testing I used a regular 1/8" stereo plug wired up mono, 10uF electrolytic capacitor on the signal line. Your plugs will depend on your amp.
My test amp is a powered bookshelf speaker, it has a headphone output. You're looking for a stereo headphone amplifier.

Got ya! Perhaps something like this? Could I run two wires to each of the clips in the back to the pot. I'd have to power it using the service plug or externally somehow

#14 5 years ago

DOG

RatShack

Pinside member

OP
Quoted from darcangeloel:
Got ya! Perhaps something like this? Could I run two wires to each of the clips in the back from the pot. I'd have to power it using the service plug or externally somehow
amazon.com link »

Yes, something like that, though that looks like it also doubles as a speaker amplifier.

On this one, you'd need to connect the audio signal from the machine to the two RCA jacks labeled LINE INPUT.

#15 5 years ago

ELD

darcangeloel

Pinside member

Quoted from RatShack:
Yes, something like that, though that looks like it also doubles as a speaker amplifier.
On this one, you'd need to connect the audio signal from the machine to the two RCA jacks labeled LINE INPUT.

Yup that makes sense. I wonder if I should get an rca to 3.5mm then hook the wires of the 3.5mm to the pot or should I just hook up two rcas directly to the pot. Its still mono but that would make the signal output at the same time to both left and right correct. Thanks for all the help!

#16 5 years ago

KPC

Gornkleschnitzer

Pinside+ Frequent

8y 69,100 949

If new ideas are still accepted - some headphone jacks have switches at the back to sense when a headset is plugged in. You could use that switch (perhaps in conjunction with a small relay if necessary, since it's probably open when unplugged) to automatically shut off the external speakers when using the jack.

#17 5 years ago

DAV

wayout440

Pinside member

Quoted from Gornkleschnitzer:
If new ideas are still accepted - some headphone jacks have switches at the back to sense when a headset is plugged in. You could use that switch (perhaps in conjunction with a small relay if necessary, since it's probably open when unplugged) to automatically shut off the external speakers when using the jack.

Yes you could do that as well. In the first figure, the plug is not inserted, so the terminal 10 and 11 switches are closed routing the audio to the speaker. In the second figure, the plug is inserted which opens the 10 and 11 contacts thus routing the audio to the headphones.

9165 (resized).png

#18 5 years ago

DOG

RatShack

Pinside member

Quoted from wayout440:
Yes you could do that as well. In the first figure, the plug is not inserted, so the terminal 10 and 11 switches are closed routing the audio to the speaker. In the second figure, the plug is inserted which opens the 10 and 11 contacts thus routing the audio to the headphones. [quoted image]

I am trying to source a 1/4" stereo headphone jack with a NC SPST or SPDT isolated switch, like this. The preamp signal from the machine isn't meant to drive headphones directly (though you probably could in a pinch). The switch would route the signal between the headphone amp or the sound board amp.

switched jack (resized).png

#19 5 years ago

DAV

wayout440

Pinside member

Quoted from RatShack:
NC SPST or SPDT isolated switch, like this.

I'm not a parts expert, but have you tried looking for NC DPDT switched jacks? You might be able to find them easier and just use one side.

#20 5 years ago

DOG

RatShack

Pinside member

Quoted from wayout440:
I'm not a parts expert, but have you tried looking for NC DPDT switched jacks? You might be able to find them easier and just use one side.

Definitely could use one side of a DPDT. I've only searched eBay so far.

#21 5 years ago

DAV

wayout440

Pinside member

Quoted from RatShack:
Definitely could use one side of a DPDT. I've only searched eBay so far.

Try Mouser?

#22 5 years ago

MVC

Pinthetic

Pinside member

Lodi, CA

13y 49,600 265 1

Years ago Data East put a headphone accessory on games at the ACME show in Reno. It was called "Hear It" and was supplied be Incredible Technologies. It had two channel, stereo, output that could be combined into "Mono".

One method was to use an audio transformer arrangement, from "Radio Shack", attached to the speaker output and the other was a direct connect to the audio pot. The board has two audio amps, LM386, and a volume pot.

I have attached the schematic for it.

See images.

DSCF1287 (resized).JPG

DSCF1563 (resized).JPG

viewer (resized).png

#23 5 years ago

ELD

darcangeloel

Pinside member

OP
Quoted from darcangeloel:
Got ya! Perhaps something like this? Could I run two wires to each of the clips in the back to the pot. I'd have to power it using the service plug or externally somehow
amazon.com link »

Just wanted to report back on this. I hooked this up using two rcas and plugging in the amp using the service outlet (the wall wart draw is like 0.3 amps so no worries lol. However I'm happy to report it works perfectly. I am able to hear all the sounds and music very clearly and the volume control works great and both ears have audio (it is still mono but it works no problem). big thanks to everyone for where I needed to tap in order to get the audio signal.

I guess the only other thing is to install a switch to turn off the cab speakers? Should I hook this to the middle lug on the volume control pot?

I will post pictures and such once I get everything put together nicely.

#24 5 years ago

MVC

Pinthetic

Pinside member

Lodi, CA

13y 49,600 265 1

Maybe this will help:

Pot Wiring To Hear It Inputs (resized).jpg

Text 1 (resized).jpg

Text 2 (resized).jpg

#25 5 years ago

ELD

darcangeloel

Pinside member

So if I put a switch on this wire here (The middle lug on the pot) that should turn the speakers off and allow me to still use my headphones right? I think that is what returns to the audio board for volume control IE if its disconnected then the speakers wouldn't make any noise?

pasted_image (resized).png

#26 5 years ago

DAV

wayout440

Pinside member