Use of Pacman SPEAKER- when wiring to stereo jack

wolfwood

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I'd like to wire the audio output from a Pacman board to a stereo jack. I do realize that the audio output should probably be attenuated if it is connected to an amplified speaker. Since Pacman is mono audio, is there any reason why I shouldn't connect SPEAKER+ through an audio attention circuit to both the left and right channels of a 3.5mm stereo jack?

In SuperGun audio attention circuits I've seen, the common pin of the stereo jack is usually connected to ground. In that case, SPEAKER- does not appear to be connected. When I look at the schematic for a Pacman board, SPEAKER- has circuitry behind it, so it feels strange not utilizing it. What role does SPEAKER- play in the audio output from the board, and is it OK to leave it unconnected? Would it be more appropriate for SPEAKER- to be connected to the common pin of the stereo jack?
 
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You can, turn the volume all the way down first. I did that on my DK cabaret to make sure it was the audio amp on the monitor that was bad. In my case I was connecting to the un-amplified audio out on the board. Pac has the amp on the board. So turn it all the way down. Also, use PC speakers, way cheaper than a stereo.

 
You can, turn the volume all the way down first. I did that on my DK cabaret to make sure it was the audio amp on the monitor that was bad. In my case I was connecting to the un-amplified audio out on the board. Pac has the amp on the board. So turn it all the way down. Also, use PC speakers, way cheaper than a stereo.
.....no? If I'm not mistaken, Donkey Kong PCBs output a line-level signal and the audio amplifier is a separate circuit board on the 20EZ monitor. What you describe sounds fine since it sounds like you were connecting a line-level output to a line-level input.

PacMan is a totally different situation because it has a speaker-level output. Anybody who follows that advice is more likely to blow-the-shit out of whatever equipment they connect it to.
 
.....no? If I'm not mistaken, Donkey Kong PCBs output a line-level signal and the audio amplifier is a separate circuit board on the 20EZ monitor. What you describe sounds fine since it sounds like you were connecting a line-level output to a line-level input.

PacMan is a totally different situation because it has a speaker-level output. Anybody who follows that advice is more likely to blow-the-shit out of whatever equipment they connect it to.

I have done it before with non line-level devices before, just turn the output volume down first. If you want to be safe connect a analog volt meter to the output and watch it jump and adjust until you peak at 1v.
 
I have done it before with non line-level devices before, just turn the output volume down first. If you want to be safe connect a analog volt meter to the output and watch it jump and adjust until you peak at 1v.

Then if its going to be a permanent installation you can measure the ohms on the volume pot, remove the pot and install a resistor in its place. This way there is no chance that the pot can be bumped and cause damage to your stereo.
Whats the purpose of this anyways? Pacs get very loud as it is. Not sure why you would want it louder than what the factory speaker will output.
 
Be careful when using any kind of 1/4, 1/8, or 3/32" headphone plug/jack. They can short momentarily when plugging in.

If you connect it directly to the amp you don't want to plug or unplug it while the power is on. If you connect it through some resistors or other type of attenuating circuit then you'll be fine.
 
Sorry, I don't think my original post was clear enough. I want to hook up the Pacman board to a Supergun type of enclosure. The enclosure will have an audio out port. When I said "stereo jack", I meant this type of connector:

2zpicuo.jpg


I already have an audio attention circuit, so the signal will be at line level.

My questions are

1) Is there any issue to wiring SPEAKER+ from the PCB to both channels (in parallel) on the connector?

2) In audio attention circuits I have seen, the common pin on the connector is always connected to ground. Why is the SPEAKER- line from the PCB never connected? Is it OK to leave it unconnected? Would it be more appropriate for SPEAKER- to be connected to the common pin of the connector?
 
My questions are

1) Is there any issue to wiring SPEAKER+ from the PCB to both channels (in parallel) on the connector?

2) In audio attention circuits I have seen, the common pin on the connector is always connected to ground. Why is the SPEAKER- line from the PCB never connected? Is it OK to leave it unconnected? Would it be more appropriate for SPEAKER- to be connected to the common pin of the connector?

1) No.

2) The speaker - is never connected because it is not ground, but the inverse of speaker +. Using it as a ground could cause damage to your amplifier.
 
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