Arcade sound amplifier, 2 volume pots and and isolator.....help - diyAudio
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Old 13th January 2010, 07:30 AM   #1
Dannymh is offline Dannymh  Australia
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Join Date: Jan 2010
Default Arcade sound amplifier, 2 volume pots and and isolator.....help

OK so I bought an old run down arcade machine and started converting her over to a MAME cabinet, all well and good, but I am having issues working out the sound and specifically how it all fits together.

So the cabinet has the following
left and right speaker (wired for Mono)
a stereo amplifier (see pics)
an audio isolator
a volume pot attached to mono sound and line out of isolator
a volume pot attached direct to the isolator

Now the amplifier has 4 pins for line in (L & R) and 4 pins for out put (L & R)

This seems simple enough, and I can get sound out of all 3 speakers if I manually attach the ground etc to the output.
This allows me some control of the L & R speakers with 1 of the volume pots but

Problem 1: The volume pot does not turn the volume right down when all the way down, just partially (more on this soon)

I can live with having direct wiring and forgetting about the isolator if the volume pot were to turn the music all the way down when I turn it down, so any suggestions here?

Problem 2: The way the system had been previously wired was for the Sub to go directly to the out put of the amp, but what I cant figure out is how the isolator fits in.

The Left and right speaker are wired to the Isolator and then this has two wires coming out, one from a loop that looks to join the speakers that go intogether to give the positive signal and a ground wire that comes directly out of the PCB.

These when I got the machine were plugged directly into the Input of the amplifier, which seemed completely bizarre to me, unless they somehow got their output from the isolator?

Now if I plug everything in how it was when I got it, i get nothing, no input sound and no out put sound.

The volume pot is also wired oddly. It was wired for 1 channel (this is a dual pot) that went to the arcade gameboard (which is fine since they are mono) but the other pins on the pot were wired directly the isolator and then to the speakers.

I have attached some photos of all the parts below and I was wondering if anyone could help me solve this. In an ideal world I would wire the inputs for the volume pot and have it lead out to the isolator etc

anyway your expert thoughts would be much appreciated.
Attached Images
File Type: jpg amp_front.JPG (67.6 KB, 20 views)
File Type: jpg binput.JPG (608.8 KB, 20 views)
File Type: jpg isolator.JPG (651.2 KB, 19 views)
File Type: jpg volume_pot.jpg (624.0 KB, 17 views)
File Type: jpg wideshot.JPG (655.2 KB, 17 views)
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