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Thread: The correct way to add volume controls to a Yamasa machine

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    Tokie Owens ngen33r's Avatar
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    Default The correct way to add volume controls to a Yamasa machine

    I recently did a volume mod on my machine. I know there are other ways for it to be done, but this is the "correct" way according to the data sheet of the amplifier chip.

    There are 4 resistors that form a 1:2 voltage divider. If these are replaced with a 2K dual gang pot you end up with a nice clean volume control. The switch still allows for low mid and high range with folume from 0-100% in each position.

    Happy modding.



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    Sandwich Shooter browne92's Avatar
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    Default Re: The correct way to add volume controls to a Yamasa machine

    The other "correct" way to add a volume control to that circuit is to use a stereo L-pad. They go between the speaker and amplifier, and they're wired such that the amplifier always sees the correct load no matter how the volume is set.
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    Tokie Owens ngen33r's Avatar
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    Default Re: The correct way to add volume controls to a Yamasa machine

    Quote Originally Posted by browne92 View Post
    The other "correct" way to add a volume control to that circuit is to use a stereo L-pad. They go between the speaker and amplifier, and they're wired such that the amplifier always sees the correct load no matter how the volume is set.
    While I do agree 100%, that method is not as clean IMO and about 5X the cost of a dual gang pot.

    None the less it is a viable option if you want to avoid messing with SMD components and tricky soldering. It also has the added benefit of being able to cleanly mount the control to the side of the cabinet if you change volumes frequently. While you could do that with the pot conversion. The longer wires in the input lines will be subject to noise and interference.

    https://www.parts-express.com/speake...8-ohm--260-251

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    Sandwich Shooter browne92's Avatar
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    Default Re: The correct way to add volume controls to a Yamasa machine

    Quote Originally Posted by ngen33r View Post
    None the less it is a viable option if you want to avoid messing with SMD components and tricky soldering.
    That's why I mentioned it. I don't know how well those circuit boards are made or how easy they are to damage. I've worked on old pinball computer boards that were almost bullet proof, and $4 Chinese arduino boards that would lift a trace if you looked at them wrong. Circuit board quality comes in a very wide range.

    If you are going to try this mod and are unsure of your soldering skills, I recommend finding someone that is, or get some practice in first.
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