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Macintosh SE audio too *loud*?

ry755

6502
I've tried to find threads about this but all I can find is people talking about the speaker being too *quiet* with regards to capacitor issues, though that is mainly on later models. I have the opposite problem with my SE though! The speaker in my Macintosh SE (non-FDHD) is uncomfortably loud even with the volume set to 1, but seemingly only with some sounds? If I'm testing only the System 6 alert sounds, Simple Beep is pretty loud, Clink-Klank is slightly quieter, and Boing and Monkey are quiet like I'd expect them to be for a volume setting of 1. Clink-Klank almost sounds like it's ever-so-slightly louder if I click it right after clicking Simple Beep, compared to clicking it right after Boing or Monkey?

Playing a game like Mouse Stampede results in beeps and boops that sound too loud to me. Lemmings acts a little weirder, the sound effects (like the "let's go!" sound at the start of a level) are quiet like I'd expect, but then the music starts playing and it once again sounds too loud for a volume of 1.

This is the only compact Mac I've ever used so I'm not familiar with the early models, but this can't be expected behavior, right?? Previously it was also making a little *pop* sound from the speaker whenever I'd quit an application, though now it doesn't seem to be doing that.

Do different sounds (plain beep tones vs higher quality sampled audio?) go through different paths on the board and/or audio chip? I don't know anything about the Macintosh audio circuitry but it feels like it could be related to something like that.
 
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Does your volume control have any effect?

You can add a series resistor to your speaker to reduce its output.
 
Seems like normal SE audio behavior to me (loud audio, loud beeps, slightly quieter on other types of sound). The pops are also 100% normal. It's the voltage to the speaker being turned off, causing a sudden DC discontinuity. Happens after some sounds too.

As ymk wrote, you can put a resistor in series with the positive line of the speaker to reduce its volume. F.ex. those fan speed reduction adapters that are included with Noctua PC fans can be used as a quick and dirty fix.
 
Check the -12V voltage rail. I bet yours is around or even lower than -13.8V. The loud speaker sound is a typical symptom of a bad bulk capacitor at the output of the -12V rail on Mac 128/512/Plus Analog Boards. It is typically a 1000 µF capacitor that has developed high ESR and reduced capacitance. To check it, you have to remove it from the board. I replaced one on a 512K AB with a good 1200 µF capacitor, and the sound level went down considerably.
 
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Very interesting, thank you all!! I'll definitely check the -12v rail, I've been meaning to open it up and reflow some of the analog board solder joints anyways. Glad to know the pops and difference in volume are normal at least!

ymk: The volume control does indeed work.
 
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