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Faulty SMSL SA300? Sub Out thuds when pressing mute.

Hotwetrat

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Mar 26, 2021
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I don't recall this happening previously but it probably did I will check.

I have an RCA splitter from the SUB OUT to 2x SB1000 Pro

When I press the mute button on the SMSL remote both the subs 'thud' kinda like a bass drum.

This happens to a lesser extent while turning the unit off and on also.

Any thoughts? Don't think it's the subs, can't surely be the cables, performance is great over all, just this issue.
 

SOUNDSONIC

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Apr 19, 2021
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Got one. Mine is just connected to a pair of Wharfedale D320. The bass is amazing even without a sub. Not experiencing the "thud" sound but there's a soft bog sound when I shift inputs. Owners also got this sound so I guess its inherent to the SA300. The amp's performance is so good I can forget or ignore that thing.
 

ASRaddict

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Apr 9, 2021
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I have the same with all channels, and my theory is that there is a DC offset at the output of the preamp, and the mute circuit is slower to disconnect the output. My amp has no DC blocking capacitor, and most likely any other protection. I did add a capacitor in series and the thud went away, and i could not hear any audio quality difference in my system. An isolation transformer worked just as well, but the cheap ones are finicky and tend to puck up hum and stray noise.
 

SOUNDSONIC

Active Member
Joined
Apr 19, 2021
Messages
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I have the same with all channels, and my theory is that there is a DC offset at the output of the preamp, and the mute circuit is slower to disconnect the output. My amp has no DC blocking capacitor, and most likely any other protection. I did add a capacitor in series and the thud went away, and i could not hear any audio quality difference in my system. An isolation transformer worked just as well, but the cheap ones are finicky and tend to puck up hum and stray noise.

Nice mod.
 
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