SVS SB12-NSD fix

Repairs Jan 25, 2025

A short writeup, because I lost all the photo's. This is what I still remember.

I love my subwoofer. It's an SVS SB12-NSD. By now roughly 7-8 years old, but still (or again) going strong. The bass it delivers is amazing.

Problem

It was about 3 years ago, 2020 or 2021 that I sometimes heard a low volume hum. It would appear and just as quickly stop again. At first I thought it was a truck driving by, so it took me a while to locate it... It was the sub. That hum grew louder over time, until it sometimes became so loud, it would sound like an earthquake before the amp would clip and turn off.

The quick solution was to switch the sub off when I wasn't using it. So at least it wouldn't suddenly burst into noise. This because I didn't know what was causing it. A bad sub amplifier? A bad signal from my recevier? A bad cable?

At first the hum would come rarely, but the frequency with which it appeared grew. Until it would hum as soon as I switched the sub on. Sometimes I would get a short growl after which I could listen normally, but in the end it would always hum.

I tried switching the cable between sub and receiver. Connecting the sub to a different channel on my receiver. Connecting it to a different power plug (and group). And even connecting a different device instead of my receiver. Nothing worked.

I eventually contacted SVS support, but obviously my warranty had just expired. Why didn't I contact them when the problem first appeared... So they send me to a dealer, who supplied me with a quote for a new amp for 489 euro's, which was almost as much I paid for the sub.

Solution

I eventually found this video describing that the problem could be fixed by replacing the capacitors on the power input.

So I disambled the amp from the sub and looked for the capacitors. I found four instead of two, and taking no risks, I sourced both pairs from Farnell (link to Dutch site, so switch to your country before ordering).

I sourced:

Desoldering was a pain but with some help I got the capacitors (which were indeed bulging a bit on the top) removed. Soldering the new ones in place was easier and the amp could be reassembled and put back in the sub.

The sub works perfectly again. No humming or earthquakes (the ones I didn't ask for at least). And much cheaper than buying a replacement amp or sub. The 6 capacitors (I know my soldering skills, so I ordered spares) including shipping cost me roughly 10% of the new amp. I paid just shy of 45 euro's.

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