What is purpose of this pcb inside my Dali subwoofer?  - Page 1
Forum section: electronics / general

author: erikbrenn
author_rank: Regular Contributor
timestamp: November 02, 2023, 10:18:34 pm
content: Inside my Dali Basis Sub I see this PCB mounted on the back of the preamp board, just behind the line input RCA connectors. There is a foam pad between it and the preamp pcb. The trace around the edge is connected to ground in two placesWhat is the purpose of this? Ground plane noise suppression?

author: Icchan
author_rank: Regular Contributor
timestamp: November 02, 2023, 10:29:52 pm
content: If that's not an EMI shield, I might go back to school...It's most probably there to shield either the amplifier circuitry, or trying to prevent the amp from emitting crap all over the place.Why separate PCB? Because they did penny pinching and didn't use 4-layer boards int eh main PCB and couldn't integrate the shielding to the main PCB so it had to be separate.Metal cans are expensive, metal enclosures are expensive... so that was their solution.

author: erikbrenn
author_rank: Regular Contributor
timestamp: November 03, 2023, 12:10:07 am
content: Thanks a lot, that makes sense.While on the topic of saving money, they also used a cheap ass cable like this soldered directly to the preamp and power-amp boards, and it's broken.I'm thinking of just replacing it with a 8-pin JST type connector cable. Are there any benefits to using a flat cable like this in an audio context?

author: coppercone2
author_rank: Super Contributor
timestamp: November 04, 2023, 09:54:12 am
content: no that cable is a piece of shityou find it in things people consider cheap bull shit. its cheaper to make.The wires are a bit separated but I never seen that cable in anything but the cheapest crap

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 04, 2023, 11:39:12 pm
content: Sinclair loved that kind of flat cables. That must be telling something.(Don't get me wrong, I hugely respect the guy and his achievements, but not really for the quality of his products.)

author: coppercone2
author_rank: Super Contributor
timestamp: November 05, 2023, 04:24:59 am
content: there is twin lead made like that on purpose. maybe some people can use the impedance of that cable to some purpose. unless its connected to a RF transmitter its probobly bullshitI suspect a multi twin lead transmission cable with that specific cable specified for something that matters would be something you see in an alternative universe. Some kinda distributor.if there is something important in a parallel cable usually it has twisted pairs in it. that is a special cable that you don't want to replace with random stuff if you see it.like I would consider this special if I saw it in a device.https://www.digikey.com/en/products/detail/3m/1700-50-100SF/145552but not what you havelike something I can think of that might be touchy is a long parallel cable that goes to a LCD. It might be LVDS controlled impedance or whatever (they prone to RF radiation to fail tests). That cable you might wanna replace with something controlled, if you want to keep it absolutely in spec.

author: erikbrenn
author_rank: Regular Contributor
timestamp: November 05, 2023, 04:23:09 pm
content: Thanks for the replies, makes sense.