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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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Posted: 04 August 2020 at 11:30am |
At first glance it seems like a pcb from an active speaker, but its actually passive. Probably the world's most complicated. 19 transistors, 17 capacitors, 21 diodes...Why, please?
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Kevin
North Staffordshire |
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studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3863 |
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I see three sections of circuitry and three relays so I would guess....it's a three way driver protection system? But without any components that need replacing after a "protection event".
Probably making a DC rail from the AC input to power the circuitry, then sensing AC RMS voltage after the passive filters - this involving the small transistors, and then using the larger transistors to operate the relays? I've seen similar circuits that use a MOSFET as the switching element. Mind you, I usually *see* them after the MOSFET has blown!
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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csg
Old Croc Joined: 17 September 2007 Location: bedford Status: Offline Points: 6086 |
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What AC input, this is a passive network is it not?
Either way, i agree, this is complex in the extreme!
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“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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well it didn't work, the mid is blown....
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Kevin
North Staffordshire |
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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the old 'hot melt glue inside a cab' gotcha
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Kevin
North Staffordshire |
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BJtheDJ
Young Croc Joined: 28 November 2012 Location: Bristol Status: Offline Points: 884 |
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The AC input would be tapped from the speaker input, aka the output from the amplifier; hopefully no DC at all
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If your vaccinations were mandatory and nobody in your class had measles,
then you know that you're not a Millenial kid.</f |
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5483 |
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Passive networks tend to take an AC input :) Think of it as stealing a little extra from the amp into a savings account (or something, I don't know). Edit: Beaten!
Edited by odc04r - 04 August 2020 at 4:47pm |
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2515 |
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Audio is an AC signal... newsflash for those that didn't know.
So yeah it is possible to power some small signal electronics from the output of a power amp, all takes is a sustained continuous average of 5-15v, enough to produce voltage rails for the circuit after rectification and filtering... which is no problem at all for most pro power amps. This electronics could be a crossover, EQ filtering, or provide protection.
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csg
Old Croc Joined: 17 September 2007 Location: bedford Status: Offline Points: 6086 |
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Im well aware that a loudspeaker signal is AC....naturally i was talking about the lack of an input from a PSU/mains
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“The fact is this is about identifying what we do best and finding more ways of doing less of it better”
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Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7199 |
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Earplugs Are For Wimps!
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madboffin
Old Croc Joined: 03 July 2009 Location: Milton Keynes Status: Offline Points: 1537 |
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Looks like some quite clever level sensing and protection. The whole board uses high quality components, shame it fell to bits...
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2515 |
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