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Old 31st August 2003, 07:54 PM   #11
trwh is offline trwh  United Kingdom
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Hi Matt

Nice work! Are those squirrelcage fans on the heatsinks? And what is that green cylindrical thing next to the two power transformers? Some sort of supression capacitor?

One piece of constructive criticism I have, is that the 10A relays on that Velleman kit are far too small for your project. The kit is specified for use with a 300W/4R PC amp at most. I am almost certain that such a large power supply could release enough energy to weld shut the the relay contacts in the event of a catastrophic fault. In fact, I remember seeing the relays used in an old Maplin 1kW MOSFET power amp design published in the 80s, which were very large and far hevier duty than the components used in the Velleman kit. Maybe you could use the on-board relays to switch power to a larger set. Also bear in mind the advice given on Rod Elliott's page about connecting the relay contacts:

http://sound.westhost.com/project33.htm

Cheers,
Tim.
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Old 31st August 2003, 08:09 PM   #12
matth is offline matth  United Kingdom
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Hi Tim,

Yep they are squirrelcage fans, they came with the heatsinks (Ebay to the rescue). The heatsinks were originally running 48A Triacs or something similar. The green thing is a 15A mains filter.
The Amplifiers themselves have shortcircuit protection built in and will not put out more than 8A approx before the output is clamped so I should be alright. Ideally I would like bigger relays but I am under a time constraint as I have a Disco to do on Friday!!!
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Old 31st August 2003, 08:39 PM   #13
trwh is offline trwh  United Kingdom
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Hi Matt

Quote:
The Amplifiers themselves have shortcircuit protection built in and will not put out more than 8A approx before the output is clamped so I should be alright. Ideally I would like bigger relays but I am under a time constraint as I have a Disco to do on Friday!!!
If the output devices fail, the speaker load is shorted to one of the supply rails regardless of any short circuit protection, which is only effective while the output devices are intact. You need bigger relays to expect effective speaker protection in the event of such a fault.

Good luck with your disco on Friday! What are you using to drive the amp?

BTW, I'd like to see more pics of your stuff, but I can't get your link to work.

See ya,
Tim.
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Old 31st August 2003, 08:47 PM   #14
matth is offline matth  United Kingdom
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OK, point taken. I bought the kit for the turn on delay and will retrofit some bigger relays soon. The url to my website is wrong but it is a mess anyway at the moment and I really only use it for hosting pictures.
I am driving the amp with a pro mixer running through a 2way active crossover (24db LR) fromt he ESP pages built into a 1U case with my own pcb boards. It contains balenced line receivers the crossover, some output buffers and balenced line drivers. The crossover freq is 310Hz. The mids and highs are run into a 200W+200W amp based on Holtons Lateral amp and the bass is run into this amp. I will post pictures of the other componants when I have more time.
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Old 31st August 2003, 08:54 PM   #15
matth is offline matth  United Kingdom
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200w amp for mid and top speakers:
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File Type: jpg 200w amp.jpg (79.5 KB, 2489 views)
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Old 31st August 2003, 08:55 PM   #16
matth is offline matth  United Kingdom
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View of crossover boards:
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Old 31st August 2003, 08:57 PM   #17
matth is offline matth  United Kingdom
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View of crossover front panel:
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Old 1st September 2003, 08:17 AM   #18
trwh is offline trwh  United Kingdom
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Nice one Matt, thanks for the pics. Like I say, have fun on Friday!

Cheers,
Tim.
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Old 1st September 2003, 08:46 AM   #19
Bricolo is offline Bricolo  France
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Nice amp!

Don't push the volume too much, on friday night. With 1000W you could prevent me from sleeping, here in Strasbourg
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Old 1st September 2003, 11:25 AM   #20
matth is offline matth  United Kingdom
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Thanks guys,

I think a total of 1400 RMS PA and 8 Bi-amped cabs should do.
You can never have to much head room
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