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Old 17th October 2008, 07:53 PM   #1
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Join Date: Feb 2006
Location: UK
Default Sumo Andromeda mods

I've recently purchased an old Sumo andromeda power amp. Before i put it into everyday use, I thought i'd make sure it was all in tip-top condition first.

I'd like to replace all electrolytics, starting with the main filter caps.

They are currenly rated at a meagre 10,000uF/50v. From what I can tell, a 350wpc into 4ohm amp should have a little more than 20,000uF per channel.

I've been looking at whats available, and I can get either 12,000, 15,000 or 22,000 that will physically fit onto the original PCB.
Brands are either:
Elna LAO or BHC Audio (12,000)
Rubycon or Nippon (15,000)
BHC 'Audio' (22,000)

I'm baffled at to which I should go for, does anybody have any suggestions? What other items should I look into upgrading while i'm there?

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Old 18th February 2009, 05:50 AM   #2
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Join Date: May 2003
Location: N. Cal
Sorry for the 5-month delay, but I just stumbled across this post.

I have the same amp, but mine is in much poorer physical condition and needs restoration. My boards are from different engineering revision levels - one has green caps like yours, the other has mostly ceramic disc caps.

I'm contemplating replacing the caps with 715P polypropylene types, and perhaps an RC snubber across the rectifier diodes. Hopefully the traces don't lift that easily. This amp uses a toroidal transformer and may also benefit from a DC blocking circuit, similar to those used on Bryston amplifiers, particularly if your house has light dimmers.

I wouldn't increase the main filter cap value that dramatically - it will increase the size of the current spikes on the transformer and diodes.

One question - in the schematic, is there any reason that the C3/C4 couldn't be lifted from ground to convert the amplifier to a balanced input?
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