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From: stevesaf@microsoft.com (Steve Safarik)
Subject: Re: DIY: World Audio kits
Date: Thu, 17 Feb 1994 23:31:30 GMT

:Does anybody have any experience of the World Audio kits, particularly
:the 20W valve (K5881?) power amp. It retails at 395ukp and I believe is
:loosely based on the Mullard 520 amp. Any comments?

I built the amp using their schematic, but not from their kit.  I located
all the parts, etc, myself and it came out very nice.  I also made mine
parallel push-pull, so it has twice the watts.  If you want to build a tube
amp, I'd highly recommend this one.  It took me 6-8 months to find all the
parts, and the kit is probably a better way to go for most people.

However, their latest version of the kit does not operate in ultra-linear
mode, and I'm not sure that that is the way to go.  It depends on the
output transformer having an ultra-linear tap, and since theirs doesn't,
there's no way you can convert the amp to use it.  I'm pretty convinced that
ultra-linear operation is better, but I think they may have been deluded
into thinking the other way (although that is a matter of debate) by Peter
Qvortrup.  Other than not having an ultra-linear tap, their output transformer
is supposed to be very good.  Their kit also uses a triode first stage, and 
the original design called for a pentode (which I used).  

I'm _very_ happy with how mine came out, and learned a lot in the process of
building it.  My cost came out around $850 for the stereo version, case and
everything else (except time, of course) included.

Steve.