I built my Hafler DH-220 amp from a kit back in the 80's and it has been working flawlessly ever since. You should be careful of the kits coming in from Asia. Some have gotten mixed reviews for quality and sound. The Velleman kits are cheap but have had problems in the reviews I have read. Be careful. Check with THE PARTS CONNECTION for starters, in Canada. (www.sonicfrontiers.com/TPC) I guess that there are some kits out of U.K., and you may see kits in AUDIO ELECTRONICS mag. Give it a try, but research carefully as many kits are expensive nowadays.
