On obtaining some very cheap ATS25/807 power tubes I then needed a schematic for the intended amp. Matt, an Electrical engineer in America, volunteered to designed an amp for me. Here is the result after a very long gestation period.

The PS is remote and generates 340V HT for the amp section. The amp connects to the PS via XLR plugs and sockets. Dissimilar gender sockets stop incorrect connections. The power tranni is Edcor and the 5H 300mA choke, Hammond. An EMI power filter is in the base with a two stage filter network. The rec tube has been replaced with a 5U4 Gold Dragon.

The bases are locally made from Australian Spotted Gum, the top and bottom plates 2mm Al and the colour "Red Delicious". Russian military inter-stage caps join driver tube - 6SN7 50 Year Treasure - and ATS25/807 power tube. 30W Edcor OPTs, wired in ultra-linear mode, connect the amp to speakers.

For an amp which only produces about 2.6W it appears to play louder than my 300BSE tested at 5W. Dynamic head room is extensive the bass extended. A good looking and excellent sounding amp.

Comments

• Mark OTL
• 28 March 2012 at 04:51AM
• Absolutely beautiful job MW. This amp is a real credit to you. Love the blue hue on the running output tubes.
  Cheers, Mark.

• Retro
• 1 June 2013 at 09:25PM
• Somehow I missed the above comment. Yes these tubes really light-up. The amp is in use every day in my second listening area. This amp sounds good with all music including my daughters dancetrance piped to in via blue tooth. It projects a huge amount of drama, very dynamic.
  
  Thanks for the nice comments.

• ross
• 5 March 2018 at 04:45AM
• nothing like looking at the '****e charge' at night!