#226 Re: Finished and working - 12 valve all DHT PP 26-71a-45
Posted: Tue Jan 01, 2019 5:39 pm
I'm a happy boy.
The 26s are both grounded Grid with droppers now. Sounded good but still buzz.
30uF cap from 45 b+ to where the virtual cathodes join and the worst of the hum disappeared. Still a buzz on the right channel.
Cap from ground to right 71A bias did nothing, but touching it to one of the grids dropped the buzz, the other made it worse. Sure enough dodgy connection on the interstage. Resoldered, buzz gone.
The amp isn't perfectly silent, but it's close. Given it's driving old Sony bookshelf speakers the sound is really good. I'll get it listenable now as it is (45 caps are just clip leaded) and put it on the lowthers. Then I can listen while I redesign the layout.
THANKS! You guys are awesome.
The 26s are both grounded Grid with droppers now. Sounded good but still buzz.
30uF cap from 45 b+ to where the virtual cathodes join and the worst of the hum disappeared. Still a buzz on the right channel.
Cap from ground to right 71A bias did nothing, but touching it to one of the grids dropped the buzz, the other made it worse. Sure enough dodgy connection on the interstage. Resoldered, buzz gone.
The amp isn't perfectly silent, but it's close. Given it's driving old Sony bookshelf speakers the sound is really good. I'll get it listenable now as it is (45 caps are just clip leaded) and put it on the lowthers. Then I can listen while I redesign the layout.
THANKS! You guys are awesome.