This amp was an attempt to get some of the tone of my Club Dawg in a smaller and simpler package. The Club Dawg has a 5725 tube up front followed by a 6N2P cathode follower then a tonstack. Then there is the other 6N2P triode followed by a LTP phase inverter and a pair of 6V6s. I really like how it turned out.
For this amp I got it down to 4 tubes instead of 5. I replaced the 5725 and 1/2 6N2P cathode follower by using a 6U8 up front. The 6U8 has a pentode and triode in the same bottle so I’m using the pentode as the input and the triode as the cathode follower. After the cathode follower is the tonestack.
The tone stack goes into the fist half of a 6N2P and the second half is a
cathodyne PI. I figured the fully bypassed gain stage and cathodyne would get me enough gain to drive the power tubes which are EL84s. the cathodyne has the usual tweaks like a big grid stopper before the PI and big power tube grid stoppers. It’s a little bit like an alternate take on a blackface. I chose EL84 because they drive easier than 6V6s.
Over all it came out pretty well. The pentode > cathode follower > tone stack is a great topology and I’m surprised it’s not used more.
Here is the schematic:
And here is a clip:
What power transformer did you use for this build? Thanks!
This one has the MPS PT275.2. I used that it a bunch of amps.
Great website! I’m a hobby builder as well and am about to do a build that will start via cannibalizing a bunch of parts from a VHT Special 44. Was looking around for something interesting to build. This is a candidate for sure. I’ve been pondering a topology like this for quite some time and it sounds killer. Do you have more clips of it somewhere else (e.g. Youtube)?
Very cool to see your use of the 6U8, especially as it solves the problem of the EF86-into-tone-stack conundrum that’s been bugging me for a while now. Much appreciated! Great website.