I have been building tube amps for almost 20 years. Now I have the following amps: 300B SET, 2A3 SET, 2A3 PP, RH84, 6EA7 SET, 6L6 SE UL, EL84 PP, ST70 rebuilt. My preamps: 6EU7 RCA phono with 6CG7 line, and 12AX7 phono with 12B4 line. I've also recently experimented with SE mosfet amps. I built an ZCA amp, and a preamp with Salas NJFET phono and a SE moosefet line amp.
My daily driver is my 2A3 SET. I made all the iron in this amp: the power transformer, the choke and the two output trannies. The circuit is a copy of the JE Labs simple 2A3 with 6SL7 voltage amp direct coupled to a 6SL7 cathode follower. The output stage is straight RCA tube manual: 300 volts B+, cathode biased to 60 volts, with plate current of 60 mA. I used a mix of resistors: Allen Bradley types, carbon film and metal film. The cathode caps are Black Gates, while the coupling capacitor are Russian PIO. The 2A3s are Sovteks, the 6SL7s are Russian. For directly heated tubes, I prefer tube rectification for their slow turn on. The rectifier tube is a vintage Sylvania ST 5V4. Filter capactors are Cerafine and Sprague.
Photos show the amp, the under the hood and the scope traces at 10 kHz which shows minimal ringing. Remember that the amp does not have global feedback.
My other 2A3 amp is PP following the JE Labs 2A3 PP circuit with notable exceptions. The long tail pair is loaded by a choke I asked Edrel to wind. The bobbin is two chambered, with both coils wound such that the center tap of both coils comes from the outer layers. I think that this arrangement is similar to the Brooks 2A3 amp. Also, noting the caution in the RCA tube manual that PP 2A3s should be balanced, I took a page from the Williamson amp to balance the output tubes. Essentially, the Williamson takes a positive voltage from the cathode circuit and injects this to the grid using a potentiometer to attain balance. Finally, while I copied the voltage doubler arrangement of the JE Labs circuit, I used an indirectly heated tube rectifier as a series element for the soft start feature.
This amp uses Chinese 2A3s, and NOS 6SN7s: RCA for the voltage amp, and Sylvania for the long tail pair. The rectifier is a NOS Mullard GZ37.
Following are photos of the amp, below the hood and the scope traces of both channels at 10kHz. Remember that the amp does not have global feedback.
For many of my amps, I use aluminum channels to make my chassis. I put the channels side by side and put on wooden sides. The chassis are stiff and strong. However, the wear and tear on the chassis are easily seen in the photos, as these amps have been rebuilt at least a couple of times.