Not being an audio designer, or electronics engineer, I have to rely largely on other people's designs, skill, knowledge and experience to put together something that will not; kill the builder, kill the end-user, burn or otherwise destroy property; and at the same time, sound decent and be reliable. It is therefore important that I not only use designs from people who really know what they are doing, but that I also understand the theory and design of the amp, so that I will not be simply soldering.
Not wanting to do the now conventional/standard RC approach, I decided that this amp should make use of technologies, designs, and topologies that are somewhat different. From reading the various information, it appears that the a 300B amp is best suited to its now 'classical' configuration, the Single-Ended (i.e., Class A) design. Further reading and research, suggests that the importance of the 'audio chain' begins backwards from the speaker. Taking this logical, the critical audio path, in regards to the power amp is as follows:
- Output Transformer
- Output Tube Stage
- Power Supply Stage
- Stage Coupling
- Driver Tube Stage
In regards to the output tube topology, there seems to be four designs; Direct coupling between output tube-transformer-power supply), Ultrapath, Parallel Feed and a combo of Ultrapath/Parallel Feed. My main reference is an excellent article in a back issue of Vacuum Tube Valley. This is an important area that I will explore later.
The coupling between the two stages can take place in a number of ways; direct coupling; RC coupling, transformer coupled, Loftin-White, using active (semiconductor) devices, and others. Given that capacitors are the components that colour the sound the most, it would seem logical to use or not use only with full and proper understanding of its implications. An area that deserves far more attention.
Finally, the power supply and driver stage will be looked into much more detail later.
After all of that, a preliminary list of the designs that are being seriously considered is as follows; (this may grow or shrink)