I have a dedicated room with a lot more invested in it than the preamp costs. No worries on that front, friends. I have not selected a Bottlehead product for cost reasons; I've selected it in preference to more expensive commercial offerings because I want both the organic richness that a 300B can bring, and the low impedance of the output buffer to drive long cables and amplifiers in parallel. Plus, I can wire an excellent remote controlled attenuator in the middle of the circuit and lose nothing for functionality. This will also be the third Bottlehead product I've owned and the fourth electronics kit I've built, so I have a pretty good idea what to expect.
The kit ships with a selection of components that are value conscious, and more can be wrung out of its excellent circuit design with a larger budget. In the context of the system it's going into, the extra dollars would not be poorly spent.
My own thoughts on the matter are:
1. I like the silver wire DH Labs made for Parts Connexion. That's definitely going in.
2. The coupling capacitors have to go. I like the older V-Cap TFTF and the newer Miflex KPCU, so I'm thinking the V-Cap ODAM would be a good choice here. They wouldn't require any additional mechanical reinforcement or relocation, and I'll only be buying 4, since I'm all SE.
3. The electrolytics in the B+ and cathode bypass seem like good candidates for replacement and the addition of low-value bypass caps. I've heard the Audio Note Kaisei are good, and expanding the chassis to use film caps is an option. There are infinite choices for bypass caps, and I lean toward trying the .1uF Duelund copper foils that are based on the Jensen tooling.
4. I do not have a good intuition for which resistors, if any, could use love. The fact that many different kinds are used in the amp, and that resistors are not generally expensive, makes me inclined to think they're probably already in a good place.
5. I don't have intuition for whether there are opportunities for meaningful improvement in the filament supply.
6. Depending on which RCA connectors ship with the kit, there might be an opportunity there.
