Ok, so, this project is still entirely ones and zeros. I KNOW. Serious lack of follow through on my part. In my deference, this is where I am right now:

That little blue dot in the Atlantic has been home for the last week. Also, my wife is pregnant with our first. It's been tough to justify working on a bass amp recently. But I'm still trying to find a little time here and there, and I had an idea a while back that I'll share today!

I may have found a solution to my digital pot problems. There just don't seem to be off-the-shelf digital pots designed for this type of analog circuitry, as far as I can tell, but what is a digital pot anyway?

Its just a network of fixed resistors and transistors (if you're over-simplifying it, which I am). There are plenty of those out there for the voltages I need. So I'll just make them myself! All I should need are 1) high watt resistors (duh), and 2) transistors that a) can handle CE voltages of ±550V, and b) can be activated by logic level voltages. I've already located some transistors that fit the bill, although their audio properties remain to be determined.

Here's what I'm thinking: "pot cards". Design the digital pot onto a separate PCB that gets inserted into a socket on the main board, using a decoder to reduce the number of contacts. This way I'll be able to replace them if I screw it up somehow, or upgrade them if I decide I need something different, say a transistor with better audio qualities, more resistors for finer control, or an entirely different idea if this proves to be a terrible one. I'm planning to start with 16 steps of resolution for my test-set with Spuntone, which is very coarse but should be an adequate proof-of-concept. If the whole putting-it-on-a-card concept isn't a complete failure, I might include it on the 0.1.0 build of the D'oro and see how it goes.

I've started thinking about some design aspects that I'd like to include for the Spuntone's cabinet design. I'm not sure why I care, since I don't plan on using this amp much long term, but I feel the need to make it special somehow. I'm planning on including an interesting kick-back feature, and I've made some drawings of the full form to get an idea of what the finished product should look like (yes, more crappy hand drawings like the main picture on this project, which I don't plan on posting since they're crappy).

I'm not going to bother with timelines anymore, since they inevitably fall flat, but lets hope I can get some progress going soon. Be on the lookout for a parts-purchase update, followed by a my-first-tube-amp post.