I would love to do a handwired More, but as mentioned above there's really no way to go to larger sized components without going to a bigger box, and part of More's charm is its size. If it were in a larger box I think it would be a tougher sell as far as usefulness.
That being said there may be a way, but it would be a trade-off. More essentially has two stages, a gain stage and a buffer, but each stage has two triodes running in parallel, and that's why it uses two tubes. It would be possible to keep the circuit the same but remove the paralleled triodes, so a single triode for the gainstage and a single triode for the buffer, which would turn More into a single-tube pedal and could therefore keep the same sized enclosure while going handwired.
So what's the catch?
The catch is that tube stages run in parallel sound better, this is something I learned first from Effectrode. It turns out hi-fi and studio units have run tube stages in parallel for decades but it isn't as common in bass/guitar stuff because we favor size, efficiency, and cost. Would More still sound good without the parallel stages? Almost certainly. Would it sound the same as it does now? Absolutely not. Is it worth trying for the sake of getting a handwired More? I have no idea. Maybe.
All the posts above pretty well nailed it, but I can summarize with a neat list:
So there are pros and cons to both as you can see, but in the end I decided that 12AX7 made the most sense moving forward, and I have stuck with them. I still love the sound of the 6N21B and I still have plenty of personal 6N21B units, but it was time to transition away from them.
- 12A*7 heaters pull 300mA at 6.3V, whereas 6N21B heaters pull up to 430mA. This means that, as you would assume, they get hotter. A fully warmed up 12AX7 will feel noticeably warm, but a fully warmed up 6N21B will actually burn you. Aside from heat, that also means you'll need more power on tap from whatever power supply you're using to run these. This means that even something beefy like a Cioks will struggle with too many 6N21B pedals plugged in.
- The small 62N21B size is awesome and allowed me to put fairly complex circuits into teeny tiny boxes, but a downside to the package of the tubes is that there's no room for thick socket-friendly pins, so the thin wires of 6N21B have to be soldered into the circuit board. This isn't a huge deal for a reasonably experienced tech, but it's a bit out of reach for the average consumer. 6N21B does have the advantage that it's a Soviet military tube, so it's designed to be extremely robust and they last for decades without failing, but it's still a consideration. Consumer devices should be serviceable.
- Tubes inherently have the potential to go microphonic. This means that mechanically they are built in such a way that the vibrations from some pieces can get amplified into the signal. Modern tubes like 12AX7 are designed such that they are dampened internally to prevent microphonics, but 6N21B don't have that luxury, and are much more likely to be microphonic. There are plenty of situations where you either won't notice or won't be bothered by it, which is why people still use them today, but again, something that had to be considered.
- All tubes have an inherent "amplification factor" referred to as mu or simply µ. 12AX7 is one of the highest mu tubes I'm aware of with a mu of 100, 12AT7 is more modest with a mu of 60, and 12AU7 is way down there with a mu of 20. 6N21B comes in between 12AT7 and 12AX7 with a mu of 75 (some sources say as high as 82, but generally in the 70-80 range is what I see). This means it doesn't drive as heavy as 12AX7, so some guitarists will turn up their noses at it, but you know what else has a mu around that level? 6SL7, the tube that gives us the glorious B-15N.
- Tubes are not a perfect amplifier. A perfect amplifier on paper would have a completely flat frequency response, amplifying all frequencies in the audio spectrum at equal levels. Tubes don't do this. There are plenty of arguments on the interwebs about how subtle these differences can be, but not all tubes sound the same. There are certain brands that inherently sound different. All 6N21B (as far as I know) come from the same factory so there's no point in "rolling" them to find tonal differences, but all 6N21B inherently have a very smooth, warm boost in the lower mids with slightly rolled off highs that make them ever so pleasant sounding. If I could find a 12AX7 that consistently sounded like that, I would put it in all my pedals and all my amps.
- Procurement is a big deal. If I was just building pedals for myself and nobody else it wouldn't be as big of a deal, but I started getting nervous as build quantity went up and I knew that the world supply of 6N21B was never going to go up. Nobody makes them anymore, and while there seem to be large stores of them out there (in Russia, obviously), they will eventually run out, and I don't expect anyone to decide to make more. I'm also glad I made the swap as the tube-users of the world became aware earlier this year what can happen if you have to rely on Russia as the sole source of something.
Slow day at work today, can you tell?
Thanks so much for the detailed explanation...! Now, back to Santa wants to know...what are the ship dates for December's builds?
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