The budget mics do use the 32mm K67 capsule and the 12AX7/ECC83, the tube because it's cheap and plentiful. The Dave Thomas mod I mentioned above, replaces the capsule with his own branded C12 clone, replaces the 12AX7 with a 12AY7/6072, lowers the B+, replaces/eliminates a few capacitors, and replaces the transformer. I have a couple of those unbranded APEX 460s that I'm going to do that to, with capsules I already had on hand. --C12 knockoffs.
Also, the Gyraf is designed for a C12 capsule, and uses an EF86. I built a simpler point to point single sided version of that. The BigUgly is based on the 2001 "RoyerMod" using a 5840 triode strapped. The actual BigUgly is a multi pattern with the G7 pattern scheme, and the Royer circuit (which is a lot like the SELA and U47 circuits. I've only done a modified single sided version of that too. I also built a version of that with a 6AK5 and a knock off K47 capsule, and pleased with the results.
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