Now that I figured out what I wanted, I had to figure out how to build it. My biggest issue was how to turn the schematics into a tag board style layout. Most builders preferred tag boards for ease of maintenance and changing out parts. Unfortunately the Ampegs were built on complicated PCBs.
My initial naive approach was to try to duplicate the PCB layout as a tag board. I searched around for original documentation and found Jess Oliver who was an old time employee of the Ampeg company. He actually was in charge of designing these amps. I spoke with Jess, and he was happy to send off scans the original V22/V4 maintenance pages, with the exact PCB layout for my reference. He said there wasn't anything available for the B25 so I'd have to just work from the schematics.
Looking at how complicated the PCB was, I knew a tag board layout based on this would be a jumpered variable capacitance mess. I took what I had to my friend, Mr. Wang, the local tube guru, to seek his advice.
"Forget about all that," he told me, waving his hand in disgust. "We'll design a cleaner more efficient power stage. You'll still get around 80W. I don't think you'll need more than that. Do a good job with the pre-amp, and you'll be set."
For tubes I wanted to go the tried and true 6550 route, but he talked me out of it. He took out a battered box full of NOS RCA tubes from the 60's. "Let's use these instead," he said with a little geek twinkle in his eyes. "These are better built than any tube you'll get today, and they are 'Made in USA'. I got them from an army base supply guy in Indonesia. They'll last you 40 years."
I was a bit sceptical at first about scrapping the V4 power section for something different, but what the hell, this was DIY, maybe I'd learn something.
I read up on the 2E26 tube, and this was a tube used a lot in radio transmitters. Some audio guys had used it to good effect but it definitely wasn't de facto. As I dug a bit deeper, and looked at the specs, it turned out that the 2E26s were little brothers to the famous transmitting tube the 6146, which essentially were like 6L6s, which were a commonly used guitar tube. I was starting to feel a little better about using Mr. Wang's obscure 2E26 tubes, now that I had a better idea of what they were capable of doing.
It was interesting to see how he was approaching amp design in terms of durability, voltage specs, and availability, rather than using what was commonly used by other guys. This taught me a lot.
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