ACME Instruments

Nerd 🚨 Alert! Found this neat-o project in a July 1957 issue of Audio Magazine, a single transistor phono preamp, and the wacky 1.5V+3V power supply, which is tapped(?) at ground, piqued my curiosity. Also a perfect use for a bag of vintage battery holders from the recent Antique Radio Swapmeet. After listening to a couple of different transistors, I wound up sticking with the first thing I tried, a ‘pinch top’ GE 2N107, which seems close to the suggestions in the parts list. The only departures were 1/4” jacks, an input cap, and a 10K pot in the place of the collector resistor, which makes an OK gain control. Used it for guitar and bass so far, time to experiment 🔬 a bit. Surprisingly colorful and pleasing to the ear, with loads of gain and low end, two of my favorite things 🎶

It’s a tough choice, but I’m thinking I’ll scrape together an xtra 6 bones for the LOUD MOUTH. Whadda bout you?

The 1961 Fender branded Spanish 12AX7 story has taken a surprising turn! A couple knowledgeable readers of my last post were curious if there were any etched numbers on these tubes. On closer inspection 🧐 I noted not only are each of the three subtly different in their markings but there is one, just one, with four numbers etched on it. They are hard to make out and even harder to capture in a photo, but pretty clearly read 0666 👀

Given the quality of Spanish horror films I can only imagine what would happen if you played the devil’s music through this valve. In the photo, which quickly dissolves into an industrial landscape, maybe you can see the 666? Lightly overlapping on the right hand side you might also make out light white screened letters PAIN. Spooky Scary! Ran ‘em thru my tester, and true to my first impression on hearing them, two of them test on the weaker side. Not surprisingly the one marked 7025 tests very strong, better than two of the Bugle Boys! The Truth About Vintage Amps

WHAT THE WHAT!? 🤯 I love seeing new things I had no idea existed! In this case what appear to be Fender branded 12AX7 tubes from 1961 that were manufactured in Spain(a bit hard to read on the right hand one), which may well be true as never have I ever seen silver plate structures like this. Stock in ‘61 Bandmaster. I’m going to have dig up my Barcelona made CMB showman copy and check what kinda 12AX7s it has. Any black belt tube nerds out there ever spied these before? About to find out how they sound…

Never seen one of these Crest branded Magnatones before. It was close to a Starlet model, and I converted it from a power transformerless ‘widow-maker’ circuit to a more conventional Varsity #108, the step up model from the same time period. Inspiration 💯 belongs to Skip from thanks fellas! All that was needed was the addition of a power transformer, and a minimal number of other changes. I’ll get some guts shots together now that I’m done tweaking👨🏻‍🔬super happy with the results!

Portrait of a Junk Yard Dog. Cleaning out the garage and threw this together, a 50’s(?) Don McGohan M 8 PA paired with a 16 ohm(!) Philco 12”. Not sure about the cabinet, Silvertone maybe? The M 8 circuit is wacky, both triodes in the 12AX7 are grid leak biased, so it’s a dirt box! The only other grid leak second gain stage I’ve seen was in a Newcomb and it also sounded too kool to mess with. The single ended 6L6 may well be good for 8 watts too, it moves some air plugged into a 4x12! Here’s to all the Hillbilly Rigs out there