A Trip Down Memory Lane

The history of tube application began with radio receivers, the telephone system, and cinema sound systems. Later, tubes began to be used in home stereo systems, and in amplifiers for electric guitars. Today, the primary markets for tubes are high-end stereo and musical instrument amplifiers. In this article Richard Honeycutt remembers his first contact with "starter" guitar amps as a teenager, progressing throughout his days as a semi-pro musician

- Richard Honeycutt

I bought my first electric guitar in 1962, at the age of 14. It had no brand name, not even a Sears-Roebuck or Montgomery Ward house brand. It was made of poplar, including the neck and fingerboard, and painted an ugly shade of yellow-green. I refinished it with a cherry-red sunburst, shading to a walnut brown on the back and edges and re-strung it. That guitar served for me to learn the differences between playing an electric guitar and playing the Silvertone arch-top acoustic that I had used up to then.

I bought the guitar and an amp for less than half the going price of a Silvertone "starter" electric guitar. The amp's maker was as anonymous as the guitar's maker. The amp itself certainly dated back to the early 1950s, or perhaps even the 1940s, because the tubes were all loctals. If memory serves, it used a 7F7 high-mu twin triode, a 7A5 beam power tube, and a 5Y3GT rectifier. The circuit was similar to that of an early Fender Princeton (Figure 1), except for the tube complement. Maximum output power from a single-ended 7A5 was about 3.3W, which in this case fed an 8" Magnavox speaker. It had one channel, one volume control, and a tone control. No tremolo or reverb. And one other prominent characteristic: hum-lots of hum.

At that point, I had studied Supreme Publications' Radio Servicing Course Book and Van Valkenburg, Nooger, and Neville's five-volume Basic Electronics course commissioned by the US Navy, so I thought that by rewiring the low-level signal path, twisting the filament leads, and adding a hum-balance potentiometer to the filament supply, I could eliminate the hum. Not so: I had yet to learn about common grounding impedance, often mis-called "ground loops," caused in the case of this amp by randomly soldering ground points to the chassis rather than using a single ground point located near the input jack. So I just tried to ignore the annoying hum for two years, until I could afford a better amp.