Mark brought this Custom 450A by our shop for close examination. It was previously owned by Lloyd Jones. This particular model 450A uses a 12AX7 for the preamp tube, unlike the published schematic of the 450 showing a 6EU7 for the preamp tube. I questioned this, and sure enough inside the cabinet was a factory printed schematic showing the 12AX7 for the preamp tube. Now the details, the 450A has 2 input channels (each with high & low gain). The inputs are preamped by either 6EU7 or 12AX7. Each channel has a volume control, tone control and a 3-position mellow-normal-bright switch. There is also a stereo input between the 2 channels. The vibrato uses a medium-mu 6CG7 for pitch shifting. The low frequency oscillator uses a split-mu 12DW7. The hi-mu side makes the LFO and the medium-mu side amplifies it. The input to the Hammond reverb (#25-0002) pan (dc input resistance: 172 ohms) is driven with half a 6DR7. The output (dc output resistance: 178 ohms) is amplified by a 2N306 transistor. There are controls for the vibrato speed and intensity as well as reverb return.

Another 6CG7 is used for phase inversion to drive the twin 6973 beam power tubes. HVdc is rectified by a EZ81/6CA4. An Oxford 12" speaker and oval 5"x7" midrange speaker (EIA code: 251-005) in an open-back cabinet make this a great little gig amp. Dimensions: 10-1/2" wide, 18-1/2" high, 23-1/4" long, Approx. Weight. 40 lbs. The original listed price in 1962 was $299.95

Approx. 25 Watts
Serial Number: 6319 also #30725 on cabinet
Owner: Mark LaJoie
Photo: ©1998 Zack Engineering. Used by permission.