ADC-1. Another gem hidden in a shoe box.
The first cartridge from ADC Corporation. This is a moving magnet design based on the General Electric VR and Empire 108 cartridges. Both the GE and Empire cartridges were designed by Peter Pritchard and patented by him.
The ADC-1 was introduced in 1961. It came with the .6 mil “R10” spherical stylus with a compliance of 20 cu/dyne and a VTF range of .75 – 3 grams. Audio magazine tested the cartridge and found it to have a frequency response of 10 – 20k Hz within 1.7dB and found the cartridge was able to track well at 0.9 grams VTF.
The ADC-1 MK II was introduced in 1962. The cartridge bodies appear to be the same except for the “MK II” label. The only difference I was able to find was that the MK II was 0.5 grams heavier although that could be within manufacturing tolerances. According to the published specifications, the difference appears to be in the stylus assembly. The compliance of the R10 stylus was increased to 30 cu/dyne and the VTF range was changed to 0.75 to 1.5 grams. An additional stylus was included with the MK II: The 0.35 mil “R30” spherical stylus with a compliance of 40 cu/dyne and a VTF range of 0.5 to 1.5 grams. The R30 was for “modern stereo recordings” while the R10 was to be used on records with “poor groove formation found on a few modern and most old recordings”.
Tests: The ADC-1 MK II fitted with the R30 stylus was installed on a Dual 701 turntable at 1 gram VTF and 1 unit of anti-skating force. Spherical styli don’t do well tracking inner bands of the record. I have a few records that have severe distortion on the bands closest to the spindle but the ADC played them fairly cleanly. Records with strong sibilance had severe distortion. I tried some of the tests from the Shure Obstacle Course with the following results:
Orchestral Bells – Distortion at level 3 and mistracking at level 4
Drum and Cymbal – Distortion at level 4
Bass Drum – mistrack at level 4
Violin – Distortion at level 3 and mistracking at level 4
Silbilance – Distortion at level 2 and mistracking at level 3
Definite emphasis in the bass and low mid-range frequencies. Especially noticeable with music containing electronic bass and vocal accompaniment.
Orchestral and choral music is clean. Classical music is clear and well balanced.
High frequencies are somewhat muted, but easily corrected by adjusting the tone controls.
I’ve found that a cartridge can handle 90% of commercial records if it can make it through level 3 of the obstacle course. I need to be selective with vocal recordings due to the high silbilance distortion, but orchestral and classical records sound very good.