Optimus CD-3420
A Radio Shack portable CD player that took a beating better than anything else in its price class, and the magazine testers noticed.
Overview
The CD-3420 is the portable that Audio (September 1995, p.28) put at the top of its shock-resistance ranking. In a five-player shootout of portable CD players, the Optimus needed 2.5 G of force before it mistracked. That beat the Onkyo DX-F71p (2.1 G), the Magnavox AZ6848/17 (1.5 G), the Panasonic SL-S490 (1.2 G), and the Sony D-335 (1.1 G). Jogging with one of these in 1995, the Optimus was the one that kept playing.
The same review noted something else. The Optimus physically resembled the Onkyo DX-F71p closely enough that Audio (September 1995, p.31) concluded Radio Shack had contracted Onkyo to build it. So the CD-3420 wasn't a generic house-brand rebadge. It was an Onkyo design wearing a Radio Shack catalog number (42-5039, per the same review's product listing).
The anti-shock buffer was rated at 2.8 seconds in the period spec listings (HiFi-Stereo 1994, p.35). That lines up with the "3-S range" the Audio testers measured for memory duration among the non-Panasonic, non-Sony players in the group. It's not a huge buffer by later standards, but buffer length wasn't the CD-3420's strong suit. How hard you had to shake the player before the buffer even mattered was.
The DAC was a single-bit, 8-times-oversampling design, per the comparison table in Audio (September 1995, p.29). Line output measured 0.75 V rms, and headphone output was 15 mW into 32 ohms. The HiFi-Stereo (1994, p.35) listing quotes a frequency response of 5-20,000 Hz with 0.004% total harmonic distortion, 100 dB signal-to-noise ratio, 96 dB dynamic range, and 90 dB channel separation. Those are respectable numbers for a 1990s portable. The 32-ohm headphone rating means the CD-3420 was happiest with lower-impedance cans, which was the norm for the earbuds of the era.
Power came from two AA batteries, and the Audio table listed roughly 3½ hours of playback on alkalines, with no spec given for rechargeable cells. There was a NiCd charging circuit built in for an optional rechargeable battery pack, per HiFi-Stereo (1994, p.35). You could top up the pack in the player rather than pulling it out for a dedicated charger. The laser was a three-beam pickup.
The Audio testers flagged one limitation: the CD-3420 had no indicator to show when the anti-shock memory was full. Most of the other players in the group did. In practice you never quite know whether the buffer is topped off or still filling, so you just trust it. The review also noted the volume control sat close to the headphone jack, which could be awkward with right-angle plugs.
Price at launch was $199.99, per the Audio (September 1995, p.29) comparison table. That's right in line with the Magnavox at $199.95 and the Panasonic at $199.95, and well under the Sony D-335 at $359.95. The Onkyo sibling listed at $240. So the CD-3420 undercut its own Onkyo-badged twin by about forty dollars, with the same basic platform and, in the shock test, better numbers.
For collectors today, the CD-3420 is a curiosity more than a grail. It's a Radio Shack-branded product from the mid-1990s, which means parts are scarce, service documentation is thin, and the plastic-bodied portables of that era haven't aged gracefully. The Onkyo connection and the documented shock-resistance result give it a legitimate story, though.
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