Harman Kardon HK3500

The HK3500 is a front-loading Dolby cassette recorder from Harman Kardon. Almost everything known about it comes from one thorough lab report in Modern Recording (June 1979, p.64). Norman Eisenberg and Len Feldman tested it and praised it highly. A separate review in HiFI-Stereo (July 1979, p.35) quotes Eisenberg saying he knew of no machine in its price class that rivaled it.

The review shows a thoughtful design. Harman Kardon used twin but separate record and play heads housed together in a single unit. The reviewers noted this meant azimuth alignment wasn't necessary. The deck has built-in 400 Hz and 8 kHz test tones for setting Dolby and bias. A bias trim knob lets the user adjust recording parameters to taste. The reviewers found they could extend high-frequency response on TDK UDXL II tape if they were willing to trade off a little distortion and signal-to-noise. Tape monitoring "as you record" was possible. The transport is mechanically operated rather than solenoid-controlled. The reviewers didn't penalize that, given the measured accuracy of speed and the very low wow and flutter.

In testing, the HK3500 exceeded its published response specification on some tapes and confirmed it exactly on others. The chrome tape gave better signal-to-noise. Standard tape offered a bit more midrange headroom and slightly less distortion, though distortion with either tape was very low. The deck has two line-level input options and a healthy 1.5-volt line output. The reviewers said this should interface readily with a wide range of sources and playback systems.

Past that June 1979 report, the record thins out. No original price, production years, or full specification sheet have turned up in surviving period sources.

What's genuinely known:

Front-loading Dolby cassette recorder with twin (separate) record/play heads in a single housing
Built-in 400 Hz and 8 kHz test tones for Dolby and bias optimization
Bias trim knob for user adjustment of recording parameters
Mechanical transport; tape monitoring during recording supported
Two line-level inputs; line output of 1.5 volts