Country of Manufacture:USA
Release dates:1949 - 1952
Speeds: 7 1/2
Max Reel Size("): 3"
Number of heads: 3
Head Composition: Permalloy
Head Configuration: Mono - Full Track
Frequency Response:(all 3 dB): 7½ ips: 100 to 5kHz
Sound quality rating:6 / 10
Long-term reliability rating: 6/ 10
Made by The Brush Development
Company, 3405 Perkins Ave, Cleveland Ohio, this “Soundmirror”
was one of the first (if not THE first) domestic tape recorders made in
the the United States (or anywhere else for that matter).
Designed to use magnetically coated quarter inch PAPER tape, (although
the later conventional plastic tape would be OK as well) the BK401 was
a three-motor, full-track mono recorder with a single speed of 7½
Frequency response was about 100 to 5kHz only.
A five-watt amplifier drove a front mounted six inch round PM speaker,
record bias was 30kHz and record level was shown by a 6E5 magic eye tube.
The simple pushbutton transport controls consisted of forward, reverse,
start, stop and record, with a tone control and playback volume, record
level and record/play mode selector switch.
Valve complement: 6SJ7 x 2 (A.F.amps), 6SN7GT x 5 (A.F. amp, oscillator & bias, erase amp power output & A.F. phase inverter), 1 x 5Y3GT (rectifier), 1 x 6E5 (magic eye) / Audio output power: 5 watts / Speaker(s): 6″ front mounted / single-track mono