Bang & Olufsen Beocord 2000

Additional Info

B&O Beocord 2000 – From The Tape recorder, June 1965

Thirty six full-page illustrations in the well-produced instruction book are devoted to the description of the many facilities offered by the Beocord 2000. This is a case where the instruction book really must be used, as an effort has been made to use universal symbols to label each control. Some of the symbols, including microphone, radio, gramophone, wind and rewind, are well known and present little difficulty in interpretation, but others, like two parallel lines with arrows at right angles, staggered or in line, to indicate ‘echo’ or ‘track to track transfer’, are a bit foxing until you have read the book and actually used the controls. Afterwards, as a reminder of the function of each button or control, they are perhaps better than printed labeling as the eye can take in a diagrammatic symbol more quickly.
The slide type mixer controls are excellent in use if the various inputs have first been adjusted so that peak recording level corresponds to nearly full setting of the slider. This means that external attenuation must be used on some inputs, for example, the radio input has a sensitivity of 2mV and has been designed to be fed from the standard DIN diode socket of Continental recorders where the diode output at the receiver volume control is attenuated to about this level. In this country, radio tuners can deliver an output of several volts with resultant violent overload of the radio amplifier in the recorder before the signal ever gets to the mixer control.
EASILY MET
The fluttergrams of fig. I show that the specification figures are easily met with RMS readings of 0.05%, 0.07% and 0.1% at 7½, 3¾ and I ips. I have provided three traces at each speed to show the extreme consistency of the readings and the flutter content. There is no discernible cumulative build-up of record and play speed imperfections, and no trace at all of cyclical speed changes due to any rotating part of the tape transport mechanism. The slight flutters shown are probably due as much to the elasticity and friction of the tape as to the tape drive.
With the Papst synchronous motor drive it goes without saying that the absolute tape speeds depend only on the mains frequency and the accuracy of the speed change mechanism. A strobe tape was used to check the speed at 7½ ips and a Philips tape-driven strobe checked the ratio of the three speeds. They were all rock steady, so that the tape speeds are exactly within the limits of the mains frequency.
Seventy, 140 and 280 uS test-tapes were played at 7½, 3¾ and I ips respectively and the level of each tone measured at the line outputs. Top and bottom tracks were identical and the responses are shown in fig. 2. It will be seen that the playback equalisation is to the desired DIN and CCIR standard characteristics to very fine limits and that the extreme low note response is maintained to the lowest frequencies on the test-tapes at all three speeds.
System noise with no tape running was 33dB below test tape level and consisted mainly of very low frequency transistor noise which could only be seen on an oscilloscope and could barely be heard on the widest range speaker with the gain at normal listening level. Weighted to match the ear’s response at low levels, the noise was 48dB below test-tape level.
The overall record play response shown in fig. 3 were taken with two different types of tape. The dotted curves are for a high coercivity Continental tape and the solid curves for a typically British tape with slightly ‘softer’ magnetic characteristics. Both tapes meet the specification responses at the two higher speeds, with a slight curtailment to 6 kHz, instead of the specified 8 kHz at I ips.
NEGLIGIBLE DISTORTION
Peak recording level, at 12dB above test-tape level, was obtained with the record level meters just indicating overload, ie the meter pointers just entering the red sector of the scale. At this level, waveform distortion was negligible, and the recorded level could be increased by a further 1dB with the Continental tape and a further 3dB with the British tape. This does not indicate any superiority of one tape over the other; a slight increase of bias would probably make the response and overload point of the Continental tape similar to the other.
The peak recording level was erased and the unweighted signal/noise ratio found to be 45dB. The weighted signal/noise ratio was 55dB.
The gliding tone record-play tests showed some head contour effects at 7½ ips, where the head dimensions were comparable to the recorded wavelength, which had been missed at the spot frequencies on the test tapes. There was also a slight fall in extreme low note response during recording.

SENSITIVE TO HUM
Listening tests on a wide-range external speaker seemed to indicate an abnormal sensitivity to mains hum on various signal sources. Tests proved that a bass rise of 6-8 dB occurred at 50Hz with the tone control set to the mid position, with the white spot at 12 o’clock and that a level bass response was obtained with the bass tone control nearly fully anticlockwise. From this level response position a bass cut of 4dB and a bass rise of 18dB was obtained at the extreme settings of the control. The treble control was level at the centre position with 12dB boost and cut at the clockwise and anticlockwise position.
COMMENT
A very smooth performer indeed! Like other top class recorders with A-B monitoring facilities, it proved very difficult to judge whether one was listening to the program directly or via the tape. Mains hum was conspicuous by its absence; I have remarked on this effect before on completely transistorised equipment; we seem to have become conditioned to a slight unobtrusive mains hum but really miss it when it isn’t there any more. I think this is the reason why the above mentioned slight mains hum from various signal sources was so obvious, apart altogether from the tone control bass rise. The tape hiss also seemed to be lower than usual, as some always seems to ‘ride in’ on recorded mains hum, but there are many other reasons why the hiss should be low; the push-pull oscillator has a very low second harmonic or DC component content, the bias and erase frequency is high at 100 kHz and the record head gap (10 microns) is relatively wide so that many more reversals of bias flux occur as an oxide particle crosses the gap. All these details add up to a noticeable improvement, although any one of them would probably not be noticed by itself.
This is definitely a recorder for the expert, and could well form the nucleus of a high fidelity installation. With 8W per channel and properly equalised plug-in preamplifiers for dynamic or crystal stereo pickups, a start could be made by adding an FM tuner and wide range speaker. A turntable, pickup and second speaker could be fitted later to give full stereo record and play facilities. Mono or stereo microphones could be added as required, and some day, who knows, the BBC may give us stereo broadcasts, so that at last the full capabilities of this recorder may be realised.
A. Tutchings.

Tape speeds
7½ , 3¾ & 1 7/8 ips
Frequency response (all 3 dB)
7½ ips: 30Hz – 20kHz
3¾ ips: 30 – 16kHz
1 ips: 50Hz – 8kHz
Wow & flutter
< 0.075% at 7½ ips, <0.11% at 3¾ ips, <0.18% at 1 7/8 ips
Signal to noise ratio
55dB
Bias frequency
100kHz
Rewind speed
170 seconds for 1800 ft tape
Audio output power
2 x 8 watts at 4 ohms
Inputs
pick-up: (magnetic) 47Kohm/2mV (ceramic) 4Mohm/40mV
radio: 5mV/100mV
mike: 200ohm/50uV
line: 50kohm/250mV
Outputs
line, speaker & headphones