Technical Details
Brand: Ampex
Model:MR-70
Category:Super High Fidelity
Application:Studio
Electronics:Tube
Equalization:IEC
Country of Manufacture:USA
Release dates:1966 - 1969
Original Price: $5175
Tracks:1/2 Rec/PB
Speeds: 7 1/2, 15, 30
Max Reel Size("): 10.5"
Number of heads: 3
Dimension: Transport 19 x 24½ x 12"
Head Composition: Permalloy
Head Configuration: Stereo
# Motors: 4
Auto Reverse?:No
Voltage(s): 110-120v
Outputs: XLR, XLR Balanced
Frequency Response:15 IPS - 50 Hz-15,000 Hz
Wow and Flutter:30 and 15 IPS - .05%
Signal-to-Noise Ratio:15 and 7.5 IPS - 65 dB
Sound quality rating:10 / 10
Long-term reliability rating: 9/ 10
Weight: Transport 130 lbs - Pre's 27 lbs/ea.
Additional Details
Description
It is rumoured that the Ampex MR-70 was specially built for Capitol Records so that they could master Beatles recordings from EMI England for the local market. Whether this is true or not, everyone seems to agree that the MR-70 was the best Ampex analog recorder ever made, even Willi.
Cost was not an issue when designing this state-of-the-art recorder. In 1965, the year of its release, a standard MR70 quarter-inch two-track cost $5175 and $5625 in console format .
Highly modified Ampex 300 transports were used for the MR-70. Massive die-case frames designed to tight tolerances permitted the heads to be mounted for fixed azimuth. Transport features included a viscous-damped reel idler, vari-speed fast wind and constant tension tape supply. Fast, positive starts were enabled by supplying power boost to reel idler and take-up motors during start function.
The electronics utilised military/industrial grade 7587 & 7895 Nuvistor vacuum tubes (only 2 types required which lessened spare parts requirements), the highest quality metal film resistors and film capacitors. Because of feedback loops in the circuitry, ultra-wide bandwidth audio transformers were essential, and these were hand-wound.
Multiple track configurations were available from one track on quarter-inch tape to up to eight tracks on one-inch tape. There were two speed options – 7½ /15 ips or 15/30 ips.
The MR-70 supported settings for NAB, CCIR and AME equalization curves and the ability to switch between them.
Another rumour surrounding this machine is that Willi Studer’s life-long goal was to make a tape recorder better than the MR-70. He tried for two decades and came to the conclusion that he could equal it but not surpass it!
It is believed that Ampex technicians hand-made only 50 MR-70s, and that each one was in some way custom-built.
Ampex MR-70 Model Options (all with in-line heads; dual speed 7.5 – 15IPS or 15 – 30 IPS)
MR-70-1 single-channel full track 1/4″ tape
MR-70-2 two channel 1/4″ or 1/2″ tape
MR-70-3 three channel 1/2″ or 1″ tape
MR-70-4 four channel 1/2″ or 1″ tape
MR-70-6 six channel 1″ tape
MR-70-8 eight channel 1″ tape
Additional Info
Ampex MR-70 Specifications
Frequency response – 15 IPS 50 Hz-15,000 Hz – 7.5 IPS 50 Hz to 12,000 Hz (NAB+ -2 DB)
Signal-to-noise ratio – 2 Track 30 IPS 67 dB – 15 and 7.5 IPS – 65 dB
Wow and flutter – 30 and 15 IPS .05% – 7.5 IPS .08%
Inputs – 20k ohms unbalanced convertible to balanced with plug-in bridging transformer. Accepts line levels from -20 to +12 vu. Low impedance mic input by use of accessory plug-in Nuvistor pre-amp
Outputs – Strappable for 150 or 600 ohms, balanced or unbalanced, +4 or +8 vu
Equalization – Automatic by speed selector, choice of curves at each speed for NAB, CCIR or AME (15 ips only). Adjustable to accommodate other curves in the 17.5 to 100 microsecond range (with or without the 3180 microsecond low frequency pre-and post emphasis
Tube complement – 6 x 7587 Nuvistors, 12 x 7895 Nuvistors (for each channel). 4 of each type for bias / erase oscillator
Erasure – A mid frequency signal recorded at peak record level will be reduced by at least 68dB when erased
Channel separation – when recording with signal on one track and without signal on an adjacent track (bias only), the signal to crosstalk ratio will be greater than 50 DB mid band
Even order distortion – 2nd harmonic distortion of a 500Hz signal recorded at peak record level is less than 0.5%
Start time – Tape within ± 0.2% of nominal speed in 0.5 seconds
Fast modes – continuously variable from 0 to 400 IPS
Rewind time – Approx. 80 seconds /2400′
Dimensions – Transport 19 x 24½ x 12″ deep (484.5 x 622.3 x 304.8 mm) Electronics (per channel) 19 x 5¼ x 12″ deep (484.5 x 133.4 x 305mm) Console 29 x 29¼ x 62¼” high (737 x 749 x 1581mm)
Weight – Transport 130 lbs (59.1 kg) Electronics (per channel) 27 lbs (12.3 kg) Console (4-channel unit) 180 lbs (81.8 kg) / full-track