Eico HF 81 Owners Manual

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general descriptionMODEL Hf - DUAL 14 WATT HI- STEREO AMP - PREAMP GENERAL The EICO Model HF-81 is a complete high fidelity stereo- phonic control center and a pair of 14watt amplifiers, all on one chassis. With it you can select preamplify, and control accurately any stereophonic source (tape, discs, or broadcasts) and feed it through the self-contained dual 14 watt amplifiers to a stereo pair of speaker systems. When you playa monophonic source, the 14 watts available per channe I adds up to a total of 28 watts for your two speaker systems. If you desire, both amplifiers can be connected in parallel and driven byone preamp I ifier-control section whi Ie the other preampl ifier-control section is free to drive an external power amplifier. In this way your old ampli- fier can be put to use in a stereophonic system. Construc- tion is of the "Iow silhouette" type that permits you to dispense with cabinetry if desired. FEATURES 1. Separate low level input in each channel for mag. phono, tape head, and microphone. Circuitry carefully designed to provide the high gain required by tape heads and high quality, low output mag. cartridges without hum and noise problems. A front panel switch permits choice of the proper NARTS tape head equalization for either 7 1/2 & 15 or 3 3/4ips tape speeds. 2. Separate high level inputs for AM, FM, and FM Multiplex. Also two auxiliary A inputs (one in eachchannel) and two auxil iary B inputs (one in each channel). Input Selector switch on front panel has positions for feed- ing FM tuner output to one channel and AM tuner to other, or FM tuner to one channel and FM Multiplex adapter output to other. 3. May be used as either two independent amplifier- preamplifiers,or one preamplifier-control section may be set free to operate an external power amplifier and the other preampl ifjer-control section used to drive both in- ternal power ampl ifiers connected in parallel at the speaker connection terminals. A top - of-chassis sl ide switch permits choice of operation. 4. Ganged level controls and a separate focus (balance) control. 5. Independent full-range bass and treble tone controls in each channel. Tone controls of the low distortion variable cross-over feedback type. 6. Identical Williamson type, push-pull EL84power am- plifiers with high quality output transformers. 7. Hum balance control, panel-mounted fuse, pi lot lamp, convenience outlets. 8. EICO "low silhouette" construction employing hori- zontal chassis for proper layout and component separation. Easy console installation, if desired, with complete shield- ing and adapatability to any panel thickness. Copy,;ght I1d 1958 Electronic Instrument Company, Inc.

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SPECIFICATIONS * Output Power:28 watts continuous; 56 watts peak. 1M Distortion (60c &7kc at 4: : 2% at 28 watts; 0. at 10 watts. Frequency Response:(2w):I:O. 5db 10c to 1O0kc. HarmonicDistortion:16 watts at less than 1% 30c to lOkc; 20 watts at I ess than 1 % 40 c to 10 kc; 28 watts at less than 1% 50c to 5kc; 8.4 watts at less than 2% at 20c. Transient Response: excellent square wave reproduction (4usec rise time) negligible ringing, rapid settl ing on 10kc square wave. Transient Distortion (60cps tone burst)less than 1% at fu II power. Inverse Feedback: 20db Stability Margin:12db Damping Factor: above 8,20 cps - 15 kc. Sensitivity (input for rated output):mag. phono 4mv; tape head 7. 5 ips - 2 mv; tape head 3.75 ips 5mv; mic - 6mv; tuners, auxiliaries - 0.5V.** Hum & Noise Level (below rated output):mag. phono 60db; tape head - 51 db; mic - 57 db; tuners, aux- iI iaries - 75 db. Tone Control Range: ::I:15db at 50c and 10kc. Speaker Connections: 48, and 16 ohms. Tubes: 4 - ECC83/12AX7, 2 - ECC82/12AU7, 4- EL84, 2 - EZ81. Size:15" wide, 4 3/4" high, 10 1/2" deep. Weight: 241bs. * Where power output is involved, figures are given for two channels combined; divide power output figures by two for specifications of each channel alone. Design property specifications refer, of course, to either or both channels. ** Measured with tone controls set "flat" , LEVEL control maximum, and FOCUS control set for maximum gain in channe I checked.

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