Brook Electronics Pre-amplifier Model 7
The audio performance afforded by unique Brook tone controls make this pre-amplifier a perfect complement to Brook Basic Models 12A and 10C, also , an ideal companion to any quality basic amplifier,… Hum well below the thermal noise of tubes, … All the features of the Brook Model 4B Pre-Amplifier, plus built-in power supply, operating from 115V, 50 to 60 cycles.
Specifications
Frequency Range: with bass control set at position 4 and treble control set at position 8, volume control set at position7, overall response is within 1 dB, 15 to 30,000 cycles
Controls: Channel Selector; Record Playback Characteristic, Bass, Treble, Volume, Pilot Light, Power Switch; Switch to cut out Automatic Bass Compensation (bass-loudness control)
Five Input Channels:
A & B for tuners (AM, FM, TV or recorders),
Gain : pre-amplifier only 40 dB flat
Input Impedance : 1 meg.
C &D for tuners, recorders or crystal pickups
Gain : 40 dB flat
Input Impedance : 250,000 ohms
E for magnetic, variable reluctance or capacitance pickup
Gain : 55 dB pre-amplifier only, at 1000 cycles, compensated for pickup along with Record Playback Characteristic Control
Jack EM for magnetic type or variable reluctance pickups,
Input Impedance 2 mag, shunted by 47 K loading resistor (resistor may be changed as required)
Also adapted for microphone with Record Characteristic Control set on Position1
Gain : 65 dB flat
Jack EC for Capacitance FM pickups
Gain : 55 dB flat
Jack R on rear panel: Output for use with recorders, or Armchair dimmer, furnished with amplifier
Record Playback
Characteristic Control : Position 1 flat for microphone input, position 2 -10 to match various types of recordings,
Bass Control : Switch-type with 10 steps of control. Two stage R-C network. Bass may be boosted as much as 24 dB at 500 cycles without boominess. This is in addition to pickup equalization and automatic bass compensation. Bass may be cut as much as 16 dB at 50 cycles
Treble Control: Switch-type with 10 steps of control. Two-stage R-C network. Steps 9 and 10 provide boost of 5 and 10 dB respectively at 10,000 cycles
Tubes: 1-6J7 (or 1620); 2-6SJ7's; 2-6C4's; All triode-connected : power supply tube 6X4.
The 1620 and 6j7 are identical except that the 1620's are especially selected for low noise.
The 6J7 gives a hum level entirely satisfactory for all normal applications. For supercritical use, the 1620 may give slightly lower hum.
Dimensions : 14-1/2" (wide); 9-1/8" (deep); 3-1/2" (high)
Luxurious gold-finished consolette, enhanced with highly polished solid walnut and blocks, has removable lucite escutcheon 13" x 2-3/4" to facilitate panel-mounting.
Net Weight: 10 lbs