9762A MICROPHONE AMPLIFIER
Now you can have the same great sound and performance as the original 9762 Dual Combo 19″ rack unit available in the 500 format! Every effort was made to retain the same audio path as the original Dual Combo rack unit design with no component or circuit compromises.
The beefy line amplifier and gain blocks are the very same designs as used in the original 9762 preamplifier. This module will deliver the full +27dBu output as the original 9762. The 9762A faithfully achieves the same performance and sound as the original 9762 Dual Combo rack unit.
The 9762A delivers the same +27dBu output level drive capabilities as the original 9762 rack unit. Internally the 9762A uses dual linear regulators with an isolated virtual ground architecture to achieve true 24V operation and no switching supplies are needed. This approach allows the 9762A to deliver the same high output level drive capabilities without sacrificing any signal overhead or the line driver and gain block performance.
Since the entire preamp is fully transformer isolated from input to output, the virtual ground technique doesn’t require the use of expensive switcher modules and the reliability/noise concerns these bring. The 9762A uses the same style transformers and the same gain block and line driver circuitry as the original rack mount unit.
- Dual gain block Neve style structure with up to 75db overall gain.
- Fully balanced transformer I/O’s (+27dbu max output).
- Low noise internal power supply fully mu-metal shielded.
- Selectable High/Low-Z input mic impedance
- Switchable 100Hz Low Pass Filter.
- Independent regulation and fuse protection per channel.
- Super Hi-Z FET instrument DI input (switch selectable).
- Improved 8-segment VU meter.
- All discrete components in the signal path.
The standard unit contains a single channel of high gain amplification capable of providing up to 75 dB of gain. All balanced input and output signals are fully transformer isolated. The output transformer is a custom Sowter part made specifically for the 9762A format. Standard features include +48V Phantom power, polarity (phase) reverse, DI source select, microphone impedance select and 100 Hz low pass filter.
THE 9762A CONTROLS
- +48V Phantom Power Enable
- +48V Power Status Indicator
- Signal Overload (OL) Indicator
- Gain Select Switch
- Signal Present (SP) Indicator
- Direct Input (DI) Source Select
- Low-Z Microphone Impedance Select
- Line Output Polarity Invert Select
- 100 Hz High Pass Filter Enable
- Line Output VU Meter Indicator
- Direct Input – Unbalanced
- Output Level Control
The 9762A also includes a few new features not found in the 19″ unit version. We added an all discrete 100Hz -12dB/octave high pass filter to roll off undesirable low frequency content when needed. You’ll also notice that we’ve expanded the LED VU meter to 8 segments and improved the meter balistics. The SP (signal present) and OL (overload) LED indicators provide the same visual indicators with peak hold indication. The heavy duty gain switch and output level potentiometer are the same exact parts as used in the original design.
THOUGHFUL PHANTOM POWER DESIGN
The phantom power switching circuitry uses a smooth power ramping design to help reduce pops and clicks during switching. The phantom voltage ramps up slowly when enabled and ramps down quickly when disabled. Phantom power is fully protected against continuous shorting via current limiting resistors.
DIP switch S1 allows the unit to be configured such that phantom power is completely disabled to the microphone; this feature is useful to protect ribbon or other microphones that could be damaged by 48V. No phantom power can be applied to the microphone when this switch is disabled regardless of the +48V switch setting on the front panel. JP1 allows configuration of the output transformer strapping and termination.
The 48V phantom LED may be configured to indicate the presence of phantom power in two modes. The use of external microphone splitter transformers (mainly in live sound) opens up the possibility that phantom power may be back-fed into another preamp via the splitter transformer. If another preamplifier is connected to the splitter and is supplying phantom 48V, then the other preamplifier could see 48V applied to its input from the other preamp on the splitter as well.
In LED mode 1, the 48V LED glows if the +48V phantom power switch is enabled or if the unit is being back-fed 48V from another microphone input source (eg, through a microphone splitter or other external source). In mode 2, the 48V LED only lights if the +48V phantom power switch is enabled. The LED will not light even if the unit is being back-fed phantom power into the microphone input from another source.
Note that you can completely disable the phantom power and LED via JP3 and the S1 DIP switch. The 48V LED can be disabled via JP3 and the power can be disabled via S1 such that all phantom power and features are disabled. Thus, the preamp can never apply phantom power to a microphone and the 48V LED and front panel switch are effectively disabled. These features allow you to dedicate the preamp module for use with non-phantom microphones if desired.