Home > Studio Recording DIY Projects> Altec 1599A Upgrade
The unit cannot work with modern condenser microphones. There is no phantom power capability. But it will work without problems using a dynamic microphone.
After verifying that the unit works, I decided on what kind of upgrades I should perform. So first things, first, open the unit!
What strikes me about the unit is the SIMPLICITY of the design. The only "exotic" thing about the design are the plugin preamps (metal cans). The rest of the electronics in the box is nothing more than XLR jacks, volume control, pad switches, power supply, and a small pre-amplifier line driver for additional gain boost.
DC Rectifier, Voltage Regulator and Line Driver
I reversed-engineered the wiring and will post schematics when I have the time. AC power enters the PCB via the Molex connectors on the right. Just behind the right capacitor are diodes that convert the AC voltage to DC voltages. I measured 38VDC at this point. The two (2) gold colored capacitors filter the DC voltage, which then goes to a 7818 voltage regulator (see the black square looking thingy, middle top). The 7818 regulates the 38VDC down to a constant 18VDC. The blue capacitor adds further ripple filtering.