DOA-12 Discrete OpAmp
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The DOA-12 is a high-performance, discrete operational amplifier well suited for demanding audio applications due to it’s low noise, high slew rate, high gain capability, high output capability, and operation over a wide range of power supply voltages. It uses the standard discrete opamp 2520/990 footprint… a roughly 1”x1” device with (6) pins, a format commonly found and used in pro-audio gear.
The DOA-12 is tested in all FiveFish Audio preamps (X12, X72, and MX5 - API VPR Certified modules) and also tested in our Equalizer module (PEQ-503, also API VPR Certified). Performance and audio quality was stellar, delivering fast transients; big bottom end, a faithful sound reproduction with a warm, classic discrete flavor.
Running at +/-24Volts supply voltage, the DOA-12 is capable of reaching +26dBu output (while loaded with a 600:600 output transformer). Using the DOA-12 to drive a wired 1:2 output transformer, it is possible to reach a maximum of +32dBu output!
Running at a slightly lower +/-18Volts supply voltage, the DOA-12 still achieves an impressive +24dBu maximum output.
Each DOA-12 is designed and tested to be stable, and oscillation-free even at maximum output levels and gain settings due to careful selection of components, efficient PCB layout, design, and construction.
The DOA-12 uses double-sided, plated-through hole PCB with full silkscreen and solder masks, 2oz. copper, .062” thick FR4 boards, 1% Metal Film low noise resistors, C0G NPO capacitors and modern transistors. The two (2) output drivers are beefy, high-performance, hermetically-sealed metal case TO-39 transistors, each capable of dissipating 10 watts!
The DOA-12 operates as a Class A amplifier at low to medium output levels and switches to Class AB mode when operating near maximum output levels. We think this is the best balance of performance and efficiency, minimizing dissipated heat and loss energy. Current consumption is fixed +/-16mA (with or without any input signal).
