Model 996VP-LZ Balanced Dual Unbalanced Discrete Amplifier

Updated May 3rd, 2023

Model 996VP-LZ Datasheet and Specifications PDF
Model 996VP-LZ Purchase Online
Model 996VP-LZ Balanced Transformerless Preamp AppNote AN-19

General Description:
996VP-LZ True Balanced I/O Dual Unbalanced Discrete Amplifier

The Sonic Imagery Labs 996VP-LZ is a high performance semi-discrete operational amplifier module designed for professional audio applications and areas where ultra-low noise and extremely low distortion is required. It is a higher performance drop in upgrade replacement for the Valley People Trans-Amp LZ. Unlike the familiar OP-AMP geometry, the Sonic Imagery Labs 996VP-LZ is inherently a fully balanced differential in/differential output device employing symetrically opposed feedback loops. Instead of the feedback being returned to the input ports, as done with traditional balanced topologies, the feedback signal is returned to a pair of feedback ports. This results in a pair of input ports configured as a high impedance fully balanced bridging input.

For differential current summing amplifier applications, the input signals are brought to the feedback ports, which now double as balanced virtual ground current summing junctions.

Where true balanced inputs are not required, the Sonic Imagery Labs 996VP-LZ can also be operated as two independent amplifiers, with each half maintaining the extremely low noise, low distortion, and high gain bandwidth performance characteristics associated with this device.

Unlike the original Paul Buff/Valley People design, the 996VP-LZ uses two precision matched pair transistors as the differential input stage. A total of 4 matched devices, with an option for an additional pair for ultra-ultra low noise applications. These devices are selected by the manufacturer at final test to Sonic Imagery Labs noise. leakage, offset, and Vbe matching specifications.

In addition to the enhanced input stage, the 996VP-LZ uses high precision temperature stable, power supply independent current sources. The original design did not use a true current source thus making its operational specifications voltage dependent for performance. Supply independent current sources allow the 996VP-LZ differential amplifiers bias to remain locked at the optimum operating point regardless of power supply voltage.

Another feature not found in the original Paul Buff/Valley People design is the addition of a matched pair active current load to give the 996VP-LZ differential input stage it’s outstanding power supply noise rejection ratio performance.

The output driver stage has been redesigned specifically to source and sink large amounts of current without degrading the output drivers linearity. High order harmonics produced by the output stages crossover distortion found in the original Valley People opamp design are eliminated. The new output stage provides exceptionally low open loop output impedance that improves stability with capacitive loads and is also protected against short-circuit and thermal overload events. This allows the Sonic Imagery Labs 996VP-LZ to drive transformers and balanced cabling directly and still remain stable.

The newly designed output stage also provides nearly rail to rail output voltage. Output levels of +28dBu differential are easily obtainable and are not limited by gain setting dependency.

The Sonic Imagery Labs 996VP-LZ can be operated from ±5V to ±18V power supplies. The redesigned input stage circuitry provides outstanding common-mode rejection and maintains low input bias current over its wide input voltage range, minimizing distortion. The 996VP-LZ is unity-gain stable and provides excellent dynamic behavior over a wide range of load conditions.

The pinouts conform to the original Valley People Trans-Amp LZ package type, allowing direct replacement.

Both the Valley People Trans-Amp LZ and the Sonic Imagery Labs 996VP-LZ is internally AC coupled, with an effective low end open-loop bandwidth of 0.0003 Hz. This results in a closed loop 3dB point of 0.3 Hz when operated at 60 dB gain, or 3 Hz for 80 dB gain.

For a DC coupled fully differential balanced operational amplifier with user defined common mode offset control refer to the Sonic Imagery Labs Model 991GC_Diff_Ticha balanced operational amplifier datasheet. (Available Late Winter 2016)

Sonic Imagery Labs also can provide custom variations of this model.
Sonic Imagery Labs can produce a variation of this model that will provide <0.450nV/√Hz equivalent input refered noise voltage performance for ultra-ultra low noise amplifier applications. The Model 996VP-LZ UULN Variant, adds an additional 3rd low noise differential pair transistor pack to lower EIN to <0.450nV/√Hz.

Contact us directly for additional options and pricing.


• Ultra Low Total Harmonic Distortion
• Ultra Low Noise, 0.89nV/rtHz
• High Current Output Drive (>150mA)
• Near Rail to Rail Output (within 0.25V)
• +28dBV Output Levels (600ohm Differential Load @ ±18V Supply)
• Standard Valley People Trans-Amp LZ Gain Block Footprint
• Differential Output thermally and short circuit protected
• Operates over ±5V to ±18V supply rails
• Lower output offset voltage than existing counterparts
• Lower input leakage current than existing counterparts
• Particular emphasis on audio performance
• Designed, assembled and produced in the USA
• 3 Year Warranty


• Balanced Line Amplifiers
• Balanced Cable Drivers
• Balanced High Input Impedance Buffer
• Balanced Active Filters and Equalizers
• Balanced Summing/Mixer Amplifiers
• High Performance Balanced Microphone Preamplifiers
• High Performance Balanced A/D front end preamplifier
• High Performance Balanced D/A back-end driver
• High Performance Balanced Phono Preamplifiers


Model 996VP-LZ Datasheet and Specifications PDF
Model 996VP-LZ Purchase Online
Model 996VP-LZ Balanced Transformerless Preamp AppNote AN-19

See Also

Sonic Imagery Labs Model 992Enh-Ticha- Discrete Op Amp DIP8
Sonic Imagery Labs Model 994Enh-Ticha- Dual Discrete Op Amp DIP8
Sonic Imagery Labs Model 995FET-Ticha- FET Discrete Op Amp 990/2520
Sonic Imagery Labs Model 990Enh-Ticha- Discrete Op Amp 990/2520

Contact us directly for OEM and quantity pricing.

All specifications subject to change without notice. The information provided herein is believed to be reliable; however; Sonic Imagery Labs assumes no responsibility for inaccuracies or omissions. Sonic Imagery Labs does not warrant or authorize any Sonic Imagery Labs products for use in life support devices and/ or systems.

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