PAIR TWO Sonic Imagery Discrete OpAmp API style…..compatible with the VTV Amplifier Custom Hypex input buffer using two per channel, but may be used in other amplifiers as well. These are an excellent upgrade from IC based opamp designs.
Here is description from Sonic Imagery:
The Model 990Enh-Ticha is a high performance discrete operational amplifier designed for professional audio application areas where ultra-low noise, low distortion and highly linear uncolored operation is required. It was designed as a high performance upgrade replacement for the Jensen JE990, Automated Processes Inc. API-2520, John Hardy Co. 990A-990C, FiveFish Studios DOA series, Seventh Circle Audio SC10, SC25, SC99, and Avedis Audio 1122 op-amp gain block. The pinouts conform to the 990 package, allowing direct replacement.
If the user is upgrading or replacing vintage or retro-clone gear, take note of the pin length required for your particular application. Older gear typically used modules with 0.480 to 0.510 inch long 0.040 pins. Sonic Imagery Labs offers this longer pin length variant at no additional charge. See the Model 990Enh-Ticha and 995FET-Ticha Mechanical Options Application Note AN-18 for mechanical details.
See table 1. below for additional discrete opamps which can be upgraded.
The all-discrete SMT design is similar to the JE990 basic topology but has been completely redesigned to use an ultra-precision differential super-matched transistor pair specifically designed to meet the requirements of ultra-low noise, ultra-low THD, highly linear uncolored audio systems. In addition to the enhanced input stage, the 990Enh-Ticha uses high precision temperature stable power supply independent current sources. Supply independent current sources allow the bias to remain locked at the optimum operating point regardless of power supply voltage.
Dual matched pair temperature stable current mirrors, dual matched pair active current loads give the Model 990Enh it’s outstanding power supply rejection performance. The enhanced low distortion Class-A output driver stage can sink or source 250mA allowing this module to drive transformers easily.
Integrated power transistor heatsinks coupled to a anodized aluminum enclosure keeps the 990Enh-Ticha operating within a wide SOA and does not suffer from Beta droop when driving heavy iron or heavy loads. Each amplifier is fully tested and meets or exceeds published specifications.
Because of the 990Enh high current drive capability, supporting circuitry impedances can be scaled down within the application circuit. This can reduce the overall system noise, without increased distortion and provides higher headroom compliance performance.
Sonic Imagery Labs also can provide a variation of this model that can operate down to ±4.5V for low power low voltage applications. Contact us and ask about the Model 990LV-Enh-Ticha.
• Ultra Low Total Harmonic Distortion, 0.00045 THD+N @1kHz
• Low Impedance Line Amplifiers
Jensen JE990 Series
Why Use a Discrete Operational Amplifier?
1. When the best possible distortion performance is demanded. Most monolithic op-amps use Class-B or Class-AB output stages, and many of them (though certainly not all) show clear crossover distortion artifacts on the distortion residual. A discrete op-amp can dissipate more power than a monolithic integrated circuit (IC), and so can have a Class-A output stage, sidestepping the crossover distortion problem completely.
2. When the best possible noise performance is required. Super-matched pair discrete bipolar transistors can outperform monolithic op-amps, particularly with low source resistances, say 1000 ohms or less. The most common examples are moving coil head amps, microphone preamps, summing structures in mixing boards, balanced cable line receivers and line drivers. These structures almost invariably use a discrete input device, with open loop gain (for linearity) and load driving capability provided by an ordinary op-amp which may itself have fairly poor noise specifications.
3. When a load requires more drive current, because of its low impedance, than a monolithic op-amp can provide without overheating or current limiting. Because discrete op-amps have high current drive capability, supporting circuitry impedances can also be scaled down within the application circuit. This will reduce the overall system noise, without increasing distortion and provide higher headroom performance.
5. When it is required to provide a low voltage supply to run a few monolithic IC op-amps. The cost of extra transformer windings, rectifiers, filter capacitors, regulators, and added complexity of powers supplies can be eliminated with the use of discrete op-amps.