PAIR TWO Sonic Imagery Labs 990Enh-Ticha Discrete OpAmp API VTV Amplifier



PAIR TWO Sonic Imagery  Discrete OpAmp API style…..compatible with the VTV Amplifier Custom input buffer (tube or solid state) using two per channel, but may be used in other amplifiers as well.  These are an excellent upgrade from IC based opamp designs.  

Full engineering datasheet here

Here is description from Sonic Imagery:

General Description:
990Enh-Ticha Discrete Operational Amplifier

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
• Ultra Low Noise 0.89nV/rtHz
• High Current Output Drive (250mA into 75 ohms)
• +26dBu Output Levels (into 600 ohms)
• Standard Gain Block Footprint
• 120dB Open Loop Gain
• Operates over ±9V to ±24V 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


• Low Impedance Line Amplifiers
• Active Filters and Equalizers
• Summing/Mixer Amplifiers
• High Performance Microphone Preamplifiers
• High Performance A/D and D/A front end Preamplifier

Table 1. Compatible Upgrade Table
The Model 990Enh-Ticha can be used to upgrade and/or replace these obsolete or end of life discrete operational amplifiers. This list is by no means comprehensive. Contact Sonic Imagery Labs for additional information.

Jensen JE990 Series
Automated Processes Inc. API-2520, 2520H, 2525
John Hardy Co. 990A-990C
FiveFish Studios DOA series
Avedis Audio 1122
Seventh Circle Audio SC10, SC25, SC99
Sound Skulptor SK25, SK99, SK47
Yamaha NE80100, NE80200
TOA PC2011
ProTech Audio Model 1000
Purple Audio KDJ3, KDJ4
Modular Devices 1731, 1757
Modular Audio Products (MAP) 5000 Series, 1731 1731A
Melcor 1731
JLM Audio 99V
Inward Connections SPA690
FAX Audio FA-100
Analog Devices 111

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.

4. When a load must be driven to higher voltages than a monolithic IC can sustain between power supply rails. Monolithic IC op-amps are mostly restricted to supply voltages of ±5 to ±18 volts. Discrete operational amplifiers provide a viable alternative because they can operate in excess of ±24 volts.

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.


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