EH90 = 6CS6 Heptode Röhre tube Audio und Studiokompressor
€2.90
Delivery time: ca. 1 - 5 days
Also known as 6CS6 variable-mu tube
Great for vintage compressor builds
Miniature B7G; Uf 6.3V, If 0.3A
EH90 / 6CS6 dual-control heptode for tube compressors
The EH90 is a compact dual-control heptode whose electron current can be influenced through two separate control grids. This makes it attractive for experimental tube compressors, gain-control stages, modulators and creative studio circuits.
Unlike a conventional preamp pentode, the EH90 is particularly useful when a second voltage or signal is intended to control stage gain. Low-distortion audio operation requires a circuit developed specifically around this behaviour.
Suitable applications
- Variable-gain and tube-compressor circuits
- Modulators, tremolo and audio effect stages
- Level-dependent studio and measurement circuits
- FM demodulator, switching and legacy RF applications
Technical specifications
- Valve type
- Dual-control heptode with two effective control grids
- Equivalent designations
- 6CS6 and EH860
- Base
- Miniature B7G, 7-pin
- Heater
- 6.3 V at 300 mA
- Typical operating condition
- Va 100 V, Vg2/g4 30 V, Vg1 −1 V and Ia approximately 0.75 mA
- Transconductance
- Approximately 0.95 to 1.2 mA/V depending on data and control condition
- Internal resistance
- Approximately 0.9 to 1 MΩ
- Typical maximum ratings
- Maximum anode voltage 300 V and maximum anode dissipation 1 W
- Dimensions
- Approximately 17 mm in diameter and 47 mm body height excluding pins
B7G connections – bottom view
- Pin 1
- Control grid g1
- Pin 2
- Cathode and suppressor grid g5
- Pins 3 and 4
- Heater
- Pin 5
- Anode
- Pin 6
- Screen grids g2 and g4
- Pin 7
- Second control grid g3
Compressor and studio design notes
Grid g1 may carry the audio signal while g3 receives a control or modulation voltage, although other arrangements are possible. Bias, signal level, control range and balanced operation are important when low distortion is required.
The EH90 is not simply a replacement for a standard remote-cutoff pentode. Its key attraction is dual-grid control rather than universal linear preamplifier service.
Questions about selection and audio use
Is the EH90 suitable for an experimental tube compressor?
Yes, the two control grids allow the audio signal and control voltage to influence the electron current separately. This makes the EH90 an affordable basis for custom compressors, limiters and automatic level-control circuits.
Is the EH90 attractive for circuits inspired by Blöhbaum's MTA concept?
Yes, its multi-grid structure offers interesting possibilities for new transconductance and control circuits. The original Linear Audio MTA uses separate triode and hexode sections with a shared cathode, so an EH90 implementation requires an additional active stage and a redesigned circuit.
Can the EH90 be used for tremolo, modulation and creative studio effects?
Yes, its second control grid can provide amplitude modulation or dynamic level control. This supports tremolo, ducking, experimental distortion structures and other analogue studio effects.
Note: All brand names mentioned, such as Marshall, Fender, etc., are registered trademarks of their respective owners and are used here for descriptive and compatibility purposes only.
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Fact sheet on EU Directive 2011/65/EURestriction of the use of hazardous substances in electrical and electronic equipment (PDF, not accessible, 2 MB)
Source: IHK Mittelfranken
Tariff Number: 85408100900
Country of Origin: DE