LL2742 100mA Lundahl Drossel Choke 10H 200mA / 42H 100mA
€132.80
Delivery time: ca. 4 - 8 weeks
Series gives 42 H/100 mA; parallel gives 10 H/200 mA supply operation
Saturation values of 140/280 mA are not continuous current ratings
80 O per coil, 1.35 kg, 95 × 75 × 50 mm and 4 kV isolation overall
Lundahl LL2742/100mA – 42 H C-core choke for low-noise valve power supplies
The Lundahl LL2742/100mA is a dual-coil B+ filter choke for valve-amplifier power supplies. With both windings in series, it provides 42 H at 100 mA recommended DC for substantial filtering impedance.
Connecting the two windings in phase and in parallel provides 10 H at 200 mA recommended DC, allowing the same choke to support a higher-current supply branch.
Suitable applications
- Low-noise LC and CLC supplies for valve preamplifiers
- B+ filtering for driver stages and smaller power amplifiers
- 42 H series operation at up to 100 mA recommended DC
- 10 H parallel operation at up to 200 mA recommended DC
- Choke-input supplies after calculation of critical inductance and minimum load
- Split filtering arrangements for improved common-mode rejection following the Lundahl diagram
Technical data
- Product type
- Dual-coil B+ power-supply filter choke
- Model version
- LL2742/100mA
- Inductance with coils in series
- 42 H
- Recommended DC current in series
- 100 mA
- Saturation current in series
- Approx. 140 mA; not a recommended continuous current
- Inductance with coils in parallel
- 10 H
- Recommended DC current in parallel
- 200 mA
- Saturation current in parallel
- Approx. 280 mA; not a recommended continuous current
- DC resistance per winding
- Approx. 80 Ω
- Total resistance in series
- Approximately 160 Ω
- Equivalent resistance in parallel
- Approximately 40 Ω with equal current sharing
- Maximum dissipation for this version
- Approx. 2 W under the documented rated conditions
- Maximum ripple voltage in series
- Approx. 640 V RMS at 100 Hz and recommended DC current
- Maximum ripple voltage in parallel
- Approx. 320 V RMS at 100 Hz and recommended DC current
- Winding-to-winding dielectric test
- 4 kV AC
- Winding-to-core dielectric test
- 2 kV AC
- Core
- Lundahl audio C-core
- Dimensions
- Approx. 95 × 75 × 50 mm
- Mounting pattern
- Approx. 35 × 75 mm with four M4 mounting points
- Weight
- Approx. 1.35 kg
Winding connections
- First winding
- Pins 1 to 3, with the winding start at pin 1
- Second winding
- Pins 6 to 4, with the winding start at pin 6
- 42 H series connection
- Join pin 3 to pin 6 and use pins 1 and 4 as the terminals
- 10 H parallel connection
- Join pins 1 and 6 together and join pins 3 and 4 together with the correct phase
- Split common-mode filtering
- Implement only as shown in the manufacturer diagram and as part of a correctly designed complete power supply
Voltage drop and selection
At 100 mA, the approximately 160 Ω series connection produces a calculated drop of about 16 V and copper loss of 1.6 W. At 200 mA, the approximately 40 Ω parallel connection produces about 8 V and the same 1.6 W loss.
Series operation prioritises inductance and filtering. Parallel operation reduces inductance and DC resistance while doubling the recommended current.
A choke-input supply requires calculation of minimum load, critical inductance, rectifier type and no-load voltage. If the load falls below the required current, the output voltage can rise substantially.
Safety notes
Lethal voltage and stored energy may be present at the choke. Install it securely with complete touch protection and adequate electrical clearances.
Questions about selection and use
Is the Lundahl LL2742/100mA suitable for a particularly low-noise CLC valve supply?
Yes, the Lundahl LL2742/100mA is suitable in its 42 H series connection for a correctly designed CLC supply operating at up to 100 mA recommended DC. Voltage drop, start-up voltage and residual ripple must suit the circuit.
Can the LL2742/100mA be connected in parallel as a 10 H, 200 mA choke?
Yes, the LL2742/100mA can operate with its windings connected in phase and in parallel as a 10 H choke for up to 200 mA recommended DC. Both windings must share the current as evenly as practical.
Is the LL2742/100mA suitable for a choke-input power supply?
Yes, the LL2742/100mA can be used in a correctly calculated choke-input supply. Critical inductance, continuous minimum load, rectifier current and possible no-load voltage must be verified before construction.
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.
Lundahl Transformers AB
SE-76150 Norrtälje
Email: order@lundahltransformers.com
The EU Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (2011/65/EU = "RoHS 2") aims to exclude certain hazardous substances from electrical and electronic equipment or to restrict the use of certain substances in electrical and electronic equipment. These include substances such as lead, mercury, cadmium, and chromium, as well as certain brominated flame retardants and plasticizers. These substances may only be used in electrical and electronic equipment up to a maximum concentration limit, unless exemptions in the annexes to the directive permit their use under certain conditions. This can reduce and eliminate harmful substances and improve the recycling of waste electrical and electronic equipment. To find out whether the component you purchased from us is permitted in your device, please refer to the current directive or the current law applicable to your country. If you are a manufacturer, please feel free to contact us to find out whether the component you require can be tested and approved according to the current directives. We would be happy to assist you.
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: 85043180
Country of Origin: SE
Weight: 1,35 kg