Lundahl transformers
Lundahl Transformers is a world leading manufacturer of high performance transformers for audio applications. The company is located in the small town Norrtälje, just outside Stockholm, Sweden.
A significant difference between Lundahl Transformers and other transformer manufacturing companies is that in addition to controlling the entire manufacturing process (including C-cores, bobbins, pin plates and housings) we also develop and build most of our production machines.
Subcategories
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Lundahl Tube output
Tube amplifier output transformers
All OPTs are built in our dual coil single C-core style and can be ordered with a choice of core air-gap for Push-Pull or Single-Ended applications. Most of our OPTs can be configured for different primary and secondary impedances.
The use of C-cores with well-defined air-gap results in an almost constant inductance throughout the whole operating voltage range. For SE transformers, the primary inductance variation due to signal level is less than 7%.
Most of the transformers below are available with amorphous iron C-cores. The amorphous cores are considered to have sonic advantages, but the signal level capability with amorphous core is about 30% less than with a conventional silicon-iron C-core.
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Lundahl Moving coil input
Moving coil input
Moving coil step-up transformers for impedance matching of low impedance cartridges to phono amplifiers.
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Lundahl Input and DC-free line output application
Input and DC-free line output applications
Line input and line output transformers for galvanic isolation, balanced-to-unbalanced conversion and for impedance conversion. Should be used with DC-free signal sources, or with a DC blocking capacitor between source and transformer.
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Lundahl Anode chokes, interstage and line output
Anode chokes, interstage and direct couple line output transformers
Our tube amplifier transformers are built in our dual coil single C-core style and can be ordered with a choice of core air-gap for Push-Pull or Single-Ended applications.
The use of C-cores with well-defined air-gap results in an almost constant inductance throughout the whole operating voltage range. For SE transformers, the primary inductance variation due to signal level is less than 7%.
Most of the chokes and transformers below are available with amorphous iron C-cores. The amorphous cores are considered to have sonic advantages, but the signal level capability with amorphous core is about 30% less than with a conventional silicon-iron C-core.
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Lundahl Mains transformers
Mains transformers
We manufacture a limited range of C-core mains transformers, primarily for tube amplifiers. Our transformers are best used with bridge rectifier circuits (four diodes), but some transformers can also be used with full wave rectifier circuits.
The hybrid power supply principle provides a bridge rectifier circuit using classical tube rectifier tubes in combination with modern diodes.
The transformer primaries are connected in series for 210 – 250V and in parallel for 105 – 125V. Secondary voltages are calculated for 230V / 115V primary voltage.
The secondary voltage listed are no-load voltage. Voltage drop because of load can be calculated from transformer copper resistance and load current. For optimal use, about 75% of power should be taken from secondary 1.
In our mains transformers, a small deliberate C-core air-gap is used to prevent from core saturation caused by any DC unbalance in the mains outlet.
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Lundahl Chokes for tube amp power supply or filament current supply
Chokes for tube amp power supply or filament current supply
The ripple voltage from a rectified sinus signal, is approx. 42% of original RMS voltage.
As long as max voltage rating is not exceeded, all our power supply chokes can be used in choke input configurations.
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Lundahl General purpose
General purpose transformers
General purpose audio transformers for ground isolation, for splitting and for balanced-to-unbalanced conversion.
General properties:
Many different connection alternatives possible
Moderate copper resistance (50 Ω per section typically)
Medium signal level capability (Max 10 dBU at 50 Hz per section typically)
Excellent magnetic and electrostatic shielding
High mu cores (mu metal or amorphous strip core) -
Lundahl Microphone transformers
Microphone transformers
Microphone transformers are normally used for impedance matching:
At mic preamp input circuits to match microphones to preamp.
In tube microphones for matching high impedance tube circuits to normal output impedance.
In ribbon microphones to transform very low voltage, very low impedance ribbon motors to normal microphone output levels.General properties of Lundahl microphone transformers:
PCB mount style (with exceptions)
High level capability
Excellent magnetic and electrostatic shielding
High mu cores (mu metal or amorphous strip core) -
Lundahl Line input
Line input transformers
High quality audio transformers for bridging input or for Zero Field input circuits.
General properties:
High impedance input
PCB mount style
High level capability
Excellent magnetic and electrostatic shielding
High mu cores (mu metal or amorphous strip core) -
Lundahl Line output transformers
Line output transformers
Line output transformers with silicon iron C cores.
General properties:
Compact
Low copper resistance
High level capability
For balance or unbalance drive
Lundahl silicon iron C coresDriving circuitry for line output transformers should have low output impedance. In order to reach the very best performance in terms of low distortion and low line output impedance, we recommend that our output transformers are used with mixed feedback drive circuitry for negative output impedance and best THD performance.
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Lundahl Problem solvers
Problem Solvers
XLR inline transformer units for breaking up ground loop in audio systems.
High level audio isolation transformers mounted in XLR connector housings. For breaking up ground loops in audio systems and for balanced-to-unbalanced conversion.
No galvanic contact between input and output connectors. Built-in transformer with amorphous strip core. Magnetically shielded housing with fitted XLR connectors or patch cable ends.
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Lundahl Digital Audio
Digital Audio
Transformers for digital audio: Isolation, impedance matching and splitting.
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Lundahl Transformers for telephone hybrids, for 100V PA systems
Lundahl Transformers for telephone hybrids, for 100V PA systems and for high power loudspeaker applications.
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Lundahl Video transformers
Lundahl Video transformers
Transformers for Closed Circuit Television(CCTV) applications. For galvanic isolation, to avoid hum bars. The transformers should be used in DC-free applications.
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Lundahl Metal Housings
Metal housings for tube amplifier transformers.Throughout the years we have received critical comments on the looks of our tube amplifier transformers, even if most users are happy with their electrical performance. To facilitate the usage of our transformer in traditionally designed tube amplifiers we commissioned an industrial designer to develop a new transformer cover concept that fit the needs of our particular style of C-core transformer. The designer came up with this very clever, ventilated, space efficient cover that provides some unique functionality.It is a four piece design that uses the transformer itself as a structural member and is configured so the transformer connections are readily accessible without removing the whole assembly from the chassis.
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Lundahl Amorphous core output transformers
Amorphous core output transformers
Some of our tube output transformers are now available with amorphous core. Listening tests, in particular for the PP versions where the core airgap is not as dominating as in SE applications, have reported a more transparent, wider bandwidth character than our silicon iron counterparts.
For connection alternatives and general application information, please refer to data sheets for our regular (silicon-iron) output transformers.
The obvious measurable difference between our silicon-iron cores and amorphous cores is that the saturation flux for the amorphous core is approximately 33% less than for the silicon-iron counterpart. This is caused partly by a lower saturating flux level, partly by a smaller fill-factor due to the thickness of the amorphous sheets.
As a result, power bandwidth is reduced by about 50%. (This means that if the max output power for a standard LL1620/40mA is 25W at 30 Hz, corresponding max. power for LL1620AM/40mA is 13W.) This is probably not a problem in most Push-Pull applications, but should possibly be considered in Single End amplifiers.
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Lundahl other audiophile type transformers
Lundahl other audiophile type transformers