Lundahl Transformer
NEWS

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News September 2009

Old News March 2009

Old News May 2008

  • Lundahl factory building substantially enlarged
    Buildingsite As the demand for our transformers has increased over the years, we now need new space for new machines and new staff. So we have started expanding the building, from today's 650 square meters to approximately 1000 square meters. We hope this will give room for some more winding machines as well as new assembling areas.
    November 13. Panelling is completed and the scaffolds have finally been removed. There are still some inside work to be completed around doors and windows, and ventilation and heating is not yet complete. Openings/connections between the old house and the new wing are made on the top two floors, but we will have to cut through a concrete wall before the new wing can be reached also from bottom level.

  • LL1931
    is a new moving coil input transformer. With this oversized (compared to conservative engineering requirements) transformer using our own amorphous strip core and copper wire from Cardas Audio, we try to satisfy even the most fastidious audiophile.

  • LL1927A
    is a very high turns ratio (1+1 : 55+55) transformer for active ribbon microphones. As the output impedance of the transformer is significant, the transformer should normally be used with an output buffer stage.

  • LL1692A
    is a tube amplifier interstage transformer with an impedance level between the LL1660 and the LL1671

  • LL2731
    is a low impedance 1+1 : 1+1 tube amp line output transformer, primarily designed for cathode follower output stages.

  • LL1693
    is a supersized LL1627, thus a high power, low impedance tube amplifier output transformer.

  • LL2418
    is a high power (400W across 4 ohms at 50 Hz) audio output isolation transformer, primarily used with solid state amplifiers.

  • RoHS Compliance
    Since autumn 2005 our production is lead free and RoHS compliant. You are welcome to download our RoHS compliance statement .

    • Old News January 2007

  • The range of Amorphous core tube amp transformers is extended.
    The following transformers and chokes are now available with amorphous C-core:
    LL1620, LL1623, LL1627, LL1660, LL1660S, LL1663, LL1664, LL1667, LL1668, LL1677, LL1679, LL1689, LL9202

  • LL1591
    is a low cost (no Faraday shield, no mu metal housing) general purpose transformer for less demanding applications

  • LL1592
    is a new high quality line input transformer.

  • LL1690
    is the amorphous strip core version of above LL1592.

  • LL1691
    is an output transformer for 845 etc. tubes. Less flexible but with better HF compared to LL1688

  • Our range of transformers for ribbon microphones is extended:
    The LL2911 is / will be replaced by LL2913 with identical functionality but a different pinout.

    LL2912 is a flying lead version of LL2911.

    LL2914 is a mu metal core version of LL2912. Same pinout as LL2912, but footprint is bigger.

    • Old News July 2004

  • Amorphous core OPTs.
    The LL1620, LL1623, LL1627, LL9202 and LL1679 are now available with Amorphous C-cores. (Sorry, no data sheet is yet available. I expect most data to be unchanged, except max signal/power level)
    If these transformers are received well, we plan to get cores also for the LL1660 size transformers.

  • LL1688
    is a new BIG tube output transformer designed for 845 applications.
    The transformer weights 4 kg and is the biggest transformer we can presently manufacture.

  • LL1689
    is a new tube preamp output transformer based on the LL1660, but with turns ratio 9+9:1+1+1+1.

  • LL1922
    is a high level line input stepup transformer (turns ration 1+1 : 4+4) similar to the UTC-LS10.

  • Due to spam problems, we have been forced to close our email accounts
    adm@lundahl.se, sales@lundahl.se and webmaster@lundahl.se
    These accounts are replaced by office/AT/lundahl/DOT/se

News Dec 2003 (Never published! Sorry!)

  • The LL1684 is an amorphous core version of the high level, low impedance transformer LL1588.
    The LL1684 is suitable for breaking up ground loops in high level system where a low insertion loss is required. The LL1683 is however not suitable as a line input transformer unless the source impedance is equal or below 200 ohms.

  • LL9202 is the most high impedance version of the LL1620 OPT family. For completeness, the LL9202 data is now incorporated in the LL1620... data sheet.
    In addition, the secondary connection alternatives for all the LL1620 family has been updated to use available copper better.

  • In addition, the following data sheets have been corrected and updated

Old News May 2003

  • OP-AMPS AND TRANSFORMERS
    In the new book "OP AMP APPLICATIONS" (Analog Devices, edited by Walt Jung) the use of (op amps and) audio transformers in line input and output applications are discussed in depth. (Book review)
    In particular the mixed feedback drive circuits for line output transformers are analyzed in great detail. I strongly recommend the book for anyone who is designing transformer line output applications.

    The "OP AMP APPLICATIONS" can be ordered through your nearest Analog Devices sales office using order code OP-AMP-APPLIC-BOOK.
    For North Americans, the book can also be ordered at http://www.analog.com/seminar

    • Old News April 2003

  • Our site should probably need a face-lift with some animated gifs etc. Instead we add some more wrinkles:
    • FAQ, a List of Frequent Asked Questions
    • We split our links page into a links page and a schematics page. The latter contains links to application schematics
    • And we add a page containg all catalog updates from last printed catalog.

  • New products:
    • LL1588 is a high level low impedance general purpose transformer. The LL1588 is primarily designed for line output or galvanic separation of lines, but the transformer performes excellently as a line level phase splitting input transformer.
    • The LL1660S is a version of LL1660 with internal Faraday shields. The LL1660S is designed for interstage phase splitting applications
    • LL1572 (galvanic isolation), LL1573 (splitting, 2 outputs), LL1589 (splitting, 3 outputs) is a new range of transformers for AES/EBU digital audio signals.
    • LL1683 is a new 120VA mains transformers designed for tube preamps and not too powerful monoblocks.
    • LL1685 is a new choke, with a capacity matching the above LL1683 mains transformer.

  • Sometimes you need to more easily switch between different output impedances on our output transformers LL1620, LL1623 and LL1627. This sheet suggests two different wiring alternatives where the OPT secondary is reconnected using only three jumpers.

  • We have studied the output balance when some of our transformers have been used in phase-splitting applications in order to optimize performance. As a result, many of the the suggested connection alternatives have been changed. The following data sheets have been updated:

  • Minor changes to data sheets:

Old News November 2002

  • New small size microphone input transformer LL1587 .
    LL1587 is a microphone transformer suitable for applications where size is a constraint.

  • New moving coil input transformer LL1681 .
    LL1681 is a moving coil transformer with an oversized mu-metal core. The objective is to make a transformer with a more "classical" characteristic than our amorphous core LL9206.

  • New tube output transformer LL1682 .
    LL1682 is a tube output transformer 5.5k : 5 ohms. The objective is to supply a LL1663-size transformer with increased turns ratio to suit high impedance tubes even better.

  • The data sheet for the LL6404 zero field input transformer have been updated due to ambiguities.

  • An 8W SE amplifier building instruction written by Claus Byrith is added.
    This schematic is also added to the list on "links" page

  • Aquablue (our BeNeLux distributor of tube amp transformers) have an impressive list of tube amp projects using our transformers.

Old News August 2002

I apologize for not having updated the web site more frequently. Here are some new transformers which have been added recently:
  • New high level audio output transformer LL1585 .
    The LL1585 has internal Faraday shields and can be used with balanced or unbalanced driving circuitry. Max output level +28dBU (19V) at 20 Hz!!

  • New high level amorphous core input transformer LL1674 .
    Turns ratio 1+1 : 4 + 4
    Can also be used as (decoupled) tube preamp output transformer.

  • New high level amorphous core input transformer LL1676 .
    Turns ratio 1+1 : 2 + 2

  • New high current interstage transformer LL1677 for 300B

  • New moving coil input transformer LL1678 for low impedance pickups.
    The LL1678 has the same structure and pinout as the LL9206 but a higher turns ratio.

  • New tube output transformer LL1679 with 36% UL tap.

  • New tube amplifier line output transformer LL1680 .
    The LL1680 is a Lundahl version of the legendary UTC LS-27 transformer.

  • New high level mu metal core input transformer LL7905 .
    Turns ratio 1+1+1+1 : 5.6 + 5.6
    Max secondary signal level 54V at 50 Hz !!!!

Old News Januari 2001

Old News November 2000

  • LL1667 and LL1668 core airgap problem
    We have found that the chokes LL1667 and LL1668 shipped before November 1, 2000 have been assembled with incorrect air-gap. LL1667 and LL1668 shipped before Nov. 1 are labeled "Choke..."
    LL1667 and LL1668 shipped after Nov. 1. are labeled "Anode Choke..."
    LL1667 and LL1668 datasheet has been updated accordingly.

Old News (Fall 2000)

Old News (April 2000)

  • Two new anode chokes, LL1667 and LL1668 are added.

  • We have designed a new line of XLR inline problem solvers, LL1584 .
    While the old LL156X line of problem solvers are high impedance line input units,
    the LL1584 is designed for general purpose 600 : 600 ohms ground isolation and
    balanced to unbalanced convertion.

  • A number of new schematics using Lundahl Transformers are added on the "links" page

Old News (Jan 2000)

  • Web site is cleaned up and is now better optimized for slow modem users like myself.

Old News (July 1999)

  • We introduce two new tube amplifier output transformers, the LL1663 (5k : 8 ohms) and the LL1664 (3k : 8ohms)

    Both the LL1663 and the LL1664 have performed extremely well in tests. Both transformers have fixed secondaries which make them much more easy to use for both novice and experienced users.
    The transformers are available in PP and SE versions.

  • We also introduce a new small size splitting transformer, the LL1583.

    Our latest splitting transformer, the LL1581XL, has performed very well as we finally understand all requirements on a good splitting transformer. The LL1583 has the same internal design as the LL1581XL, but is only about 1/3 as big. Thus we expect that the LL1583 can be used where space is limited and where signal levels are appropriate.

  • We have understood that the general purpose transformer LL7902 is one of the best audio transformers available. The LL7902 has often been used as input transformer in tube amplifiers. To meet the need for better impedance matching we have designed a new microphone input transformer based on the LL7902 configuration, the LL7903.

    The LL7903 has already been tested by a few very fastidious designers and in their opinon the transformer performes extremely well.

  • We introduce the LL1574 AES/EBU to S/P DIF digital audio interface transformer.
    The transformer is a 110 : 75 ohms impedance matching transformer for digital audio.

  • A list of our distributors is now available

  • The following data sheets are updated:

    LL1545A line input transformer
    LL1566 AES/EBU digital audio transformer
    LL1575 video isolation transformer
    LL1581XL splitting transformer
    LL1638 Mains choke
    LL1660 interstage transformer
    LL5402 line output transformer
    LL7901 and LL7902 audio transformer (This data sheet now contains connection information for a number of different applications)

Old News (April 99)

  • The data sheet for the LL1581XL splitting transformer is updated with more information on how to arrange splitting in a real world situation.

  • We introduce a new line output transformer, LL1582 . The LL1582 is pin compatible with our popular LL2811, but is supplied with internal shields. The shields are important to reduce common mode noise in analog output from digital systems.

  • We introduce a pair of new XLR inline problem solver units, the LL2615-3FXPHM and the LL2616-3MXPHM. . The new units are specially designed for interfacing computer sound boards to professional, balanced equipment. The built-in transformer has a small step-up turns ratio to compensate for any signal loss in the unit.

  • As a result of a number of questions on our transformer designs, we have compiled a design philosopy paper. The paper discusses some of the aspects of transformer design we find important.

    • Old News [Jan 99]

  • The splitting transformer LL1580 did not come out as well as we thought. It is already replaced by the LL1581XL splitting transformer.
    The L1581XL is designed for high immunity to input common mode signals, to large ground differences between receiving systems and to stray magnetic fields. We thus think it will be ideal for all type of on-stage splitting.

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    Per Lundahl, web_master/AT/lundahl/DOT/se
    Lundahl Transformers AB
    Tibeliusgatan 7
    SE-761 50 Norrtälje
    SWEDEN
    Phone: +46 - 176 139 30
    Fax: +46 - 176 139 35
    Email:     office/AT/lundahl/DOT/se