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 cores

Driving 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.

In the 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. We strongly recommend the book for anyone who is designing transformer line output applications.

The book is available on-line at
www.analog.com/library/analogDialogue/archives/39-05/op_amp_applications_handbook.html
and the mixed feedback cuircitry is discussed at Chapter 6 (3.2Mb), page 6.71 and forward.

Sectioning of transformers are discussed in a separate paper.

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Line output

Type Turns Ratio Size LxWxH Max Prim. Level @ 30 Hz Drive Type
Applications / Comments
LL15171+1,ct : 1+1 47x34x19+24 dBU Universal output.
LL15551+1+1+1 : 1+1 33x26x20+27 dBU For balanced drive. Small size..
LL15392 : 1+1 47x34x21+27 dBU For balanced drive
LL15241+1 : 1+1 48x34x22+24 dBU For balanced drive.
LL15821+1 : 1+1 31x26x23+24 dBU For balanced or unbalanced drive Pin compatible with LL2811, but with internal electrostatic shields.
LL15851+1 : 1+1 47x34x21+30 dBU High level universal output transformer.
LL27341+1 : 1.4+1.4 + 0.3+0.3 66 x 39 x 53 +25 dBU Single end class A, 100mA DC For solid state SE output circuits, based on LO1166A
LL28111+1 : 1+1 31x26x23+24 dBU For balanced drive. Four section windings. Small footprint. Fits three in a row across a Euroboard
LL54022 : 1+1 43x28x21+18 dBU For unbalanced drive
LL74011+1 : 1+1 47x34x17+20 dBU For balanced drive.


Active output splitting transformers

TypeTurns Ratio Size LxWxH Max Prim. Level @ 30 Hz Drive Type Applications / Comments
LL15602+2 : 1+1+1+147x34x23+20 dBU For balanced drive. Four independent outputs active split.
LL19441+1 : 1+1+1+1 47x34x23+ 23 dBU For balanced drive. Four independent outputs active split.