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Line Output Transformers


Line Output Transformers


Line output transformers

Line output transformers with silicon iron C cores.

General properties

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
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.

Line Output

Type  Turns Ratio Size LxWxH Max Primary Level @ 30Hz
LL1517 1+1,ct : 1+1 47x34x19 +24 dBU  
 Universal output.
LL1555 1+1+1+1 : 1+1 33x26x20 +27 dBU  
 For balanced drive. Small size.
LL1539 2 : 1+1 47x34x21 +27 dBU
 For balanced drive
LL1524 1+1 : 1+1 48x34x22 +27 dBU
 For balanced drive.
LL1582 1+1 : 1+1 31x26x23 +24 dBU  
 For balanced or unbalanced drive, Pin compatible with LL2811, but with internal electrostatic shields.
LL1585 1+1 : 1+1 47x34x21 +30 dBU  
 High level universal output transformer.
LL2734 1+1 : 1.4+1.4 + 0.3+0.3 66x39x53 +25 dBU  
  Single end class A, 100mA DC For solid state SE output circuits, based on LO1166A.
LL2811 1+1 : 1+1 31x26x23 +24 dBU  
  For balanced drive. Four section windings. Small footprint. Fits three in a row across a Euroboard
LL5402 2 : 1+1 43x28x21 +18 dBU  
 For unbalanced drive
LL7401 1+1 : 1+1 47x34x17 +20 dBU  
 For unbalanced drive

Active Output Splitting Transformers

LL1560 2+2 : 1+1+1+1 47x34x23 +20 dBU
 For balanced drive. Four independent outputs active split.
LL1944 1+1 : 1+1+1+1 47x34x23 +23 dBU
 For balanced drive. Four independent outputs active split.

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