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Lundahl

Microphone Transformers

Microphone transformers

Microphone transformers are normally used for impedance matching:
  • In 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)

Isolation transformers

Type  Turns Ratio Size LxWxH Max Primary Level
LL1527 1+1 : 1+1 38x24x17 +16 dBU  
 The "standard" problem solver. Ground isolation, MS decoding, splitting 1 direct + 1 isolated outputs. Mic input 200:800 Ω.
LL1528 1+1 : 2.5+2.5 38x24x17 +10 dBU  
 200 : 5 k Ω
LL1530 1+1 : 3.5+3.5 38x24x17 +10 dBU
 200 : 10 k Ω. Also used in DI-boxes 10k : 200 Ω
LL1538 1+1 : 5 38x24x17 +10 dBU
  200 : 5 k Ω. Probably the best 1:5 microphone input transformer available.
LL1538XL 1+1 : 5 38x24x20.5 +13 dBU  
 200 : 5 k Ω. High level version of LL1538
LL1550 1+1+1+1 : 4+4 30x23x14.5 +2 dBU  
 200 : 3.2 k Ω if used 1:4. Many other connections possible.
LL1570 1+1 : 1+1 38x24x17 +10 dBU  
 200 : 200 Ω or 200 : 800 Ω. For low impedance input mic preamps such as Jensen JE-990
LL1571 1+1 :
1.75 + 1.75		 38x24x17 +10 dBU  
 200 : 2.5 k Ω.
LL1576 1+1 : 7 38x24x17 +10 dBU  
 200 : 10 k Ω. Same pinout as LL1538
LL1577 1+1 : 14 38x24x17 +10 dBU
 50 : 10 k Ω. Same pinout as LL1538. For low impedance source.
LL1578 1+1 : 10 38x24x17 +10 dBU  
 50 : 5 k Ω. Same pinout as LL1538. For low impedance source.
LL1578XL 1+1 : 10 38x24x20.5 +13 dBU 
 50 : 5 k Ω. Same pinout as LL1538. For low impedance source.
LL1587 1+1 : 4 26x17x12 +10 dBU  
 200 : 3.2 k Ω. Small size.
LL1636 1+1+1+1 : 10+10 30x23x14.5 -14 dBU  
 Mic Input. DI-box. Moving coil input.
LL1926 1+1+1+1 : 4+4 37x23x12 +7 dBU  
 50 : 3.2 k if used 1 : 8. Many other connections possible.
LL1927A 1+1 : 55+55 30x23x14.5 +10 dBU  
 Ribbon microphones (used 1:110). Amorphous core. For active output stage
LL1935 1+1 : 5+5 38x23x16 +7 dBU  
 DI (Direct Input) used 10:1. Mic input 200 : 20k.
LL1936 (2+1)+(2+1) :
4 + 4		 48x29x20 +14 dBU  
 Can be connected for 75, 150, 300 and 600 Ω microphones into 1200 Ω.
LL1940 9 : 1+1 31x25x16
 Tube microphones. Silicon-iron C-core, which results in a transformer with more "transformer sound character", compared to a classic mu metal lamination transformer. PCB mount style.
LL2912 1 : 37 27 mm x diam. 18.5   
 Ribbon microphones. Amorphous core. Flying leads. No housing.
LL2913 1+1+1+1: 37 30x22.5x14.5
 Ribbon microphones. Amorphous core. PCB version of LL2912. With mu metal housing.
LL2914 1+1+1+1: 37 38x24x17   
 Ribbon microphones. Mu metal core version of LL2913.
LL2915 1 : 37 36 mm x diam. 22   
  Ribbon microphones. Mu metal lamination core. Flying leads. No housing
LL2916 1+1 : 55+55 38x23x26
  Mu metal lamination core version of LL1927A.
LL7903 1+1+1+1 : 2+2+2+2 66x32x21 +16 dBU  
 200 : 13 k Ω (used 1:8) This is the ultimate microphone input transformer, designed for high quality tube equipment.
LL7905 1+1+1+1 : 5.6 + 5.6 66x32x21 +16 dBU  
 High level 600 Ω tube amplifier mic/line input (used 2 : 11.2) Designed for high quality tube equipment.
LL7906 1+1+1+1 : 5.6 + 5.6 66x32x21 +16 dBU  
  Improved version of LL7905.

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