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)

Microphone Transformers

PhotoTypeTurns RatioSize LxWxHMax Primlevel @ 50HzApplications/Comments
LL15271+1 : 1+138x24x17+16 dBUThe "standard" problem solver. Ground isolation, MS decoding,
splitting 1 direct + 1 isolated outputs. Mic input 200:200 or 200:800 Ω.
LL15281+1 : 2.5+2.538x24x17+10 dBU200 : 5 k Ω
LL15301+1 : 3.5+3.538x24x17+10 dBU200 : 10 k Ω. Also used in DI-boxes 10k : 200 Ω.
LL15381+1 : 538x24x17+10 dBU200 : 5 k Ω. Probably the best 1:5 microphone input transformer available.
LL1538XL1+1 : 538x24x20.5+13 dBU200 : 5 k Ω. High level version of LL1538
LL1550 1+1+1+1 : 4+430x23x14.5 +2 dBU200 : 3.2 k Ω if used 1:4. Many other connections possible.
LL15701+1 : 1+138x24x17+10 dBU200 : 200 Ω or 200 : 800 Ω. For low impedance input mic preamps such as
Jensen JE-990
LL15711+1 :
1.75 + 1.75
38x24x17 +10 dBU200 : 2.5 k Ω.
LL15761+1 : 7 38x24x17+10 dBU200 : 10 k Ω. Same pinout as LL1538
LL15771+1 : 1438x24x17+10 dBU50 : 10 k Ω. Same pinout as LL1538. For low impedance source.
LL15781+1 : 1038x24x17 +10 dBU 50 : 5 k Ω. Same pinout as LL1538. For low impedance source.
LL1578XL1+1 : 10 38x24x20.5 +13 dBU 50 : 5 k Ω. Same pinout as LL1538. For low impedance source.
LL15871+1 : 4 26x17x12+2 dBU 200 : 3.2 k Ω. Small size.
LL16361+1+1+1 : 10+1030x23x14.5 -14 dBU Mic Input. DI-box. Moving coil input.
LL19261+1+1+1 : 4+437x23x12+7 dBU50 : 3.2 k if used 1 : 8. Many other connections possible.
LL1927A1+1 : 55+5530x23x14.5 Ribbon microphones (used 1:110). Amorphous core. For active output stage.
LL19351+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.
LL19409 : 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.
LL19511+1 : 14 37x22x17 +10 dBUCompatible with LL1577, but with reduced internal capacitance.
LL19682 : 125x15.8x14.5+15 dBUOutput transformer for solid state microphones.
LL196923 + 1 : 636x22x16+ 18 dBUSame structure as the BV12 microphone transformer.
To be used in U67 replicas.
LL29121 : 37 27 mm x diam. 18.5 Ribbon microphones. Amorphous core. Flying leads. No housing.
LL29131+1+1+1: 37 30x22.5x14.5Ribbon microphones. Amorphous core. PCB version of LL2912.
With mu metal housing.
LL29141+1+1+1: 37 38x24x17Ribbon microphones. Mu metal core version of LL2913.
LL29151 : 37 36 mm x diam. 22 Ribbon microphones.
Mu metal lamination core. Flying leads. No housing
LL29161+1 : 55+5538x23x26Mu metal lamination core version of LL1927A.
LL79031+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.
LL79061+1+1+1 : 5.6 + 5.666x32x21+16 dBU Improved version of LL7905.

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