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
| Photo | Type | Turns Ratio | Size LxWxH | Max Primlevel @ 50Hz | Applications/Comments |
|---|---|---|---|---|---|
 | LL1527 | 1+1 : 1+1 | 38x24x17 | +16 dBU | The "standard" problem solver. Ground isolation, MS decoding, splitting 1 direct + 1 isolated outputs. Mic input 200:200 or 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 | +2 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 | 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. |
|
 | LL1951 | 1+1 : 14 | 37x22x17 | +10 dBU | Compatible with LL1577, but with reduced internal capacitance. |
 | LL1968 | 2 : 1 | 25x15.8x14.5 | +15 dBU | Output transformer for solid state microphones. |
 | LL1969 | 23 + 1 : 6 | 36x22x16 | + 18 dBU | Same structure as the BV12 microphone transformer. To be used in U67 replicas. |
 | 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. |
 | LL7906 | 1+1+1+1 : 5.6 + 5.6 | 66x32x21 | +16 dBU | Improved version of LL7905. |
