Lundahl Transformers - Microphone transformers

Microphone transformers

Microphone transformers are normally used for impedance matching:: - In mic preamplifier input circuits to match microphones to preamp amplifier circuits.; - In tube microphones for matching high impedance tube circuits to normal output impedance; - In ribbon microphones to match very low signal, very low impedance microphone sensors to normal microphone output levels.
General properties of most Lundahl microphone transformers:: - PCB mount style; - High level capability; - Excellent magnetic and electrostatic shielding; - High mu cores (mu metal or amorphous strip core)

"Normal" microphone transformers, often used in preamp input or tube microphone output applications.

Type Turns Ratio Size (LxWxH mm) Max Prim. Level.
1% dist, 50Hz (Prim. in parallel) Application examples

LL1527 1+1 : 1 + 1 38x24x17 +10 dBU 200 : 200 ohms or 200 : 800 ohms
For low impedance input mic preamps such as Jensen JE-990

LL1528 1+1 : 2.5+2.5 38x24x17 +10 dBU 200 : 5 k ohms

LL1530 1+1 : 3.5+3.5 38x24x17 +10 dBU 200 : 10 k ohms.
Also used in DI-boxes 10k : 200 ohms

LL1538 1+1 : 5 38x24x17 +10 dBU 200 : 5 k ohms.
Probably the best 1:5 microphone input transformer available.

LL1538XL 1+1 : 5 38x24x20.5 +13 dBU 200 : 5 k ohms.
High level version of LL1538

LL1550 1+1+1+1 : 4+4 30x22.5x14.5 0 dBU 200 : 3.2 k ohms if used 1:4.
Many other connections possible.

LL1570 1+1 : 1 + 1 38x24x17 +10 dBU 200 : 200 ohms or 200 : 800 ohms
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 ohms.

LL1576 1+1 : 7 38x24x17 +10 dBU 200 : 10 k ohms.
Same pinout as LL1538

LL1577 1+1 : 14 38x24x17 +10 dBU 50 : 10 k ohms.
Same pinout as LL1538. For low impedance source.

LL1578 1+1 : 10 38x24x17 +10 dBU 50 : 5 k ohms.
Same pinout as LL1538. For low impedance source.

LL1578XL 1+1 : 10 38x24x20.5 +13 dBU 50 : 5 k ohms.
Same pinout as LL1538. For low impedance source.

LL1587 1+1 : 4 26x17x12 +2 dBU 200 : 3.2 k ohms.
Small size.

LL1636 1+1+1+1 : 10+10 30x22.5x14.5 -14 dBU Mic Input. DI-box. Moving coil input.

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 ohm microphones into
1200 ohms

LL7903 1+1+1+1 : 2+2+2+2 66x32x21 +16 dBU 200 : 13 k ohms (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 ohms tube amplifier mic/line input (used 2 : 11.2)
Designed for high quality tube equipment.

Type	Turns Ratio	Size (LxWxH mm)	Max Prim. Level. 1% dist, 50Hz (Prim. in parallel)	Application examples
LL1527	1+1 : 1 + 1	38x24x17	+10 dBU	200 : 200 ohms or 200 : 800 ohms For low impedance input mic preamps such as Jensen JE-990
LL1528	1+1 : 2.5+2.5	38x24x17	+10 dBU	200 : 5 k ohms
LL1530	1+1 : 3.5+3.5	38x24x17	+10 dBU	200 : 10 k ohms. Also used in DI-boxes 10k : 200 ohms
LL1538	1+1 : 5	38x24x17	+10 dBU	200 : 5 k ohms. Probably the best 1:5 microphone input transformer available.
LL1538XL	1+1 : 5	38x24x20.5	+13 dBU	200 : 5 k ohms. High level version of LL1538
LL1550	1+1+1+1 : 4+4	30x22.5x14.5	0 dBU	200 : 3.2 k ohms if used 1:4. Many other connections possible.
LL1570	1+1 : 1 + 1	38x24x17	+10 dBU	200 : 200 ohms or 200 : 800 ohms 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 ohms.
LL1576	1+1 : 7	38x24x17	+10 dBU	200 : 10 k ohms. Same pinout as LL1538
LL1577	1+1 : 14	38x24x17	+10 dBU	50 : 10 k ohms. Same pinout as LL1538. For low impedance source.
LL1578	1+1 : 10	38x24x17	+10 dBU	50 : 5 k ohms. Same pinout as LL1538. For low impedance source.
LL1578XL	1+1 : 10	38x24x20.5	+13 dBU	50 : 5 k ohms. Same pinout as LL1538. For low impedance source.
LL1587	1+1 : 4	26x17x12	+2 dBU	200 : 3.2 k ohms. Small size.
LL1636	1+1+1+1 : 10+10	30x22.5x14.5	-14 dBU	Mic Input. DI-box. Moving coil input.
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 ohm microphones into 1200 ohms
LL7903	1+1+1+1 : 2+2+2+2	66x32x21	+16 dBU	200 : 13 k ohms (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 ohms tube amplifier mic/line input (used 2 : 11.2) Designed for high quality tube equipment.

Special application microphone transformers. These do not have a Faraday shield and are normally used as microphone output transformers.

Type Turns Ratio Size (LxWxH mm) Application Comment

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

LL1927A 1+1 : 55+55 30x22.5x14.5 Ribbon microphones (used 1:110) Amorphous core. Normally requires active output stage

Type	Turns Ratio	Size (LxWxH mm)	Application	Comment
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
LL1927A	1+1 : 55+55	30x22.5x14.5	Ribbon microphones (used 1:110)	Amorphous core. Normally requires active output stage

Per Lundahl, email: web_master/AT/lundahl/DOT/se

Lundahl Transformers AB
Tibeliusgatan 7
SE-761 50 Norrtälje
SWEDEN
Phone: +46 - 176 139 30
Fax: +46 - 176 139 35
Email: office/AT/lundahl/DOT/se