
Line Output Transformer for Tube Amplifiers
LL1680
The LL1680 line output transformer is made to match or exceed the specs of the UTC transformer LS-27. The
LS-27 was used in the RCA Tube Mike Pre (which was used in BC-2B Consoles).
For the internal insulation of the LL1680 high impedance sections we have used paper (and not polypropylene foil)
to minimize internal capacitance. Each coil consists of three sections to optimize leakage inductance versus inter-
winding capacitance. The transformer has a special audio C-core of our own production.
Turns ratio: 9 + 9 : 1+1+1+1
Winding schematics, physical dimensions, pin and mounting hole layout (all dimensions in mm)
Weight Turns ratio Static resistance,
winding 9-11 and 16-14
Static resistance,
winding 2-4 and 8-6
Static resistance,
winding 1-3 and 7-5
0.35 Kg 9 + 9 : 1 + 1+ 1+ 1
580 Ω 11 Ω 15 Ω
Isolation between primary and secondary windings / between windings and core: 4 kV / 2 kV
Max standing DC current through any primary section
50 mA
Type
LL1680/5mA LL1680/5mA LL1680/5mA LL1680/5mA
Application 15k : 600 ohm
Balanced output
15k : 600 ohm
Unbalanced
output
15k : 150 ohm
Balanced output
15k : 150 ohm
Unbalanced
output
Connection Alt A Alt B Alt C Alt D
Turns ratio 18 : 4 18 : 4 18 : 2 18 : 2
Primary DC current for 0.9
Tesla
5mA 5mA 5mA 5mA
Primary Inductance 210H 210H 210H 210H
Frequence response,
+0, -1.5dB (ref. 1kHz)
Source impedance
Load
15 Hz – 50 kHz
15kΩ
600 Ω
15 Hz – 40 kHz
15kΩ
600 Ω
15 Hz – 55 kHz
15kΩ
150 Ω
15 Hz – 40 kHz
15kΩ
150 Ω
Max primary signal voltage
(RMS) at 30 Hz
150V 150V 150V 150V
Max output
voltage @ 30 Hz
33V RMS 33VRMS. 16V RMS 16V RMS
R041019
Bottom view
4 x M3
Mounting holes
66
24
50
9 + 9
1+1+1+1
TRANSFORMERS
S-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
1
2
3
5
6
8
9
11
14
16
7
4
9
11
3
1
4
2
6
8
5
7
16
14
Coil 1
Coil 2