
Tube Amplifier Interstage Transformer / Line Output Transformer
LL1660
LL1660 is an interstage / line output transformer for tube amplifiers. The transformer is available with different
core air gap for PP or SE drives.
The transformer is wound with a special low capacitance winding technique to achieve best high frequency
performance. The transformer has a special high flux, low distortion audio C-core of our own production.
The LL1660PP is assembled with a small core air gap to allow for some DC current unbalance.
For the S.E. versions of the LL1660, the core air gap is chosen such that the denoted DC current (18mA for a
LL1660/18mA) generates a no signal core flux density of 0.9 Tesla when used with all primaries in series. This
leaves a flux density swing of 0.7 T for the signal.
Winding schematics, physical dimensions, pin and mounting hole layout (all dimensions in mm)
Weight Turns ratio Static resistance,
winding A
Static resistance,
winding B
Static resistance,
winding C
0.75 Kg 1+1+1+1 : 2.25+2.25
315 Ω 240 Ω 625 Ω
Max. current through any single section: 50 mA
Isolation between primary and secondary windings / between windings and core: 4 kV / 2 kV
Type
LL1660 PP LL1660 PP LL1660/18mA LL1660/10mA
Connection Alt M´´
PP to PP Interst.
2.25+2.25 : 2+2
Alt N
PP Line output
2.25+2.25 : 1
Alt Q
SE Line Output
4.5 : 1
Alt S
SE to SE Interst.
4 : 4.5
Primary DC current for
0.9 Tesla
- - 16 mA 10 mA
Primary Inductance 290H 290H 100H 130H
Freq. Response (+/-1dB)
@ source impedance (*)
Secondaries open
20 Hz – 25 kHz
15kΩ
16 Hz – 30 kHz
15kΩ
11 Hz – 35 kHz
3 kΩ
25Hz - 40 kHz
14 kΩ
Max output
voltage @ 30 Hz
2 x 260V r.m.s. 130V r.m.s. 57 V r.m.s. 250 V r.m.s.
Type
LL1660/10mA LL1660/10mA
Connection Alt T
SE to SE Interst.
2 : 4.5
Alt V
SE to PP Interst.
2.25 : 2 + 2
Primary DC current for
0.9 Tesla
20 mA 18 mA
Primary Inductance 33H 42H
Freq. Response (+/-1dB)
@ source impedance (*)
Secondaries open
25 Hz - 30 kHz
3.5kΩ
25 Hz - 30 kHz
3.5kΩ
Max output
voltage @ 30 Hz
250 V r.m.s. 220 V r.m.s.
73
Bottom view
4 x M3
Mounting holes
36
56
TRANSFORMERS
Tibeliusgatan 7 International Domestic
S-761 50 NORRTÄLJE Phone +46 - 176 13930 0176-13930
SWEDEN Fax +46 - 176 13935 0176-13935
2
3
4
5
7
8
9
10
13
16
18
21
13
16
4
3
5
2
21
18
A
B
8
9
B
7
10
A
C
C
(*) The source impedances used in
the tables indicates a recommended
upper limit, unless freq. response can
At lower source impedance resonance
peaking will occure. It can be
reduced using secondary load
resistors.