Tibeliusgatan 7 S-761 50 NORRTÄLJE SWEDEN

LUNDAHL TRANSFORMERS

International +46 - 176 13930 +46 - 176 13935

Phone Fax

Domestic 0176-13930 0176-13935

Tube Amplifier Output Transformers LL1688 LL1688 is an output transformer, designed primarily for 845 tube amplifiers, but the LL1688 is available with different core air-gaps for different types of output stages. The transformers are highly sectioned with harmonically sized sections, which results in a minimum leakage inductance. This, combined with a low capacitance coil winding technique results in a wide frequency range. The primary winding can be tapped for 33% UL connection. The transformers have a special audio C-core of our own production. The transformers are unpotted, open frame type suitable for mounting inside an amplifier housing.

Physical dimensions, pin and mounting hole layout LL1688 (all dimensions in mm) 58

Primary connections

Secondary connections

B8 B7 B6 B5 B4 B3 B2 B1

I

4 x M4 Mounting holes

118

II

II

140

I

Bottom view 1

3

5

9

B15

B17

11 13 B18

95

B16

B13 B14

B11 B12

95

R040312

Pin spacing module: Row spacing: Weight: Turns ratio:

5.08 mm (0.2") 91 mm approx. 4 kg 50 + 50 : 1 + 2 + 2 + 1 + 1 + 2 + 2 + 1 Winding schematics: Coil I

1

3 33

1 B14

5

B13

13

17

2 B1

Coil II

17

2 B11

B4

11

1 B2

B3

1 B12

LL1688 -1-

B16

33

2 B7

B6

9

2 B8

B15

1 B17

B5

B18

LL1688 50 + 50 : 1 + 2 + 2 + 1 + 1 + 2 + 2 + 1

Turns ratio: Static resistance of primary (all in series)

260 Ω (130Ω + 130Ω)

Static resistance of secondary windings (in -> out)

0.3Ω, 0.7Ω, 0.7Ω, 0.4Ω 7 mH

Primary leakage inductance (all in series)

200mA

Max recommended primary DC current (heat dissip. 10W) Max. primary signal voltage r.m.s. at 30 Hz (all in series)

Push-Pull (1.6T) 1220V

Single End (0.7T) 530V

Isolation between primary and secondary windings / between windings and core: 4 kV / 2 kV

Electrical characteristics Primary Load Impedance, Max power and power loss. Sec. connection for 4/8/16 Ω (See next page) -/B/C B/C/D C/D/E Primary Load Impedance (transformer copper resistance included)

LL1688

20.5 kΩ

Max. Power, P-P at 30 Hz Max. Power, S.E. at 30 Hz Power loss across transformer

72W 15W 0.15 dB

9.2 kΩ Power and Loss 160W 30W 0.25 dB

5.5 kΩ 320W 60W 0.5 dB

Primary DC Current

Core Air-gap and Primary inductance LL1688/70mA Core Airgap 240 µ (delta/2) Single end standing current for 0.9 Tesla 70mA (recommended operating point) Primary inductance 70 H

Frequency response, LL1688/70mA (source impedance 2.2k, load impedance 10 ohms. Primary winding is series, secondary winding “alt. C”. Secondary winding not grounded. Primary signal level approx 10V) 10 Hz – 25kHz +0 / -1 dB 5Hz – 33 kHz +0 / -3 dB

LL1688 -2-

Primary connections, Push-Pull

Primary connections, Singe End

Tube Anode

1

UL tap 33%

3

3

5

5

V+ Tube Anode UL tap 33%

Tube Anode

1

V+

9

9

11

11

13

13

Secondary connections Indicates phase

B1

B11

B1

B11

B2

B12

B2

B12

B3

B13

B3

B13

B4

B14

B4

B14

B5

B15

B5

B15

B6

B16

B6

B17

B7

B18

B8

B7

B

B8

C

B16 B17 B18

Max secondary Voltage RMS @ 30 Hz P-P: 37V SE : 16V Sec. copper resistance Windings in series 3 0.2 Ω

Max secondary Voltage RMS @ 30 Hz P-P: 25V SE : 11V Sec. copper resistance Windings in series 2 0.15 Ω

B1

B11

B1

B11

B2

B12

B2

B12

B3

B13

B3

B13

B4

B14

B4

B14

B5

B15

B5

B15

B6

B16

B6

B16

B17

B7

B18

B8

B7 B8

D

Max secondary Voltage RMS @ 30 Hz P-P: 50V SE : 22V Sec. copper resistance Windings in series 4 0.5 Ω

E

B17 B18

Max secondary Voltage RMS @ 30 Hz P-P: 74V SE : 32V Sec. copper resistance Windings in series 6 1Ω LL1688 -3-