Lundahl
tube amplifier output transformers




Each model number is available in a Push-Pull (PP) and several Single-Ended (SE) versions.

The difference is the thickness of the "airgap". The PP versions use a 25 micron air-gap and this small gap allows a 15% DC unbalance of the output tubes. The SE versions have much larger airgap's. The purpose of the airgap is to accept the DC current of the output tube without saturating the core, but still leaving enough headroom for the sound signal. As a result of the airgap, the primary inductance is lower for SE output transformers compared to the PP versions.

Some models are available as multi-impedance types. These models have multiple separate secondary coils. By connecting these coils in a certain way the transformers can be wired for different output impedances (4, 8, 16R ) and/or they can be used as transformers with a different primary impedance. How to do this is explained in the data sheets.



Transformers arranged by model number
Each model number is available in a PP and several SE versions.
     
 
Type
 data sheet

Primary impedance

Secondary impedance
Weight (Kg)
     
 
LL1620 LL1620-3-7-9202 3.3K, 6.0K or 11.5K
4, 8, 16 Ohms
2.5
LL1620-CFB LL1620-CFB 3.3K, 6.0K or 11.5K + cathode feedback
4, 8, 16 Ohms
2.5
LL1623 LL1620-3-7-9202 1.6K, 3.0K or 5.6K
4, 8, 16 Ohms
2.5
LL1627 LL1620-3-7-9202 650R, 1.2K or 2.3K
4, 8, 16 Ohms
2.5
LL1663 LL1663 5K, UL tap.
8 Ohm
1.4
LL1664 LL1664 3K , UL tap.
8 Ohm
1.4
LL1679 LL1679 2.6K, 4.5K or 9.7K , UL tap.
4, 8, 16 Ohms
2.5
LL1682 LL1682 5.5K, 33% UL tap.
5 Ohm
1.4
LL1688 LL1688 5.5K, 9.2K or 20.5K, 33% UL tap.
4, 8, 16 Ohms
4.0
LL1691 LL1691 9K
8 Ohm
4.6
LL1691B LL1691B 20K
8 Ohm
4.6
LL1693 LL1693 600R, 1K or 2.3K
4, 8, 16 Ohms
4.5
LL2735B LL2735B 9K
8 Ohm
1.4
LL9202 LL1620-3-7-9202 6.5K, 11K or 23K
4, 8, 16 Ohms
2.5



Transformers arranged by Primary impedance
Each model number is available in a PP and several SE versions.
   
Primary Imp.
(KOhms) 		Type
Max power 30 Hz, Push-Pull (W)
Max power 30Hz, Single- Ended (W)
4 Ohm
8 Ohm
16 Ohm
Fixed sec.
output

Weight
(Kg)
0.6K LL1693
700
140
Alt C
Alt D
Alt E
4.5
0.65K LL1627
250
50
Alt C
Alt D
Alt E
2.5
1K LL1693
360
70
Alt B
Alt C
Alt D
4.5
1.2K LL1627
125
25
Alt B
Alt C
Alt D
2.5
1.6K LL1623
250
50
Alt C
Alt D
Alt E
2.5
2.3K LL1627
62
13
Alt B
Alt C
2.5
2.3K LL1693
180
35
Alt B
Alt C
4.5
2.6K LL1679
188
36
Alt C
Alt D
Alt E
2.5
3.0K LL1623
125
25
Alt B
Alt C
Alt D
2.5
3.0K LL1664
55
10
8 R
1.4
3.3K LL1620
250
50
Alt C
Alt D
Alt E
2.5
4.5K LL1679
105
20
Alt B
Alt C
Alt D
2.5
5.0K LL1663
40
8
8 R
1.4
5.5K LL1688
320
60
Alt C
Alt D
Alt E
4.0
5.5K LL1682
40
8
5 R
1.4
5.6K LL1623
62
13
Alt B
Alt C
2.5
6.0K LL1620
125
25
Alt B
Alt C
Alt D
2.5
6.5K LL9202
125
25
Alt B
Alt C
Alt D
2.5
9.0K LL1691
160
30
8 R
4.6
9.2K LL1688
160
30
Alt B
Alt C
Alt D
4.0
9.7K LL1679
45
9
Alt B
Alt C
2.5
11K LL9202
125
25
Alt B
Alt C
Alt D
2.5
11.5K LL1620
62
13
Alt B
Alt C
2.5
16K LL2735B
-
5
8 R
1.4
20K LL1691B
160
30
8 R
4.6
23K LL9202
62
13
Alt B
Alt C
2.5
   
   


LL1620, LL1620-CFB, LL1623, LL1627, LL1663, LL1664, LL1679, LL1682, LL2735B are also available with amorphous C-core