Tube amplifier output transformers
Below you find a list of all our tube amplifier output transformers (OPTs), sorted by primary impedance.
All OPTs are built in our dual coil single Ccore style and can be assembled with a huge range of core airgaps for PushPull or SingleEnded applications. As you can see, most of our OPTs can be configured for different primary and secondary impedances.
The use of Ccores with well defined airgaps results in an almost constant inductance throughout the whole operating voltage range. For SE transformers, the primary inductance variation due to signal level is less than 7%.
 If you need to more easily switch between different speaker impedances on our output transformers LL1620, LL1623 and LL1627, this sheet suggests two different wiring alternatives where the OPT secondary is reconnected using only three jumpers.
 The LL1620CFB is a special version of the LL1620 where the primary windings have been split to allow for cathode feedback connections.
 The 2.5kg and the 1.4 kg transformers above are available with amorphous iron Ccores. We expect all application parameters to be similar for the amorphous core and the silicon iron cores, except that the amorphous cores signal handling capability is slightly smaller.
From a purely engineering point of view, we can not justify the fairly high price of our amorphous core OPTs. But we have actually received a lot of praise for their sound qualites, such as this report.
When considering testing an amorphous core transformer, please note that they are said to require much longer break in time than what is normally required for siliconiron cores.
Primary impedance (kOhms) 
Secondary impedance (Ohm) 
Max power capability at 30 Hz, PushPull 
Max power capability at 30 Hz, Singel Ended 
Weight kg 
Transformer type 
Configuration 
0.6 k 
4 Ω 
700W 
140W 
4.5 kg 
LL1693

C 
0.65 k 
4 Ω 
250W 
50W 
2.5 kg 
LL1627

C 
1.0 k 
4 Ω 
360W 
70W 
4.5 kg 
LL1693

B 
1.2 k 
4 Ω 
125W 
25W 
2.5 kg 
LL1627

B 
1.2 k 
8 Ω 
125W 
25W 
2.5 kg 
LL1627

C 
1.2 k 
16 Ω 
125W 
25W 
2.5 kg 
LL1627

D 
1.6 k 
4 Ω 
250W 
50W 
2.5 kg 
LL1623

B 
1.6 k 
8 Ω 
250W 
50W 
2.5 kg 
LL1623

C 
1.6 k 
16 Ω 
250W 
50W 
2.5 kg 
LL1623

D 
2.3 k 
8 Ω 
62W 
13W 
2.5 kg 
LL1627

B 
2.3 k 
16 Ω 
62W 
13W 
2.5 kg 
LL1627

C 
2.3 k 
8 Ω 
180W 
35W 
4.5 kg 
LL1693

B 
2.3 k 
16 Ω 
180W 
35W 
4.5 kg 
LL1693

C 
2.6 k 
4 Ω 
188W 
36W 
2.5 kg 
LL1679

C 
2.6 k 
8 Ω 
188W 
36W 
2.5 kg 
LL1679

D 
2.6 k 
16 Ω 
188W 
36W 
2.5 kg 
LL1679

E 
3.0 k 
4 Ω 
125W 
25W 
2.5 kg 
LL1623

B 
3.0 k 
8 Ω 
125W 
25W 
2.5 kg 
LL1623

C 
3.0 k 
16 Ω 
125W 
25W 
2.5 kg 
LL1623

D 
3.0 k 
8 Ω 
55W 
10W 
1.4 kg 
LL1664

 
3.3 k 
4 Ω 
250W 
250W 
2.5 kg 
LL1620

C 
3.3 k 
8 Ω 
250W 
50W 
2.5 kg 
LL1620

D 
3.3 k 
16 Ω 
250W 
50W 
2.5 kg 
LL1620

E 
4.5 k 
4 Ω 
105W 
20W 
2.5 kg 
LL1679

B 
4.5 k 
8 Ω 
105W 
20W 
2.5 kg 
LL1679

C 
4.5 k 
16 Ω 
105W 
20W 
2.5 kg 
LL1679

D 
5.0 k 
8 Ω 
40W 
8W 
1.4 kg 
LL1663

 
5.5 k 
4 Ω 
320W 
60W 
4.0 kg 
LL1688

C 
5.5 k 
5 Ω 
40W 
8W 
1.4 kg 
LL1682

 
5.5 k 
8 Ω 
320W 
60W 
4.0 kg 
LL1688

D 
5.5 k 
16 Ω 
320W 
60W 
4.0 kg 
LL1688

E 
5.6 k 
8 Ω 
62W 
13W 
2.5 kg 
LL1623

B 
5.6 k 
16 Ω 
62W 
13W 
2.5 kg 
LL1623

C 
6.0 k 
4 Ω 
125W 
25W 
2.5 kg 
LL1620

B 
6.0 k 
8 Ω 
125W 
25W 
2.5 kg 
LL1620

C 
6.0 k 
16 Ω 
125W 
25W 
2.5 kg 
LL1620

D 
6.5 k 
4 Ω 
250W 
50W 
2.5 kg 
LL9202

C 
6.5 k 
8 Ω 
250W 
50W 
2.5 kg 
LL9202

D 
6.5 k 
16 Ω 
250W 
50W 
2.5 kg 
LL9202

E 
9.0 k 
8 Ω 
160W 
30W 
4.6 kg 
LL1691

 
9.2 k 
4 Ω 
160W 
30W 
4.0 kg 
LL1688

B 
9.2 k 
8 Ω 
160W 
30W 
4.0 kg 
LL1688

C 
9.2 k 
16 Ω 
160W 
30W 
4.0 kg 
LL1688

D 
9.7 k 
8 Ω 
45W 
9W 
2.5 kg 
LL1679

B 
9.7 k 
16 Ω 
45W 
9W 
2.5 kg 
LL1679

C 
11 k 
4 Ω 
125W 
25W 
2.5 kg 
LL9202

B 
11 k 
8 Ω 
125W 
25W 
2.5 kg 
LL9202

C 
11 k 
16 Ω 
125W 
25W 
2.5 kg 
LL9202

D 
11.5 k 
8 Ω 
62W 
13W 
2.5 kg 
LL1620

B 
11.5 k 
16 Ω 
62W 
13W 
2.5 kg 
LL1620

C 
16 k 
8 Ω 
 
5W 
1.4 kg 
LL2735B

 
20 k 
8 Ω 
160W 
30W 
4.6 kg 
LL1691B

 
23 k 
8 Ω 
62W 
13W 
2.5 kg 
LL9202

B 
23 k 
16 Ω 
62W 
13W 
2.5 kg 
LL9202

C 