Output transformers and chokes

Output transformer for tube amplifiers

[AOT-40 technical data]    [Other transformers]    [Chokes]

A high-quality output transformer is the heart of the tube amplifier. A poor output transformer fitted in a well designed amplifier will spoil its performance.
Needless to say that the design and optimization of an output transformer takes high skill and know-how because performance requirements are complex and high. The transformer must deliver adequate and constant power without core saturation. It should provide wide frequency bandwidth at a minimum distortion. Moreover, it should provide a constant outstanding performance to retain the open, spacious qualities of recorded music.
The sound quality of ASV transformers is exceptional: low distortion and an extremely wide frequency and dynamic range. The present AOT-40 transformer has a double C core and has been carefully wound, has no internal solder joints, is impregnated and encapsulated in metal housing. There are two threaded mounting bolts for easy installation.


Typical applications include push-pull triode, ultralinear and pentode power tube configurations. It could be equally used in new designs and for upgrading old ones.


Photo (15 KB) Connections on bottom
ASV AOT-40 transformer Bottom side with connections


Technical specifications for the ASV AOT-40 transformer

Suitable tube types EL 34, 6CA7, 6L6, two pairs EL 84
Nominal output power 40 W
Nominal primary impedance 4.7 kohm
Nominal secondary impedance 6 ohm
Maximum dc primary current 120 mA
Turns ratio 14+14 : 1
Screen grid tap 40%
Frequency range (with
resistive load at 1 mW)
17 Hz - 125 kHz (-1 dB)
7 Hz - 135 kHz (-3 dB)
Power bandwidth start (-3 dB) 17 Hz
Primary inductance, Lp (a-a) 320 H (at 230 V, 50 Hz)
Primary leakage ind., Lsp (a-a) 6.6 mH
Primary capacitance (a-a) 290 pF
Primary resistance 154 ohm
Secondary resistance 0.20 ohm
Insertion loss 0.44 dB
Quality factor (Lp/Lsp) 48,500
Frequency decade factor 4.3
Harmonic distortion (with
measuring amplifier at 1 W, 1 kHz)
Measures 100x100 mm, height 90 mm
Weight 3.3 kg


Other transformers
for tube amplifiers


ASV filter chokes are constructed with high quality double C cores with precisely defined air gap. They can be supplied with mounting brackets or encapsulated in metal housing. On special request, we can supply chokes with inductances and DC currents different than those in the table.

ASV filter chokes - Specifications

Type Nominal inductance (H) Nominal DC current (mA)
D 16-160


D 10-200 10 200
D 6-260 6 260
D 4-320 4 320
D 2-400 2.5 400
D 1-520 1.5 520