25W 6600 Ohms Ultra Linear Push Pull Output transformer


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SKU: PWPP25W6K6 Categories: , , Tag:
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This transformer is the culmination of many weeks of work to produce an output transformer for the Mullard 5-20 amplifier using EL34 output valves. I wanted something that would give me plenty of bass, down past 20Hz, and perform at the top end past 20KHz.

I have settled on this design as the analysis showed excellent results, giving a flat response less than 20Hz and, due to the winding methodology used, over 30KHz.

May be used in any push-pull design where an anode to anode impedance is 6600 Ohms.


Multi section winding, for reduced leakage inductance.
6600 Ohms Anode to anode
40% UL taps


Inductance approx 50H.
Leakage inductance 16mH


Wide bandwidth, 20-30KHz. (-1dB)


Output impedance 4,8 and 16 Ohms.


High quality Grain Orientated M6 0.35mm.
Hand laminated for the best stacking factor, and accuracy.

Winding wire

Double coated Grade 2 enamelled copper wire.
Wound using CNC winders for highly accurate wire placement and turns count.

Connecting wire – stand up only

High quality PVC 600V 20 AWG UL1015


Stand up, Drop through and frame.



Additional information

Weight 2.3 kg
Mounting style

Stand up, Drop through, Frame

Output Impedance

4, 8 & 16 Ohms, 4 Ohms, 8 Ohms, 16 Ohms


Here are dimensional diagrams for this transformer.
Please refer to the relevant key below for the dimensions.


Shroud With Feet Drawing Key

Label Description Dimension (mm)
A Width 79
B Height 98
C Depth 86
D Mounting depth 51
E Mounting width 64
F Hole width 5

Frame Drawing Key

Label Description Dimension (mm)
A Width 98
B Height 83
C Depth 60
D Mounting height 64
E Mounting width 64
F Mounting depth 48
G Overall depth 70
H Mounting hole width 5

Drop through Drawing Key

Label Description Dimension (mm)
A Width 79
B Length 95
C Height 60
D Cutout width 48
E Cutout length 64
F Fixing length 79
G Fixing width 64
H Mounting hole diameter 4