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EL 84 SE 5K Output Transformer

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#21
The bigger the core, the greater the loses in it. There is always a compromize between copper and iron loses. Mathematically can be demostrated than when equal both, the optimum design. Sometimes in order to save costs, it is admisible increaing one or other to a cheaper design.

Designing a good audio transformer involves interleaving primary and secondary to reduce leakage inductance but increases parasitic capacitance. So here too is a compromise.
 
#22
Separate windings for the secondary?
With the proper ratio of primary to secondary windings, then
4 equal secondary windings (8 leads) can give you 1, 4, 9, and 16 Ohm outputs, depending on how you connect the secondaries.

I still have 5k and 3k primary, single ended output transformers with four secondaries that can be connected for all four of those output impedances.
(all four windings are all always used).
 
#23
6A3sUMMER said:
1. Power = ((Vrms)Squared) / Load Impedance
141Vrms squared / 5000 Ohms = 4 Watts (not 5 Watts).
141Vrms x 1.414 = Volts Peak = 200V peak.

Have fun getting 5 Watts - (undistorted, good frequency response, and good damping factor), from a single ended EL84 in Pentode mode (hard to do).

2. As long as you are winding your own single ended output transformer, you may want to include an Ultra Linear Tap.
For an EL84, perhaps 26% from B+ to the UL tap, and of course finishing the primary to 100% (5k Ohms).

That way, you can easily compare the differences of power, distortion, and damping factor of Pentode mode, UL mode, and Triode mode.
Start all that without using negative feedback (you can do that later).
Negative feedback reduces gain and distortion, but increases damping factor.
Click to expand...
final form of my calculations:
Primary impedance : 5,2K
Secondary impedance : 0 - 4 - 8 ohm
frequency response : 50hz
output power : 6watt
for EL84 tube

Nuber Of Primary Turn:1279
Thichness of primary wire:0,2mm
Primary Voltage :177v
Sum of Plate Current:0,08a

Number Of Secondary Turn:50
Thichness of secondary wire:0,6mm
Secondary Voltage :6,92v
Secondary Current:0,87a
MFD :9500 gauss
windows cross section:6cm^2

I'll wrap it like this. I hope it works.
 
#24
You have to split the primary into at least 3 sections and the secundary into at least 2, then interleave them. Any less than that, and you will not be able to reach 20 KHz. It may still sound good anyway, many radiograms were built without interleaving.
 
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