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|6th April 2011, 12:51 AM||#1|
Join Date: Jan 2008
Single Ended Output Transformer
I want to build EL34/6L6 SE guitar power amp, but I also want to wound OT.
According to Valveheart, full calculation goes like this(for my example):
Power P= 10W(3.6K EL34-6L6)
Low freq response fd=82Hz
Primary Impedance Ra=3600 Ohm
Secondary Impedance Rs=4/8 Ohm
Flux density B - 5000Gauss
According to Valveheart core dimension is determinated by the eq:
Q=sqrt( (Pout*G*10^6) / (fmin*B*Is)) - where:
- Pout is the output power
- G is coefficient of weight between copper and iron /G=1.5 - 1.0/
- f min is the lowest desirable frequency
- Is is the density of current in the wire - Ampere/sq. millimeter (1.5 - 2.5 A/sq. mm).
- B is Magnetic Field Intensity in Gs
I don't get this equation cause every time I calculate it I think it's wrong.
Here's mine example:
Q=sqrt( (10*1.5*10^6) / (82*5000*1.5))=4.9cm^2
I'm confused because of the lower equation, cause for the same input I get:
I wonder how they got 20?Can someone explain this to me
I will take 6.25cm^2 core for the rest of an example:
Np= n1*U1=1667 turns - 1665 (5layers - 111turns, primary is divided in 3 parts, so (5*111)*3=1665
Ia=SQRT(Pout/Ra))*1000=SQRT(10/3600))*1000 = 52.70mA
Ia'=73mA(this is bias for tube)
wp=SQRT(Ip*0,001/3)*1,13=SQRT(125.70*0,001/3)*1,13=0.23mm - 0.3m wire is chosen
ws=SQRT(Is4*0,001/3)*1,13=SQRT(1.58*0,001/3)*1,13 = 0.82mm - 0.7m wire is chosen
Can someone who is experienced in winding OT's can confirm this, before i start wounding the transformer.
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