anormalearthlyman
New member
The methodology is from http://www.geofex.com/Article_Folders/xformer_des/xformer.htm
Winding a OT for a Vox AC30.
Power = 30W
Primary Impedance : 3700 Ohm / 4kOhm (depending on the source you use. I went with 3700)
Secondary Impedances : 4/8/16 Ohm
Lowest Frequency= 70Hz
Highest Frequency= 12Khz
Bobbin Area = 3.75 square inches
Using equation Primary Turns = (Vrms x 108)/(KfbA)
where
V= voltage swing in RMS
K= 4 dependent on stacking factor
F= lowest frequency
b = maximum flux density (went with 14KG)
A = Area of stacked tongues (bobbin area)
To find V in this source it shows the AC30 has a voltage swing of 295V peak to peak although the wording is a bit unclear. Converting to RMS we get ~ 105Vrms.
Applying in the above equation I get 714.2857 turns .
HOWEVER in this source at the very end it states that Vrms is 1.1xB+ , which in this case is 345. giving a value of 380Vrms for the input. This is quite a dilemma. I'm unsure about which value to use as comparatively my value for turns is very low compared to a document I found about winding a AC30 transformer , albeit their core was smaller. Please help me get over the last piece of this puzzle ! Thank you all so much.
Winding a OT for a Vox AC30.
Power = 30W
Primary Impedance : 3700 Ohm / 4kOhm (depending on the source you use. I went with 3700)
Secondary Impedances : 4/8/16 Ohm
Lowest Frequency= 70Hz
Highest Frequency= 12Khz
Bobbin Area = 3.75 square inches
Using equation Primary Turns = (Vrms x 108)/(KfbA)
where
V= voltage swing in RMS
K= 4 dependent on stacking factor
F= lowest frequency
b = maximum flux density (went with 14KG)
A = Area of stacked tongues (bobbin area)
To find V in this source it shows the AC30 has a voltage swing of 295V peak to peak although the wording is a bit unclear. Converting to RMS we get ~ 105Vrms.
Applying in the above equation I get 714.2857 turns .
HOWEVER in this source at the very end it states that Vrms is 1.1xB+ , which in this case is 345. giving a value of 380Vrms for the input. This is quite a dilemma. I'm unsure about which value to use as comparatively my value for turns is very low compared to a document I found about winding a AC30 transformer , albeit their core was smaller. Please help me get over the last piece of this puzzle ! Thank you all so much.
