Resource to calculate, building and measuring Hi Fi Loudspeakers and more...
Home
Email
Links
Audio Measurement Links
Loudspeakers
Tube Amplifiers
Audio Manufacturers
Headphone Manufacturers
Tweak Sites
Forums
DECWARE Audio Forums
Audioholics
Acoustics Forum
AudioCircle
AudioForums
AudioAsylum
FullRangeDriver.Com
HiFi-Forum (german)
Head-Fi: Covering Headphones, Earphones and Portable Audio
Techtalk at Parts-Express Forum
Tips
Articles
The Chain is as Strong as Its Weakest Link
Perceptual Study of Loudspeaker
Crossover Filters
Measuring
Thiele-Small Parameters
Measure PreAmp
Stepped Attenuator
CD Jitter + Timing
CD Jitter Problem
Jitter + Timing Errors
How many watts do I need?
Plasma Loudspeaker
Dipole Loudspeaker
Proper Signal Alignment
A great idea which falls...
Mains filtering: shocking!
The Worlds first True Subwoofer!
Stepped Attenuator
AC Power
Acoustic
Loudspeakers
History
Loudspeaker
Understand Frequency Response
Subwoofer Placement
Turntables
History
Turntable
Tonearm/Cartridge Capability
Phono Cartridge Specifications
Step-Up Transformer
Cleaning Vinyl
Compact Disc
History
CD's
DIY Cables
Interconnect
Power Cable
How to...
test a Capacitor
reanimate a dead
Electrolytic Capacitor
test a Transformer
measure cabinet vibrations
build a simple
Contact Microphon
"How It's Made"
Something about Espresso
Disclaimer
For Sale
Calculators
Loudspeakers
Loudspeaker Enclosure Plans
Recommended Minimum Wire Sizes for Loudspeaker Cables
TSP Database (ext.)
Loudspeaker Basics
History
Basics
What's are TSP?
Closed System
Bass Reflex
Passive Radiator
Onken Bass Reflex
Open Baffle
Transmission Line
TMLine Basics
TMLine Calculator
Horns
Bass Horn
Exponential Horn
Electrostatic Loudspeaker
Plasma Loudspeaker
Linkwitz Transformation
Transformation Basics
Transformation Calculations
Setting Up Speakers In A Rectangular Room
Measurements on Drivers
Analog
Computer
Acoustical
Electrical
How to measure Frequency Response
Nearfield
Farfield
Groundplane
Measurement Data for Simulation Programs
Stereo Polarity & Sweep Test
Loudspeaker Glossary
Projects
My System
My System
CD Master Clock Generator
Components explained
Recommended Records
Measurement Software
Calculate Tonearm/Cartridge Capability
Phono Cartridge Specifications
Acoustics
About Acoustics
Reflection control
The Chain is as Strong as Its Weakest Link
Diffusor Basics
Acoustical Measurement Basics
Acoustic Calculations
Acoustic Glossary
Absorbtion factors(Excel)
Specials
Audio Specials
Audio Pioneers
Wednesday, November 22, 2017
3298 users online
How to Calculate Audio Output Transformer Load Resistance
To determine the turns ratio we apply an ac voltage to the primary, and measure the voltage in the secondary.
A transformer ( 10 - 15 volts ) is used to apply the ac voltage to the primary of the Output Transformer (OT)
An ac voltmeter is connected to the secondary of the OT to measure the output voltage.
Now, measure then primary voltage of the OT
For example, if the voltage on the primary measures
13 volts
and the secondary measures
0.52 volts
the turns ratio is
25:1
To determine the load resistance for the desired given speaker load, square the turns ratio you calculated and multiply that number by the desired speaker load (i.e. 4, 8, 16 ohms).
Measured Voltage across the secondary taps ( Vout ) =
Volts
Measured Voltage across the primary taps ( Vin ) =
Volts
Desired speaker load (i.e. 4, 8, 16 ohms) =
Ohms
Turn Ratio =
Load resistance for the desired given speaker load =
Ohms
Replace Output Transformer
Lets assume we have a set that has an output transformer with an open winding that must be replaced, and the output tube is a single 2A3 Triode.
First we look at the 2A3 Tube Datasheet and see that a 2A3 should work into a load resistance of approximately 2500 ohms.
With this information we can determine what the turns ratio should be. By dividing the secondary load of the loudspeaker ( 4, 8, 16 ohms ) into the 2500 ohms required by the 2A3, we get an impedance ratio of 312.5 : 1
If the impedance ratio is the square of the turns ratio, then the turns ratio is the square root of the impedance ratio.
Taking the square root of 312.5 gives us a 17.7 : 1 ratio, so an output transformer with a turns ratio in this range should work.
Tube Datasheet Links
211
2A3
300B
5881
6550
6A3
6AS7
6BQ5
6CA7
6L6
6V6
EL34
EL509
EL84
No part of this website may be reproduced in any form without written or e-mail consent from the author.
The designs are free to use for private DIY-purposes only, commercial use is strictly prohibited.
Copyright mh-audio © 1999 - 2017