Boogie Simulclass biasing

[Gregg]

COP = coefficient of performance.
Every device has a COP which is never 100%. OTs are no exception.
When determining the turns ratio and the impedance of an OT secondary you apply AC on the primary and get a voltage reading from which you calculate the impedance. This voltage however is with the secondary UNloaded. If you attach a load to it you'll get a lower voltage reading from which you get the actual secondary impedance. For example if you get 10VAC at the 8 Ohm secondary without load but 9VAC with an 8 Ohm load (more likely 5-6.7VAC which is the DCR of an * Ohm speaker) attached you have a COP of 9/10=90%. Then you divide the unloaded voltage by 0,9 and get the actual impedance.
In some OT calculation methods you have the COP in the formulas from the beginning. For 100W OTs it's usually 90-95%.

[Helmholtz]

COP = coefficient of performance.
Every device has a COP which is never 100%. OTs are no exception.
.

Thanks for reply.

Seems COP corresponds to efficiency.

The difference between the theoretical primary impedance as found from the turns ratio squared and the somewhat higher real primary impedance as seen by the power tubes is due to the primary and (reflected) secondary wire DCRs.

To get the real primary impedance, I connect a precise load resistor and measure primary AC resistance (@ 1kHz) using my LCR meter.
This method includes all loss effects.

[J M Fahey]

Below is the original simul class OT data......

Thanks for a very useful post.

I have wound MB OTs but straight using own calculations (trust them more he he ) but itīs nice to know "what were they thinking"