O.T. ohm questions.

[Only1way]

I have seen some amps that are advertised that you can hookup any ohm speaker to their amps. Like Emery sound amps.
My first amp build was a Gilmor Jr. It had a Mercury Magnetic O.T. rated at 16 oms and the designer of the amp said you could hookup any ohm speaker to it.
So how is that these amps can run on any ohm speaker?

[Diablo]

Maybe they have a multitap OT with a switch that selects the right impedance for the speakers? That's what my 35 year old Ampeg V4 has.

[Only1way]

There is no switch for a multitap OT.

[pdf64]

Generally, driving a load impedance higher than the OT secondary impedance rating is what causes problems, these including increased screen grid dissipation, and flyback voltages on the primary causing insulation breakdown.
The worst case being an open circuit load.
Driving a load impedance lower that the OT secondary impedance rating doesn't usually cause damage, although the plate dissipation may be increased.

[Enzo]

The reason you can do it is that the impedance thing is not nearly as critical as many people think it is.

[Only1way]

Thank you so much for your input!

[Only1way]

Thanks