Marshall Amp Forum - View Single Post - Pros and Cons of using 4ohm vs. 8ohm vs 16ohm outputs?

JohnH · 10-31-2008, 04:28 PM

I havn't tried these tests to hear the sound difference. But from an electrical point of view, I think theres an advantage in using 16Ohms rather than 4Ohms, in terms of stress on the transformer.

So long as the impedances match, then the tubes are happy, and so are the primary windings. But with the secondary windings that drive the speakers, at four ohms, there is twice as much current flowing than at 16 ohms for a given power output (P=I^2xR). That means more power dissipated in each inch of the windings, and it's all in just 1/4 of the secondary winding length as compared to that used for 16Ohm output. I think that adds up to the same total power loss in the windings, but conncentrated into just 1/4 length.

Presumably transformers are designed to work like this and its all OK, but the 16Ohms seems more relaxed theoretically.

John

10-31-2008, 04:28 PM	#12 (permalink)
JohnH Senior Member Join Date: May 2008 Location: Wollongong NSW Posts: 778	Re: Pros and Cons of using 4ohm vs. 8ohm vs 16ohm outputs? I havn't tried these tests to hear the sound difference. But from an electrical point of view, I think theres an advantage in using 16Ohms rather than 4Ohms, in terms of stress on the transformer. So long as the impedances match, then the tubes are happy, and so are the primary windings. But with the secondary windings that drive the speakers, at four ohms, there is twice as much current flowing than at 16 ohms for a given power output (P=I^2xR). That means more power dissipated in each inch of the windings, and it's all in just 1/4 of the secondary winding length as compared to that used for 16Ohm output. I think that adds up to the same total power loss in the windings, but conncentrated into just 1/4 length. Presumably transformers are designed to work like this and its all OK, but the 16Ohms seems more relaxed theoretically. John __________________ DSL401 8412 cab Crate Powerblock 1 x 12 Vintage 30 cab '76 Shergold Masquerader '93 Les Paul Studio '83 Roadstar