I’m looking at the Power Station PS-2 for my Fender Super Reverb, which is a 2 ohm cabinet. I’ve heard that the PS-2 is very good in the sense of not creating flyback voltages into the amp’s output transformer. But I’m confused about the role of impedance matching in preventing flyback voltage. I was under the impression that it’s best to have an exact match between the amp and the reactive load, but the Power Station has one setting that covers both 2 ohms and 4 ohms. Does that mean it wouldn’t match my amp as well as a reactive load that has a distinct 2 ohm setting? Would it be safer to install a diode across the amp’s output transformer when using the 2/4 ohm setting on the PS-2?
I’ve contacted other manufacturers with loads that go down to 4 ohms, and they say it can be used with a 2 ohm amp, but that it’s optimal to use a 4 ohm amp with their product, to be safe. Can you clear things up for me?
Great question, first about the Power Station. From the very beginning, Steve was testing and thinking about vintage amps like the Super Reverb, so it is absolutely safe and he would not have done it otherwise. Since Power Station was released, there have been no issues with this.
To the second point, people online don’t really know what they are talking about when they use terms like flyback. It’s true diodes are used to protect switches from flyback voltages, but this won’t work with a speaker. Sensible tube amp designs like Fryette’s have protection circuitry inside the amp for this purpose. They are also the only manufacturer I know that uses double-insulated wire on all output transformers. They really care.
PM me if interested in knowing more about flyback; I won’t clutter up the forum with my physics/electronics
Thanks. Glad to hear it’s safe for my amp. Other than safety and flyback, is there any reason why it might be better to go with a load that has a 2 ohm setting? Would tone or attenuation abilities be different than the PS-2 with a 2/4 ohm setting?
The PS already has flyback protection and there isn’t anything on the output side for which additional protection will matter.
Keep in mind that the numbers 2, 4, 8 and 16 are approximations meant to classify speaker applications by general categories. They’re not hard numbers that need be rigidly conformed with.
Depending on the load and power amp capability, impedance can vary wildly with frequency - from a very low value to as much as 100 ohms typically. A speaker is only, lets say 2 ohms, at a specific frequency and driven at 1W for testing purposes. Also, 2 ohms is not that far away from a short circuit.
The PS designs split the difference between 2 and 4 to take advantage of the overlap you normally see between speakers in those very general categories.
