Quick (dense?) question regarding OT's primary impedance & power ratings

[jutsin]

Hey guys,

I'm working on building an EL34 power amp. I started looking into OT's to use, and realized that a 2xEL34 OT is almost exactly the same primary impedance as the 5150 (4x 6L6GC) OT that I have left laying around. If my 5150 (4x 6L6GC) OT is about 3.4K rated for 100 watts, there's no harm in using it for a 2 EL34 power amp right? It's just over rated on the wattage? Any harm or benefit to that? Thanks!

[R.G.]

The devil is in the details.

[trobbins]

It's just over rated on the wattage?
Not if you design for 11 on the vol. pot.

Any harm or benefit to that?
At lower power throughput you will get less distortion at low frequencies, and lower losses.
It will be larger and heavier.

A bird in the hand ....

[Chuck H]

I've never been sorry for using over rated iron WRT OT's. I'd be interested in the "details" of which R.G. speaks. You could also run that OT with a pair of big bottles into double it's rated load for a 6.8k impedance (very close to the common 6.6k generically used for both 6L6's and EL34's) and decide which you like best.

As noted, you can expect more bottom end clarity than is typical from guitar amps in general. It can actually be "boomy" without compenating circuitry... Sometimes.

[Wilder Amplification]

As to the "details" which RG speaks...

The valves have no way of knowing the power rating of an OT. All they see is voltage and current, which is determined by how hard they're being driven vs the reflected impedance of the transformer. This means that if the reflected impedance is the same then the valves won't know any different.

The power rating just states how much heat it can safely dissipate.