Question: Is a 30-watt amp head going into a 2x12 cab good enough for medium-sized gigs?

[ecc83]

I really don't want to start an argument, I really don't.
Firstly, what do you mean by "physical description" ? Fit, form, and function?
Secondly, how would someone go about measuring the "inductance" of a transformer i.e. inductor?

Strictly speaking a transformer, when correctly terminated is not an inductor. This is how audio transformers 'can' give a flat, extended frequency response but beware! They are rarely perfectly driven or loaded and so are not totally' flat'.

Transformers all have losses of course and one test is to measure the impedance of say the primary with all the other windings shorted. In theory the primary should be just the DC winding resistance but in practice there will be a small inductance. This is termed "leakage inductance".

Dave.

 

[Old Music Guy]

Strictly speaking a transformer, when correctly terminated is not an inductor.

I'm sorry, but that is totally incorrect. Properly terminated or not, a voltage across a primary winding of a transformer, wrapped around a common core, induces a voltage on the secondary, that is directly proportional to the ratio of the primary winding to the secondary winding.
How can it possibly NOT be an inductor?

 

[drtechno]

Firstly, what do you mean by "physical description" ? Fit, form, and function?
Secondly, how would someone go about measuring the "inductance" of a transformer i.e. inductor?

Diameter and height.
It will narrow down who I bug for a transformer. Because certain people only deal with certain core sizes.

 

[ecc83]

I'm sorry, but that is totally incorrect. Properly terminated or not, a voltage across a primary winding of a transformer, wrapped around a common core, induces a voltage on the secondary, that is directly proportional to the ratio of the primary winding to the secondary winding.
How can it possibly NOT be an inductor?

OK, LAST thing I wan ti is a cow with YOU friend but consider a "perfect" 1:1 ratio transformer in the OP stage of a mixer say? We expect and find, to a first approximation, the the frequency response is decently flat from say 40Hz to well beyond human hearing. Were the transformer behaving as an inductor that could not be! Of course, if you put a winding on an LCR bridge you can measure its inductance...WITH the coils O/C.

If there are any Power engineers here they would tell you that line transformers have to be "balanced" so as to present a reasonably resistive load otherwise the power Co gets very miffed and you can have terrifying voltage spikes. The same applies with large capacitive loads but in that case you get huge out of phase currents.

Transformers are not perfect of course, they have resistance, leakage inductance and Iron losses. These failings can be minimized of course but Sod's Law states that "better" is always more "expensive"! Traffs are also made in a range of ratios and it is a fact that the further you go from one to one the harder it is to keep high performance

All sorts of electronic "devices" LOOK like one thing but behave differently in circuit. EQs often use "Gyrators" these are a collection of just Cs and Rs round op amps but BEHAVE like inductors.

A single loudspeaker in a cabinet is a small inductor but over its operating range the complex impedance caused by the cone movement and the air load can make it "look" like a capacitor at some frequencies.

IF this stuff was easy anyone could do it and I would be a freaking sight better off!


Dave.

 

[Old Music Guy]

OK, LAST thing I wan ti is a cow with YOU friend

'nuff said.