How To Measure "Current" In An Amplifier?

@atmasphere Thanks for the clarification. If you don't mind, I may quote you when I recommend the kit. :)

Since I don't build tube amps, I'll defer to your mastery of the subject.

By the way, the LM-1 is a free-to-build kit in honor of my hero, Dr. Marshall Leach Jr.  All the design docs are online and I make no money at all when someone builds the kit.


Best,


Erik

HELP!
I was following this thread, I thought, pretty well.
But, Damping factor came into play.
I read a Wikipedia page explaining it, and it sounded like a high damping factor allowed an amp to control a speaker cone better than a low one.
So, what makes having a high damping factor bad?
Sorry if this is something obvious...
Bob

Atmasphere, If I may: wouldn't that variable impedance load provide for a less linear frequency response and resulting timber distortion than the steadier impedance load of the Thiel via tube amplification?

You may! :)

The answer though is 'no'. The variable is how much feedback the amp has, not whether its tube or not.

Its not going to take a lot of feedback to get the voltage response needed for flat output on Erik's speaker. My guess in looking at the curves is that about 6 db is all that's needed. Most tube amps with feedback have more than that.

Damping factor is usually measured as (8 Ohms / output impedance). So an amp with 100 df has an output impedance of 0.08 ohms. 20 has around 0.4 Ohms.

The higher the apparent output impedance (i.e. the lower the damping factor) the more the Voltage response will track the speaker impedance chart, instead of reamining flat.

By the way, adding feedback essentially improves damping factor. The normal way to improve df without feedback is to use massive banks of parallel output stages.

Best,


Erik

Atmasphere, I don't understand. What does feedback have to do with linear power output into varying impedances?