Welcome to THE zapper’s forum!

=> I think I zapped for too long and it's taken me a few days to recover.
In just a session, you came from “I want to believe…” to “Ho S…! It works really!!
Congratulations!

=> then why does it matter what frequency is used?
YES, WHY?

Because without so many “special” frequencies, zapper will be a so simple device, there will be nothing left for publicity (:-(

You should look at zappers from two different points of view.
1_ The original one, as you beautifully describes-it
As designed, the only effect we want is tiny direct current flowing through us. Whoever the current goes, microbes dye. Simple enough?
Frequency permits to current to better pass through the skin barrier. Dr Clark found that 30kHz was best for this purpose.

2_ But if ANY frequency does, for this basic zapper’s effect, could we choice a specific frequency to ADD, IN TOP OF THIS, an additional “frequency effect?
Why not!

Frequencies can be used to kill specific pathogen families, as per Dr Clark Frequency table, or to any other use as described by many frequency experimenters.

=> Some zappers connect into the wall…. …
A zapper cost between 1/3 of a cent to 3 cents per 7-20 session in battery's weariness.
How much sessions can you pay with the additional cost of a wall plug powered device ? (they are usually quite expensive. Not the wall plug, the “improved zapper”)

I can use my zapper, costing me 1 cent per hour, in constant zapping, anywhere with full freedom, including in the middle of “nowhere”, where wall plugs doesn’t exist, because there is no walls.

There is another point out of this question : Industrial electricians are making a good living out of replacing “full/fool proof devices” with half a dozen of official approvals, because they all end up failing for all kind of good, and not so good reasons.

Most zappers out there, using a wall plug transformer have no approval at all for the whole device. Only for the transformer, not even approved for "medical use", on someone alive, and wanting to stay so.

So, what do you prefer : Having a tiring experience out of a 9V battery’s zapper, or wanting a good, solid, zapping experience from the 110/220VAC line?

I have survived from many 600VAC “zapping” experiences, in industrial field. But I still remember them, as a glowing, swearing experience.

I prefer 9V batteries. Period.