[Harp-L] Squeal Killer anti-feedback pedal

[r_buschner@xxxxx]

The ticket to feedback or not feedback is open loop gain.
With an amp/speaker setup, you want to move air. Much air.
This can be done by higher gain forcing low speaker membrane
surface area with more amplitude, or with lower gain forcing a
big surface area with lower amplitude. The first one is more
sensitive to feedback, because a small change at the input leads
to a big (to big) change at the output, reacting like a warm coke.
Keep over all gain low and there you go with high volume of moved
air (high volume) and low sensitivity to feedback.

Seeya,
Ralf

-----Ursprüngliche Nachricht----- 
From: Ronnie Schreiber
Sent: Monday, September 11, 2023 10:00 AM
To: harp-l at xxxxx
Subject: [Harp-L] Squeal Killer anti-feedback pedal

I'm not going to knock someone for being able to sell 5 resistors
(including a 5 watt wire wound in a low current 9V circuit!), a small
electrolytic capacitor, some connector strips, a 12AT7 preamp tube, an
enclosure, a wall wart power supply, and some jacks for $300, but this
is what an engineer who I hire to design circuit boards says about the
Squeal Killer:

> The squeal killers tube could probably be replaced by a ~47pf cap. Pretty 
> astonishing he was able to patent that circuit! You’re right, it’s just in 
> there for marketing, and it’s probably working! I showed it to some of the 
> PhD’s at work and they all had a good laugh. Essentially he’s using the 
> parasitic capacitance of the tube and no signal is passing _thru_ the 
> tube.

I'm not saying it doesn't work. It probably works as well as any other
simple notch filter or EQ will, but I think that's pretty much what it
is, low pass and high pass filters where one of them is using a tube as
a capacitor. If I'm wrong, please correct me. Heck, adding a pot to give
you some control would have just added about 80 cents to the cost of the
circuit, but then they'd have to drill another hole in the enclosure.

Disclaimer: I make the Harmonicaster, the electric harmonica that is
feedback free in normal playing conditions, but if I find an
anti-feedback circuit that works and is not too expensive to produce,
I'll gladly make and sell them to harp players who are married to their
microphones.

Ronnie Schreiber
The Electric Harmonica Co.
http://www.harmonicaster.com