[Harp-L] Re: kinder harp maximizer and midbass cut - AFB+ Knobs

[HTownFess <Spschndr@xxxxxxx>]

Conceptually, one should bear in mind that with typical vintage-style
mics/amps, there are two likely feedback areas.  The low-end feedback
centers around 200 Hz IIRC, and is the low rumbling type that is hard
to anticipate because you don't hear a squeal starting--you may even
think it's another instrument onstage doing something, while the
audience wonders why the earthquake isn't actually shaking anything.
Since what people hear as "fat" harp tone has a lot to do with the 240
Hz (especially) and 125 Hz ranges, you can run into that low-end
feedback if you get greedy about that freq range.  IMO, it sounds best
to fix that problem at the amp itself and leave the UB knob entirely
off, fully counterclockwise.  That UB knob (the Midbass Cut circuit)
has another function: the way it notches out the low feedback freqs
can take the muddiness out of an amp's tone and define it better
against a mix--much like finding you can hear yourself better against
the band if you turn the bass knob on the amp down a little.  If you
listen to the UB knob in isolation at home, you can hear how it
"skinnies up" the low end into a form that can punch through a mix
better.  So you can use it to stop low end feedback and/or to clarify
low end; but as I said, better IMO to fix those at the amp and leave
the UB knob off for a more natural tone.  Your amp already shouldn't
do bass feedback at normal proximity or have muddy low end.

Squealing high feedback is not as high as one might think it is, since
both guitar speakers and vintage mic elements tend to roll off so hard
above 5K.  IIRC the squeal is more of an upper-mid/low treble
phenomenon, and is likeliest to live somewhere in the 800-2K Hz
range.  The "presence" range of around 4K-5K can also be touchy
sometimes, but we usually aren't trying to push it as much as the mid-
to-upper midrange.  Again, it's best to tune the amp itself to
minimize the likelihood of "high"-range feedback, but a lot more rigs
are likely to do the squeal than the rumble, so one is likely to put
the AFB knob to work.  I'm another one of those people who nonetheless
does not like to run the AFB (righthand) knob above about 1 o'clock.
No UB and little AFB can sound fairly transparent if the calibration
is right.

About Calibration: People mentioned getting "crunch" with the help of
their AFB+.  Well, certain kinds of solidstate devices will crunch up
the leading edge of a note a little, either from clipping distortion
due to getting hit with too much signal input, or from a micro-delay
derived from the SS elements synthetically generating a note with
different harmonics than the original note had.  Note that the Kinder
manual says the AFB+ does something about odd-order harmonics to fight
feedback.  The Lone Wolf Harp Octave pedal is another device that
generates different harmonics; in this case it's the one-octave-higher
overtones.   Serendipitously, during testing we discovered that the
Harp Octave tends to suppress feedback somewhat, decoupling its output
from its input enough [through the synthetic harmonic content] to make
it more difficult for feedback loops to start.  It can also add a bit
of crunch; Randy @ LW explained that we can hear the micro-delay in
generating the higher overtones as crunchy distortion.  However, it
may turn into unwanted crunch with the wrong player/mic/amp
combination--hard to predict, really have to plug in & try--and I
think that's analogous to what can happen with the AFB+ settings.

Which brings up the Calibration knob: Seems like it may be at least
partly meant to index the Kinder box to the strength of the player's
mic's input signal, so that the box isn't clipping.  Also seems that
some people like that kind of clipping just fine: more power to them.
Ditto for changing the odd-order harmonics.  And it seems that some
people can make that Calibration light flicker no matter where the
knob is set.  My impression is that people have said that turning the
Calibration knob up too far makes the rig sound unnatural and bad
faster than the other two knobs do--one can see how solidstate
clipping could do that, and that minimal use is again better: noon to
1 o'clock or so at most for me.

The heavy notching-out of trouble freqs that the other two knobs do
can also sound unnatural.  I once took an AFB+ versus a 16-band mono
EQ + mic buffer combo and used them with the same mic right next to an
amp that otherwise would feed back hard, so that the AFB+ was turned
up too far by my standards.  Notching about 12dB out of about 200 Hz
and (I think it was) 1K via the EQ also stopped the feedback and
sounded similarly unappetizing to my ears: killed the feedback but
removed elements I wanted to hear.  I always think of it as a
"hollowed-out tone."  YMMV.  I only use my AFB+ with one amp, and then
as transparently as I can set it, not to stop feedback entirely, but
to make it a little harder to start, so that I can relax in the amp's
vicinity, move around and do vocals.  When the AFB+ is set at low
enough levels, the additional detail/texture it delivers due to its
mic buffering function (the Maximizer circuit), especially in front of
pedals, means the overall tone can still sound organic but better
overall for me than the same rig without the Kinder box, and feed back
enough less for me to relax a lot more.

Hopefully someone who really knows what they're talking about,
technically, will be provoked to post by the above.  But it's how I
understand the matter after having a thirdhand (no manual) AFB+ about
a year--Stephen Schneider