SIGNAL CHAIN
DEAN FARLEY
The Well-Tempered Ear
How’s everybody doing? It dawned on
me that there might be a few readers
who feel some of the topics discussed in
this column are a bit unorthodox. To be
honest, I used to question some of these
ideas myself—until I had a chance to test
them under real working conditions, that
is! A month or so back, we jumped into
the world of biasing an amplifier by ear.
Since that particular column was published
[August 2008], I have received several
requests from Premier Guitar readers asking for some advice on how to perform
this ear biasing procedure. One reader
actually got a phone call from me to
assist him with fine-tuning his amplifier
to get it to sound good. It was a three-channel amplifier, but the distortion
channel didn’t sound very big and the
clean channel sounded quite thin. It
was really out of balance any way you
sliced it.
halfway mark for starters. The reason is
simple: you’ll need adequate volume to get
the harmonic overtones reacting and ringing
out together. It’s also important to bias the
amplifier at gigging volume so you know
it’ll be right when you turn it up at a gig.
Sounding multiple notes and playing open
strings (as partial or full chords) is quite useful, because as more notes are put into the
harmonic stew, you’ll begin to notice a mystical “swirling” motion to the chords you’re
playing. This effect is what makes a great
sounding amp a truly unique instrument.
see red glowing plates at any time. You can
suck the life right out of the power tubes.
Keep your eyes peeled and you’ll be fine.
Once you have the clean sound dialed in,
you’ll want to listen for any excessive hum.
If the clean sound is big, rich and swirling,
the noise you hear should be at normal
levels. When an amp is happy it sounds
incredibly good! Now turn the amplifier up
a bit more…you should hear the notes of a
chord getting more complex in tonality.
If you don’t feel competent
When the clean tones sound right, it’s time
to kick in the distortion channel or, if you
have a non-master volume amplifier, turn
it up to maximum volume to check how it
sounds (and feels). Is it thick and even? Is
the noise level acceptable? Do the power
tubes’ plates look okay?
to perform these techniques,
This month, I’m going to give you more
insight into what I listen (and look) for
when biasing an amplifier by ear. First,
I think of a sound from any number of
classic records and decide whether the
amplifier can deliver it. If I feel it can,
then it’s time to get down to business
and dial it up.
do not attempt them yourself.
Have a qualified technician
What are some good benchmark reference tones to ponder? Imagining great
Fender combo amp tones by chance?
Then listen to the 1978 Dire Straits
debut album. Magical Fender tones are
found here in spades, and this record is
a general benchmark for Blackface Fender
tones—that’s a Vibrolux amp you hear,
with a 1961 Stratocaster in tow (played
with bare fingers). In a Marshall mood? Try
listening to Humble Pie’s classic 1971 live
album Performance: Rockin’ the Fillmore.
Those amps were Tremolo 100 watt heads
with vintage 4x12 Marshall cabinets. If
you’re a Hi Watt freak, listen to anything
from Pink Floyd’s post 1968 catalog. David
Gilmour has been using the same Hi Watt
amps forever.
help you.
There is another trick that I’ve be known to
use when biasing my amplifiers, something
I thought of many years ago when I needed
to confirm proper operating tube temperature. The Jim Kelley amps run at a whopping 490 – 495 volts, and this makes for a
very hot amplifier running four 6V6s. One
day, a friend came over to have me bias his
Kelley amplifier when I thought of a way
to compare his amp to my own: I call it the
“spit test.” I actually took a tiny bit of my
saliva and applied it directly to the power
tube. Pssssst! That’s all it took to confirm
the tubes were running at proper voltage.
I hope this month’s installment has given
you some more tonal food for thought.
Enjoy, and we’ll see you next month.
There are some basic rules to observe here
as a guide. The first is to bias your amplifier on a cleaner setting. Usually, you’ll
have to pump your amp up to around the
You’ll notice this phenomenon when you
let a chord sustain freely; the notes will
speak together and interact in a most
musical way. Remember that when correctly biased, the clean setting will ultimately dictate how the distorted channel
will sound, not the other way around. The
second rule is to keep a sharp eye on your
tubes’ internal plates. Avoid cranking the
bias trimpot to the point where your power
tubes are glowing a very bright red. You’re
way over the line if you see this happen.
When I describe this red glow, understand
that I mean that the whole plate structure
is visibly red, not just the center filament
that goes up the middle of the tube (that’s
okay). Turn the bias control down if you
Dean Farley
is the chief designer of "Snake Oil Brand Strings"
( sobstrings.net) and has had a profound influence
on the trends in the strings of today.
