Myth VS. Reality
the course of a recent interview, I was asked how the Trem-o-Verb
gets its great vintage performance--without being wired point-to-point,
and "would it be even better if it were?"
Perhaps this wasn't such a surprising question since the
author had recently reviewed some pricey amplifiers whose
manufacturers emphasized that their amps were indeed wired
point-to-point, as if that mere fact would indicate (to those
"in the know" at least) a product of precious distinction.
What Is It?
In point-to-point, the resistors and capacitors are
joined with wires to solder points laid out on an insulating
tag board. Wires from each solder joint then run off to the
tube sockets, switches, and controls. One manufacturer has
even rejected the tag board and uses phenolic terminal strips
screwed to the chassis instead. This method deserves recognition
for being the slowest, most labor-intensive and most error-prone
wiring method of all. Point-to-point is probably about the
oldest construction style and it's still appropriate for making
a "one-off" piece of electronics. But does it produce
a better sounding amp?
My job as designer has always been to focus on the "black
magic" of amplification: first, how to get it and, second,
how to get it consistently. And there, my friends, is the
biggest disadvantage with point-to-point, consistency is very
hard to maintain.
What We Do
From the first, Mesa/Boogies have used a combination
of point-to-point and printed circuit board methods in order
to ensure absolute consistent placement of critical parts
and conductors. It is easy to demonstrate how moving some
parts or lead wires as little as 1/4" can make a huge
difference in the top end "transparency" of the
sound--exactly where a lot of the magic lives--or dies.
Inside a typical point-to-point amplifier are signal wires
leading from the component board to the preamp tube sockets.
Because many of these can be quite critical, we always locate
our tubes along the center line of a printed circuit board
so the lengths of traces can be extremely short and perfectly
Great care and many scrutinized revisions result in a circuit
board layout that avoids any unwanted "stray couplings"
that can rob tone, or may even include a few nuances of intentional
interaction (black magic) which cannot be reliably duplicated
in the point-to-point style.
And Why We Do It
For example, the great top end of the Dual Rectifier
has an aggressive bite but avoids the harshness by the way
two very important traces are laid out on the board. One trace
is on the top and the other runs right beneath it on the bottom
side of the board. Thus the very small--but significant-amount
of capacitance coupling these two together through the board
performs a subtle filtering kind of negative feedback in a
critical region where the harmonics can be made to line up
just right. Obviously the alignment of the traces on both
sides of the board must be precise and consistent for this
Here's an illustration of the different wiring techniques.
Think of printing books versus writing them out longhand.
Once the type is properly set each printed page will be the
same--no errors. Now go one step further and imagine trying
to line up the letters on both the top and bottom sides of
a sheet of paper--this time by writing longhand. It's all
but impossible. Yet such precise alignment is critical to
achieving the performance we're after--each and every time.
With a printing press or a printed circuit board it's easy.
Where do we still wire point-to-point? Anywhere it makes
a better amplifier is the brief answer. Many manufacturers
try to put everything on printed circuitry, but we individually
mount and point-to-point wire all jacks, switches, transformers
and 8-pin power tubes. The reasons are increased reliability
and total ease of replacement. If those parts are PC mounted,
major disassembly is required to get at them. Even worse,
they can cause the whole PC to fracture if they're bashed
in hard enough, then the amp is practically non-repairable.
Our commitment is to provide a professional instrument which,
with minimal maintenance, can last a lifetime or more. All
our circuit boards are double-sided and "plated through"
meaning that each and every hole has a platinum and copper
sleeve formed inside of it which is integral with the copper
traces on the top and bottom. This way each component lead
is soldered three times: top, bottom and inside the hole.
Most manufacturers use singlesided boards where there is
only one solder connection per part on thin foil glued to
the boards surface. Moreover, these boards, once installed
can't be hand-soldered for repair or replacement without totally
dismantling the amplifier.
Let's Talk History
I must have repaired thousands of old Fenders--and
I was the guy who could usually get rid of the stray noises--but
not always. I finally found out why some of these noisy amps
seemed incurable. The noise was originating in the point-to-point
tag board itself! The board material can absorb moisture and
become slightly conductive. The factory's recommendation was
to bake the boards in a drying oven then dip them in melted
wax to seal out the moisture!
Here's another: Tag boards warp, and the warpage increases
the space between eyelets. Years ago, a guy phoned me, freaking
out that his Fender had gone down before a big gig. I listened
to his description of the problem, then advised him to pull
out the chassis and look for the brown-black-brown-silver
resistor running lengthwise across the board. "Give it
a little tug and you'll probably find it's broken loose at
the solder joint," I told him. He called back relieved
and ecstatic--said that he'd never fixed anything before in
his life. No sweat. I must have fixed a hundred black face
Fenders where point-to-point board warpage had caused this
problem. Don't get me wrong, I love Fenders. Without them,
it's safe to say, none of us would be here!
So there you have it, four specific advantages of
the printed circuit board: 1.Consistency of location, 2.Ability
to use the board for intentional coupling, 3. Immunity to
noise-causing moisture, and 4.It does not warp.
Now what about the way in which a conductor affects the sound?
Is a round copper wire better than a flat copper trace on
a circuit board? Not according to Randall Research (no relation
to me!) who has studied audio conductors under all conditions,
including at the molecular level under an electron microscope.
His opinion is that if there is any advantage either way,
it would be with the circuit board trace whose profile offers
far greater surface area. It is well established that audio
signals (especially the higher frequencies) tend to flow on
the surface of the conductor, not through its core.
All this is not to say that there aren't great sounding point-to-point
amplifiers-obviously there are. But having built lots of amplifiers
both ways myself, the mere fact that an amplifier has been
wired this way is, as far as I can see, a guarantee only that
it will cost more. If there was an intrinsic sonic benefit
to using point-to-point throughout, you can bet that we would