Recording - May 2020 - 58

REVIEW

Heiserman
H47tube Microphone
An impressive homage to the U 47, with
great sound and some old world touches
REVIEW BY PAUL VNUK JR.

Chasing the 47

Heiserman Audio is a new North Carolinabased microphone company formed
around the partnership of capsule builder Eric Heiserman and gear builder Matt
Mitchell. Eric has been handcrafting,
OEM supplying, and selling capsules to
the DIY community since 2012.
Since the discontinuation of the Neumann U 47 microphone 55 years ago,
dozens of companies have planted their
flags on Hill U 47. As it's virtually impossible to offer a 1:1 structural, functional,
and (many would argue) sonic clone of
the venerable classic, most adopt designs
that are 'inspired by', i.e. tributes and
homages. Heiserman Audio is the latest
team to tackle the U 47 sound and style.

A tale of two 47s

There are two microphones on offer in
the Heiserman line, with a third coming
soon (see our March 2020 NAMM report for details).
The Heiserman H47 is a large diaphragm solid state FET condenser available in a choice of red, gray, or black. This
is the Heiserman take on the Neumann U
47 FET. The second model is the Heiserman
H47tube on review here; this model sets its
sights on the Neumann U 47.

The H47tube

The H47tube mic capsule, transformer,
and external power supply are made in
the US. The body is machined in Canada
and the US; manufacturing of the mic
body is moving to North Carolina soon.
From Germany, it uses NOS tubes, NOS
polystyrene capacitors, and Sommer cabling, rounded out by the old-school UKmade PSU connector on the cable. Mic
58 RECORDING May 2020

building and testing are done in-house in
North Carolina and Nashville.

Heiserman capsules

As a respected capsule manufacturer,
Heiserman offers a crop of K47, M7,
K67/87, and vintage CK12 capsules, all
hand made by Eric or Matt. The parts are
machined locally on an advanced CNC
machine with strict tolerances. This allows them to make precise tweaks at the
construction level, offering detailed fine
tuning of both capsule and microphone.

A tale of two capsules

tensioned, tuned, precisely matched,
and then simply fixed together. Matt told
me that they went through many different iterations, making adjustments that
measured 1/1000 of an inch, before
they settled on the final version.

The Neumann U 47 used two capsules in its run: a single-backplate K7
capsule with a glued PVC membrane,
and from 1960 onward, an K47 capsule, also a single-backplate design,
with a screw-based metal tension ring
and Mylar membrane.
Heiserman offers a choice of both.
The H47tube comes stock with an HK47
capsule; for $100 more, you can order
it with their HM7 capsule for a slightly
more rolled-off vintage tone. My review
mic came with the stock HK47.

Looks, style, and attention
to detail

HK47 capsule

The circuit and tube

The Heiserman HK47 capsule is not a
strict K47 clone. The original K47 was
a single-backplate design that was difficult to tune and tension equally on both
sides. In the 1960s, Neumann switched
to the dual-backplate K67 capsule, still
used in current U 87 and U 67 models. The Heiserman HK47 is a combination of the two (being a dual-backplate
K47 design), meaning that multiple
single membrane diaphragms can be

The H47tube measures 10" x 2.5" and
looks every inch a 47, from its expertly
replicated headbasket and mesh to the
dual-position integrated pattern switch.
Like the classic, the H47tube offers a
choice of cardioid or omnidirectional
polar patterns, selectable via a recessed
white slide switch located on the grille
assembly, as opposed to the more common practice of offering three to five
pattern choices on the power supply.

Internally, the H47tube sticks close to the
original design as well, with through-hole
components staged in horizontal circular
layers. The most obvious difference: the
H47tube uses a glass NOS EF800 tube
rather than the 'unobtanium' steel Telefunken VF14 tube or a clone thereof. Other
internal components include a custom USmade BV08 transformer, NOS Mial polystyrene and Soviet paper-in-oil capacitors,
and Ohmite thick film and Vishay resistors.

Recording - May 2020

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