Countryman DT85S Data Sheet

COUNTRYMAN ASSOCIATES INC

TYPE 85S

STEREO DIRECT BOX

The Type 85S Stereo Direct Box is a two-channel version of the classic Type 85 FET
Direct Box. Each channel uses the same FET-based Class A circuit as the Type 85 to
connect any high-impedance instrument pickup to a balanced microphone (XLR) input.

Use the rock-solid transformer isolation of the Type 85S to eliminate hum,

buzz, and RF interference from your long XLR runs.

Indestructable

Connectors and switches are recessed into a single-piece extruded case with extra
thick walls. You can literally drive a truck over the Type 85S without hurting it. Internal
electronics are molded in epoxy and fully protected against electrical damage. The input
can withstand 220 VAC and static spikes up to 20,000 V.

Battery or Phantom Power

Most mixing consoles provide 48V phantom power, and the Type 85S will automatically
use it. If you don’t have phantom power, or if your phantom power is very low, the Type
85S will run for about 130 hours from a single internal 9 V battery. We designed the
Type 85S so that you only need to provide phantom to Channel A to power the unit.

Simply Exceptional Sound

Each channel of the Type 85S uses only hand-selected high-quality discrete
components woven into a single-ended Class A circuit, much like a classic tube
microphone preamp. The Type 85S has an incredibly smooth, sweet sound. Unlike
many active DI boxes, the Type 85S can always isolate ground, even when running on
phantom power, to help eliminate hum and buzz from ground problems.

Frequency Response:

20 Hz – 20 kHz (+/- 1 dB)

Noise (shorted input, BW = 22 Hz – 20 kHz):

0.63 μVrms (-122 dBu)

Power Requirements:

9V battery or 1.6 mA @ 48V Phantom

Input Protection: 220Vrms and 20kV discharges

Gain Options:

-10dB (0dB pad), -25dB (-15dB pad),

-40dB (-30dB pad)

RF Low-Pass Filtering: 250 kHz (in), 30 kHz (out)

Maximum Input Level (1% THD):

5 Vpp (0dB pad)
28 Vpp (-15dB pad)
158 Vpp (-30dB pad)
(Equal to 800 Watts into 4 Ohms)

Distortion:

0.018% THD @ 1 kHz and 1Vpp in

0.08% IMD 10 kHz/60 Hz 1Vpp in

Cross-Talk Rejection: >105dB (20 Hz – 20 kHz)

Input Resistance:

10 MΩ (0dB pad), 10 kΩ (-15, -30dB pad),
20 kΩ (RCA and 1/8” inputs)

Input Capacitance:

160 pF (equal to 2 ft of low-capacitance guitar
cable)

Output Polarity: Pin 2 positive (Note that the
one-channel Type 85 is Pin 3 positive.)

Dimensions:

2 x 4 x 6.25 in (51 x 102 x 159 mm)

Weight: 31.2 oz (.88 kg)

Type 85S: History and Performance

History of the Type 85 FET Direct Box

In the 1970s, Carl Countryman designed a revolutionary circuit for
interfacing unbalanced instrument signals to balanced, mic-level mix
board inputs—the first “active” direct box. The circuit allowed artists
to isolate their instrument ground from the mixing console ground
without loading their instrument, distorting their sound, or adding
noise to the signal. This design quickly caught on with big name
groups in the US as artists realized that, with this new Countryman
box, their audio quality would never be compromised on the way to
the mix board. The box evolved over the next few years, until in 1985
it became known as the Type 85 FET Direct Box. Still today, the Type
85 thrives as one of the most popular direct boxes in the world: a true
legend of the industry. Now the Type 85 is joined by the Type 85S, a
stereo direct box crafted with the same care as the original 85.

What Makes the Type 85 Sound so Smooth?

Most DIs do not handle high signal levels with grace. The Type85
and Type 85S use only the highest quality, hand-selected discrete
components to achieve exceptional performance—even for large
signals. The circuit uses a Class A FET amplifier that overloads smoothly
in a way that will never sound harsh or brittle. In contrast, numerous
other active DIs—except the Type 10 or Type 10S, of course—use old
and cheap op amps plagued by poor overload characteristics; most
notably, a phenomenon known as phase inversion.

Phase inversion is where the op amp output will abruptly transition
from one supply to the other when the input gets too close to the
negative rail. As you can imagine, such a sharp transition leads to
countless non-linear artifacts. In fact, phase inversion will even mask
the original fundamental frequency of the source.

We measured the output from the Type 85S and a popular—and
more expensive—competitor active DI with a 300Hz pure tone on
the input. We increased the amplitude of the pure tone to 6Vpp with
a typical load such that both boxes were distorting their outputs.
The Type 85S output is in black, and the competitor DI output is in
red. The differences are striking: while the Type 85S output starts
to gently smooth its valley at the bottom end of the sine wave, the
competitor DI output clips and exhibits phase inversion.

When the outputs are analyzed in the frequency domain with an FFT
(Fast Fourier Transform), the results are remarkable. The Type 85S
exhibits normal harmonic distortion, primarily composed of even­order components. On the other hand, for the competitor DI, it is
virtually impossible to even locate the original fundamental frequency
that was applied to the input. The resulting output is not only harsh
and brittle, but sounds nothing like the source.

The Type 85S is so rugged that a truck can run over it. That’s
why it can withstand years of abuse on the road.

Output of the Type 85S (black) compared to a popular
competitor active DI (red) with the same 6Vpp sinewave at
300Hz applied to the input—the 85S overloads gracefully while
the competitor DI harshly exhibits phase inversion.

Input Connectors

When you’re setting up at a venue and have to deal with all kinds of sources
and connectors, you’ll still be set with the Type 85S. You also won’t need
to worry about intermittent connections because of corroded contacts, or
connectors getting damaged just because you dropped your box.

The Type 85S uses only the highest quality connectors. On the input, your
connector options include metal-threaded-nose 1/4” jacks, gold-plated
super-rugged RCA jacks, and a gold-plated stereo 1/8” jack. We also protect
all connectors by recessing them inside an architectural aluminum housing
strong enough to support an 18-wheeler.

Countryman Associates, Inc. 195 Constitution Drive, Menlo Park, CA 94025

Phone: [phone] or [phone] Fax: [phone] Email: [e-mail] Web: www.countryman.com

FFT plot of the Type 85S (black) and competitor DI (red)
outputs. The Type 85S exhibits normal harmonic distortion
while for the competitor box the original fundamental
frequency is virtually lost in the array of non-linear artifacts.