Benchmark h1 User manual

The Benchmark H1 is a high-power audiophile-grade stereo headphone
amplifier. The H1 features sonic purity that fulfills even the most demanding
headphone applications.
The H1 is designed to power all headphones that have a load impedance of
30 Ω or higher. It is not designed to power headphones that have 8 Ω load
impedance. The H1 requires a bipolar power supply, such as theBenchmark
PS-1 or PS-12.
H1
Audiophile Grade Stereo Headphone Amplifier

Connect the signal input lines to the input connectors. These connectors are located on
the back of the H1. Whether feeding from a balanced source or an unbalanced source, you
should wire the input as though it were receiving its signal from a balanced source. Use the
“forward reference” technique outlined in the Benchmark Media Systems application note –
“A Clean Audio Installation Guide”. This application note is available for download from the
Benchmark web site. Using this wiring technique will help eliminate hum pickup from the
system.
Connect the power cord extending from the back of the H1 to a PS-1 or PS 12 power
supply. Because the H1 power input is bridge-rectified it will operate normally with the + and –
supplies reversed, so you can use either a reversing or non-reversing RJ-11 coupler as
necessary. The H1 must be powered from a bi-polar DC power supply with a recommended
minimum power voltage of ±9 volts and an absolute maximum power voltage of ±18.7 volts.
Voltages that are less than ±9 will generally not provide adequate output volume from the
headphones. Voltages that are higher than ±18.7 may cause damage to the H1. The
Benchmark PS-1 or PS-12 power supplies are ideally suited to power the H1.
Connections
Power Gain
Headphones
H1
MEDIA SYSTEMS

Circuit Design
Input Stage
The input stage of the H1 features balanced 200-kΩ inputs with over-voltage protection. The
balanced inputs provide common-mode rejection of interfering signals. Maximum input level
is +29 dBu at +/- 15 V, and +27 dBu at +/- 18 V. 0.1% precision resistors provide a common
mode rejection of approximately 60 dB without trimming. This stage has a bandwidth of 356
kHz and a gain of -6 dB.
Volume Control Stage
The variable gain stage has a range of “off” (– infinity) to +26 dB and a bandwidth of 730 kHz.
The overall gain of the H1 is from “off” to +20 dB.
Output Stage
The output stage consists of a high current buffer inside a high-bandwidth feedback loop.
The feedback virtually eliminates any distortion caused by the headphone load. The buffer
provides output current of up to 0.5 amps. This current capability is sufficient to adequately
drive most modern headphones. The “0 Ω” output of the amplifier stage directly drives the
diaphragms of the headphones. The overall bandwidth of the H1 exceeds 300 kHz. As such,
the H1 has a very high damping factor and excellent high frequency, transient, and distortion
performance.
Left Input Right Input
Power
PS- 12 or PS- 1
Right Input
Left Input
PS- 1
Balanced
Audio
Source
Syracuse NY- Made in USA
BENCHMARK MEDIA SYSTEMS, INC
PS-12 Regulated DC Power Supply
Maximum Output 750mA

Input
Input Clip
Output
Output Imped-
ance
Output Clip
Load Impedance
Output Level
Output Control
Gain Range
Bandwidth
THD+N
Noise Floor
Power
Peak Output
Max Avg Output
Dimensions
Weight
Stereo 200 kΩ Balanced Inputs with over-voltage protection
+26.5 dBu with ±15 volt supplies
Stereo, for use with 1/4” Tip/Ring/Sleeve plugs only, short-circuit protected
“0 Ω”
Dependant upon power voltage and load [+20 dBu @ ±15V and 60 Ω
load]
30 Ω or higher
Up to +20 dBu into 60 Ω [dependent upon power source]
Dual log taper response
Off to +20 dB
0.1 Hz to 300 kHz minimum
0.0003% typical at headphone inputs - under load!
Better than -75 dBu at maximum gain
(Bipolar) ± 9 to ± 18 volts, bridge-rectified, maximum peak current needed
= 1.1 Amp at maximum peak output into 30 Ω
7.5 watts [±18 volt supplies. 30 Ω load]
1.35 watts [-8 dB peak to average ratio]
5.5” (139.7mm) Deep
1.5” (381.1mm) High
5.5” (139.7mm) Wide.
1.17lb
Specs
H1 Instruction Manual, Revision 1
Copyright © 2006 Benchmark Media Systems, Inc.
All rights reserved.
Benchmark Media Systems, Inc.
5925 Court Street Road
Syracuse, NY 13206-1707 USA
[phone], FAX [phone]
1-800-BNCHMRK (1-800-262-4675)
benchmarkmedia.com