Stello HP10000
Owner’s Manual
Stello HP10000
Pure two channel high-end
Preamplifier &Headphone Amplifier
April Music, Inc.
Thank you
HP100 is not just an ordinary low-priced headphone/preamplifier
in the market but a simply true high-end audio quality preamplifier
equipped with special made headphone amplifier section.
Best quality components and world-class design features are
adopted to make HP100 as one of the best quality preamplifier in the
world with its size.
Above the normal pure preamplifier section, we have added special
designed headphone amplifier circuitry to enable to drive the almost
of the headphones with power and details.
With this HP100, you can drive your power amp when used as a
preamplifier and also enjoy your private time with your headset
when you are not in the mood of sharing music with other people.
Under any circumstances, HP100 will remain by your side to give
you the real meaning of Hi-Fi and what the price tag says means
almost nothing to your music life.
You will instantly acknowledge that there is something in HP100
which could not be explained with ordinary words.
We call those, ‘Nuance of Music’.
Start as a pure preamplifier for your main audio. And add one
headphone for you to find out the another exotic world of music!
April Music, Inc.
1. Overview
1) Pure preamplifer & Headphone Amplifier in a Chassis
HP100 is a flagship design which combines the concept of pure 2 channel
preamplifier and dedicated headphone amplifier within a compact-sized chassis
by connecting two separate blocks.
Traditional headphone preamplifiers are mostly designed for the headphone
use only and a dedicated circuit for the headphone is adopted.
HP100 has 2 analog inputs and one analog output to be used as a pure 2
channel preamplifier.
And all the circuits for this preamplifier section are true high quality, highend design to guarantee the breathtaking high-end audio preamplifier
characteristics when used as a pure preamplifier for your main hi-fi system.
In addition to this circuit, specially designed headphone amplifier is
attached to be used as a reference-quality headphone amplifier.
2) Class A Operation discrete circuit
For higher quality sound, HP100 has adopted pure class A operated discrete
push pull circuits.
Super low noise J-FETs are used for the input stage of the preamplifier section.
The output for the preamplifier as well as headphone amplifier use pure bipolar
transistors for high-end sound quality and high efficiency of driving.
Input impedance is designed at 1 Meg Ω to prevent stable operation.
And all the circuitries except the DC servo control of the headphone section
are full discrete circuit which is possible for only those high-priced preamplifiers.
3) Premium Quality Components
Main components of HP100 are world best WIMA polyprophylene capacitors
and all the resistors are super low noise 1% grade level.
All input/output connectors are gold-plated connectors.
Decoupling capacitors are Audiophiler (by Mundorf of Germany) for the best
quality of signal.
Main volume is Blue Velvet form ALPS for detailed operation and stability.
All these premium quality components are used for the playback of the real HiFi sound through this HP100.
No compromise, only the music matters!
4) Powerful Power Supply
Power supply for HP100 is also specially designed.
25VA custom-made toroidal power transformer is used for the fluent supply of
energy for the circuitries.
And the regulation circuit has a very low output impedance (20mΩ@10Khz) to
support the high quality of output power supply for the circuits with its super
low hum and riffle characters.
You can easily change supply voltage by selecting the proper one with a slide
switch. From 100~117V to 220~240V/50-60 Hz, you can use HP100 in any
places in the world.
5) Versatile and handy functions
HP100 is equipped with 2 pairs of unbalanced RCA inputs and 1 pair of
unbalanced analog output for external power amplifier connection.
And it also comes with Neutrik XLR type headphone jack to adopt specialmade XLR type headphone jack as well as the normal headphones.
Gain switch is located on the front panel to select the gain (Low : 11.3 dB,
High : 16.3 dB). These two gain mode has exactly same frequency range to
sustain the quality of sound.
On the center of the rear panel, ‘Filter’ switch is ready. You can select your
favorite filter depending on the music you are listening. You can even change it
easily during playback.
2. Front Panel
POWER : Turn the switch lever up to turn on the unit.
Red LED will be on to indicate the HP100 is operating.
INPUT : Select one input you want to listen out of 2 analog inputs.
GAIN : Select H (high) or L (Low) to adjust the input
for your power amplifier
or your headphone.
Low : 11.3 dB
High : 16.3 dB
VOLUME : Adjust the volume level by rotating this knob.
Rotating clockwise will increase the output level.
3. Rear Panel
INPUT : Unbalanced RCA type 2 inputs (INPUT1 & INPUT2) are ready.
Connect your tuner, CD Player, or from DAC (ex. DA100 output).
OUTPUT : Unbalanced RCA type output is ready.
Connect to your power amplifier. Be sure to connect your
Interconnect correctly (R : Right, L : Left).
FILTER : Two type of filter is provided (A & B, default is A).
Choose one while you listen with your power amplifier
or headphone.
4. Connection & Operation
4.1 How to connect
4.2 How to operate
1) Make sure that the level of your preamplifier or integrated amplifier set
to low volume level.
2) Turn the ‘Power’ Switch up (Red LED will lit).
3) Select your input 1 or 2 with the toggle switch.
4) Adjust volume control knob to set it at your preferred listening level.
5) You can change your input during playback. But we recommend you to
turn the volume down when you change GAIN. A ‘click’ sound can be
heard during the switching mode, but this is very normal.
6) Filter is set to A when it is released from the factory.
If you want softer sound, place the ‘Filter’ switch down position.
5. Features & Specifications
Line inputs and outputs
unbalanced input : 2 pairs
unbalanced output : 1 pair
headphone output : 1 Neutrik XLR phone jack
Front panel control
power on/off toggle switch & power on indication LED
line input selection toggle switch : input1, input2
gain selection toggle switch : high, low
volume control knob
Rear panel
line input1, line input2 : RCA jack
filter selection toggle switch : A(off), B(on)
line output for preamplifier use : RCA jack
AC receptacle
Input sensitivity
low gain : 2.7 Vrms
high gain : 1.5 Vrms
Maximum allowable input
12 Vrms (23.8dBu)
Recommended impedance (headphone)
Frequency response
16 Ω ~ 2400 Ω (1kHz)
5 Hz ~ 200 kHz ( 20kHz when filter is on)
Maximum gain (switch selectable) low : 11.3dB
high : 16.3dB
Headphone output
16 Ω : 2800mW + 2800mW
64 Ω : 1200mW + 1200mW
300 Ω : 300mW + 300mW
600 Ω : 150mW + 150mW
2400 Ω : 40mW + 40mW
Input impedance
Output impedance
pre-out : 50 Ω
phone out : 2.2 Ω
Power requirement
100~117 VAC/ 220~240 VAC selectable
50/60 Hz
212(W) x 55(h) x 290(D) m/m
3.5 kg (4.5 kg, packaged)
April Music, Inc.. supports 2 years of free warranty for HP100 under normal
use from the date of delivery.
This warranty extends only to the original purchaser and does not apply to the
parts that have been subjected to misuse, or abnormal operations. If the second
hand user wants to inherit the warranty period, he (she) should contact April
Music, Inc., by send an e-mail or a letter to activate the remaining warranty.
In the event of failure during the warranty period, April Music, Inc.. will repair
the HP100 at no charge as long as the unit is not working under normal use.
If the unit is damaged by the abnormal use (incorrect voltage connection,
spilling coffee over the top etc.) and if you or your dealer can not fix the
problems, the unit should be returned to the factory.
In this case, the estimate repair fee (including shipping & handling) will be
submitted before the repair for shipping.
A return authorization is required when sending the units for repair. They must
be shipped to April Music, Inc., prepaid and with its original cartoon (preferred).
There are no user serviceable parts inside except the voltage changing. And
HP100 is running very hot inside because all analog outputs are full class-A
operated discrete circuit. Care should be taken.
If you or any unauthorized persons have tried to change or modify the circuits
without any prior consent from April Music, Inc., all the warranty will be void
even the units are under warranty period.
* Do not try to modify the products by any unauthorized persons!
The warranty service is valid only when purchased from an authorized dealer. A
valid proof of purchase must be supplied for all warranty services. Any
unauthorized work, modification or service rendered on the player will void the
Warranty Period
Date of Purchase
Authorized Stello Dealer
Serial No.
Authorized Stello Service Center
2 years
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