Bellari HA540 MK2 User Manual
headphone amplifier
HA540 MK2
MADE IN USA
Volume
input 1
input 2
Power
Input select
power
HA540 MK2
Headphone
MADE IN USA
The warning section of the manual. Boring, but
hey we care about your hearing and health.
WARNING
USING THIS PRODUCT AT EXCESSIVE VOLUMES CAN CAUSE
In order to use this system safely, avoid prolonged listening at excessive sound pressure
levels. Please use the following guidelines established by the Occupational Safety Health
Administration (OSHA) on maximum time exposure to sound pressure levels before hearing
damage occurs. 90 dB SPL at 8 hours
CAUTION: Plugging a mono 1/4” or 1/8” TS plug into the Headphone Out-
puts on the HA540 will cause permanent damage to the unit because one side
would be shorted to ground. Never plug a mono plug into any of the Head-
phone Outputs THE HA540 WILL BE PERMANENTLY DAMAGED
This is a TRS or
stereo jack that
is compatible
with the HA540
Headphone
Outputs.
PERMANENT HEARING DAMAGE.
USE AS LOW A VOLUME AS POSSIBLE
95 dB SPL at 4 hours
100 dB SPL at 2 hours
105 dB SPL at 1 hour
110 dB SPL at 1/2 hour
120 dB SPL - avoid or damage may occur
Tip
Ring
Sleeve
(ground)
115 dB SPL at 15 minutes
This is a MONO
jack and should
never be plugged
into the Headphone Output of
a HA540.
Tip
Sleeve
(ground)
WARNING: THE MINIMUM HEADPHONE IMPEDANCE FOR THE
HA540 IS 8 OHMS. THE MAXIMUM HEADPHONE IMPEDANCE IS 2000
OHMS.
DO NOT OPEN THE HA540. REMOVING THE UNITS COVER COULD
POTENTIALLY DAMAGE THE UNIT OR CAUSE HARM TO UNQUALIFIED PERSONS. THE UNIT OPERATES AT +150 VOLTS INSIDE.
HIGH VOLTAGES EXIST INSIDE THE UNIT EVEN WHEN THE UNIT
IS NOT POWERED ON. ALL WARRANTIES ARE VOID IF ANY INTERNAL COMPONENTS ARE DAMAGED DUE TO USER ERROR.
HA540 MK2 Headphone Amp
SPECIFICATIONS
Input Impedance: 47K ohms
Max Output Gain: 19.6 dB
THD: 0.04%, 20Hz-20KHz, at 1V RMS
S/N Ratio: 85 db, unweighted
Indicator: 1 Power LED
Max Output Power: 332 mW/side, 664 mW/Channel (30 Ohms)
Frequency Response: 6 Hz - 51 KHz +/- 3 db
Phase Shift (In to Out): 0 Deg.
Crosstalk: -75 dB
Headphone impedance: 8 Ohms to 2000 Ohms
Input Connectors: CH 1: RCA, 1/8" (3.5mm)Stereo; CH 2: RCA
Outputs: 1: 1/4" TRS Stereo jack
1: 1/8" (3.5 mm) TRS Stereo jack
PWR: 15 VDC 500mA
Size: 6"w x 2.5"h x 5.4"d
Weight: 2 lb.
Salt Lake City, UT
12/18
Connection guide
Thank you for purchasing the HA540. We spent a considerable amount of time designing and developing the HA540.
Hundreds of hours listening and improving the design. We
hope you enjoy using the HA540, and that it makes listening
to your music collection rewarding. We sincerely appreciate
the opportunity to build a product for you and participate in
your love of quality music and sound. We love what we do
and we’re happy to help. All Bellari products are hand built in
Salt Lake City, Utah by people who care about high quality
music.
The HA540 uses one 12AX7 tube running at 150 volts. The
input signal is connected directly to the grid of the tube and
almost all of the gain of the HA540 is from the tube. The
output section is a pair of MOSFET's to drive headphones.
This is called a "hybrid circuit". The HA540 has no feedback
circuit or Integrated Circuits in the audio path, it is all analog.
CONNECTION:
1 - Connect your source to the HA540’s “in” RCA
jack or 1/8" stereo jack.
2 - Connect the supplied PS27s adapter to the
jack labeled “POWER.” Do not use any other
adapter, or the unit might not be happy and you would need
some repair work done. Reversed polarity adapters will
cause damage.
3 - Connect your headphones to the jack, marked “headphone”. You can use either the 1/8” or 1/4” jack or both at the
same time.
4 - Enjoy your music.
What's in the box?
1 - Made in USA HA540
1 - 15V power supply PN PS27s
1 - This owners manual
1 - Love for great audio
FAQ:
Q:What is a N.O.S. tube?
A: N.O.S. refers to (new old stock) it is a tube that was man-
ufactured long ago and never used. These tubes are very
sought after. They may or may not sound any better, but it is
generally thought that most N.O.S. tubes are better in many
ways over new foreign manufactured tubes.
Q: What kind of tubes can I use in the HA540?
A: Tubes that can be used in the HA540 are:
12AX7 - The industry standard for preamp tubes.
12AX7A - Same as a 12AX7 but generally has a slightly
higher output.
7025 - This is the Military part number for a 12AX7.
ECC83 - This is the same as a 12AX7 it is the European part
number.
12AX7WA - This is a 12AX7 with slightly lower output.
5751 - This is a Military part number for a 12AX7WA.
There are many other tubes that can be used, but you get
where this is going they are essentially the same tube with
dierent part numbers doing almost exactly the same thing.
Q: What is the best sounding tube I can get for the HA540?
A: This is an unanswerable question. Everyone has dierent
tastes. It is up to the individual to decide as all tubes sound
slightly dierent. For me the best tube I have ever heard in a
HA540 was a N.O.S. 5751 Telefunken tube.
Q: Does the tube need time to warm up before use?
A: Yes, it will be usable in about 30 seconds. Longer warm
up times are not needed, there is no benet to warming the
tube up longer than 30 seconds. Warm up simply means
powering the unit on.
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