Hafler HA75 User manual

HA75
User Guide
Tube Head
Headphone Amp
Haer is a division of Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam
BC, Canada V3C 5M5
[phone] info@haer.com
www.haer.com

Table of Contents Page
Overview ................................................................................ 1
Features ................................................................................. 2
Connect .................................................................................. 4
Testing Your Connections....................................................... 6
AB Switch ............................................................................... 6
Feedback Control ................................................................... 7
Understanding the Focus Control........................................... 8
Understanding the VOX Control............................................. 9
Warranty .................................................................Back Cover
Thank you for purchasing the Haer HA75 Tube Head. This
warm sounding tube headphone amplier is designed to be
easy to use while providing the user with many customizable
features to further enhance enjoyment. This manual has been
written in order to provide you with all of the details so that you
may take full advantage of these extra features. As such, we
ask that you take a few minutes to read it. If you nd yourself
looking for more information, please visit the HA75 FAQ page on
the Haer web site. This is where we post answers to questions
from users that are often helpful. Then, if you are still missing
something, feel free to send us an email at info@haer.com and
we will do our best to reply in short order.
HA75 'TUBE HEAD' HEADPHONE AMP
USER GUIDE
CAUTION
HIGH VOLTAGE
There are high voltages inside the HA75. Before opening the unit - It
must be unplugged from the power supply and allowed to discharge
for at least 30 minutes. Touching the wrong place can cause a severe
shock. High voltages present at the tube socket will remain present for
some time after switching the HA75 off. There are no user serviceable
parts inside. Only use indoors in a dry space. Do not open unless you
are a qualied technician or have experience with tubes.

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
1
WARNING
HIGH POWER AMPLIFIER
The powerful amplier inside the HA75 is designed to accommodate
all types of headphones from 8Ω to 400Ω. As we have no way of
determining the headphone impedance, the amplier is very loud.
Exposure to high sound pressure levels for an extended period of
time can cause irreparable ear damage. Please consult your local
health authority to ensure you do not expose yourself beyond
recommended limits. Radial shall not be held responsible for
using the HA75 without due care or beyond recommended legal
limits imposed by your local government. Use by children is not
recommended and therefore must be carefully monitored by parents
or guardians.
OVERVIEW
The Haer HA75 uses a 12AX7 tube as part of the signal amplication.
Tubes are preferred by audio enthusiasts and recording engineers for
their smooth, natural sound. The HA75 tube sound will reduce ear fatigue
compared to typical solid-state counterparts.
The HA75 is also able to generate tons of power. Unfortunately, this
opens the door to potential risks that you must be aware of. The high
output tube amplier is intended for use by recording professionals to
enable them to monitor dynamics without constraint when using a wide
range of headphones of varying impedances. This means that non-
professional home users must take special care to prevent excessive
exposure over a long period of time. You should therefore consult your
local health authority for details on allowable exposure limits in order to
prevent damage to your hearing. This is particularly important when using
ear-buds as these are designed to accommodate low output ampliers,
which means they can be very loud with very little output power.

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
1. ON: Activates the HA75. It is recommended to warm up the tube for
15 minutes to achieve thermal stability.
2. SELECT: From the front panel you can select between two different
inputs designated as A (balanced/unbalanced) and B (unbalanced).
3. FEEDBACK: Controls the amount of negative feedback that is
being introduced back into the circuit.
4. GAIN: Used to adjust the volume for headphones.
5. FOCUS: Active matrix lets you control the width of the stereo image
to replicate listening to loudspeakers in a room.
6. VOX: Three position switch lets you enhance low
frequencies to suit the listening level and program material.
7. HEADPHONE OUTPUTS: Dual ¼” TRS outputs to enjoy the
listening experience with a friend or client. For best results use two
matched headphones as the impedance determines the loudness.
2
FEATURES
2 3 4 5 6 71
VOX Switch
A - Bass enhancer
Ø - Bypass / O
B - Loudness

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
3
8. POWER: ±16V 1600 mA external power supply included.
9. TUBE OUT: Add the Tubehead's warm tube character to a signal
path between a preamp and power amp if desired.
10. THRU: Un-buffered thru-puts that bypass the HA75 circuitry.
11. INPUT-B: Unbalanced RCA inputs to connect any -10dB line level
source to the HA75.
12. INPUT-A (RCA): Switch-able balanced and unbalanced inputs for
any hi- system. Standard RCA connectors.
13. INPUT-A SELECT: Switches between RCA and XLR connections
for INPUT-A.
14. INPUT-A (XLR): Balanced input for hi- system or studio use. XLR
inputs follow the AES standard with pin-1 (ground), pin-2 (+) and
pin-3 (-).
15. 12AX7 TUBE: Dual triode tube operates
with a B+ of about 140 Volts.
15
8 9 10 11 12 13 14

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
4
CONNECT
Connecting to and from the Haer HA75 is easy. It features standard RCA
connectors for home use and balanced XLR-F inputs for professional
use in studios. Before making any connections, turn off your audio
system. This will prevent plug-in or turn-on transients from damaging
more sensitive components such as tweeters.
If you are connecting your HA75 to a hi- system, simply take the auxiliary
output, tape monitor output or some other -10dB line level output from
your receiver or source device and connect to the HA75 input-A RCA
inputs. Make sure the input switch on the rear panel is in the 'out' position
and that you retain the left-right standard to ensure you experience the
music the way it was engineered during the recording process. Once
you are up and running, you can add a second source to the HA75 by
connecting it to input-B. Switching between the two sources is done
using the front panel select switch.
Connect the power supply. This external switching supply employs a
locking XLR connector and is able to handle input voltages ranging from
100V to 240V for use around the globe. Simply ensure the AC connector
matches your country’s power system using a standard IEC cable.
PHONO INPUT OUTPUT
L R
Turntable
Receiver
Input-B
⅛" to RCA HA75

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
5
If you are using the HA75 in the studio, it is equipped with balanced XLR
female inputs that follow the AES standard with pin-1 (ground), pin-2
(+) and pin-3 (-). These are paired with the input-A connectors. Use the
selector switch on the rear panel to toggle between the unbalanced RCA
inputs and the XLR inputs. Only one source can be selected at a time.
Also, available are two sets of RCA connectors labelled as THRU and
TUBE OUT. The THRU outputs are un-buffered and a simple pass
through (VOX or FOCUS will have no effect). The TUBE OUT delivers
the signal after it has been processed by the HA75’s tube amplier. This
can be used to position the HA75 in between a preamp and power amp
to add a warm tube character to the signal path. In the studio it can be
applied to recordings to 'warm-up' stale digital tracks or give instruments
and voice added character, particularly if pushed hard. Be careful! The
HA75 is a powerful beast and can easily overload the input of a mixing
desk if care is not taken.
DAW
Input-A XLR
Preamp Output RCA
Power Amp Input
Tube Out
RCA
DAW Input-A XLR
Tube Out
RCA to XLR

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
6
TESTING CONNECTIONS
Set all of the front panel knobs and switches to the start position with
AB select to A, volume to zero, feedback control fully counter clockwise,
focus switch off and loudness (VOX) to the middle position.
USING THE AB SELECT SWITCH
The intent is simple: let’s say you have your regular hi- source such as
a CD player or preamp connected to input-A and then the audio output
from a laptop computer connected to input-B. This would enable you to
quickly switch between sources without having to disconnect one or the
other. Connecting the HA75 in between the hi- preamp and power amp
using the Thru output also lets you route the signal from your laptop to
your power amp using the HA75 to select the active input and control
the levels.
Plug in your headphones and then turn up the source audio system to
a low level. Slowly increase the level on the HA75 using the big volume
control knob in the middle. Testing at low volume will prevent damage
to your headphones and protect your hearing should a connection be
faulty. If no sound, check to make sure you have the front panel select
switch set to input-A. If all seems OK, increase the volume until you have
reached a comfortable listening level.
In the studio you can use the XLR inputs to connect from your recording
system and the RCAs to listen to guest mixes from iPhones or tablets.
Simply make up the appropriate cable and connect to the HA75 input-B
RCAs and select when needed.
Input-B
Input-B
Input-A
Input-A

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
7
DUAL HEADPHONE OUTPUTS
The benet of having two headphone outputs on the HA75 means you
can share the listening experience with a friend or client! Using matched
headphones is best as the impedance determines the loudness.
Otherwise there may be a substantial level difference. This is also a
great way to set and monitor the volume for someone else and ensure it
is not excessive. (See disclaimer at the front of the manual)
FEEDBACK CONTROL
The HA75 is unique in that the user may control the amount of negative
feedback that is being introduced back into the circuit.
Varying the amount of feedback from the output of
each channel back to the cathode tube will make the
sound more or less 'tubey'. Listening tests concluded
that some songs sound great with maximum tube
effect (less negative feedback) while other recordings
need less (more negative feedback). This means that
no one amount of feedback works in all situations.
The feedback control can vary from none up to a
point where the circuit becomes a little unstable.
Changing the feedback will affect the overall gain.
HA75 Feedback
control lets you ad-
just the degree of
warmth added to
the signal.
When the feedback switch is in the out (off) position, the feedback control
is preset to approximately 2 o’clock. To activate, depress the switch. The
feedback control is congured so that when in the full clockwise position
(5 o’clock) there is no feedback and the gain of the HA75 is at maximum.
This position will introduce more harmonics and warmth but will also
measure higher THD as the tube is operating wide open. This is what
you can call ‘old school Class-A tube circuit sound’.
As the feedback CONTROL is rotated counter clockwise the amount of
feedback is increased. This will reduce the amount of 'tubey' sound and
the resulting gain of the HA75 will be reduced. Increasing the feedback
will lower the THD introduced producing a cleaner more clinical tone.
When the feedback switch is in the OUT position, the feedback control
reverts to the 2 o'clock 'preset' position. This feedback setting was
selected through listening tests as a nice in-between amount. We invite
you to try different feedback settings to hear the effect. There is no
right or wrong setting. Just be aware that the feedback control affects
headphone output level and a level adjustment may be required.

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
8
THE FOCUS CONTROL
One of the particularly cool features built into the HA75 is the Focus
control. This enables you to simulate the effect of listening to music in a
free air space, as if playing music through speakers in a typical room. In
essence, you can adjust the stereo image to suit.
Here’s the point: When listening to loudspeakers, the sound emanating
from the right loudspeaker will be heard in both ears, not exclusively the
right side. But with headphones, you only get the left program material in
the left ear and the right program material in the right ear. This can make
extreme 'left right' imaging sound more dramatic than it was intended,
likely pushing you away from the artist’s intended mix.
The solution is the Focus control. This is an active matrix that mixes a
mono ‘blend’ of the two channels back into the stereo image. This control
is much more precise than a typical passive mono blend. Controlling the
amount of width brings the stereo image from wide to narrow as you
increase the control from counter-clockwise to clockwise. Upon listening
– depending on the program material - you will notice a greater sense of
realism. When recording in the studio, this allows the engineer to quietly
mix as if listening to neareld monitors.
To activate, simply depress the Feedback ON switch and adjust to suit.
When engaged, this will cause the volume to increase slightly as you
are now combining multiple signals together to create a new stereo mix.
Simply lower the gain control to compensate.
Listening with headphones
Narrow field
Listening with speakers
Wide field

HA75 'TUBE HEAD' HEADPHONE AMP
Haer
9
THE VOX CONTROL
This three-position VOX or loudness control switch serves two functions.
The rst is as a traditional loudness control, the second to enhance bass.
Back in the 1970's, most integrated receivers were outtted with a
loudness switch that would enhance bass at low volumes to make up
for loudspeaker inefciency and the human ear’s greater sensitivity to
mid-range frequencies. This countered the Fletcher-Munson curves
that demonstrated how the human hearing changed based on sound
pressure levels. We felt that when listening to music at low levels, say
while reading a book, enhancing the low frequencies would enhance the
listening experience. To set the HA75’s VOX switch to normal loudness,
set the switch in the down position.
The other issue is one that has come about in recent times - headphones
with exaggerated bass that are now all too common. When comparing
headphones, the difference can be astonishing. Some have extended
high frequencies, others so much bass they can cause your head to
spin. Another problem is listening to music that may have been recorded
in the 1960's or 70's that may lack bass.
Set the VOX switch in the up position to increase the bass and simulate
the effect of these over-exaggerated headphones or offset bass-lacking
mixes. This also allows the recording engineer to simulate listening to
various headphones to get a sense of how the program material will
translate.
For the purist, simply set VOX control to the middle position (bypass) to
hear the natural mix without enhancement.
ABOUT THE TUBE
Most of the voltage amplication inside the HA75 is done with a 12AX7
dual triode tube operating with a B+ of about 140 Volts. This tube may be
unplugged and replaced with any other brand of 12AX7 if the user does
not agree with our selection or has some other preference. It is however
important to note that the HA75 is biased for the 12AX7 and use with a
12AU7 or 12AT7 will not sound good at all.
Note: High voltages are present inside the HA75. For safety we suggest
that the tube only be changed by a qualied technician.
VOX Switch
A - Bass enhancer
Ø - Bypass / O
B - Loudness

THREE YEAR TRANSFERABLE LIMITED WARRANTY
HAFLER (A division of Radial Engineering Ltd.) (“Haer”) warrants this product to be free from defects
in material and workmanship and will remedy any such defects free of charge according to the terms
of this warranty. Haer will repair or replace (at its option) any defective component(s) of this product
(excluding nish and wear and tear on components under normal use) for a period of three (3) years
from the original date of purchase. In the event that a particular product is no longer available, Haer
reserves the right to replace the product with a similar product of equal or greater value. In the unlikely
event that a defect is uncovered, please call 604-942-1001 or email service@haer.com to obtain a RA
number (Return Authorization number) before the 3 year warranty period expires. The product must be
returned prepaid in the original shipping container (or equivalent) to Haer or to an authorized Haer
repair centre and you must assume the risk of loss or damage. A copy of the original invoice showing
date of purchase and the dealer name must accompany any request for work to be performed under
this limited and transferable warranty. This warranty shall not apply if the product has been damaged
due to abuse, misuse, misapplication, accident or as a result of service or modication by any other
than an authorized Haer repair center.
THERE ARE NO EXPRESSED WARRANTIES OTHER THAN THOSE ON THE FACE HEREOF
AND DESCRIBED ABOVE. NO WARRANTIES WHETHER EXPRESSED OR IMPLIED, INCLUDING
BUT NOT LIMITED TO, ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR
A PARTICULAR PURPOSE SHALL EXTEND BEYOND THE RESPECTIVE WARRANTY PERIOD
DESCRIBED ABOVE OF THREE YEARS. HAFLER SHALL NOT BE RESPONSIBLE OR LIABLE
FOR ANY SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSS ARISING FROM
THE USE OF THIS PRODUCT. THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS, AND
YOU MAY ALSO HAVE OTHER RIGHTS, WHICH MAY VARY DEPENDING ON WHERE YOU LIVE
AND WHERE THE PRODUCT WAS PURCHASED.
www.haer.com
Haer HA75™ User Guide - Part #: R870 1302 00
Copyright 2015 Haer All rights reserved.
Specications and appearance subject to change without notice.