HA75 'TUBE HEAD' HEADPHONE AMP
Hafler
7
duAL HeAdPHone ouTPuTS
The benefit 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 configured 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.
