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ZÄHL HM1 MANUAL V 1.0
Dual Mono vs. Balanced amplifier design
With its dual mono design, the HM1 features the same advantages as a balanced output stage but avoids the drawbacks.
The drawbacks of a balanced output stage are the significantly increased number of electronic components -
a balanced output contains two output stages per channel which work in reverse phase. Two output stages result
in doubling the output impedance. More components result in an increased risk of non-linearities.
¼ inch jack compatible
Another advantage of the HM1 architecture is that unbalanced headphones with ¼ inch jack plugs can also be
operated without any problems.
Line Outputs
The signal at the line outputs corresponds to the signal in the headphones, except that it does not pass through the
headphones amplifier, but through balanced or unbalanced line output stages and is routed to connectors on the
rear.
Connect active speakers, power amps or other gear
Balanced and unbalanced outputs may be used simultaneously to drive power amplifiers, active speakers, level
meters or other components. If, for example, the HM1 is used for comparing two stereo sources, the result may be
recorded using one of the outputs. The same applies when using the HM1 as a mixing console.
„A Thru" Output
The "A Thru" signal is tapped from Input channel A, post input amplifier. The switchable 15dB gain stage at Input A
affects the "Thru" signal. The Thru output has an unbalanced output stage.
Setup your own test bench / experimental bench
A signal connected to Input A can thus be routed to another application without loss. Application example: "A Thru"
is routed to a sound processing device or effects unit, the output of this unit is fed to Line Input B. The ratio
between original and processed signal can be set by the A/B volume controls. Of course, this setup is also excellent
for testing any device: Channel A supplies the original, channel B the signal coming from the unit to be tested.
Output Select
The output select toggle switch - located on the front panel above the XLR headphones output - is very useful if
you are using your HM1 to drive your headphones as well as to drive a power amp or active speakers at the line
outputs. In the upper position only the line outputs are active, in the lower position only the headphones output is
active. In the middle position both are active, which makes sense in case you have a recording or metering device
(or other) connected to the line outputs.
P.14 | DETAILS
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