Crown D-150 - PK Panel Kit Installation; 5-D Walnut Enclosure

Because the output wire gauge and length raises the resultant
source impedance or lowers the Damping Factor by adding series: «
resistance,
the
nomograph
(Figure..3-11)
is
provided
for
wire
selection. For dynamic moving-coil loudspeakers the valueRy --
should preferably be. that. measured by an ohmmeter across the
voice coil, rather than the manufacturer's rating. For elec
speakers
and
such,
theynanufacturér’s
rated
impedance
should
Pa
be used for R, -
ff the load (matching. teanstoriner, inductance, or ibe
electrostatic speaker system) appears as a short-circuitatiow freé
quencies, a large non-pélarized: capacitor’ (paralleled with a
resistor)-should-be-placed:in
series.
withthe.
jgad.
For electrostatic speakers (if the manufacturer has not provided a
lar Capacitor oF S90- 708 mitdand 4
ohn power resistor should be placed in senes with the plus +)
speaker lead. This. will prevent lerge low-frequency currents from
darnaging ‘the: electrostatic” tansfortier ‘or from unnecessarily
activating the D-150's protectivé.system. An effective test to
determine if such parts are-needed is to measure the DC re-
sistance between the output-terminals with a
résistarice-is tess than 3 ohms, the parts si
shown schematically in-Figare- Ss 9.
40,200...
FIGURE 3:9.
SCHEMATIC FOR FULL RANGE
ELECTROSTATIC SPEAKER, CONNECTION
should nét be used. A cormmon exariple is the standard 3-
circuit “inch phone jack. and lug awen. wired - for stereo
sound. .
4. Connectors having low-current-carrying capacity are “vers.
5. Connectors having any tendency to short, or having shorted
leads, are unadvisabie. on
Most commercially-available- headphones employ a A-circuit 4%
inch phone plug which violates condition No. 2. This is no handi-
cap if # pad is inserted between'the atip: jack, which is only
sensibie when such a large amp! is coupied to such a small
HE this precaution is not only may the trans-
ducer te-Gairned out but permanent hearing loss could result. The
recommended pad is shown in Figure 3-10.
“FIGURE 3-10:
SCHEMATIC ‘OF EARPHONE PAD
3.9 CONNECTING INPUT LINES
Connecting the inputs will require observance of three basic pre-
cautions: Undesirable signals.to-the inputs, “ground foops;“and
feedback from output(s) to input(s). °
in high fidetity audio applications any good vacuun?-tube or solid-
State control center will operate’successfully into the 25K ohm
inputs “of the D-150. Occasionally a high-impedance output of
poorly-designed preamps will be encountered, and/or a larger
_ output coupling capacitor may be required (o prevent excessive
— fow-tr quency rolloff).
For. joudspeaker-driving applications, the vane should-be free of
large sub-audio or undesired low frequencies, as they cause over-
heating and overloading of the loudspeaker. To remove such low
frequencies, a series capacitor may be placed in the input signal
line. (The graph of Figure 3-12 indicates the effectofthe size of the .
capacitor on the frequency response. 1) Only a low-leakage paper,
oF cause general overload
‘sewing -tate stage of the amip (which is employed to provide RF
overload protection). The following filters are recommended for
such applications (Figure 3-13),
A second precaution is “ground loops” — electronic jargon for un-
desirable circulating currents flowing in a grounding system. A
commion form of loop (possibly resulting in hurn In heoutpuld is a
pair of input cables whose area is subjected to a magnetic hum