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G8MNY > TECH 13.05.25 19:00l 117 Lines 4682 Bytes #10 (0) @ WW
BID : 32480_GB7CIP
Subj: Phantom Bal Mic Preamp+Gun Mic
Path: JH4XSY<JE7YGF<LU4ECL<VK2RZ<VE3CGR<GB7YEW<GB7CIP
Sent: 250513/0948Z @:GB7CIP.#32.GBR.EURO #:32480 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Jul 18)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Phantom powered Mic Preamp +12 to +48V with balanced 600� O/P Z.
ﾚﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄ10Kﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄｿ
ｳ ｳ R2 100K ｳ ｳ
ｳ R1ｳ ｳR3 ｳ ｳ C6 +
ｳ 22K ｳ 3ｳ`\ｳ8 ﾚﾄﾄﾄ)ﾄﾄﾄﾄｴﾃﾄﾄﾄﾄﾂﾄﾄﾄ270Rﾄﾄ + phase
ｳ ｳ ﾚﾄﾄ)ﾄﾄﾄﾄﾄﾄﾄﾄｳ+ `\__ｳ ｳ 22u 50V ｳ R11
ｳ+ ｳ 1u ｳ ﾃﾄ10Kﾄﾂﾄﾄｳ- ,/ 1ｳ ｳ R9
ﾄﾁﾄ ｳ 25V ｳ ｳ R6 ｳ 2ｳ,/ ｳ ｳ 10K BALANCED
ﾄﾂﾄC1 ﾃﾄﾄｴﾃﾄﾄｴ ｳ ﾀﾄﾄﾄﾄﾄR7ﾄﾄﾙ ﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ PHANTOM
ｳ100uF ｳ C2 ｳ ｳ +ｳ C4 ｳ +ve POWER
ｳ25V ｳ+ ｳ ｳ ﾚﾄﾄﾄﾄﾄR8ﾄﾄｿ ===100u R10
ｳ MIC ｳ ｳ ｳ 5ｳ`\ ｳ ｳ 40V 10K
ｳ CAPSULE ｳ ﾃﾄﾄﾄﾄﾄ)ﾄﾄｳ+ `\__ｳ ｳ ｳ
ｳ ｳ ﾀﾄﾄ)ﾄ10Kﾄﾁﾄﾄｳ- ,/ 7ﾀﾄﾄﾄ)ﾄﾄﾄﾄｴﾃﾄﾄﾄﾄﾁﾄﾄﾄ270Rﾄﾄ - phase
ｳ ｳ ﾚﾄﾄﾄｴ R5 6ｳ,/ｳ4 ｳ C5 + R12
ｳ ｳ C3+ｳ ｳ ｳ ｳ 22u 50V
ｳ ｳ 10u=== 100K ｳ ｳ
ｳ ｳ 25V ｳ ｳR4 ｳ ｳ
ﾀﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾁﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ Shield
Any 8 dil dual opamp e.g. CA3240, LM358N, MC1458C, NE5532N, NJM4558,
OPA2604AP, TL072, TL082, etc,
Gain of each phase = R7orR8/10K
Typical values R7=R8= 100K, gives 10x gain/phase, x20 overall gain (26dB).
The polarity of the C2 in series with the electret mic depends on the DC bias
level needed for the perticular mic capsule. So test the relative DC levels
before inserting capacitor.
The value of R9 & R10 can be changed to better suit the phatom powering voltage
e.g. 12V use 4K7, 48V use 22K.
LF tayloring can be incorperated if C2 in series with the mic can be reduced to
about 0.1uF. Also the 2 O/P Cs (C5,C6) are reduced, values depend on external
load.
WHAT DOES WHAT.
R11&R12 condition O/P Z to approx 600�, & supply some RFI & spike suppression.
R9&R10 with C4 decouple the DC phantom IC supply from out going line AF.
R2 with C1 decouple the DC supply for the mic.
R1 supplies DC current to the mic.
C2 passes mic AF into R5 load, & hence determins LF responce.
R3,R4 & C3 provide a decoupled ｫ DC rail bias point for the op amp.
R5, R8 & R6, R7 provide the 2 opamp voltage Negative Feed Back, setting gain.
C5 & C6 pass O/P AF into the line.
- ve PHANTOM POWER
If you phanton supply is -ve voltage, just re-connect R9 & R10 from C4 +ve to
the bottom rail & rewire the earth to the +ve of C4. Reverse the polarity of C5
& C6.
ﾚﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄ10Kﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ +ve Shield
ｳ ｳ R2 100K ｳ ｳ
ｳ R1ｳ ｳR3 ｳ ｳ + C6
ｳ 22K ｳ 3ｳ`\ｳ8 ﾚﾄﾄﾄ)ﾄﾄﾄﾄﾄｴﾃﾄﾄﾄﾂﾄﾄﾄ270Rﾄﾄ + phase
ｳ ｳ ﾚﾄﾄ)ﾄﾄﾄﾄﾄﾄﾄﾄｳ+ `\__ｳ ｳ 22u 50V ｳ R11
ｳ+ ｳ 1u ｳ ﾃﾄ10Kﾄﾂﾄﾄｳ- ,/ 1ｳ ｳ C4 R9
ﾄﾁﾄ ｳ 25V ｳ ｳ R6 ｳ 2ｳ,/ ｳ +ｳ100u 10K
ﾄﾂﾄC1 ﾃﾄﾄｴﾃﾄﾄｴ ｳ ﾀﾄﾄﾄﾄﾄR7ﾄﾄﾙ === 40V ｳ BALANCED
ｳ100uF ｳ C2 ｳ ｳ ﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄｴ PHATOM
ｳ25V ｳ+ ｳ ｳ ﾚﾄﾄﾄﾄﾄR8ﾄﾄｿ ｳ R10 -ve POWER
ｳ MIC ｳ ｳ ｳ 5ｳ`\ ｳ ｳ 10kK
ｳ CAPSULE ｳ ﾃﾄﾄﾄﾄﾄ)ﾄﾄｳ+ `\__ｳ ｳ + ｳ
ｳ ｳ ﾀﾄﾄ)ﾄ10kﾄﾁﾄﾄｳ- ,/ 7ﾀﾄﾄﾄ)ﾄﾄﾄﾄｴﾃﾄﾄﾄﾄﾁﾄﾄﾄ270Rﾄﾄ - phase
ｳ ｳ ﾚﾄﾄﾄｴ R5 6ｳ,/ｳ4 ｳ C5 R12
ｳ ｳ C3+ｳ ｳ ｳ ｳ 22u 50V
ｳ ｳ 10u=== 100K ｳ ｳ
ｳ ｳ 25V ｳ ｳR4 ｳ ｳ
ﾀﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾁﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄﾙ
SIMPLIER PHANTOM POWERED CIRCUIT!
ﾚﾄﾄﾄﾄﾄﾄﾂﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ\______ + Phase Live
ｳ ｳ+ on off
ｳ MIC
ｳ CAPSULE
47K ｳ - +
ｳ ﾃﾄﾄﾄﾄﾄｴﾃﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ - Phase
ｳ 47K 10uF 16V
ｳ ｳ
ﾀﾄﾄﾄﾄﾄﾄﾁﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄﾄ Gnd
With this simple circuit DC is only taken from the live phantom. The capules is
insulated from its hum avoiding earthed surround shield. The 47K live to ground
is a balancing R to ensure equal +/- signals.
MAKING A GUN MIC
If the Mic capsule is inserted tightly (sealed) into a long 30mm dia tube that
has holes or slots made down it's length, a very directional gun mic is made,
(over the frequency range where the sound waves are columnmated in the tube).
: : : : : : : : : : : : : : : : : : : sponge windshield
: : -- --- --- --- --- --- --- --- ----
: : [] mic capsule
: : -- --- --- --- --- --- --- --- ---- slotted pipe
: : : : : : : : : : : : : : : : : : :
See also "Phantom Balanced Mic Preamp" & "DC sources for coax/AF" bul.
Why don't U send an interesting Bul?
73 de John G8MNY @ GB7CIP
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