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Old 5th December 2004, 10:24 AM   #1
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Default Remove resistence to A75 for unbalanced use?

To A75 amplifier for unbalanced use I can remove R28 , R5.
R29 and R2 can be romoved?
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Old 5th December 2004, 11:52 AM   #2
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look here the circuit A75
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Old 5th December 2004, 12:52 PM   #3
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Danyele82,

>> To A75 amplifier for unbalanced use I can remove R28 , R5.
Yes, you can...

>> R29 and R2 can be romoved?
Well, I don't think so.

For the cost of 4 resistors, 2 XLR's and 2 switches, it's a shame to
remove the Balanced inputs of the A75.!! Who knows, you'll probably
build a balanced preamp sooner or later...

PS: Now with my CCS-X-Bosoz preamp I use my A75 balanced, and I prefer this type of connections, the balanced mode has great advantages...
And using Belden 89207 twinaxial cable, its not so costly to have balanced cables..

Alain.
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Old 6th December 2004, 12:47 PM   #4
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For unbalanced use the gain is determinated by (R81 + R3//R27)/(R2//R29)?
If it's right the input resistence (R4) can be eliminated (or it's necessary for the low-pass with C1)?.
The quality of C7 and C5,C6 are important to the final result?
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Old 6th December 2004, 10:57 PM   #5
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Danyele82,

>> If it's right the input resistence (R4) can be eliminated (or it's necessary >> for the low-pass with C1)?.
>> The quality of C7 and C5,C6 are important to the final result?

Keep R4, it wont interfere in the 75 K Ohms unbalanced impedance,
but globaly there must be symetry between positive and negative input's.

Norman Thagard and Nelson Pass tells: the only requirement being that corresponding values on the positive and negative input networks be matched.

For the quality of C3,4,7 4.7uF, 16V, electrolytic
C5,6 220uF, 16V, electrolytic

I have used Panasonics, quite standard types...

Regards.

Alain.
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