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Old 8th April 2012, 04:12 PM   #1
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Default how change the balance input to unbalance input in PASS amp?

how change the balance input to unbalance input in PASS amp?
because my preamp is unbalance output.

question maybe this:
how to connect the RCA input to the balance input?
for example in Alpeh-X(balance input)?
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Old 8th April 2012, 04:18 PM   #2
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RCA hot to pin 2 of XLR

RCA gnd to both pins 1&3 of XLR
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Old 8th April 2012, 07:18 PM   #3
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Please keep in mind that when you do what was suggested, you will lose half thge voltage (lose 6dB).
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Old 8th April 2012, 07:29 PM   #4
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correct , but there is better definition - he'll need double input voltage for same output
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Old 10th April 2012, 06:41 AM   #5
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How about the passive balanced input option Nelson often talks about ?
Let's say, define the output Z of your pre. Easy, Use a sine in and a pot on the output.
Adjust pot until read voltage reaches 1/2 of the non loaded output. That is your output Z.

Then, use balanced input of the power amp; but terminate - in by a resistor of same value of Z out on the positive half ...

Any clues ???? That's named "passive balanced" I guess ...

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Old 10th April 2012, 09:54 AM   #6
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I think "passive balanced" is the same as Jensen's pseudo balanced.
The output of the unbalanced source is converted to a balanced impedance output, but with signal only on the hot. The cold is connected to Signal Ground. Pin1 is connected to chassis.

The impedance looking back into the source is identical on both hot and cold. That is a requirement for a balanced connection.

Implement Jensen's modification and your unbalanced source becomes compatible with all balanced receivers.
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Old 18th April 2012, 09:54 AM   #7
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Quote:
Originally Posted by AndrewT View Post
I think "passive balanced" is the same as Jensen's pseudo balanced.
The output of the unbalanced source is converted to a balanced impedance output, but with signal only on the hot. The cold is connected to Signal Ground. Pin1 is connected to chassis.

The impedance looking back into the source is identical on both hot and cold. That is a requirement for a balanced connection.

Implement Jensen's modification and your unbalanced source becomes compatible with all balanced receivers.
Thanks AndrewT Acting this way, we'll only get half the gain that would occur by normally shorting - input to ground right (not recommended though as this throws out some gain) ? Whilst retaining noise performance of a true balanced input

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nAr
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Old 19th April 2012, 03:51 AM   #8
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No, No, and No.

If you take an Aleph 2 and short pins 1 and 3, the gain of the amplifier
remains the same.

Passive Balanced? Who knows what they're talking about.

If you want the noise rejection of balanced with a single-ended source,
you do like I showed in the A75 article (how many years ago?).

Use balanced cable and terminate pin 3 through the appropriate value to
ground at the source.

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Old 19th April 2012, 09:34 AM   #9
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Nelson Pass View Post
,,,,,,,Use balanced cable and terminate pin 3 through the appropriate value to
ground at the source.
That sounds like a description of Jensen's Pseudo Balanced output schematic.
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Old 19th April 2012, 10:02 AM   #10
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Jensen's term pseudo balanced is referring to a unbalanced-balanced connection where symmetrical cable is used and pin 3 and shield are connected at the source, inside RCA-connector for example. Impedance balanced On the otherhand is a method discribed by Mr. Pass where you connect pin3 to GND at the source with a resistor equal to output impedance.
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