Wanted->Discrete balanced to unbalanced CMR converter - diyAudio
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Old 20th September 2003, 02:40 PM   #1
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Question Wanted->Discrete balanced to unbalanced CMR converter

I've seen OP-Amp designs. I've also seen audio transformer designs.

I'm looking for the bare minimum discrete CMR circuit to convert balanced to unbalanced & new balanced signals.

Any recommendations?
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Old 20th September 2003, 03:42 PM   #2
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Here is something I came up with:
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Old 20th September 2003, 05:51 PM   #3
jam is offline jam  United States
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Brian,

How about buffering the outputs of the phase inverter?

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Jam
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Old 20th September 2003, 06:04 PM   #4
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Yes, I thought of that as well. My goal here was to use the least amount of silicon in the circuit. Also, aditional buffers may add DC drift to the outputs. As long as the VGS of Q1 & Q2 are well matched & the +/- supply is balanced, output should be biased very close to 0v.

BTW, the 180 ohm resistors should be changed to 470 ohm, otherwise their load will exceede 1/2 watt.
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Old 20th September 2003, 07:56 PM   #5
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Quote:
Originally posted by Brian Guralnick
Yes, I thought of that as well. My goal here was to use the least amount of silicon in the circuit. Also, aditional buffers may add DC drift to the outputs. As long as the VGS of Q1 & Q2 are well matched & the +/- supply is balanced, output should be biased very close to 0v.
Have you considered Nelson's Balanced Zen Preamplifier?

Look, Jam! No transformers!
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Old 20th September 2003, 08:20 PM   #6
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Default Re: Wanted->Discrete balanced to unbalanced CMR converter

[QUOTE]Originally posted by Brian Guralnick
[B]I've seen OP-Amp designs. I've also seen audio transformer designs.

I'm looking for the bare minimum discrete CMR circuit to convert balanced to unbalanced & new balanced signals.

--------------------------------------------------

Any circuit will affect sound quality. Why not just take signal from the balanced output directly. Coupling capacitors particularly affect the sonics however good.
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Old 20th September 2003, 08:51 PM   #7
OliverD is offline OliverD  Germany
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Quote:
[b]Originally posted by fmak[b]
Any circuit will affect sound quality. Why not just take signal from the balanced output directly. Coupling capacitors particularly affect the sonics however good.
If you take only the (+) and GND line from a balanced signal to make it unbalanced (as seen in many amplifiers with RCA and XLR connectors wired in parallel), your CMR will be zero.
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Old 20th September 2003, 08:58 PM   #8
OliverD is offline OliverD  Germany
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Another good way would be this approach as used in the Accuphase C-290V. This circuit gives you both balanced and unbalanced outputs (unbalanced after Amp.1) and can restore a balanced signal with unequal amplitudes on (+) and (-) lines to perfect symmetry again. Also, if you short one side of the balanced output to ground, the circuit will continue to operate and the output voltage will be the same.

The "Amp" modules are discrete unity-gain opamps.
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Old 20th September 2003, 09:32 PM   #9
jam is offline jam  United States
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Steve,

You almost gave me a heart attack.....................
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Old 20th September 2003, 09:35 PM   #10
jam is offline jam  United States
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