why o why doesn't this work ? Balanced 549 - diyAudio
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Old 25th January 2004, 09:21 PM   #1
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Default why o why doesn't this work ? Balanced 549

I tried this idea to drive the balanced output of my Roland E660 in a gainclone. Used chips are OPA549. No bad smell, no DC on the output but also no sound They are powered with 2 12v batteries wich gives a -12 and +12 rail. Also there's a 0,1 F cap over the 2 rails.

Click the image to open in full size.

Even when i connect just one on a unbalanced output still nothing.

The only thing i hear is a slight *pop* in the speakers when I power the 549's.
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Old 26th January 2004, 12:44 AM   #2
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i asume you mean the OPA549? what have you connected the current limiting and Vref pins to? there will be no output unless the are both set. the easiest way to do this is to connect them both to ground. this will set the current limit to maximum (10A).

have fun.
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Old 26th January 2004, 03:15 PM   #3
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both are connected to the ground, wich in this case is the plus and minus from each batterie. -12 gnd +12
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Old 26th January 2004, 03:30 PM   #4
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Is the ground of output from the Roland connected to anything? Quite often balanced outputs are created without a transformer, and since your input is transformerless, you really need to connect the grounds together.

Rune
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Old 26th January 2004, 03:44 PM   #5
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yup, those are connected to the ground as well.

mmm, i was fiddeling a bit. Now i got his very hard sounding clipping music true the speakers. Well not music, more static/hum on the beat of the song.
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Old 26th January 2004, 04:29 PM   #6
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Excuse me, maby I need a cold beer, but is that a balanced GC?
Two IGCs?
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Old 26th January 2004, 05:23 PM   #7
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Quote:
Originally posted by SpaBlauw
both are connected to the ground, wich in this case is the plus and minus from each batterie. -12 gnd +12
yes.

sorry to hear about the hum. i cant really help more, as i dont know anything about balanced inputs/outputs.
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Old 26th January 2004, 05:52 PM   #8
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I just red the datasheet over again, in wich stated that ref. pin must be als low as the negative voltage if V- is used. So in my case -12. Sadly enough I don't have anymore samples avaible so this project has to wait.

@carlosfm, actually this is a bridgeclone. But you can call it a balanced amplifier since you use the - in / + in to drive it.
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Old 26th January 2004, 06:08 PM   #9
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What have you done with the E/S pin? (It shouldn't be connected to anything when REF and ILIM is at GND)

As long as you have a psu voltage above +/- 4V, you can connect REF and ILIM to GND.
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Old 26th January 2004, 06:18 PM   #10
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E/S pin is cut off
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