Discussions on Balenced Amplifers - Page 3

millwood · 3rd January 2004, 07:22 PM

Quote:

Originally posted by theChris

just out of curiosity, how is that IC balenced

I think it is not balanced too.

However, if you put two buffers in front of it, then the whole thing should be balanced,

usekgb · 3rd January 2004, 07:37 PM

What about using the BB INA134 for converting balanced to unbalanced? It looks like a great chip: INA134 .

Cheers,
Zach

theChris · 4th January 2004, 06:25 AM

that IC looks to have the same issue as the previous ones -- it does convert a voltage differance into a voltage with respect to a referance, but it does not have equal input impedances unless the voltage at both terminals is 0v. i would think a true IN-AMP would be required to get both conditions -- same noise on both lines and differential inputs.

The high CMRR of the chip is nice though, as the noise rejection will be affected by the ability to reject common-mode signals, but the input imedance of the inverting terminal is a function of the signal on the output.

djk · 4th January 2004, 11:54 AM

"I guess the fuzz is that +in has 110k impedance to GND and -in 9.1k impedance to gnd in your case."

Close, the inverting input would be 10K. Hardly qualifies as balanced, do you think?

SE is right, transformers are a better solution.

Studio and pro gear frequently had octal sockets for your transformers. You invest in good transformers and keep them when you sell the gear.

Jensen makes some of the best.

Electronically balanced inputs are a waste of time and money, even those with laser trimmed CMRR.

http://www.edcorusa.com/sound/matchers/s2s10k_10k.htm

90% of the Jensen quality for 10% of the price.

usekgb · 6th January 2004, 02:40 PM

I do agree with using the Jensens. I was just trying to find a more cost effective alternative to this problem. You would be surprised how little pro gear is loaded with transformers these days.

Cheers,
Zach

4th January 2004, 06:25 AM	#23
theChris diyAudio Member Join Date: Dec 2001 Location: SIUE, Illinois, USA	that IC looks to have the same issue as the previous ones -- it does convert a voltage differance into a voltage with respect to a referance, but it does not have equal input impedances unless the voltage at both terminals is 0v. i would think a true IN-AMP would be required to get both conditions -- same noise on both lines and differential inputs. The high CMRR of the chip is nice though, as the noise rejection will be affected by the ability to reject common-mode signals, but the input imedance of the inverting terminal is a function of the signal on the output. __________________ if only it could be used for good, not evil...

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3rd January 2004, 07:37 PM	#22
usekgb diyAudio Member Join Date: Feb 2003 Location: Salt Lake City, UT, USA	What about using the BB INA134 for converting balanced to unbalanced? It looks like a great chip: INA134 . Cheers, Zach

4th January 2004, 11:54 AM	#24
djk diyAudio Member Join Date: Feb 2001 Location: USA	"I guess the fuzz is that +in has 110k impedance to GND and -in 9.1k impedance to gnd in your case." Close, the inverting input would be 10K. Hardly qualifies as balanced, do you think? SE is right, transformers are a better solution. Studio and pro gear frequently had octal sockets for your transformers. You invest in good transformers and keep them when you sell the gear. Jensen makes some of the best. Electronically balanced inputs are a waste of time and money, even those with laser trimmed CMRR. http://www.edcorusa.com/sound/matchers/s2s10k_10k.htm 90% of the Jensen quality for 10% of the price.

6th January 2004, 02:40 PM	#25
usekgb diyAudio Member Join Date: Feb 2003 Location: Salt Lake City, UT, USA	I do agree with using the Jensens. I was just trying to find a more cost effective alternative to this problem. You would be surprised how little pro gear is loaded with transformers these days. Cheers, Zach