Can OPA627 short output to ground?

klitgt · 17th February 2006, 12:24 PM

I have got a second-hand Denon DCD2700 CDP for nothing, it's in a good mechanical condition and should be worth giving some other opamps than the

uPC4570 ones. The BA15218 for filtering will be replaced by SSM2139, the ones that are in the DCD S1.

I have a number of OPA627 on adapters (for pin-compatibility) that I plan to use, also for the output buffers. They do not have any DC-offset and I may remove the coupling cap in each channel (marked red in attachment).

But after the cap there is a 150 Ohm resistor and then a relais that shorts signal to GND during Stop & Pause. Will the OPA627 tolerate to be shorted to GND at the output? There is no information in the datasheet as far as I can read.

I guess it will not fry

because of the 150Ohm resistor and because current will be low also as the DC offset is next to nothing.

But rather be safe

than sorry

, so I ask the experts!

jean-paul · 17th February 2006, 07:25 PM

That won't be a problem. Have no fear. I use 47 or 100 Ohm mostly for termination at that spot and I never experienced broken opamps. OPA627 is also short circuit protected....

klitgt · 18th February 2006, 08:58 AM

Quote:

Originally posted by jean-paul
That won't be a problem. Have no fear. I use 47 or 100 Ohm mostly for termination at that spot and I never experienced broken opamps. OPA627 is also short circuit protected....

Thank's a lot, I will go on!

Leolabs · 19th February 2006, 06:15 AM

You can go for 10 ohms.

klitgt · 19th February 2006, 09:53 AM

Quote:

Originally posted by Leolabs
You can go for 10 ohms.

Any reasons for going that low? Please explain pros/cons with resistor values at this point, I do not really understand why there is such a wide margin. The default value is 150 Ohms.

AndrewT · 19th February 2006, 10:02 AM

Hi,
200r output impedance allows for medium capacitance of interconnects.
60r would allow for very long cables as in pro sound systems.

Some domestic go as high as 1k0 but these suffer from hi freq roll-off when shortish cables (2m) are used

klitgt · 22nd February 2006, 08:05 AM

Quote:

Originally posted by AndrewT
Hi,
200r output impedance allows for medium capacitance of interconnects.
60r would allow for very long cables as in pro sound systems.

Some domestic go as high as 1k0 but these suffer from hi freq roll-off when shortish cables (2m) are used

Of course! It is the values in the R/C coupling that determines the cut off frequency of a low pass filter. Thank's for reminding me

davidsrsb · 22nd February 2006, 09:06 AM

There is a compromise. A higher value of series resistor isolates the opamp from the cable capacitance and prevents oscillation.

17th February 2006, 07:25 PM	#2
jean-paul diyAudio Moderator Emeritus Join Date: Sep 2002 Location: The Netherlands	That won't be a problem. Have no fear. I use 47 or 100 Ohm mostly for termination at that spot and I never experienced broken opamps. OPA627 is also short circuit protected.... __________________ It's only audio

19th February 2006, 10:02 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, 200r output impedance allows for medium capacitance of interconnects. 60r would allow for very long cables as in pro sound systems. Some domestic go as high as 1k0 but these suffer from hi freq roll-off when shortish cables (2m) are used __________________ regards Andrew T.

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19th February 2006, 06:15 AM	#4
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	You can go for 10 ohms.

22nd February 2006, 09:06 AM	#8
davidsrsb diyAudio Member Join Date: Dec 2005 Location: Kuala Lumpur	There is a compromise. A higher value of series resistor isolates the opamp from the cable capacitance and prevents oscillation.

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