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lordearl 12th July 2010 04:49 AM

unity gain stable single channel DIP opamp
looking for something to replace two single OPA627 (currently on adapters) I have in the output stage of my DAC

any suggestions would be great!

Mooly 12th July 2010 06:27 AM

There are literally dozens of threads on this subject, however for great sonics I still think the OPA2604 has a bit of magic about it.

You are just going to have to try a few and see what you think.

lordearl 12th July 2010 07:24 AM

Thanks mate - I've read dozens and dozens of threads about this type of thing over the past year or two, but it's the "unity gain stable" thing that gets me - what is the statistic on the data sheet that lets me know whether it is unity gain stable or not?

Mooly 12th July 2010 07:34 AM

Usually mentioned specifically as one of the main features... if not you have to read through the data sheet. There's no "parameter" as such in the specs that indicates it is or isn't... although words such as "internally compensated" usually mean it is, and devices that have "external compensation" usually aren't.

jcx 13th July 2010 05:42 AM

how can anyone offer meaningful advice without the basics of V or Iout, what signal levels, power supply V?

Mooly 13th July 2010 06:13 AM


Originally Posted by jcx (
how can anyone offer meaningful advice without the basics of V or Iout, what signal levels, power supply V?

The OPA2604 covers most bases having a supply range of -/+4.5 to 24 volts, 600 ohm drive capability and good (it's docile to work with) stability.
As a replacement for the OPA627 (on dual adapters as the OP uses them) I feel it it should operate perfectly in a DAC whether used as I/V conversion/filter buffer etc.
If you want to retain the single devices and adapter use the OPA604
Whether the OP can hear any difference subjectively will be interesting to know.

lordearl 13th July 2010 06:48 AM

Sorry, yes, a schematic will help:

Mooly 13th July 2010 07:18 AM

OPA604 should be perfect. When you mentioned using adapters thought you meant making a dual out of two single SMD devices.

Read the last part of this data sheet "sound quality",

that's Burr Browns take on it... in use I have found it offers excellent sonics, can't really say more than that... only you will know if you hear/detect/like the device.

lordearl 13th July 2010 07:22 AM

OK thanks, I'll give them a go. I tried out the LME49710NA (as you can read in that thread), but did not notice a huge difference, so it should be interesting to try the OPA604 and compare it with both the OPA627 and LME49710NA.

I don't think there are many other candidates there that would be suitable opamps. I'm leaving the four OPA627 in the filter stage as it's too expensive to replace all 6 chips!

qusp 15th July 2010 07:38 AM

remember they also need to be bipolar input for your dac.

mooly, I recommended the BUF634 to lordearl, as I figured they were single channel opamps acting as unity gain buffers (the stock opamp is OPA134), but of course we didnt get good results as they are also taking a bipolar input

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