Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720

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elskardio

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Joined
Sep 29, 2010
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560
Location
Montreal - Canada
Hi Guys,
anyone has real test results using the OPA2134 or the LME49720 to drive a 600 ohm 1:1 output transformer?
Both data sheets mention that it can "drive easily 600 ohm load", but how do they perform at full output swing?
I'm planning to use a simple line driver like the following schematic:
line-driver.png

Any hint would be appreciated.
Thanks and stay safe ;)
 
Implementation will affect the final outcome. As a starting point there is some excellent info in this opamp distortion pdf.

https://www.nanovolt.ch/resources/ic_opamps/

 
> "drive easily 600 ohm load", but how do they perform at full output swing?

As said: in the Data Sheet.

Getting 14.14V peaks with 15V supplies at 0.01% THD is not very shameful. Drops off real fast at 12V peak (8.5Vrms). To my mind/ear, 0.0001% THD is fantasy, meaningless.
 

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depends on what is really attached to the secondary, rare to see audio gear with a 600 ohm load unless it is vintage like a Pultec EQP or something like that,

and what kind of transformer? a steel core will probably take more current to excite than a 50/50 nickel core,

 
john12ax7 said:
Implementation will affect the final outcome. As a starting point there is some excellent info in this opamp distortion pdf.

https://www.nanovolt.ch/resources/ic_opamps/

Wow! a lot of great info indeed. Thanks

CJ said:
depends on what is really attached to the secondary, rare to see audio gear with a 600 ohm load unless it is vintage like a Pultec EQP or something like that,

This will be at the output of a mic preamp. With more and more vintage equipment clones out there, I want to make sure it performs well at 600 ohm.

CJ said:
and what kind of transformer? a steel core will probably take more current to excite than a 50/50 nickel core,

I bought a batch of vintage Jensen steel core transformer and I'm planning to use them for this project. Maybe I should add a current buffer at the output of the opamp?
 
It will be just fine. I have a Behringer distribution amp driving a pair of Edcor XMS 600:600 on the input of my reference amp and it sounds dam great if you ask me.  None of that saturated sound either.
 
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