elskardio

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:

Any hint would be appreciated.
Thanks and stay safe ;)


JohnRoberts

Re: Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720
« Reply #1 on: June 06, 2020, 03:06:10 PM »
their data sheet should say that too...

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

john12ax7

Re: Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720
« Reply #2 on: June 06, 2020, 04:40:32 PM »
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/


PRR

Re: Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720
« Reply #3 on: June 06, 2020, 08:25:38 PM »
> "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.

CJ

Re: Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720
« Reply #4 on: June 06, 2020, 08:58:12 PM »
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,

If I can't fix it, I can fix it so nobody else can!
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elskardio

Re: Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720
« Reply #5 on: June 08, 2020, 10:23:32 AM »
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

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.

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?

analag

Re: Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720
« Reply #6 on: June 09, 2020, 01:29:41 AM »
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.
Audio engineering suffers from misinformation, disinformation, and downright lying more than most fields of endeavour.

Re: Driving 600 ohm 1:1 output transformer with OPA2134 or LME49720
« Reply #7 on: June 09, 2020, 03:35:34 AM »
You should really get the LM4562 instead of the LME49720, same thing but cheaper.


 

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