OPA548 unity gain

[kacernator]

Problem solved

I have found the problem. I had a leakage from input coupling, which separates high voltage output from tube preamp.

Thank you guys.

 

[FoMoCo]

I have found the problem. I had a leakage from input coupling, which separates high voltage output from tube preamp.

Thank you guys.

Glad you found it. Even gladder that you told us what you found.

 

[JMFahey]

I have found the problem. I had a leakage from input coupling, which separates high voltage output from tube preamp.

Thank you guys.

Thanks for nothing.
You never ever showed a tube connected to that input.
At most you commented

I want to drive unity gain power opamp with tube preamp.

which speaks about future, not that there is a tube connected there *now*.
And you didn't answer

Measure voltage to ground from + and - IN pins.

Talk about sending us on a wild chase. 🙁
That said, glad you found the problem on your own, pity Forum couldn't help you.

 

[Mooly]

Thanks for the update. As I always say... all the evidence is there 🙂 Pleased you have sorted it.

 

[kacernator]

Completed amplifier

Whole completed amplifier can be found here:

http://www.diyaudio.com/forums/tubes-valves/226405-simple-hybrid-amplifier-35w-8ohm.html