When you increase the feedback resistor you will get more instability. Check also the datasheet.

I think it is a DC servo or some other servo.

Unveiled triode magic... headphone sound in luxury class.   Review in the swedish magazine Hifi & Musik issue 3 March 2014.   The minus = expensive   The plus = the sound   The reveiwer was rather pleased.   The designer has the nick "villemarsvin" at diyaudio.

I wanted to go SMD all the way but my latest SMD has modified footprint for easier hand soldering. Now the pads are more outside and more accessible.

It was a mistake. It wasn't the thread starter who had erased all (except for one) messages, some other guy.

A weird thread where all posts by the thread starter has been deleted by himself?

I must correct you a bit:   The amp consists of a current feedback amp buffered with a diamond buffer. The power supply is not a shunt regulator. It's a series regulator with "Super Regulator" topology.

Which opamp do you use? Can the opamp you have handle only 9 volts in supply voltage? Measured your ground? Do you have a connection between all ground points?

Where have you the ground connected then? Opamp type? Supply voltage?

Never thought of having some gain? If you set the gain to 100 or 1000 then you won't need any high resolution of your voltmeter.

You may use a soft start for the amp in order to limit the inrush currents.   Suitable keywords for Google could be   soft start softstart toroidal transformers

Most good RIAA amps (including mine) can drive headphones pretty good.

A good pair of tweezers is nice to have. http://www.ideal-tek.com/product-358.html   http://sjostromaudio.com/pages/hifi-projects/36-hifi-projects/95-jsr01-sjoestroem-super-regulator?start=4   Nice film, Warren!

AD8610/20 is also one of my favorites not only because they sound good but they are also stable in the function.

Tommy, the LME49720 has 0.00003% (typ) distortion if you have a proper pcb and power supply. Adding a class A circuit will hardly create even lower distortion. I think you will get a decreased sound quality in fact. It's better to put your efforts in the power supply.