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.

I think it's a good start but I can't understand why they choose NE5534 as opamp because the there are lot's of other better opamps.

Quote: Just grounding one of the inputs.  

Quote: The documentation is published so all you have to do is to look at the schematic.   Besides that I think it's a good design, well done.

OK, but the rules say that I'm not allowed to share anything so it makes no sense to first not being able show my stuff and then arrange a group buy.

Quote: The documentation for this project was for free and so it is in an another forum.    

Some people may have noticed that my thread about my headphone amp project disappeared. The reason is that someboby reported me and now I'm a member of trade and the limit for qualify for this is zero. This means (if I have understood it correctly) that I'm not allowed to share anything such as...

Quote: What is "hardcore flat" for a us coming from non-english countries?   A flat frequency response, can it be more than flat?

Did you read the links I gave you? Re: Power supply for QRV07   The output jack Suzy has used has switches so when you insert the plug you will also break signals to something else and this could be a loudspeaker for instance. Suzy's jack has three inputs and three outputs which she...

How did the circuit look like? Did you use a buffer between the opamp and the headphone?

Pictures?