[Rpell]

Here's an interesting article about a headphone amplifier based on the Texas Instruments THS6012 op amp (originally designed as an ADSL line driver):

http://sound.westhost.com/highspeed.htm

To quote the author: "As a headphone amplifier, these opamps are superb, with not a single negative aspect. I really doubt that there is a better headphone amp on the planet."

 

[Apheared]

Trust The Rod, The Rod Is Good.

I bet it sounds fine. Layout and compensation is gonna be hyper critical.. 100MHz+ chips can be a nightmare for a hobbyist DIYer to implement... Oscillation city.

(Although saying the NE5532 is "one of the fastest VFB opamps available" in a 07/01 article is stretching it just a bit.

)

 

[ppl]

Most interesting artical. The point i would like most viewers of that artical to study is Zobeles as rod calles them. The Correct USA term is Snubber when dealing with Electronic Circuits and The only time I have heard the term Zobel is on the Impedance correction Part of the Crossover network. An R/C Series resistor is placed across the Voice coils af Cone type Woofers and Midranges. Dome and ribbin types have a lot flatter impedance curve and most often do not need them.

HOWEVER: on the out put of output stages and most importently as rod Points out High Current Fast output stages a Snubber (Zobel) is not a luxury but required to make shur the Circuit is stablev after conecting your cables to the output. Headphone cables more-so than Loudspeaker or Interconnect cables get very reactive and can Turn the Most perfect Simulated Amp design into a RF transmitter capable of interupting radio and TV comunications throught the Neborhood.

Current Feedback OpAmps can be a real pain for not just a beginner but Experenced Engineers also have quite a time Taiming these. Some things to remember about Current Feedback Opamps are. The resistor Between the Output and the (-) Input Also controls the Openloop bandwidth of the Opamp. so lowering it's value will increce the bandwidth and make the device more prone to oscilation. This is regardless of the Other feedback resistors value this output to (-) input resistor should be constant and adjust the gain with the resistor from the (-) input to ground. NEVER put a capacitor acoss the Feedback of a CFB type Opamp. Input Impedance is low and input Bias current is high so hooking a pot on the Input for volume is out of the question unless a DC servo is used. I like to Use a pair JFET source flowers between the Volume and OPamp input.

Burr Brown as well as others have Composit opamp Applification Notes comboning a VFB with a CFB to get the Best of Both Worlds. Also semiconductor application Notes on CFB opamps are available. just look.