[morsel]

It is obvious from reading the pdfs of these opamps and other related documentation that they require bypassing and feedback caps and relatively low resistor values to work properly. I don't see this as a layout issue. Sure, if we had more space we could have marginally optimized the placement of the bypass caps, but that is rather trivial compared with not using the correct components to begin with. The LM6171 will probably work just fine if all of the requirements are observed. As for DC offset varying with volume level, perhaps using a 10K pot along with the other lower resistor values would help.

Having said that, I'm not clear the LM6171 will actually sound better.

 

[aos]

No, they don't require feedback caps (those are not feedback caps or bandwidth reduction caps by the way, but compensation caps). While in many cases those caps can be used to fix the problem, they aren't always required. And layout does matter - in my PPA DAC LM6172 runs stable without any compensation due to careful layout of components and traces to minimize parasitic capacitances.

 

[ppl]

If you like this op amp then i would sugest yoy try the AD8065 this is stable with the DB and HA-5002 has low DC offset since its a fet input and all the speed you need
http://www.analog.com/Analog_Root/pr...8065%2C00.html
and a similer op amp to the THS you like i tried in the PPA is the AD-8021 now this is of similer topology to the THS series and also has DC offset issues in the PPA however what made me want to try it cause pin 5 is a comp pin just like the AD744 and thus allow you to bypass the op amps internal output stage. this requires not using the casscode current source to bias the op amp into class a since you are now driving the Buffer from a Class A VAS stage see where comp pin is connected. now this gave a DC offset from 1 mv at below 8 oclock and 100 mv at half and 800 mv at max with no bass boostso just imagine what it was with bass boost. however i really liked what i heard quite 3D however to get this to work you would need a servo or input bias current cancilation circuits on the input. this is why the LT1028 works in the PPA so well it has normaly high input bias currents however bias current compensation asures DC balance regardless of the input resistences and imbalance.
http://www.analog.com/Analog_Root/pr...8065%2C00.html

in addition since its internal output stage is no longer in the loop the opamps phase margin is improved because the added phase shift of the internal output stage is now not included in the systems overall phase shift allowing no compensation and complete stability.

Disclaimer > You really should not do any of the above and just stay with safe op amps

 

[IpsilonSound]

A couple of days ago I received a new pair of Alessandro headphones to replace my Grado and did further testing for the opamp switch. It just took a few days for the new phones to arrive, very good company to deal with, I'd highly recommend it to everyone.
These headphones(Alessandro MS-1) are similar to SR-125 by Grado and are extremely revealing compared to other brands. I did lots of listening tests switching between AD8610, OPA134, OPA627/637, LM6171 and THS4061/81. The clear winner is again THS4061!!! Extremely transparent and pleasing sound, giving crystal clear details, tiny nuances which I couldn't hear before, sounding very effortlessly and unveiled. THS4061, however, shouldn't be used, since it outputs twice the current of the THS4081 and consumes more power. I'll stay with THS4081, which is almost the same as THS4061 and as detailed as well. Compared both chips, I would say, the former sounds a little bit quiet and less dynamic, but not inferior to 81. Definitely, dual THS4062 will the Choice#1 for my DAC I/V conversion stage soon.

Anyone already tried THS chips with PPA?