https://gr-research.com/product/gr-headphone-amp/This headphone amp is perhaps the best tube headphone amp I've come across. I have the prototype of this, which is essentially the same as the units Danny is selling. The only real difference between mine and the GR Research production model is mine has a laminate transformer, and the chassis is more pedestrian compared to the one Danny is selling.
The quality of parts is truly top of the line. The amp is dead quiet, and can drive the majority of headphones quite easily. The design can accommodate everything from a low impedance Grado to the high impedance models. The sound from the amp is simply amazing. Bass is tight, midrange is almost holographic, and treble is clean and extended.
I've owned a lot headphone amps, both tube and solid state. This amp ranks right up there near the very top.
Standard tube compliment is a 6SL7 front end, and a 6080 power tube. The power supply is so overbuilt, tube rolling does not change the sonic signature as much as a lot of other designs. I've tried a number of 6SL7 types, and they all sound very good. I have a slight preference for the RCA Red Base 5691, or the Tung - Sol round plates.
The Tung-Sol 6080 and the Chatham 6080 really sound great with this. I also tried a 6AS7 for a different sound signature, and the one supplied by GR Research is outstanding. Vocals are so holographic, it's almost spooky how realistic they can sound.
If you are a headphone enthusiast, audition of this product is strongly encouraged.
