I assume you mean worth it in sound quality and I am with you taking it on faith and the feedback from fellow headfiers, but this thing is THE swiss army knife of headphone amps. It takes single ended and balanced inputs. It puts out out single ended, balanced, or portable balanced outs. That...

  Thank you.

My post was meant for tube recommendations for s1rrah. It was not aimed at you, nor to start a tube vs solid state debate. :D

I found changing the rectifier tube from the sophia electric to a mullard GZ34 or USAF596 tightened up the bass considerably with my WA6SE. This was with 6DR7 output tubes on the PS1000.

I own an OD300 with the stepped attenuator option since this summer. I have been using it with my Fostex TH-900s. I will spend some time with my PS-1000s(not e version) on it and report back on the results.  One week after I ordered it Al emailed me pictures of the build in progress and the next...

This Mullard looks quite different than Gibosi's between the top 2 spacers and got me thinking where I had seen this before. I pulled out my 80's Thompson 6080WA and they could be twins. Did the french factory use Mullard tooling? This tube is what I mean...

It's nearly a year old now so it should be broken in. Sounded fantastic at Axpona last March with LCD-3s. It grabbed my attention in a room with auralic, chord hugo, and cavalli amps. It tames the highs on the Grados without sounding rolled off so I assume the low impedance output sweet spot is...

No, but with lower impedance headphones(TH900, LCD-X) the treble seriously rolled off. I am assuming most iems are low impedance here...

My Audio Research VT100 is differential balanced, but I would have to dig the manual out of the attic to see what it does with the RCA inputs. I also have nightmares about retubing all the 6550's...

Intriguing, I would have guessed Sylvania because of the angled plates. I just assumed CBS got gobbled up by a bigger company by the time the 6SN7GTB "rolled" around.

I have used clear nail polish on a few tubes and it worked just fine. 

If you are changing the output to fixed tweezers will fit nicely. I would face the rear of the box towards you so you can see the exposed 3rd row of pins. I was facing the front panel when I switched mine. On my first attempt I grabbed the front of the jumpers in the front and the exposed pins...

You wont be disappointed. I originally bought the TH-600 for fun phones and found them to be great for all genres. If your upstream components are up to it you will really appreciate the small but significant differences stepping up to the TH-900s. For me its worth the extra dough.

Sorry about the crickets. It's been difficult to nail down any particular sonic traits to the M920.  As a DA converter the resolution of detail is excellent, but not what I would call analytical or dry or sterile sounding. The thing gets micro and macrodynamics right so the music ebbs and flows...

Thanks for this. I have about 60 hours on my X's and my listening sessions have been making me nutty. I am at the part where the midrange is kind of shouty.