a little less bass than my black 325 with hp1k drivers but they are soo comfortable because theyre so light. 
You seem to be terribly unhappy with Grado's responses to your inquiries. Is this correct? I wonder why you would torture yourself with this unhappiness?
The problem of communication with Grado doesn't seem to be solvable. Their responses are inconsistent, it's apparently the way they are, depending on who the person responding is and what mood she or he happens to be in. My sense of the Grado company is that it's a small enterprise and very busy. I'm guessing they prefer not to hire a full-time person with people skills who's knowedgable about their products, amps/headphones/cartridges, to solely answer phone call and email questions all day long.
Perhaps another headphone manufacturer would be more available for questions and respond in a way you deem acceptable.
In my own humble and personal opinion, I'm under the impression that you are, which is why I responded the way I did. No offense intended.
Let's be honest...this is Grado we are talking about.
They keep it short n sweet...not long n sour
It will use a couple of damper diode tubes and that will serve as my rectifier.....power tubes can be 6AS7....6080.... if you use the 5998 tubes as power tubes you can run them at a stronger current on the plates of the tube, by flipping a switch, this is because the 5998 can accept more than most 6AS7 tubes, so Glenn provides this as an option. Most amps just run these at same current as all 6AS7 tubes
The driver tube will be a 6/12/25 SN7....again a flip of a switch to the proper voltage for the proper tubes....he provides this option if wanted also....a 25SN7 tubes sounds just like a 6SN7 tube, you just have to run it at 25 volts, which most amps do not do....the tubes cost a fraction of the cost of 6SN7 tubes, because most people can not use them, they are cheap
Then there are more tubes that I can even mention that you can use as drivers with a simple adapter.
I also got the upgrade that Glenn provides so that you can use 6336 tubes , again by the flip of a switch.. those are just for low impedence cans, like Grados....anything under 100 ohm impedence I believe
It truely is going to be my dream amp.
I have the HD800 , and for the most part, that is what the amp was built around.....I can't wait to try my Grado with it also....should be interesting.
