One day last year, while planning my Carbon build, I thought it would be neat to have a dynamic headphone amplifier in a matching case. The Dynahi suggested itself, though I wanted something a little less overkill. Then it occured to me that I might be able to stuff a Dynahi and a Dynalo into one case, and so make an amplifier capable of driving any headphone. So I made this, which I called the DDCA (Dynalo-Dynahi Combination Amplifier): one set of inputs feeding two amps, with separate output protection circuits, separate volume pots, three GRLV power supplies, and one transformer. It was a 3D puzzle to fit everything in (if I were to make another one, I'd position the Dynahi boards right-side up, turned out there is enough clearance that way and it would have simplified assembly) and the wiring took forever (plus keeping it perfectly tidy is beyond my skill).
I lowered the gain on both the Dynalo and the Dynahi, since on most amps, I have the volume at 10 o'clock or less, and I wanted to use more of the volume control. Have to admit: the RK50 on the Carbon spoiled me, and the TKD 601 pots here don't live up to it. Not bad, though.
Like I posted a couple of days ago, I couldn't bias the Dynahi section as high as I wanted, but even at 0.40V across the 20ohm output device resistors it runs fairly warm, so I decided to leave it alone for now. I also need to get the top anodized black. Maybe add some speaker binding posts... wonder how much of a speaker load I can drive from the Dynahi?
Both sections sound great to me, though I don't have an HE-6 or K1000 to really put the Dynahi through its paces.
As usual — many thanks to @kevin gilmore and @spritzer for all the designs and boards. This wouldn't exist without you guys. Thanks to @vilts for making matching titanium knobs, thanks to @Zashoomin for getting extra sand with me so we could make matched sets, and thanks to everyone here for group buys and all the help and support.