[djbnh]

Had this question up earlier last week, and now re-posted for consideration. Does anyone (Klaus?) know if the Tempest can be modded to provide a low impedance (Grado: 32 Ohms) headphone 1/4" output jack? I've been doing more late night (headphone) listening, and would like to know if the above option is available. I know I can purchase a separate headphone amp, but would like to consider the  above option first.

[KarlDL]

OK, I'll take a go at this.

Direct answer:  NO.  Consumer:  Get a separate amp.  DIYer:  read on

I've been mulling over my options for driving my Sennheiser HD-600s for some time.  My tentative conclusion is to add a very good headphone driver amp within the spacious Tempest chassis, though that sends me outside the "warranty zone" (hey, I'm an EE, I fix it myself anyway).

Once starting down the "no warranty" path, I'm free to relocate the power switch to the rear panel (where it belongs) and put the headphone volume control on the large left-hand front panel knob.

Having reverse-engineered the Tempest (and Stratos), one of my notions was to utilize a clone of the Tempest's output stage as a headphone amp.  I simulated this by driving my Senns directly form the Tempest output.  Contrary to my expectations, I wasn't impressed.  I will revisit this approach with a breadboarded identical circuit soon, but I found the sound to be somewhat harsh at "get into it" levels.  The simple explanation, electronically, is that the Tempest output stage just doesn't have sufficient idle (bias) current to stay in Class A operation when I listen loudly.  Further experimentation should reveal more.  As for djbnh's Grados, their current demands are way too much for this circuit.

I'm a DIYer, so I'm looking closely at the upcoming PPA v2, MP^3, and an adaptation of the Gilmore Dynalo (http://www6.head-fi.org/forums/forumdisplay.php?s=&forumid=6), using its own DC power supply sourced off the Tempest's overkill-rated, under-utilized primary power transformer.  I'll build these as stand-alones first and then port the best of the bunch into the Tempest case, unless further evaluation/tweaking of the Tempest circuitry shows that to be the viable option that I originally expected.  Were I using Grados, I would probably skip all of this and just go straight to the Gilmore Dynalo design.

Finally, don't even think about the Gilmore Dynahi.  I have the circuit boards and they won't fit - nearly take the whole case on their own!

[djbnh]

KarlDL,

Thanks for your response. An interesting read, though obviously not necessarily what I wanted to hear. I'm about as handy with a soldering iron as a 9 iron, and voiding warranties is not attractive to me, either.

Re: Gilmore Dynahi - yes, Head-Fi forums reported the size and number of these boards needed in a head amp, and I can see where a Dynahi-based kit wouldn't fit into the Tempest. One can look at the size of the commercially available Dynahi vs. the Gilmore Lite type design and easily see the differences in at least size.

I was thinking about trying the phones via my Tempest's second set of outputs, but your comment about the current-hungry Grados makes sense.

Before I go the commercial, Gilmore Lite route, can you recommend a reputable Head-Fi DIYer that could make a Dynahi-design amp for less $ than gsferrari's Dynahi-EC or -SA Veda Audio versions [if yes, please pm]? [Note I didn't say Headamps Dynahi design amp, which starts at $1,800. If I wanted to throw that much down, I'd start considering changing preamps to one with a built-in, nicely functioning headphone section. Of course, that would mean letting go of the Tempest, which has so many positive attributes I don't know where to begin.]