I believe I just blew a tube on my Darkvoice 336SE

I recently purchased a Darkvoice 336SE.  Out of the box, it didn't sound so good with my AKG 702's.  Specifically the attack/decay and speed were pretty poor.  The goosebumps I would get from listening to Vendi's requiem just wasn't there with this amp.

I've heard mixed reviews on the combo, so thought maybe I'd made a mistake, but borrowing other people's headphones and reading the threads here on Head-Fi convinced me that the stock Chinese tubes had to go. Oddly there was also a mild low-frequency hum with the stock tubes that really started to grate on my nerves.

A local guy was selling tubes from his Woo, so I grabbed his Tung Sol 5998. In my brief listening Tung Sol tube, the amp sounded much closer to what I was hoping for, and I had high hopes that a Sylvania Bad Boy up front would have brought me really close to happiness .

But that hum was still present and making me very grumpy.  I wanted to check if it was the inputs, and in a fit of absolute stupidity I pulled the RCA jacks from the back of the 336SE with the amp still on.  In my defense, I'd just been mucking about with networking and USB cables, and my mind was on the solid-state digital switching world.

I'm pretty sure I just blew the tubes, as I now only have mild volume out of the left-channel, and there's burn-marks on the back of the glass envelope's of both tubes.

My questions are:

* Did I FUBAR the whole amp, or just the tubes?  I have two CBS tubes en route, and I don't want to risk them if I've damaged the amp.

* Being soder-illiterate, are there shops or people in the Seattle area that someone would recommend for doing a Fitz mod to squash the hum?

* Is there a "tube amps for idiots" guide I should have read and paid more attention to before mucking about with the amp?

Thanks in advance for any thoughts.

I tried swapping back in the one tube I replaced (the factory 6AS7) but the left-channel was the only output, and that only at low volume.

Since there was no smoke or negative consequences, I'll try swapping both tubes when a replacement set arrives and see what happens.  Hopefully the electronics aren't fried. 

Thanks for the support Graphicism.

With great relief today I identified the problem point.

The trouble kept weighing on my mind, as here was this beautiful piece of hardware on my desk, and I couldn't enjoy it.  I thought of one last troubleshooting step I could make while waiting for the new front tube, and it was a winner.

I disconnected the RCA cable and ran it to my Audioengine A2's.  To my great delight the right channel was silent.  The el cheapo Radio Shack cable had bit the dust.

A quick run to my local Magnolia Hi-Fi and a coule of new audioquest silver cable's (temp solution until my HRT Streamer II arrives later in the week) and I'm back up and running.  Better yet, my 5998 tube lives!  Oh yes, and it sounds incredible.

Thanks again for the moral support and suggestions.