I think if you use it on location, I would leave it stock. There is always a chance that a mod, no matter how well done, will have unintended consequences, like you might pick up some RF. Or just post on the Gearslutz page and see if anyone has had any issues on location just to get a little perspective. Could be all the modders are happy campers no matter what, but worth asking.

If you are looking to use it as an audiophile recorder, with high end mics, chances are you have already a high end preamp like the Grace, which you can slave the Tascam to and get the steady clock and high end main pair on tracks one and two. If you are using lower grade mics, there is no point in mods: whatever is in your mics will be way worse than the modded parts in the recorder.

However, Busman is highly regarded in the modding community. Mine is stock. Busman claims 8dB noise reduction. My Tascam is quiet enough for location work.

I don't really have a bone to pick with the stock pres. They are clean and clear, with a hint of sparkle and no mud. However, if I did have a quibble, it is that the very slight color they impart, is on the clean and clear side, as opposed to the ever so slightly warm and yet still transparent side. And high speed op amps in a mod might do just that. The stock sound does not sound op ampy, however. Just a bit clearish.

Cheap preamps: Onyx * channel, $300 on eBay * channels of Onyx pres. Oink. "Class A" (I love class A) RME Octamic II Digital Preamps (great for everything) RME Octamic XTC (a pun on the Ecstasy line of pres) NB The new RME has remote control. Handy. High end: Grace Audio 2 or 8 channel

If you live in the Bay Area you can borrow one of my super duper high end preamps and waste a whole week seeing if you can hear the difference. I have done it many times and I can hear a small difference, and yet I leave the preamps at home because the weigh too much. So a mod has the advantage of not changing the weight of the gear bag.

So for $300 on the busman mod, that is pretty cheap on the scale of things. Life is an adventure; just have fun.

That's a great price on the DR-680. I have one and am very happy with it. Highly usable for production work. There's even a Portabrace case that fits it perfectly.