I fixed link

Did they fix the issue that recording stops if you pull out USB power?? This makes both the DR-60D and DR-70D unusable for me with external power :( Am getting an external power set up for my Sound Devices 552 however.

In for one. Use it for travel.

The Model is DR 70D. If you are not recording yes it will ask. If you are recording it will tell you power was unplugged and revert to internal batteries. If while still recording you replug in the external usb battery it will show the symbol on the display but not otherwise ask you about external power. I suppose I should add that if you stop recording it will than ask if you want to use external power again.

Good offer.

Tascam DR-70D 4-Channel Audio Recorder, $185

After rebate

http://www.adorama.com/tsdr70d.html

I've had this unit for a few months so here are my impressions:
The Good: small, lightweight, sounds good
The bad: stupid battery design, cheesy USB power connector, buggy firmware.

This is a real deal for the price. Note that the pres are not exactly the same as in the eight channel, on paper, they have a higher noise figure. However, noise is not really a factor in this design.
The converters and preamps are excellent, I prefer them to the SD. Compared to the Fostex FR2LE, the are a touch brighter and a touch clearer. The same applies to the DR 680, but the difference is smaller. There's plenty of gain.
The converter chip is a Cirrus Logic CS42L52-CNZ, which is not exactly the top of the line, but it's very good. I'm guessing the chip is circa 2013, and almost all of the functions of the 70D are coded into the chip, so the box is sort of an interface for the chip.

The TRS jacks on my unit do not pass the phantom power. This could be an annoyance in the fielod, but it isn't a deal breaker and could even come in handy at times. Unlike many other recorders, the P48 is switchable for each channel.

The battery indicator is worse than useless. A major flaw. Also, the recording times are overrated. You will chew through batteries with decent, phantom loving mics. You can, however, set the P48 to 24 volts to drive, for example, a Schoeps CMC6.

For $11 you can get a thin, rectangular power bar that fits very well with tape or velcro or whatever. I bought one, and it gives you some serious battery, maybe not 20,000 mah but I recorded for about 8 hours.
http://www.ebay.com/itm/20000mAh-UltraThin-Dual-USB-Portable-Power-Bank-External-Battery-Backup-Charger-/331541674213

If you yank out the plug while recording, and you have batteries, it will still keep recording.

On my unit, little bugs kept cropping up, like it kept asking me to set the time and date, and the rotten battery meter, etc.

Level indicators are hard to work with. Takes some getting used to. The are "fast" which is good, but it is hard to get a reading sometimes.

The battery door is kind of cheesy. But, you can access it from the side. Sort of.

The pots for gain: there are four, which is OK, but there is a dead spot at the bottom. The lock button locks the gain.

Also, it is picky about cards. I'm using a PNY 64gb, so far, no issues. We will see. It's really stupid that the firmware/design does not allocate the buffer properly. Four channels of audio just does not need a fast card--after all, I can use a turtle card on my 680 to record 8 channels. So, Tascam, you are stupid. Don't blame the card.

Online, ppl talk endlessly about premps, preamp noise, take measurements, etc. This is all totally BS. You have to plug it in to a bunch of mics--like Neumanns that draw a lot of juice and have no self noise--and listen. The pres are clear and quiet.

Now, if you wanted better slew rates from your op amps, the chips are really hard to get to. But you could swap out the op amps for some better ones and swap out the caps
LME49720MA op amps
Wima MKP-2 poly caps

The chips on the back of the PCB AFAIK are for the output. So you could get away with just modding the input.

There is a plate to attach stuff to the top of the unit, and so you could hook it up to a camera, a light, or some mics. Decent rig connectivity.

There's a new firmware out today, I'll report on it later. Update: I'm not sure what the new firmware does, but the battery meter is till messed up. It could be that if you are using Eneloops you need to set the meter to Alkaline. On ongoing problem.

Pet peeves:
There's no way to set the input gain to the same level precisely, or gang the channels. The gain knobs are tiny and easy to bump into another setting (although you can lock the gain with the lock button).
When you turn it on, it asks you for each Phantom power channel if you really want phantom power. I just want to get to the gig, turn it on and hit the record button.
There's no way to record more than 4 hours (or maybe a certain file size) without starting a new file. Most recorders have this problem, but it is stupid. OTOH, some DAWs can't handle really long files.

"Recommended" card: https://www.amazon.com/SanDisk-Extreme-SDSDXPA-064G-X46-Flash-Memory/dp/B007NDL54C

You need to go to checkout now and also apply code - 1ZOOMLENS1

Having used this unit for a while now, I can say that I absolutely love it.

The battery is annoying, but quickly fixed with external battery pack!

Make sure to upgrade to newest firmware.

Only really annoying thing is that unit takes a few seconds (about 15) to switch on.

I love having 4 inputs available at all times. I also purchased chip upgrade, but just need a spare hour to swap.

I assume this upgrade would be a 3rd party upgrade, a pre-amp upgrade I guess? As that is a common choice of mods.

The recorder is overly picky about media, and TASCAM is slow to update its approved media list. The fact is, a four channel audio recorder does not need special or fast media, it needs a well-designed buffer system: TASCAM dropped the ball here--how is it that the DR 680 can record 8 channels on standard media but the 70D requires a special card for half the data? The only explanation is software design or that the company simply did not put enough internal buffer in the device--I hope the former is the case and these issues can be resolved with a firmware update. Incidentally, the manual does not contain instructions on how to perform the firmware updates.

It can not only come from lack of buffer, it can also come from very poor software.

As the old times it could be written by experienced developers and now it can be partly just outsourced to some Indian firm. Writing file to SD while doing many other things (LCD display, polling of controls, etc) is not so easy as it seems.

I am more willing to believe it is poor software. I just can't believe that people say, Oh, you need a fast, exotic card from batch X made in Country Y for the audio recorder to work for 4 channels, when the DR 680 will write to the absolute slowest card in my studio with twice as many channels.

By idea it must work with any cheapest Class 4 cards.

Price is showing $259.99, $229.99 after rebate?