Pros: sound quality, ease of use
Cons: display sucks
I have used the Joplin for about half a year now. Before that, I used Apogees Duet FW converter.
Equipment used: Well Tempered Amadeus turntable and arm, Cartridgeman Music Maker cartridge, Nagra BPS phono preamp, iMac computer, Shindo Apetite and Stello Ai 700 integrated amps, Audio Note E speakers, Audeze LCD2 and Grado 325i headphones running from Eximus DP1 converter.
The Joplin is an ADC to convert Vinyl, tapes or whatever source you may have into a digital file with 16 to 32 bit resolution at sample rates up to 384kHz. No DSD. I use 192/24 for my recordings. The front panel shows a display that is designed nicely, but is not very practical in use. The dot matrix makes it difficult to see the meters move and to read the selected options. There is a rotating push button for selecting amplification, RIAA curve, other EQ curves for old records, EQ curves for tapes, sample rate, bit depth and other options that I will never need but which may be nice to have. The back has RCA sockets, Toslink out, USB out and coaxial SPDiF out, which is good if you like to use the Joplin as a phono preamp. To use it as a phono preamp, connect it to a DAC, perferably by coax, select RIAA on the front, use the correct amplification, connect your turntable and it works. Sound quality is very good if you use a MM or MI system. I could't try it with an MC without phono preamp, so I can't comment on connecting it directly.
Setup for recording is rather simple: plug the unit into your Mac (PCs with special M2-driver), hook up a source, set the volume to the correct level and record to a recording software. I have used Audacity and Pure Vinyl with good results. You could also connect your TT to the Joplin, select RIAA from the menu, set the volume accordingly and record. But be warned: take some time to understand how your recording software works or you will be really pissed off because of computer problems.
The device has a push button that lets you go through its settings, which is straightforward and easy to understand if you read the manual. Very loud sources need special plugs for attentuation, because the Joplin easily clips (this may have to do with the 1.7V input sensitivity). It was not possible to connect an Ayre phono preamp to it without permanent clipping. Funk Tonstudiotechnik in Berlin offers custom adaptors that work if you provide the necessary values to them.
Sound quality is very good, although the Joplin uses a cheap wall wart power supply. In its stock form, I think it captures nearly all of the sound quality a good vinyl setup offers. In a comparison I tried a record and the file played back at the same volume (set by ear - I know that's not scientific) and I was not able to hear a difference. A friend of mine was sure that there was a difference, but it was so minor that it fell into the category "a little bit more air and impact on the record". There was something, but nothing that could keep me from using the Joplin. Could have been my DAC which may not be up to the standard of the Vinyl setup or whatever.
Compared to the Apogee Duet, the Joplin is clearly better and makes a big difference, which it should concerning the difference in price. The recording via the Joplin is much more transparent, dynamic and coherent. No, not because of the higher bit and sampling rate, but there are explantions found elsewhere in this forum: http://www.head-fi.org/t/415361/24bit-vs-16bit-the-myth-exploded and on the web http://www.lavryengineering.com/lavry-white-papers/
What I like: very good sound quality, simple handling. If you have a digital-only setup, the Joplin saves you a separate Phono pre and a line level preamp if you want to get into Vinyl replay.
What I don't like: insufficient headroom for recording volume. For home recording of my Vinyl records, I really would prefer something like a tape deck: if the signal is too loud, turn it down on the device. Not possible with the Joplin. Other converters have software that softens peaks that are too loud and lead to clipping, so that you don't need to record the whole side of your record again. The display sucks.
Improvements I would like to see: software for your computer that helps in setting up and controlling the device. If you use it, there's a computer connected to it anyway, so adjustments would be easier if done in software. Apogees Maestro software is great in this regard.
Alternatives to the Joplin: the Lynx Hilo, I think.
I would really like to try Prism Sound's Lyra2 and see how it can improve on the Joplin. It's costlier, but does DA conversion as well.