The SuperNatural sound engine, the digital voice of the synth - the structure is based on the Integra 7 architecture.
Four Digital Parts - each part can consist of up to three tones or partials - which in itself is a mini-voice with:
450 source waveforms
Multi-mode digital filter with separate HPF
VCF ADSR Envelope
VCA ADSR Envelope
Pitch AR Envelope
Up to three can be combined into a single part.
As with the analog side, each part has access to a dedicated MFX with 70+ algorithms.
Finally this all goes via TFX 1+2 and delay and reverb (common FX)
Additionally, you can route the digital parts (all together) to the Analog filters - routing is done per analog part so you could have up to four filters. Though this is done in paraphonic mode as a mix routing - so if you want to have a long pad, the digital voice will need to have long release as it passes through the analog VCA post filter.
Really, the SuperNatural engine does sound pretty good and works well with the analog side to help create some extremely lush and complex tones. I did check the PWM aliasing issue (as asked by Kevin Nolan in the comments) and it's still there, high rates and pitches result in some very audible aliasing.
I did find that there can be quite a lot of menu diving to set up parameters at program, part and tone levels if you want to get into stuff not on the front panel.
One nice little surprise was that the JD-XA will respond to poly aftertouch - not via it's own keyboard but from incoming MIDI.
Splits and Layers
Parts can be split and layered via key ranges, though one thing I found was that these don't apply to external MIDI input , set up part 1 on C-1 to B1 part 2 on C2 to B2 etc and although this will split via the internal keyboard, via external MIDI it doesn't each part just plays across the entire key range - actually quite frustrating. It is not possible to velocity layer parts or tones.
This one has generated a lot of interest as it's smaller brother the JD-Xi implemented a limited number of features - people were hoping it would build on that.
It's a 16 part MIDI sequencer, parts 1-8 correspond with the Analog and Digital parts - patterns can be up to four bars (64 steps) with sixes and twelves catered for. Shuffle is possible with a dialable strength, but only on record - it is not possible to quantize after recording, which is rather disappointing. Tracks can be routed to the CV and Gate outputs for controlling external 1V/Oct gear, which I did try and seemed to work fine. Tracks 9-16 are available only when the JD-XA is in MIDI Controller Mode (dedicated button) are is routed to external MIDI (USB or MIDI Port).
Additionally you can record parameter changes into the sequencer per part to create pretty complex changing sound shifts - it's a nice feature.
There are however serious limitations - it is not possible to transpose sequences via the keyboard or any other method. However, if you are running the arpeggiator on specific tracks, you can transpose those by selecting the tracks that will respond to the keyboard and playing the notes you want.
More serious is the fact that you cannot chain patterns. In the JD-Xi it was at least possible to queue up patches so that the sequencer would play the next selected pattern. Not so in the JD-XA, you are stuck with a single Patch memory and whatever sequence you have.
I do find this odd, as they have included a dedicated click output, which you could route to a drummer or whoever, but with this single pattern limitation it seems rather pointless.
This is an area where the JD-XA goes against convention, essentially there is no granularity to the patches - you save an overall program which is setup, parts, programs for each part, tone setup and sequencer data. Thats it. you can copy parts, tones and sequences from other programs via the copy function, but it's not possible to audition these, so you need to know where specific elements are stored to make use of it.
MIDI and audio are both supported via USB, you do need a driver though, it won't hook up to your iPad, at least not in the two that I tried. Audio is pretty simple - just two channels in and out - no access to the analog and digital parts separately, nor the audio input. Similarly, the MIDI ports are just in and out too - I think it would have been sensible to add more to this aspect of the USB connection. Additionally, there's a USB host port for attaching storage for patch and MIDI/Sequence data storage and playback.
The JD-XA has a pretty massive sound sculpting potential, with the four analog voices plus 64 SuperNatural and effects you can create some huge soundscapes. Add the arpeggiator and to some extent the sequencer and you have great sonic potential. However, the poor implementation of the sequencer does rather let the side down. It feels like with some more attention to this aspect the £1500 asking price would be more justifiable.
The build quality is OK - it is plastic, with metal bracing and considering the asking price, one might expect something a little more solid, it's not unacceptable.
Some wont get past the red on black colour scheme - I confess, that operationally it does require a bit of squinting.
In my judgement, it feels a little overpriced , though we have become rather spoiled when it comes to bang for the buck, indeed Roland pointed out that under the hood it's got: Integra 7 engine (list price £999), VP-7 Vocoder technology (£399) and of course the 4 Voice Analog Synth (£?)the sum of the parts does clearly seem reasonable.
Roland JD-XA price is £1569/$2199 and is available for pre-order now and will be in the stores shortly.