What are you guys using the CV functionality of your A4s for? Is it any good compared to some eurorack modules?
The reason I ask is because I have a DFAM and a Subharmonicon, and was thinking about getting some Eurorack modules to give me LFOs, quantizers, etc. But then I thought if an A4 and the CV output might come useful. I know one can send out LFOs in various shapes, envelopes, clock, and notes from the A4 through the CV. But I´m not completely sure what are all the possible use cases.
I do 2x pitch and gate to a couple other synths. Now it’s an A6. 
Use it to modulate the Mk2’s exp input
Use it for low pitched audio
Use it for random clock pulses
Use it for whatever takes your fancy, it’s quite flexible
I have used my A4 to sequence DFAM. It’s pretty great, especially if you get bored with the DFAM’s built in sequencer. The way I had A4 set up:
CV A - 1V/oct
CV B - Linear Voltage
CV C - Linear Voltage
CV D - Clock
Clock into the DFAM ADV/Clock, 1V/oct into VCO 1 CV (or VCO 2 depending on what you want to do), Linear Voltage into Velocity (PLock this where you want notes), other Linear Voltage into any other DFAM input you want - you’ll want to use an LFO on this channel most likely.
This is basically mimicking the DFAM sequencer, but you have 64 steps, PLocks, trig conditions, and an LFO.
EDIT: now that I think of it, I don’t think you really need to clock the DFAM with this setup. Patch the clock to DFAM Trigger, and make sure to turn the velocity all the way down on each DFAM sequencer step.
Same, but I’m using it as an A5. Want to use the second set of CVs for the filter.
I use it for sequencing basslines on my Moog Minitaur.
I use it for sequencing basslines on my Dark Energy III.
I use it for so much. In fact in addition to my Analog Keys, I’d like an Analog Four.
Why? I’ve said it many times before - it is in my opinion the single best “control center” for any analog rig, particularly those with poor calibration or flaky scaling. It works with all of my old stuff, even ornery machines like the VCS3 (which is neither 1v-per-octave, nor V-to-HZ). It can also pump out a nice high gate or trigger such as those expected by an old ARP 2600 (which wants to see 10v-12v).
A typical configuration for me might be:
Analog Keys CV track to Moog Model 10 (which can easily be scaled to four or five octaves using the AK).
Second Analog Keys CV pair (using another AK track) to VCS3 (much more accurate than the DK2 keyboard)
MIDI or analogue pulse from one of the Analog Keys routed through an audio or MIDI output and used to clock the analogue sequencers in my big Synthesizers.com system
One or more of the above instruments routed back into the Analog Keys’ inputs for effects (I really like the way the effects sound).
MIDI clock from Analog Keys to Keystep to drive the 2600.
Remaining AK tracks for internal sounds.
This kind of setup is really quite powerful - and nearly ideal for me. The only thing that would make it better is a dedicated Analog Four (MkI) to rack up with my Octatrack and Rytm MkI which are currently sat between the VCS3 and Model 10.
I use a gate out from the A4 to advance the sequencer on my dfam. I set the cv track to only hold four trigs or steps and it allows me to do double or 3/2 time really quickly from the step sequencer.
Sometimes I’ll use them to play the dfam chromatically
And I’ve been wanting to experiment using the dfam sequencer through the exp inputs, but I haven’t gotten curious enough to do it yet 
Maybe Syntakt will be an AH/DT/DN sized box with nothing but CV and gate I/O.