Volca Kick
Available solder points
MIDI Out
What the input/output/bias points do to be determined once measured. Seems to be a similar arrangement to the FM.
The above image is from https://www.reddit.com/r/volcas/comments/etj4fd/mod_all_of_the_things_volca_kick/

KORG volca kick MIDI Implementation Version 1.00 (2016.07.29)
1.TRANSMITTED DATA
No message is transmitted.
(The volca kick is not equipped with a MIDI Out jack.)
2.RECOGNIZED RECEIVE DATA
2-1 CHANNEL MESSAGES [H]:Hex, [D]:Decimal
+--------+---------+-------------+-----------------------------------------+
| Status | Second | Third | Description |
| [H] | [H] [D] | [H] [D] | |
+--------+---------+-------------+-----------------------------------------+
| 8n | kk (kk) | vv (vv) | Note Off vv=0~127 *1|
| 9n | kk (kk) | 00 (00) | Note Off *1|
| 9n | kk (kk) | vv (vv) | Note On vv=1~127 *1|
| Bn | 28 (40) | vv (vv) | PULSE COLOUR *1|
| Bn | 29 (41) | vv (vv) | PULSE LEVEL *1|
| Bn | 2A (42) | vv (vv) | AMP ATTACK *1|
| Bn | 2B (43) | vv (vv) | AMP DECAY *1|
| Bn | 2C (44) | vv (vv) | DRIVE *1|
| Bn | 2D (45) | vv (vv) | TONE *1|
| Bn | 2E (46) | vv (vv) | RESONATOR PITCH *1|
| Bn | 2F (47) | vv (vv) | RESONATOR BEND *1|
| Bn | 30 (48) | vv (vv) | RESONATOR TIME *1|
| Bn | 31 (49) | vv (vv) | ACCENT *1|
+--------+---------+-------------+-----------------------------------------+
n : MIDI Channel = 0 ~ F
kk : Note# = [H] [D] [H] [D]
00 (00) ~ 7F (127)
vv : Value = [H] [D] [H] [D]
00 (00) ~ 7F (127)
*1 : This message is recognized when the "MIDI RX Short Message" is set to "On".
2-2 SYSTEM COMMON MESSAGES [H]:Hex, [B]:Binary
+-----------+-----------+-----------+------------------------------+
| Status[H] | Second[B] | Third[B] | Description |
|-----------+-----------+-----------+------------------------------+
| F2 | 0xxx xxxx | 0xxx pppp | Song Position Pointer |
+-----------+-----------+-----------+------------------------------+
pppp : 0~15 = STEP 1 ~ STEP 16
x : ignored
2-3 SYSTEM REALTIME MESSAGES [H]:Hex
+-----------+----------------------------------------------+
| Status[H] | Description |
+-----------+----------------------------------------------+
| F8 | Timing Clock *2|
| FA | Start *2|
| FB | Contiune *2|
| FC | Stop *2|
| FE | Active Sensing |
+-----------+----------------------------------------------+
*2 : This message is recognized when the "MIDI Clock Src" is set to "Auto".