Explainer · RME M-1620 Pro D
Your M-1620 Pro D doesn't change its sample rate when the MADI signal coming into it does. Synklok watches the converter and changes it for you. Here's how that works, what you need, and where the limits are.
01 · THE PROBLEM
Sample rate is how many times per second digital audio is measured — 44.1k, 48k, 96k and so on. Every device in a digital chain has to run at the same rate, ticking in step with one shared clock.
MADI is a single cable that carries up to 64 channels of audio between your MADI interface and the M-1620. When you change your session's rate, the interface switches, and so does the signal on that cable. The M-1620 Pro D doesn't. It stays at whatever rate it was set to — on its front panel or in its web remote — until someone changes it.
“The external clock must match the sample rate configured”
When the two disagree you get clicks, dropouts, or audio at the wrong speed and pitch — until someone walks over to the rack and fixes it.
02 · WHAT SYNKLOK DOES
The M-1620 has a remote-control interface built in, documented in RME's manual. Synklok uses it to talk to the converter directly — over a USB cable or your network. Nothing gets installed on the M-1620, and no audio ever passes through Synklok.
It watches the converter, not your software. Pro Tools, Logic, Cubase, Reaper, a live console or a MADI router all work the same way: if the rate arriving at the M-1620 changes, Synklok follows.
If the M-1620 and a locked MADI input still disagree after three seconds, the metronome in your menu bar turns into a warning triangle.
Need the converter to stay put? Switch off Auto-sync in the menu. Synklok keeps showing you the rates but stops changing anything.
If it can't reach the M-1620 — a cable pulled, the unit switched off — it tries again every three seconds, and can send you a notification when the connection drops.
03 · WHAT YOU NEED
Plug a standard USB cable from your Mac into the USB port on the back of the M-1620. It appears at 172.20.0.1, which is where Synklok looks by default — nothing to set up. The port carries control only, not audio.
If the M-1620 is on your studio network, open Settings → Connection, turn on Use custom IP / hostname and enter its address (like 192.168.1.42 or m1620.local) — or pick it from the devices Synklok finds. Press Test to check.
04 · SETTINGS
Click the metronome, then Settings… There are two tabs: Connection and General.
Point Synklok at a network address instead of USB. Test shows whether the M-1620 answers and what rate it's set to. RME devices found on your network are listed for one-click use.
A Mac notification when Synklok changes the rate, and another if the M-1620 disconnects. Both are on until you switch them off.
Show the current rate — “96k” — right next to the metronome, so you can check it without clicking. Off by default.
Copies a plain-text report — versions, connection, rates, lock state and recent log lines — ready to paste into a message or a GitHub issue. Nothing is sent anywhere unless you paste it.
Synklok checks synklok.app once a day and installs new versions in one click. Switch it off, or Check now, in the General tab.
Start Synklok with your Mac so it's always watching. You'll also find this switch in the menu.
05 · HONEST LIMITS
Other RME converters may have a similar remote-control interface, but Synklok hasn't been tried on them.
Synklok follows the coaxial MADI input. If your M-1620 takes its clock from optical MADI or word clock, it won't follow yet — both are on the roadmap.
MADI can carry 88.2 and 96 kHz in two ways: the “96k frame” or the older “S/MUX” method. RME's manual says the M-1620 can only detect the rate by itself with the 96k frame. We haven't confirmed yet how this affects Synklok. If it doesn't follow your session above 48 kHz, check your MADI interface's frame setting and let us know.
If it's still installed, Synklok notices and shows you how to remove it, so the two don't fight over the rate.
RME has said a future M-1620 firmware will follow its MADI input on its own. When that ships you may not need Synklok — until then, it does the job for free.
No accounts, no analytics. Besides your M-1620, Synklok only checks synklok.app once a day for updates.