Marantz Receiver

Marantz AV receivers and pre-amplifiers (Cinema, SR, NR, AV-series, AV10/AV8805 processors) are controlled over the same Sound United Telnet protocol used by Denon. GEM has had Denon coverage for years; the marantz_receiver driver is the Marantz-branded entry point with input codes pre-tuned for the Marantz product line.

What's controlled

• Main-zone power on/off
• Master volume (absolute, up, down) — auto-scaled from the unit's MVMAX reply
• Mute on/off and a client-resolved mute toggle
• Input selection (SI...) including the Marantz-specific streaming codes ONLINE, NETUSB, M-XPort
• Surround-mode switches (multi_channel_stereo, pure_direct)
• Status polling every 25s for power / volume / mute / input

The driver does not expose Zone 2 / Zone 3 in this revision; see "Known limitations" below.

Prerequisites

• A modern Marantz network-capable receiver. Older units (pre-2015) may speak a subset of this protocol — most of the basics work, but a few of the streaming input codes will be rejected.
• Network Control enabled with the "Always On" option so the Telnet socket stays open while the receiver is in standby. Without this, the first power_off severs control.
• No other Telnet client connected. The receiver only allows one Telnet session, so close the Marantz mobile app and any HEOS controller while integrating.

Setup

1. Give the receiver a static IP (or DHCP reservation).
2. On the receiver: Setup → Network → Network Control → Always On.
3. In GEM, add a device with driver marantz_receiver and set the IP attribute. Port 23 is the default.
4. On connect, the driver issues ZM?, MV?, MU?, SI? to seed the cached state and starts the 25-second status poll.

Attributes

Device — required

Attribute	Type	Description
ip	string	Receiver LAN IP.

Device — optional

Attribute	Type	Default	Description
port	int	23	Telnet port.
status_interval	int	25000	Status poll interval in ms.
max_volume	int	(auto)	Read from MVMAX on connect. Read-only — clients use this to scale volume sliders.

The driver also auto-populates power_state, volume, mute_state, input, and surround_mode as state attributes on the device when the receiver reports them.

Zone address format

Marantz units expose only main-zone volume/mute control through this driver. There are no per-zone GEM zones — link the device to an AV zone via av_zone.volume_device_id so the zone-level volume slider reflects the receiver. Zone 2/3 control is a known limitation.

Known limitations

• Main zone only. Zone 2 (Z2...) and Zone 3 (Z3...) commands are not exposed. Multi-zone receivers will still answer Marantz's full protocol but the GEM command map is intentionally scoped to the main zone in this revision.
• No surround-mode picker. Two convenience commands (multi_channel_stereo, pure_direct) are exposed; the full MS... namespace is left for future work.
• No HD Audio listening-mode reporting beyond the raw string. surround_mode is stored verbatim from the MS response — clients can read it but the driver doesn't translate the codes into friendly names.
• One Telnet client at a time. This is a hardware limitation, not a driver bug. Any other app connected to the same unit will lock GEM out.

Troubleshooting

Symptom	Check
No response from receiver	Network Control is set to "Always On", not "On while on". The latter drops Telnet in standby.
Commands work intermittently	Close the Marantz mobile app, the HEOS controller, and any other dashboard talking to the same unit. The receiver only accepts one Telnet client.
PARAMETER ERROR reply on an input pick	Older firmware uses different input codes (e.g., NET vs ONLINE vs NETUSB). Pick the input on the receiver itself, watch the SI? response in the GEM device log to see which code the unit emits, and use that one in the dropdown.
Volume slider scale is wrong	max_volume is read once on connect. Trigger a reconnect to re-query MVMAX.

See also

• denon_receiver — same wire protocol, Denon-branded input list. Pick whichever driver matches the unit's badge; their command surfaces are deliberately parallel.