GRACE DESIGN m303s
PRICE ON ENQUIRY
GRACE DESIGN m303s fully isolated stereo active DI: custom-wound transformers, 1 MΩ inputs, pad, ground isolation, phantom powered. Available in India from Shivansh Electronics, Kolkata, West Bengal, India.
VISUAL GUIDE — See Every Photo, Spec & Setup Step (PDF)
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Electrical specifications
| Gain, pad off / on (13.6 kΩ load) | -6 dB / -19 dB |
| Frequency response ±0.2 dB (50 Ω source) | 82 Hz - 27 kHz |
| Frequency response ±3 dB (50 Ω source) | 20 Hz - 80 kHz |
| THD+N, -10 dBu out, 1 kHz | -102.8 dB (0.00072 %) |
| THD+N, -10 dBu out, 50 Hz | -83 dB (0.0073 %) |
| THD+N, -10 dBu out, 25 Hz | -72 dB (0.023 %) |
| High‑pass filter | 2nd order Bessel, -3 dB at 20 Hz |
| IMD SMPTE/DIN 1:1 / 4:1, -10 dBu out | -106 dB / -99 dB |
Noise and levels
| Output noise, A‑weighted, pad off / on (50 Ω) | -118.6 dBu / -115.5 dBu |
| Output noise, 20 Hz - 20 kHz, pad off / on (50 Ω) | -116.2 dBu / -113.1 dBu |
| Max. input level, pad off / on (1 kHz, 0.1 % THD+N) | +14 dBu / +27 dBu |
| Max. output level, 13.6 kΩ / 3.65 kΩ | +8 dBu / +7.3 dBu |
| Input impedance, pad off / on | 1 MΩ / 115 kΩ |
| Output impedance | 330 Ω |
| Peak LED | +11 dBu (pad off) / +21 dBu (pad on) |
| Power | 48 V phantom power (IEC 61938), 4 mA max. |
General
| Channels | 2 |
| Dimensions (L x W x H) | 134 x 99 x 44 mm (5.30 x 3.9 x 1.73 in) |
| Weight | 0.54 kg (1.2 lb) |
| Operating temperature | -10 °C to 60 °C |
| Warranty | 5 years, parts and labour |
Product overview
The GRACE DESIGN m303s is a high performance, fully isolated stereo active DI with custom-wound transformers, phantom powered, in a rugged 1/4" wall extruded aluminium chassis built in the USA.
The m303s is a dual channel active DI that converts high impedance unbalanced signals to low impedance balanced signals: for passive or active instrument pickups and line level sources such as keyboards, synthesisers and computers. Its high impedance FET input amplifier preserves the tone of passive pickups. The power supply converts 48 V phantom power to an isolated bipolar supply, so the GND-ISO switch completely isolates the instrument input ground from the output XLR ground for the highest rejection of ground induced noise. Custom-wound transformers with a high-nickel core and mu-metal magnetic shield give high headroom, low distortion and protection from hum and buzz.
| Output noise, A‑weighted | -118.6 dBu |
| Response, ±3 dB | 20 Hz - 80 kHz |
| Input impedance, pad off | 1 MΩ |
| Phantom current, max. | 4 mA |
Key features
- Stereo, phantom powered active DI with full galvanic isolation
- Custom-wound transformers with magnetic shield
- Ultra low noise output: -118 dBu (A-weighted); wide bandwidth 20 Hz - 80 kHz (-3 dB)
- Low frequency headroom: THD+N 0.007 % at -10 dBu out, 50 Hz
- 1 MΩ input impedance for any pickup or line source; 13 dB input pad
- Peak LED 3 dB before clipping; power LED; through connectors
- Draws only 4 mA of phantom power; fully ESD and RFI protected
- Gold contact toggle switches; rugged 1/4" wall extruded aluminium chassis; 5 year warranty
Front and rear panel
The front carries per channel PAD switches, 1/4" TS inputs, red peak LEDs, parallel THRU jacks for a stage amplifier and a green power LED. The rear has the GND-ISO switch and the OUT 1 and OUT 2 XLR connectors, which receive phantom power and send the balanced outputs; the m303s can be powered from either XLR, and phantom power to each channel is recommended when both are used.
Built for stage and studio
An advanced power supply design provides great headroom and dynamic range, and the transformers deliver low-end clarity and high frequency detail. The LEDs can be seen from a distance even in bright daylight.
In the box
- m303s stereo active DI
GRACE DESIGN m303s: frequently asked questions
Does it need batteries or a power adaptor?
No. It runs on 48 V phantom power from the mixer or interface and draws only 4 mA.
Can I connect a keyboard at line level?
Yes. Engage the PAD: with it the m303s accepts up to +27 dBu. Never connect it to a power amplifier output.
How do I remove hum?
Set the GND-ISO switch to ISO to isolate the input ground from the output ground.
What are the size and weight?
134 x 99 x 44 mm and 0.54 kg (1.2 lb).
Where can I buy the GRACE DESIGN m303s in India?
The GRACE DESIGN m303s is available from Shivansh Electronics, Kolkata, West Bengal, India, with delivery across India.
Workflow 1: Bass guitar DI and stage amplifier
Bass players on stage and in the studio.
Connections
| Connect | To |
|---|---|
| Bass guitar | IN jack |
| THRU jack | Bass amplifier |
| XLR OUT | Mixer or interface input with 48 V |
Setup
- Connect the instrument, amplifier and XLR output.
- Switch on 48 V phantom power at the mixer.
- Check the green power LED.
- Set the level at the mixer.
Tip: Switch 48 V on after connecting and off before disconnecting.
Workflow 2: Stereo keyboard or synthesiser
Keyboard players feeding a PA or recorder.
Connections
| Connect | To |
|---|---|
| Keyboard left / right outputs | Two m303s inputs |
| XLR outputs | Two mixer channels |
Setup
- Connect both keyboard outputs.
- Engage the PAD for high output sources.
- Apply 48 V to each XLR output used.
- Watch the peak LEDs.
Tip: The pad lets the DI accept up to +27 dBu.
Workflow 3: Computer playback into the PA
Live sound with backing tracks.
Connections
| Connect | To |
|---|---|
| Computer audio outputs | DI inputs |
| XLR outputs | Stage box |
Setup
- Connect the computer outputs.
- Use the PAD if needed.
- Set GND-ISO to ISO against hum.
- Bring up the channels.
Tip: Galvanic isolation keeps computer ground noise out of the PA.
Workflow 4: Hum or buzz on stage
Engineers fighting ground loops.
Connections
| Connect | To |
|---|---|
| Instrument | DI input |
| XLR | Mixer |
Setup
- Listen for hum.
- Set GND-ISO to ISO.
- The input ground is isolated from the output ground.
- Check the signal.
Tip: The inputs can be isolated from the outputs, not from each other.
Workflow 5: Passive acoustic guitar pickup
Recording or live acoustic instruments.
Connections
| Connect | To |
|---|---|
| Acoustic guitar | DI input |
| XLR | Interface |
Setup
- Leave the PAD off for passive pickups.
- Apply 48 V.
- Set the preamp gain.
- Record.
Tip: The 1 MΩ input impedance preserves the tone of passive pickups.
Workflow 6: Studio DI for two channels
Studios recording several line sources at once.
Connections
| Connect | To |
|---|---|
| Line sources | DI inputs |
| XLR outputs | Mic preamps or interface |
Setup
- Patch the sources.
- Apply 48 V per channel.
- Set the pads.
- Record all channels.
Tip: Each channel is powered from its own XLR output.
