1. Introducción
The SMSL DO300EX is a versatile MQA DAC, Bluetooth 5.1 balanced headphone amplificador y preamplifier designed for high-fidelity audio systems. It integrates advanced audio technologies to deliver exceptional sound performance across various input and output options.
This manual provides detailed instructions for setting up, operating, and maintaining your DO300EX to ensure optimal performance and longevity.

Figure 1: SMSL DO300EX MQA DAC Headphone Amplificador PreampLificador con control remoto incluido.
2. Características principales
- Advanced DAC Chips: Equipped with AK4191+AK4499EX and XMOS XU-316 chips, supporting up to 32bit/768kHz PCM and DSD512.
- MQA & MQA-CD Decoding: Full support for MQA and MQA-CD audio signal decoding, restoring original studio sound quality.
- Múltiples entradas: Features USB, optical, coaxial, and I2S inputs for broad compatibility with various audio sources.
- Salidas versátiles: Offers 4.4mm and 6.35mm headphone outputs, alongside balanced XLR and RCA line outputs.
- Pantalla de alta calidad: Suspended display window with tempered glass, full-laminated color IPS display, and DOP independent display function.
- Componentes de primera calidad: Constructed with chamfered high-grade aluminum, 9 high-end dual op amps, audiophile components, and a self-developed CK-03 clock processing circuit for reduced jitter.
- Bluetooth 5.1: Integrated Qualcomm Bluetooth 5.1 chip supporting LDAC 24bit/96kHz, APTX-HD, SBC, and AAC codecs.

Figura 2: Sobreview of the SMSL DO300EX highlighting its core features and technologies.
3. Guía de configuración
3.1 Desembalaje e inspección inicial
Carefully remove the DO300EX from its packaging. Inspect the unit for any signs of damage. Ensure all accessories are present:
- SMSL DO300EX Unit
- Cable de alimentación de CA
- Cable USB
- Mando a distancia
- Antena Bluetooth
- Manual de usuario
- Tarjeta de garantía

Figure 3: Included accessories for the SMSL DO300EX.
3.2 Conexión de fuentes y salidas de audio
The DO300EX offers a wide range of input and output options. Refer to the diagram below for proper connection guidance.

Figure 4: Detailed diagram of the input and output ports on the SMSL DO300EX, illustrating connections to various audio devices.
- Entradas: Connect your digital audio sources (PC, CD/DVD player, TV, other audio devices) to the USB, Optical, Coaxial, or I2S input ports. For Bluetooth, ensure the antenna is connected and pair your mobile device.
- Salidas de auriculares: Use the 4.4mm balanced or 6.35mm single-ended jacks on the front panel for headphones.
- Salidas de línea: Conectarse a una fuente de alimentación amplifier or active speakers using the balanced XLR or unbalanced RCA outputs on the rear panel.
- Fuerza: Connect the AC power cable to the DC 12V input on the rear panel and then to a power outlet.
4. Instrucciones de funcionamiento
4.1 Controles del panel frontal
The front panel features a multi-functional knob and an IPS display for intuitive control and status monitoring.
- Perilla multifuncional: This knob controls volume, input selection, and menu settings. Rotate to adjust volume or navigate menus. Press to confirm selections or switch inputs.
- Pantalla IPS: Shows current volume level, active input, sampling rate, and other operational parameters. Supports DOP independent display for decoding format.
- Tomas de auriculares: 4.4mm balanced and 6.35mm single-ended outputs for direct headphone connection.

Figure 5: Front panel design of the SMSL DO300EX, highlighting the display and multi-functional knob.
4.2 control remoto
El control remoto incluido proporciona acceso cómodo a todas las funciones a distancia.

Figure 6: Layout of the full-function remote control for the SMSL DO300EX.
- Encendido/apagado: Enciende o apaga la unidad.
- Volumen +/-: Ajusta el volumen de salida.
- Seleccionar entrada: Recorre las fuentes de entrada disponibles.
- Menú/Aceptar: Accede al menú y confirma las selecciones.
- Silenciar: Silencia o reactiva la salida de audio.
- FN (Define in the menu): Botón de función personalizable.
4.3 Reproducción de MQA
The DO300EX supports MQA and MQA-CD decoding. Ensure your audio source is providing a genuine MQA-CD signal and that the fiber optic or coaxial signal output by the CD player is unprocessed source code for optimal MQA experience.

Figure 7: MQA-CD decoding is supported via Coaxial and Optical inputs, ensuring high-quality audio playback.
5. Especificaciones
| Característica | Detalle |
|---|---|
| Modelo | DO300EX |
| Chips DAC | AK4191 + AK4499EX |
| Chip USB | XMOS XU-316 |
| USB-Samptasa de ling | PCM de 32 bits/768 kHz, DSD512 |
| Óptico/Coaxial Samptasa de ling | PCM 24 bits/192 kHz |
| Entradas | USB, Optical, Coaxial, I2S |
| Salidas de auriculares | 4.4 mm equilibrado, 6.35 mm de un solo extremo |
| Salidas de línea | XLR Balanced, RCA Unbalanced |
| Versión de Bluetooth | 5.1 (LDAC, APTX-HD, SBC, AAC) |
| Headphone Output Power (4.4mm) | 2570mW x 2 (32Ω/THD+N < 1%) |
| Headphone Output Power (6.35mm) | 640mW x 2 (32Ω/THD+N < 1%) |
| Dynamic Range (XLR) | 132 dB |
| Dynamic Range (RCA) | 127 dB |
| THD+N (XLR) | 0.00006 % (-124 dB) |
| Consumo de energía | <20 W |
| Energía en modo de espera | <0.5 W |

Figure 8: Comprehensive product parameters and specifications for the SMSL DO300EX.
6. Mantenimiento
To ensure the longevity and optimal performance of your SMSL DO300EX, follow these maintenance guidelines:
- Limpieza: Use a soft, dry cloth to clean the exterior of the unit. Avoid using harsh chemicals or abrasive materials, which can damage the finish.
- Ventilación: Asegúrese de que la unidad esté ubicada en un área bien ventilada para evitar el sobrecalentamiento. No obstruya ninguna abertura de ventilación.
- Apagado: Always power off the unit and disconnect it from the power source before cleaning or when not in use for extended periods.
- Ambiente: Evite exponer la unidad a temperaturas extremas, humedad o luz solar directa.
7. Solución de problemas
If you encounter any issues with your DO300EX, please refer to the following common troubleshooting steps:
- Sin energía:
- Compruebe si el cable de alimentación está conectado de forma segura tanto a la unidad como a la toma de corriente.
- Asegúrese de que la toma de corriente funcione.
- Sin salida de sonido:
- Verify that the correct input source is selected on the DO300EX.
- Check all audio cable connections (USB, Optical, Coaxial, I2S, XLR, RCA, headphone jacks).
- Asegúrese de que el volumen no esté silenciado o demasiado bajo.
- Confirm that your connected headphones or speakers are working correctly.
- Sonido distorsionado:
- Verifique la calidad de su fuente de audio y cables.
- Asegúrese de que el sampling rate settings on your source device match the capabilities of the DO300EX.
- Reduce the volume level to check if distortion is due to overdriving.
- Problemas de conexión Bluetooth:
- Asegúrese de que la antena Bluetooth esté instalada correctamente.
- Verify that Bluetooth is enabled on your source device and the DO300EX is in pairing mode.
- Intente desvincular y volver a vincular el dispositivo.
Si el problema persiste después de seguir estos pasos, comuníquese con el servicio de atención al cliente.
8. Garantía y soporte
The SMSL DO300EX comes with a Garantía de 12 meses from the date of purchase. Additionally, the product can be returned within 30 días from the date of purchase if you are not satisfied.
For any questions or technical assistance, our customer service team provides Soporte en línea las 24 horas. Please feel free to contact us through the official channels provided with your product or on the manufacturer's websitio.
9. Vídeos de productos
No official product videos specifically for the SMSL DO300EX were found from the seller in the provided data. The available videos are for a different product (Fosi Audio ZH3) and are therefore not included in this manual to maintain relevance and accuracy.