Audio T Verdict
The Audio Note Cobra brings traditional Class A valve amplification and a genuinely useful selection of digital inputs together in one distinctive integrated amplifier.
Its 28-watt output, four EL34 power valves and custom double C-core output transformers provide the foundations, while the internal TDA1543 DAC allows a CD transport, streamer, television or computer to connect without a separate converter.
Loudspeaker matching and ventilation still require care, and there is no phono stage, headphone output or Bluetooth. Within an appropriately assembled system, however, the Cobra is one of Audio Note’s most flexible amplifiers.
Audio Note Cobra Class A Valve Integrated Amplifier with DAC
The Audio Note Cobra is a Level 1 integrated valve amplifier delivering 28 watts per channel through a Class A push-pull output stage.
Four EL34 output valves are partnered by two 6AU6 input valves and two 5670 driver valves, with custom Audio Note double C-core output transformers coupling the amplifier to the connected loudspeakers.
Three stereo analogue inputs are joined by coaxial, optical and USB digital inputs feeding the Cobra’s internal Philips TDA1543 digital-to-analogue converter.
28 Watts per Channel
The Cobra is rated at 28 watts per channel, which is considerably more than many single-ended Audio Note valve amplifiers.
Power output alone does not determine whether an amplifier will drive a particular loudspeaker successfully. Speaker sensitivity, nominal impedance, minimum impedance, room size and expected listening volume must all be considered.
The Cobra can work with a broader range of speakers than its power figure may initially suggest, but demanding low-sensitivity or difficult-impedance designs should be assessed through a proper demonstration.
Loudspeaker Matching Matters
A 28-watt valve amplifier should not be selected using wattage alone. Two speakers with the same nominal impedance or sensitivity can still present very different electrical loads.
Audio T can check the specification of your existing speakers or help select a suitable new pair before you order.
Class A Push-Pull EL34 Output Stage
The output stage uses four EL34 pentode valves arranged in a Class A push-pull configuration.
In a push-pull amplifier, the output valves work in complementary pairs to reproduce the music signal. Class A operation keeps the valves conducting throughout their working cycle.
This design produces significant heat even when the amplifier is not being driven hard, making ventilation and safe placement essential.
Complete Valve Complement
The Cobra uses eight valves in total.
- Four EL34: power-output pentodes
- Two 6AU6: small-signal pentodes used in the input circuitry
- Two 5670: dual-triode driver valves
Valves are consumable components and will eventually require replacement. Only correctly specified replacements should be fitted, and servicing should be carried out by a suitably qualified technician.
Custom Double C-Core Output Transformers
The Cobra uses a pair of double C-core output transformers custom-designed and manufactured by Audio Note.
Output transformers provide the electrical interface between the high-voltage valve output circuit and the much lower impedance presented by the loudspeakers.
Their design and construction are central to the operation of any valve power amplifier, and Audio Note manufactures the Cobra’s transformers specifically for this circuit.
Three Stereo Analogue Inputs
Three line-level stereo RCA inputs allow the Cobra to accept analogue sources such as a CD player, streamer, tuner, cassette deck or external phono stage.
These are standard line inputs and do not provide the additional gain or equalisation required by a turntable cartridge.
A separate phono stage must be placed between the turntable and Cobra unless the turntable already has a suitable phono stage built in.
Analogue Sources
- CD player with RCA outputs
- Streamer with analogue outputs
- Tuner or cassette deck
- External phono stage
- Turntable with built-in phono stage
Digital Sources
- CD transport through coaxial S/PDIF
- Streamer through coaxial or optical S/PDIF
- Compatible television through optical S/PDIF
- Computer through USB
- Other compatible PCM digital sources
Built-In Philips TDA1543 DAC
The Cobra’s three digital inputs feed an internal digital-to-analogue converter based on the Philips TDA1543.
The TDA1543 is a 16-bit converter also used in several Audio Note digital products. Its native bit depth is 16-bit, so higher-bit-depth signals accepted by the coaxial and optical inputs are reduced to the converter’s supported bit depth.
The onboard DAC allows the Cobra to form the centre of a digital system without requiring a separate converter and additional analogue interconnect.
Input Compatibility and Conversion Are Different
The coaxial input can accept signals with a specification higher than the TDA1543’s native 16-bit conversion capability.
Accepting a 24-bit signal does not mean the internal DAC converts at 24-bit resolution. Data above its native 16-bit depth is truncated before conversion.
Coaxial S/PDIF Input
The coaxial RCA digital input accepts PCM signals up to 24-bit/176.4kHz.
It can be used with a compatible CD transport, network streamer or other digital source equipped with a coaxial S/PDIF output.
A purpose-designed 75O digital coaxial cable is recommended rather than a standard analogue RCA interconnect.
Optical S/PDIF Input
The optical Toslink input accepts PCM signals up to 24-bit/96kHz.
It provides a useful connection for televisions, streamers, disc players and other compatible sources.
When connecting a television, its digital audio output should normally be configured for two-channel PCM. Dolby Digital, DTS and other surround formats are not supported by the Cobra’s stereo DAC.
USB Digital Input
The USB input accepts signals up to 16-bit/48kHz from a compatible computer or digital source.
The connected device may need the Cobra to be selected as its audio output within the operating system or playback software.
USB compatibility should be confirmed if you intend to use an unusual source, adapter or mobile device.
Digital Input Limits
- Coaxial: up to 24-bit/176.4kHz PCM
- Optical: up to 24-bit/96kHz PCM
- USB: up to 16-bit/48kHz PCM
Not Supported Directly
- Dolby Digital or DTS surround sound
- DSD playback
- HDMI or HDMI eARC
- Network streaming without an external source
- Bluetooth audio
No Bluetooth or Network Streaming
The Cobra does not contain Bluetooth, Wi-Fi, Ethernet or a built-in music-streaming platform.
Streaming can still be added using a separate network streamer connected through one of the analogue or digital inputs.
Keeping the streaming hardware separate also allows that part of the system to be updated independently as services and software change.
No Built-In Phono Stage
Despite the Cobra’s combination of analogue and digital inputs, it does not contain a moving-magnet or moving-coil phono stage.
A conventional turntable must connect through a separate phono stage selected to suit the fitted cartridge.
A turntable with an integrated phono stage can connect directly to one of the Cobra’s analogue line inputs when its line-level output is enabled.
No Headphone Output
The Cobra does not provide a dedicated headphone socket or internal headphone amplifier.
Private listening requires a separate headphone amplifier and an appropriate method of feeding it from the source or system.
The required arrangement should be discussed before purchase because the Cobra is not designed with a conventional fixed-level record output specifically for this purpose.
Remote Volume, Input Selection and Mute
The supplied remote control operates the volume, input selection and mute functions.
The amplifier can also be controlled from its sloping front panel, with separate controls for source selection and listening level.
Front-panel indicators identify the currently selected input.
Speaker Matching and Room Size
Speaker sensitivity provides a useful starting point when matching the Cobra, but it does not tell the whole story.
The speaker’s impedance curve, crossover design, cabinet loading and the size of the listening room all affect how demanding it will be.
Higher-sensitivity speakers with a relatively stable impedance generally allow the Cobra to achieve greater volume and dynamic headroom.
Exposed Valves and Heat
The valves are exposed on the top of the Cobra and become extremely hot during normal operation.
The amplifier must be positioned where children and pets cannot touch it. Combustible objects should be kept away from the valves and ventilation openings.
Never cover the amplifier, place it inside an unventilated cabinet or position another component directly above it.
Important Placement Warning
The exposed EL34 valves operate at temperatures capable of causing burns. The Cobra should not be installed where a child, pet or passing person can reach across it.
Leave generous ventilation above and around the amplifier and allow it to cool completely before touching the valves or moving the unit.
Warm-Up and Everyday Use
Valve amplifiers require a short warm-up period after switch-on before reaching their normal operating condition.
The Cobra should be switched off when it will not be used for an extended period. Leaving it running continuously wastes electricity, generates unnecessary heat and shortens valve life.
Always reduce the volume before changing sources and make sure the amplifier is switched off before connecting or disconnecting loudspeaker cables.
Black Finish
Audio Note currently supplies the Cobra in black only.
Its narrow 340mm-wide enclosure uses a sloping front control panel with the eight valves and transformer covers positioned across the top.
The complete dimensions include the valves, controls and rear connectors, so sufficient shelf depth and clearance must be allowed.
System Connections
Before switching on, connect the loudspeakers securely and make sure that the left and right channels and positive and negative terminals are consistent throughout the system.
Never operate a valve amplifier with incorrectly connected or short-circuited speaker cables.
If you are unsure which speaker terminals or impedance connection should be used, ask Audio T to confirm the correct arrangement for your loudspeakers.
Key Features
- Audio Note Level 1 integrated valve amplifier
- 28 watts per channel
- Class A push-pull pentode operation
- Four EL34 output valves
- Two 6AU6 input valves
- Two 5670 driver valves
- Custom Audio Note double C-core output transformers
- Three stereo RCA analogue inputs
- Built-in Philips TDA1543 DAC
- Coaxial S/PDIF digital input
- Optical Toslink digital input
- USB digital input
- Remote volume control
- Remote input selection
- Remote mute function
- Sloping front control panel
- Black finish
Frequently Asked Questions
How powerful is the Audio Note Cobra?
It produces a maximum of 28 watts per channel from its Class A push-pull EL34 output stage.
Will 28 watts drive my speakers?
That depends on the speaker’s sensitivity, impedance behaviour, the room and required volume. Audio T can check compatibility before purchase.
Does the Cobra have a built-in DAC?
Yes. Its coaxial, optical and USB inputs feed an internal Philips TDA1543 digital-to-analogue converter.
Does it have Bluetooth?
No. Bluetooth is not included. Wireless playback requires a separate streamer or Bluetooth receiver connected to a suitable input.
Does it have built-in music streaming?
No. The Cobra has no Wi-Fi, Ethernet or integrated streaming platform. A separate network streamer can connect through an analogue or digital input.
Can I connect a television?
A television with an optical PCM output can connect to the Toslink input. Set the television’s output to two-channel PCM rather than Dolby Digital or DTS.
Can I connect a turntable?
Yes, but a conventional turntable requires a separate phono stage. A turntable with a built-in phono stage can connect directly at line level.
Does it have a headphone socket?
No. A separate headphone amplifier and suitable system connection are required for private listening.
Does it support high-resolution digital audio?
The coaxial input accepts PCM up to 24-bit/176.4kHz and optical accepts up to 24-bit/96kHz. However, the TDA1543 DAC has a native 16-bit depth, so higher-bit-depth data is truncated before conversion.
Can it decode Dolby Digital or DTS?
No. Digital sources must output compatible two-channel PCM.
Are the valves covered?
No. The valves are exposed and become extremely hot. The amplifier must be positioned away from children, pets and combustible materials.
Is a remote control included?
Yes. It provides volume adjustment, input selection and mute control.
Which finishes are available?
Audio Note currently lists the Cobra in black only.
Why Buy From Audio T?
- Experienced Audio Note valve-amplifier specialists
- Loudspeaker sensitivity and impedance checks
- Digital source and format compatibility advice
- Turntable and external phono-stage guidance
- Streamer and television connection support
- Safe placement and ventilation advice
- In-store demonstrations through participating branches
- Ongoing valve replacement and servicing support
Contact your local Audio T store
to discuss speaker matching, source compatibility or a demonstration of the Audio Note Cobra.