Audio T Verdict
The Leema Acoustics Hydra II is a remarkably flexible power amplifier with the strength and control needed to drive demanding loudspeakers.
In standard stereo mode it delivers 148W per channel into 8 ohms, rising substantially into lower impedances. Its dual-mono construction, large toroidal transformers and low-impedance output stages give it excellent grip, scale and dynamic headroom.
The Hydra II can operate as a conventional fixed-gain stereo power amplifier, form part of a LIPS-controlled Leema system or be bridged into a powerful monoblock. Balanced XLR and unbalanced RCA connections also make it suitable for systems built around equipment from other manufacturers.
Matched with a capable pre-amplifier such as the Leema Pyxis, the Hydra II provides a powerful, controlled and highly adaptable foundation for an ambitious hi-fi system.
Leema Acoustics Hydra II Stereo Power Amplifier
The Leema Acoustics Hydra II is an intelligent, bridgeable stereo power amplifier designed for high-performance two-channel, bi-amplified and multichannel systems.
Designed and manufactured in Wales, it combines substantial output power with a configurable control system that allows it to perform several different roles.
Its principal features include:
- 148W RMS per channel into 8 ohms
- 292W RMS per channel into 4 ohms
- 320W RMS per channel into 2 ohms under the published test conditions
- 392W RMS into 8 ohms in bridged monoblock mode
- 785W RMS into 4 ohms in bridged monoblock mode
- Dual-mono amplifier construction
- Two large toroidal power transformers
- Low-impedance output stages
- One stereo balanced XLR input pair
- Three stereo unbalanced RCA input pairs
- One stereo RCA pre-output
- Fixed-gain and LIPS-variable operation
- Selectable stereo and mono gain structures
- Two-channel, left-channel and right-channel LIPS addressing
- Dedicated surround-system configuration
- Bridgeable monoblock operation
- Thermal protection
- Black or silver finish
Power for Demanding Loudspeakers
The Hydra II delivers 148W RMS per channel into a conventional 8-ohm loudspeaker load.
Its output increases substantially as the connected impedance falls:
- 148W RMS per channel into 8 ohms
- 292W RMS per channel into 4 ohms
- 320W RMS per channel into 2 ohms under Leema’s published test conditions
This demonstrates the amplifier’s ability to supply considerable current rather than producing its headline power only into an easy loudspeaker load.
The result is an amplifier capable of maintaining control during demanding bass passages and large musical changes without sounding compressed or strained.
Speaker Compatibility Should Still Be Confirmed
A published power figure into 2 ohms does not mean that every loudspeaker with a difficult impedance curve will automatically be suitable.
Nominal impedance, minimum impedance, electrical phase, sensitivity, room size and preferred listening level should all be considered before choosing a speaker partner.
Dual-Mono Amplifier Construction
The Hydra II uses a dual-mono layout in which the left and right channels have their own amplifier circuitry and substantial power-supply resources.
This separation helps reduce interaction between the two channels and supports:
- Strong stereo separation
- A stable central image
- Clear placement of voices and instruments
- Consistent power delivery to both loudspeakers
- Reduced channel-to-channel interference
- Convincing soundstage width and depth
The internal layout allows the Hydra II to operate as a conventional stereo amplifier or be reconfigured for more specialised systems.
Two Large Toroidal Transformers
Two substantial toroidal power transformers support the Hydra II’s dual-mono amplifier architecture.
The power supply must provide the voltage and current required by the output stages while maintaining stable operation during sudden musical peaks.
Generous transformer capacity contributes to:
- Strong dynamic headroom
- Controlled bass reproduction
- Stable lower-impedance operation
- Consistent left and right channel performance
- Reduced strain during demanding passages
Low-Impedance Output Stage
The Hydra II uses refined output stages with low output impedance.
A low amplifier output impedance helps control the movement of the connected loudspeaker drivers, particularly after a strong musical transient.
This can contribute to:
- Tighter bass
- Improved timing
- Cleaner stopping and starting of notes
- Greater control at higher playback levels
- More consistent tonal behaviour with different speaker loads
Wide 5Hz to 80kHz Frequency Response
Leema specifies a frequency response from 5Hz to 80kHz within a +0/-3dB tolerance.
This bandwidth extends well beyond the conventional audible range and helps maintain controlled phase behaviour through the upper frequencies.
The final system bandwidth will also depend on the pre-amplifier, source and loudspeakers.
Low Noise and Distortion
The Hydra II is designed to deliver substantial power without obscuring low-level musical information.
Leema specifies:
- 0.004% distortion at 90% of rated output
- A noise floor below -100dB
Low distortion allows the amplifier to preserve tonal character, fine detail and instrumental texture even as the playback level rises.
Conventional Fixed-Gain Stereo Operation
In fixed-gain mode, the Hydra II operates like a conventional stereo power amplifier.
The connected pre-amplifier controls:
- Source selection
- Listening volume
- Balance
- Mute
- Any tone or room-correction functions
The Hydra II then provides the power required to drive the left and right loudspeakers.
This mode allows it to be used with Leema pre-amplifiers or compatible equipment from another manufacturer.
Balanced XLR Input
One stereo pair of balanced XLR inputs is provided.
A balanced connection may be particularly useful where:
- The pre-amplifier provides genuine balanced outputs
- Longer interconnects are required
- Signal cables must run close to mains cables
- Resistance to common electrical interference is important
- The wider system already uses balanced connections
The XLR inputs make the Hydra II a natural partner for the balanced outputs on the Leema Acoustics Pyxis Pre-Amplifier.
Three Unbalanced RCA Inputs
Three stereo RCA input pairs are provided for unbalanced analogue connections.
The additional inputs allow the Hydra II to support specialised LIPS-controlled configurations, including systems involving more than one source or control zone.
Potential applications include:
- A conventional stereo pre-amplifier
- A Leema LIPS control master
- A home cinema pre-amplifier output
- A compatible multiroom controller
- A Leema source capable of controlling amplifier volume through LIPS
The active input and operating mode must be configured correctly for the intended system.
Selectable XLR or RCA Connection
A recessed rear-panel selector determines whether the Hydra II uses its balanced XLR or unbalanced RCA input connection.
Choose the connection type according to the partnering pre-amplifier and interconnects.
Switch the Amplifier Off Before Changing Its Configuration
Rear input and operating-mode switches should only be changed while the Hydra II is switched off and disconnected from mains power.
The amplifier reads its mode-switch positions during startup, so changes made while it is operating will not provide a safe or predictable result.
Leema Intelligent Protocol System
LIPS stands for Leema Intelligent Protocol System.
It allows compatible Leema components to exchange control information and operate as a coordinated system.
Depending on the selected mode and partnering equipment, LIPS can communicate:
- Power commands
- Volume information
- Balance information
- Input-selection commands
- Left-channel or right-channel addressing
- Surround-system commands
Leema lists the Hydra II as capable of operating as either a LIPS master or slave.
LIPS Variable-Gain Mode
In LIPS Variable mode, the Hydra II can respond to volume, balance, source and power commands from a compatible Leema control master.
The analogue interconnect can carry a relatively high signal level while the listening volume is regulated within the Hydra II.
This arrangement is intended to support a strong signal-to-noise ratio through the interconnect and provide coordinated operation across a complete Leema system.
Fixed-Gain LIPS Operation
Fixed Gain disables LIPS-based volume adjustment while retaining compatible power-control communication.
This mode is appropriate when:
- A conventional pre-amplifier controls volume
- The Pyxis is operating as a variable-output pre-amplifier
- The Hydra II is used as a normal stereo power amplifier
- The Hydra II is added to a Tucana-based bi-amplified system
Surround Mode
A dedicated Surround setting allows the Hydra II to respond to appropriate surround-channel LIPS commands within a compatible Leema multichannel system.
The Hydra II may also be used with the variable pre-amplifier outputs of a suitable AV receiver or surround processor when configured as a conventional power amplifier.
In either case, the connected processor must provide safe and reliable volume control.
Stereo and Mono Gain Settings
A separate rear switch selects the appropriate stereo or mono gain structure.
The Stereo setting is used for normal unbridged operation and allows the amplifier to track correctly with suitable partnered Leema equipment.
The Mono setting reduces gain by 6dB. It is intended for systems combining bridged Hydra II monoblocks with unbridged Leema amplification under LIPS control.
This helps equalise the volume structure across channels using different amplifier configurations.
Two-Channel, Left and Right LIPS Addressing
A further switch determines which LIPS channel information the Hydra II responds to.
Available settings are:
Two Channel is used for conventional stereo operation.
Left or Right addressing can be selected where one Hydra II is positioned close to a single loudspeaker and its two amplifier channels are used to bi-amplify that speaker.
Bi-Amplifying a Compatible Loudspeaker
One Hydra II can be assigned to the left or right channel within a compatible LIPS-controlled system.
Its two amplifier channels can then drive separate sections of one loudspeaker, for example:
- One channel driving the bass terminals
- One channel driving the midrange and treble terminals
A second Hydra II can be configured for the opposite loudspeaker.
Remove the Loudspeaker Terminal Links
When passive bi-amplifying a compatible loudspeaker, the links between its crossover terminals must be removed.
Leaving the links fitted can connect two amplifier outputs together and cause serious damage. Seek advice from Audio T before attempting a bi-amplified installation.
Bridgeable Monoblock Operation
The Hydra II can be converted from a stereo amplifier into a high-powered bridged monoblock.
Leema specifies:
- 392W RMS into 8 ohms in bridged mode
- 785W RMS into 4 ohms in bridged mode
A stereo system using bridged operation requires two Hydra II amplifiers, with one unit driving the left loudspeaker and the second driving the right.
Bridged mode may be useful where:
- Greater power is required
- The loudspeakers need substantial dynamic headroom
- A larger room is being used
- The system will be upgraded gradually
- Separate monoblock amplification is preferred
Bridged Mode Requires Careful Configuration
The Normal/Bridged selector must only be changed while the Hydra II is switched off and disconnected from mains power.
In bridged mode, only the left input connections are active and the loudspeaker connects across the two red output terminals using the polarity marked on the rear panel.
A loudspeaker with a minimum impedance below 4 ohms must not be used with a bridged Hydra II. Professional setup by Audio T is strongly recommended.
Stereo or Bridged Operation?
Choose Stereo Operation When
- One Hydra II will drive both loudspeakers
- 148W per channel provides sufficient output
- The speakers present a demanding lower-impedance load
- A simpler system is preferred
- Rack space and mains connections are limited
- The budget should prioritise sources or speakers
Choose Bridged Operation When
- Two Hydra II amplifiers can be accommodated
- Greater power and headroom are required
- The speakers remain suitable for bridged operation
- Separate monoblocks suit the system layout
- The pre-amplifier can drive both units correctly
- The complete system justifies the additional investment
One Stereo RCA Pre-Output
The Hydra II includes one stereo RCA pre-output for compatible system expansion.
Its use will depend on the selected operating mode and wider installation, so the required signal routing should be confirmed before connecting additional amplification or processing equipment.
Thermal Protection
Thermal protection helps protect the amplifier if its operating temperature rises beyond the intended range.
Protection should not be treated as a substitute for correct installation.
To maintain reliable operation:
- Allow clear ventilation around the chassis
- Do not block the upper or side ventilation openings
- Do not place another hot component directly on top
- Keep the amplifier away from radiators and direct sunlight
- Use suitable loudspeakers and secure cable connections
Matching the Leema Pyxis Pre-Amplifier
The Leema Acoustics Pyxis Pre-Amplifier is the natural control partner for the Hydra II.
Together they provide:
- Balanced XLR connectivity
- Extensive analogue source selection
- Moving-magnet and moving-coil phono capability
- LIPS system communication
- Remote volume and source control
- A separate pre-amplifier and power-amplifier architecture
The Hydra II may be operated at fixed gain with volume controlled by the Pyxis, or configured for compatible LIPS-variable operation.
Using the Hydra II with Another Pre-Amplifier
The Hydra II is not restricted to a complete Leema system.
In conventional fixed-gain mode it can be connected to a compatible pre-amplifier from another manufacturer using:
- Balanced XLR interconnects
- Unbalanced RCA interconnects
The pre-amplifier must provide a variable output and should be electrically compatible with the Hydra II’s input sensitivity and gain.
Hydra II or Tucana II Anniversary?
Choose the Hydra II When
- A separate pre-amplifier is already owned
- The Pyxis will control the system
- Bridged monoblock operation may be required
- Specialised LIPS configurations are useful
- Bi-amplification is planned
- Power amplification will be upgraded separately
Choose the Tucana II Anniversary When
- One integrated amplifier is preferred
- Built-in source selection and volume control are required
- A separate pre-amplifier is unnecessary
- A front headphone output is useful
- A simpler installation is preferred
- 150W per channel provides the required output
The Leema Tucana II Anniversary combines high-current stereo amplification and pre-amplifier control within one full-width component.
Hydra II or Elements Integrated Amplifier?
Choose the Hydra II When
- Substantially greater power is required
- A separate high-quality pre-amplifier is available
- Balanced stereo power amplification is the priority
- Bridgeable monoblock operation is useful
- Large or demanding loudspeakers are being used
- A full-width 18kg amplifier can be accommodated
Choose the Elements Integrated When
- A compact half-width amplifier is preferred
- Built-in volume and source control are required
- Optical, coaxial and USB inputs are useful
- A headphone output is required
- 56W per channel suits the speakers and room
- A simpler and more affordable system is wanted
The Leema Elements Integrated Amplifier is a compact integrated model with analogue and digital inputs, DAC and headphone output.
Loudspeaker Matching
The Hydra II is suitable for a broad range of standmount and floorstanding loudspeakers.
Important matching considerations include:
- Nominal and minimum impedance
- Electrical phase behaviour
- Sensitivity
- Recommended amplifier power
- Room size
- Listening distance
- Preferred playback level
- Whether stereo or bridged operation will be used
The Hydra II’s substantial current and power reserves can control demanding speakers, but correct matching should be established through demonstration whenever possible.
Speaker-Cable Selection
Use high-quality speaker cable with secure terminations suitable for the Hydra II and connected loudspeakers.
Cable selection should consider:
- The length of each run
- Conductor area
- Connector quality
- The demands of the loudspeaker
- Whether the amplifier is operating in stereo or bridged mode
- The balance of the complete system
The amplifier must be switched off and disconnected from mains power before speaker connections are changed.
Browse speaker cables available from Audio T to compare suitable options.
Equipment Support and Ventilation
At approximately 18kg, the Hydra II requires a strong, rigid and level equipment shelf.
Install it where:
- The shelf can safely support its weight
- Air can circulate around the chassis
- The upper ventilation openings remain clear
- The rear configuration switches remain accessible
- Interconnects and speaker cables are not strained
- The amplifier is protected from moisture and excessive heat
Do not install the amplifier inside a sealed cabinet or stack another heat-producing component directly on top.
Black and Silver Finishes
Audio T currently lists the Hydra II in:
Both versions use the same internal amplifier specification.
The finish can be matched with other full-width Leema components including the Pyxis and Tucana II Anniversary.
Key Features
- Intelligent bridgeable stereo power amplifier
- Designed and manufactured in Wales
- Dual-mono amplifier construction
- Two large toroidal power transformers
- Refined low-impedance output stages
- 148W RMS per channel into 8 ohms
- 292W RMS per channel into 4 ohms
- 320W RMS per channel into 2 ohms under published test conditions
- 392W RMS into 8 ohms in bridged mode
- 785W RMS into 4 ohms in bridged mode
- 0.004% distortion at 90% rated output
- Noise floor below -100dB
- 5Hz to 80kHz frequency response
- One stereo balanced XLR input pair
- Three stereo unbalanced RCA input pairs
- Selectable XLR or RCA operation
- One stereo RCA pre-output
- Conventional fixed-gain operation
- LIPS variable-gain operation
- Dedicated LIPS Surround mode
- Stereo gain configuration
- Mono gain configuration with 6dB reduction
- Two-channel LIPS addressing
- Left-channel LIPS addressing
- Right-channel LIPS addressing
- LIPS master or slave operation
- Compatible Leema system power control
- Compatible volume and balance control through LIPS
- Bi-amplification capability
- Bridged monoblock operation
- Surround-system integration
- Thermal protection
- Black finish
- Silver finish
- 440mm width
- 110mm height
- 320mm depth
- 18kg weight
- Five-year manufacturer warranty
Frequently Asked Questions
What is the Leema Acoustics Hydra II?
It is a dual-mono stereo power amplifier that can also be configured for LIPS-controlled, bi-amplified, surround or bridged monoblock operation.
Does the Hydra II include volume control?
It does not operate like a conventional integrated amplifier. Volume is normally controlled by a connected pre-amplifier or through a compatible LIPS control master when LIPS Variable mode is selected.
How powerful is it in stereo mode?
Leema specifies 148W per channel into 8 ohms, 292W per channel into 4 ohms and 320W per channel into 2 ohms under its published test conditions.
Can it drive 2-ohm speakers?
Leema publishes a 2-ohm output measurement, but compatibility with a particularly difficult loudspeaker should still be confirmed before purchase.
How powerful is it in bridged mode?
Leema specifies 392W into 8 ohms and 785W into 4 ohms.
How many Hydra II amplifiers are required for bridged stereo?
Two. One bridged Hydra II is required for the left loudspeaker and another for the right.
Can a speaker below 4 ohms be used in bridged mode?
No loudspeaker with a minimum impedance below 4 ohms should be used with a bridged Hydra II.
How is the speaker connected in bridged mode?
The loudspeaker connects across the two red output terminals using the polarity shown on the rear panel. Bridged setup should be completed with the amplifier disconnected from mains power.
Which input is used in bridged mode?
Only the left input connection is active while the Hydra II is bridged.
Does it have balanced inputs?
Yes. One stereo pair of balanced XLR inputs is provided.
How many RCA inputs are provided?
Three stereo unbalanced RCA input pairs are fitted.
Can the XLR and RCA inputs be used simultaneously?
A rear selector chooses balanced XLR or unbalanced RCA operation. The connection type must be configured for the intended system.
What is LIPS?
LIPS is the Leema Intelligent Protocol System, which allows compatible Leema products to exchange power, source, volume, balance and channel-control information.
What is LIPS Variable mode?
It allows a compatible Leema control master to regulate volume and other functions within the Hydra II.
What is Fixed Gain mode?
It configures the Hydra II as a conventional power amplifier, with volume controlled by the connected pre-amplifier.
What is Surround mode?
It allows the amplifier to respond to appropriate surround-channel information within a compatible Leema LIPS system.
What does the Mono gain setting do?
It reduces gain by 6dB so bridged Hydra II amplifiers can be level matched with unbridged Leema amplification in a LIPS-controlled system.
Can one Hydra II bi-amplify a single speaker?
Yes. It can be assigned to the left or right channel, with its two amplifier channels driving separate crossover sections of one compatible loudspeaker.
Can it be used with a pre-amplifier from another manufacturer?
Yes. Select fixed-gain operation and use the compatible XLR or RCA connection from the pre-amplifier.
Which Leema pre-amplifier is the natural partner?
The Leema Pyxis is designed to partner the Hydra II and provides balanced outputs, extensive source connectivity and LIPS control.
Does it have a phono stage?
No. Phono amplification and source selection are handled by the connected pre-amplifier.
Does it include a DAC?
No. The Hydra II is an analogue power amplifier.
Does it have a headphone output?
No. A headphone output would normally be provided by the pre-amplifier or a separate headphone amplifier.
Does it have an RCA output?
Leema lists one stereo RCA pre-output for compatible system expansion.
Does it have thermal protection?
Yes. Thermal protection is included, although adequate ventilation remains essential.
Can the configuration switches be changed while it is operating?
No. Switch the amplifier off and disconnect it from mains power before changing the input, operating or bridge configuration.
Does it support two pairs of speakers?
No. It provides one stereo loudspeaker output set in normal operation.
What is the frequency response?
Leema specifies 5Hz to 80kHz within +0/-3dB.
What is the published distortion figure?
0.004% at 90% of rated output.
What is the published noise floor?
Below -100dB.
What are the dimensions?
Approximately 440 x 110 x 320mm (W x H x D).
How much does it weigh?
Approximately 18kg.
Which finishes are available?
Audio T currently lists black and silver versions, subject to availability.
What warranty is included?
Audio T currently lists a five-year manufacturer warranty, subject to Leema Acoustics’ full terms and proof of purchase.
Related Leema Acoustics Products and Audio T Guides
Why Buy From Audio T?
- Leema Hydra II demonstrations
- Pyxis and Hydra II system demonstrations
- Comparisons with integrated amplifiers
- Loudspeaker impedance and sensitivity matching
- Balanced XLR and unbalanced RCA connection advice
- Fixed-gain power-amplifier setup
- LIPS Variable configuration
- Stereo and bridged monoblock setup
- Left, right and two-channel LIPS configuration
- Passive bi-amplification advice
- Home cinema and surround-system integration
- Pre-amplifier compatibility checks
- Speaker-cable selection and termination
- Equipment support and ventilation guidance
- Black and silver finish selection
- Home demonstrations may be available by arrangement
- Part exchange may be available on suitable existing equipment
- Leema manufacturer-warranty guidance
- Ongoing system and after-sales support
Contact your local Audio T store to arrange a demonstration or discuss pre-amplifiers, loudspeaker matching, LIPS configuration, bi-amplification and bridged operation for the Leema Acoustics Hydra II.