Product Details

ANK Interstage 300B Monoblock Power Amplifier (Pair)

The ANK Interstage 300B Monoblock Amplifiers represent one of the most refined expressions of single-ended triode amplification. Designed around the legendary 300B directly heated triode, these reference-grade monoblocks employ a transformer-coupled interstage driver rather than conventional capacitor coupling — a design approach widely regarded by purist engineers as one of the most transparent and musically convincing ways to drive a power triode.

By replacing the traditional coupling capacitor with a 1:1 interstage transformer, the signal path gains exceptional control, tonal density, and dynamic realism. The result is a presentation that is richly textured through the midrange while maintaining remarkable authority and composure across the entire frequency range.

This architecture follows the philosophy used in some of the world’s most respected single-ended amplifiers, including flagship designs from Audio Note UK.

The Interstage Monoblock delivers the unmistakable character that has made the 300B tube legendary among audiophiles — vivid midrange presence, dimensional imaging, and effortless musical flow — while adding an additional layer of control and clarity provided by transformer coupling.

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Interstage Transformer Coupling

Instead of using a traditional driver stage with capacitor coupling, the amplifier employs a wide-bandwidth interstage transformer to directly drive the 300B output tubes.

This approach provides several key benefits:

• Greater signal integrity through the driver stage
• Improved dynamic control and transient precision
• Enhanced tonal density and midrange realism
• Reduced signal path components for greater purity

The large bifilar-wound interstage transformer is built on an oversized core, allowing excellent bandwidth and strong bass performance — something rarely achieved in conventional 300B amplifier designs.

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18W Parallel Single-Ended Configuration

This version of the Interstage Monoblock uses a Parallel Single-Ended (PSE) 300B design, delivering approximately 18 watts per monoblock.

Two 300B output tubes operate in parallel to provide greater output capability and improved control over demanding loudspeakers, while retaining the tonal purity and harmonic structure that makes the 300B triode so revered.

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Premium Transformer Architecture

This amplifier version features premium C-core transformers for both the output and interstage stages.

C-core transformers are prized for their excellent magnetic linearity and wide bandwidth, helping deliver:

• Greater micro-detail retrieval
• Improved bass authority
• Lower distortion
• Superior dynamic expression

Combined with the transformer-coupled driver stage, the result is a remarkably direct and coherent signal path.

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Circuit Design

The amplifier uses a carefully selected 6SH7 input stage, chosen by Audio Note circuit designer Andy Grove for its excellent impedance characteristics and compatibility with high-quality line stages.

Signal flow is kept extremely direct:

6SH7 Input Stage → Interstage Transformer → 300B Output Stage → Output Transformer

The power supply uses a 5U4GB rectifier tube and a high-capacity choke-filtered supply incorporating Mundorf M-Lytic 4-pole capacitors, delivering excellent noise performance and dynamic stability.

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Construction

The Interstage Monoblocks are built on a rigid 3 mm aluminium chassis with a beautifully machined solid copper insert plate for improved mechanical damping and thermal stability.

Additional design highlights include:

• Stainless steel hardware throughout
• Countersunk fasteners for clean assembly
• High-quality PTFE tube sockets
• Audio Note RCA inputs and speaker binding posts
• PTFE silver-plated internal wiring
• Hard-wired internal construction

The amplifiers are engineered for durability while maintaining the elegant aesthetic associated with classic tube amplification.

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Key Features

• Parallel single-ended 300B triode amplifier
• Transformer-coupled interstage driver stage
• Premium C-core output and interstage transformers
• 18W Class-A output power per monoblock
• 6SH7 input stage
• 5U4GB tube rectification
• Mundorf M-Lytic power supply capacitors
• Solid copper insert plate construction
• Hard-wired circuitry
• Designed for high-efficiency loudspeakers

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Specifications

Output Power
18W Class-A (Parallel Single-Ended)

Output Tubes
2 × 300B per amplifier

Input Stage
6SH7

Rectifier
5U4GB

Inputs
1 × RCA

Speaker Outputs
4Ω / 8Ω / 16Ω

Recommended Speaker Sensitivity
88 dB or higher

Dimensions
Width: 24.5 cm
Height: 20.5 cm
Depth: 50 cm

Weight
48 kg (pair)

Chassis
3 mm aluminium with solid copper insert plate

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Build & Availability

Each ANK Interstage 300B Monoblock amplifier pair is assembled to order to ensure the highest level of build quality and testing.

Please allow several days for assembly, final inspection, and performance testing prior to dispatch.

If you would like to discuss build timing, available upgrades, or possible custom modifications, please feel free to contact us prior to placing your order.

Other more cost-effective versions of this amplifier are also available with alternative transformer configurations. Please contact us if you would like to discuss these options.