Harmonia v3.1 45/2A3/300B

2025 Harmonia v4 - The Harmonia v4 will continue on only as a DHT output stage. A volume control will no longer be supplied with the V4.

2025 Production pictures posted soon.

Notice: The Harmonia is not a "buffer stage". It is a true DHT output stage. The Harmonia products DO NOT use a cathode follower circuit like other buffer stages on the market where you do not benefit from the full potential of the DHT tube. With the Harmonia you are hearing the full 45/2A3/300B sound. 

The industry's one and only DHT vacuum tube output stage

The Harmonia is a DHT (Directly Heated Triode) vacuum tube output stage designed to enhance audio systems with the sonic richness of single ended triode tubes.

1- The DHT tube is the core component providing the SET sound.

2- Relay Based input selector allows connection of up to four source components. In the balanced version, all inputs and outputs are transformer coupled.

3- The optional volume control enables volume adjustment.

4- Dual DC regulated power supplies feed clean DC voltage to the tube filaments.

The Harmonia is a unique vacuum tube output stage designed around the two most popular SET tubes; You have a choice of a design based on the 45/2A3 or 300B tubes. Over the past several years, Musica Bella has been working on enhancing this DHT tube output stage design.

OVERVIEW
The Harmonia was and still remains the worlds first audiophile grade output stage designed around the a DHT tube. This Harmonia is the first DHT vacuum tube output stage that is designed to a level that is at home in even the most exotic audio and video systems. It is designed to be used as a stand-alone DHT output stage to bring you closer to your music by introducing the sonic richness of the 45/2A3 or 300B tube into your system. We have all lusted for the SET sound but found amplifiers using this tube offered limited dynamic control over many of today's heavy load speakers. With the new v4 using a high quality relay based input selector you can have the richness of a SET output stage for up to four source components in even the most powerful of solid state systems.

For higher gain systems, the Harmonia v4 can also be ordered as a zero gain DHT preamplifier with volume.

Inside the Harmonia v4 chassis you will find that Response Audio continues its tradition of using only the best parts.  Like our other products, you will not find a circuit board in sight other than the independent dual DC regulated power supplies for the tubes' heaters.  Both the power supply and analog circuit utilize 100% point to point wiring.

The all important circuit contains what we have found to be the best combination of passive components to bring the Harmonia alive. High quality capacitors provide sonic richness as well as maintained extension and detail.

Like all Response Audio products, the Harmonia V4 utilizes a hearty power supply. Starting with the high current transformer to the fully regulated DC filament supplies for each of the tube filaments, the Harmonia's power supply is designed to perform. A new regulated DC filament supply has been designed for the V3 series allowing a constant 2.5V or 5v and able to handle high filament current tubes. The main B+, filament supplies are all each powered by separate high current transformers. The B+ feeding the tubes utilizes a CLCRC topology with a choke loaded anode for each 300B tube. What does this mean? Rather than feeding the plate from a capacitor or resistor, a choke is used in its place. Musica Bella is known for providing some of the quietest components available. The Harmonia has an extremely low noise floor resulting in a jet black background.

The Harmonia finds its happiness between any source component, tape loop of integrated amplifiers and receivers (*).  Placing the Harmonia after any high quality CD player, DAC or phono stage, tube or solid state, brings a sense of SET richness, smoothness and organic quality to any system without sacrificing any of the quality traits one would come to expect from a high end audio product.

The Harmonia can transform your dry, fatiguing home theater into a system your guest will think is driven by SET tubes. One thing the Harmonia cannot do is transform inferior components into giant killers. The Harmonia can only enhance and bring forth more of the potential your system has to offer.

For the tube rollers out there, we highly recommend some experimentation with your favorite DHT tube

The Harmonia is available in either a fully balanced or all single ended version.

Please note there is no LED power indicator on the Harmonia. Upon powering the Harmonia up, the last used input LED indicator will light

Installing the Harmonia into any system is as easy as installing any source component.

The sonic results are as follows:

Restores proper frequency balance through better impedance matching due to its extremely low output impedance.
Improves tone and weight without adding bloom
Adds DHT smoothness, richness and organic qualities to sterile or dry solid state and tube source components
Improves dynamics of source components that do not employ proper impedance matching,
Enhances detail, resolution and transparency.
Reduces listener fatigue.
Enhances the 3D soundstaging of better electronics and recordings.

Design Features

Signal Stage
- All inner signal wire is of high quality copper to provide optimum performance
- High quality tube sockets 
- Neutrik RCA jacks insure low connector loss and high signal transfer 
-  Balanced output transformers (balanced version only)
- Transformer coupling of both balanced and RCA single ended inputs and outputs (balanced version only)
- Neutrik XLR connectors
- Quality output coupling capacitors for smooth, full bodied sound while maintaining air, extension and detail. 
- Tube cathode bypass capacitors bypassed with high quality film capacitors 
- XLR/RCA ground switch on balanced version allows for best grounding plan for your application
- Equipped with 2 pieces Sovtek 2A3 tubes

Power Supply (5AR4 Tube Power Supply Available On Request)
- High current toroidal transformers.
- Regulated DC tube filament supplies running off separate transformer taps for exact voltage. One for each DHT tube
- Choke filtered
- UF diodes used for rectifying stage
- Each DHT tube is choke loaded on the anode

Applications:

-DHT Source selector between sources and preamplifier (recommended), integrated amplifier, solid state receiver, tape loop

- Use between preamp and amplifier to get that DHT emotional sound.

- Use as preamplifier in high efficiency system.

Current In-Stock Chassis
- Aluminum

-3/8" Thick Aluminum Faceplate. You choose the color

-Custom Charcoal Powder Coat Chassis

- Laser Engraved Front Panel

-Heavy damping material applied

Specifications

- Output gain: <1dB
- Output impedance: 180 ohms balanced
                                              150 ohms single ended- Gain: <1dB
- Tubes: 2x 45, 2A3 or 300B
- 16" W x 16" D x 4.5" H with feet
                          9.5" H with tubes

 Direct price Balanced:  $4,995 

2A3 VERSION CLEARANCE PRICE WHILE CURRENT CHASSIS LAST$2,995 

Subtract $250 for single ended             

Footnotes:

(*) - Please note that when used between a preamplifier and amplifier, there is a slight potential for noise depending on your system configuration.