There are many challenges in designing high end audio components. First and foremost, a properly design circuit from the power supply to the final output. With Purity, the next step is to come up with something that has never been done before. Leave it to Purity Audio Design to pursue these challenges. Purity has become known for developing true audiophile grade tube buffers providing balanced connection. Now we have continued this tradition with an audiophile grade buffer using SET tubes.
The Harmonia Buffer/Preamp has been designed for the truly passionate music lover. It is not a preamp. It is not a gain stage. It 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 2A3 or 300B tubes. Over the past several years, Purity Audio Design has been working on developing this SET tube buffer/preamp. We now have what we believe is the passionate music lovers dream come true.

The Harmonia DHT Preamp/Output stage was and still remains the worlds first audiophile grade, dedicated output stage designed around the a DHT tube. This Harmonia is the first SET vacuum tube 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 tube output stage to bring you closer to your music by introducing the sonic richness of the 45/2A3/2.5V 300B. 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 v3.0 using a high quality relay based input selector and attanuator from Khozmo you can have the richness of a SET output stage for up ------ source components in even the most powerful of solid state systems.

Inside the Harmonia v3.0 chassis you will find that Purity Audio Design 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 ClarityCap capacitors provide sonic richness as well as maintained extension and detail.

Like all Purity Audio Design products, the Harmonia v3.0 utilizes a hearty solid state power supply. Starting with the high current toroidal 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 v3.0 allowing a constant 5v and able to handle high filament current tubes. We now provide adjustment for the DHT tube filament voltage. The main B+, filament supplies are all each powered by separate high current transformers. The B+ feeding the tubes utilizes a CLCL-L 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. Purity Audio Design 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 can be used as a DHT output stage for any source component. With the switch of a knob, you will bypass the volume control. The Harmonia finds its happiness between any source component and preamplifier. Placing the Harmonia after any high quality CD player, DAC or phono stage, tube or solid state, brings a sense of DHT 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.

As can be seen in the photos above, the tubes protrude from the top panel of the unit making placement more versatile while also allowing for tube rolling ease. Not to mention what will be considered one of the sexiest looking components in your system.

For the tube rollers out there, we highly recommend some experimentation with your favorite 2.5V DHT tubes
The Chassis is constructed of high quality aluminum.

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

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 45/2A3 or 300B (2.5V versions) 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 uses solid core copper wiring to provide optimum performance
- High quality tube sockets 
- RCA jacks insure low connector loss and high signal transfer 
- Balanced input/output transformers (balanced version only)
- Transformer coupling of both balanced and RCA single ended inputs and outputs (balanced version only)
- Neutrix  XLR connectors
- Clarity "Purity Range" 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 (balanced version)
- Equipped with 2 pieces Sovtek 2A3

- Adjustable DHT filament voltage with LED readout

- Khuzmo remote attenuator with white LED readout

Power Supply
- High current toroidal transformers. Separate transformers for B+ supply and filament supplies.
- Regulated DC tube filament supplies running off separate transformer taps for exact voltage. One for each DHT tube
- Choke filtered
- Stealth diodes used for rectifying stage
- Each DHT tube is choke loaded on the anode

- Outboard capacitor filter bank comprised of 100% polypropylene capacitors. (optional)

- Black Powder Coat aluminum chassis
- Heavy damping material applied

- Output impedance: 180 ohms balanced
                                  150 ohms single ended- 
- Tubes: 1x 2A3 per channel
- 16" W x 16" D x --- H with feet
                            --- H with tubes

October 2021: Starting now, Purity Audio Design will not take orders on the Harmonia v2.0. We are redesigning the chassis and will be pre-building this product prior to offering for sale. 

Notice: Beginning January 2022, The Harmonia will be built with only 2.5V filament DHTs. Including the 45, 2A3 and 2.5V 300B tubes.


Some Feedback:

I have always been fascinated with equipment utilizing “tubes” since I was a child, maybe it was watching my brothers changing out the Cathode-Ray Tube in our TV. For over 25 years, my system has been outfitted with all or some type of tube electronics in the chain. During this period, I have owned many tube pre-amplifiers utilizing 12AX7, 12AU7, 6922 and my favorite, the 6SN7 which has a much fuller and refined presentation than the other smaller signal tubes.
My impressions of my favorite 6SN7 tubes changed drastically when I inserted the Purity Audio Design, Harmonia V2.0 2A3 Directed Heated Triode (DHT) into my system last year and I was unprepared for what I was about to hear even before complete burn-in…The first thing that struck me was how “real” instruments sounded with more body/fullness and with clarity, dimensionality, decay and spatial cues; it was like musicians were occupying a space in my listening environment.
After numerous 6SN7/2A3 comparisons, it was obvious that the DHT was better sounding in every way even with average capacitors and run of the mill 2A3 tubes but I had few ideas on some upgrades that I wanted to explore down the road after spending some time with this amazing pre-amplifier: After 11 months of ownership, I contacted Bill to enquire about upgrading the stock DynamiCap to some VH Audio ODAM bypassed with VH Audio CuTF capacitors : )
The beauty of these upgraded capacitors was obvious on my initial listen but knew from experience that these capacitors, especially the CuTF can take up to 600 hours to burn-in and form. This upgrade was definitely worth its cost…The unit now sounded like I inserted a pre-amplifier that was twice the cost of the original pre-amplifier with the soundstage growing wider/deeper in size, more vibrant and tighter image focus, uncanny textures and effortless layering, pitched black background with clarity and transparency that are off the charts…Highly recommend upgraded capacitors on initial build!
I was considering another DHT Pre but when I saw Purity Audio Design Harmonia V2.0 release, I knew that’s the direction I was headed as I wanted something that was not influenced by other tube typologies, I wanted to hear the “Purity” of the 2A3 DHT. My Purity Audio Design Harmonia V2.0 is hand wired and has operated flawlessly and is a testament of Purity Audio Design commitment to excellence!
If you are looking to increase your listening experience and finally ditch the merry-go-round of equipment entering and leaving your home, I HIGHLY recommend that you contact Bill at Purity Audio Design and get in the Queue for your DHT Pre-Amp 2A3/300B; You will not regret your decision…

Ron - Harmonia v2.0

Model  Current  Price - 
Single Ended $
Balanced $

Prices, details and specifications subject to change w

Notice: The Harmonia IS NOT a 'buffer' stage as it DOES NOT use a cathode follower circuit like other DHT preamplifiers 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 sound. 

Notice: Beginning January 2022, The Harmonia will be built with only 2.5V filament DHTs. Including the 45, 2A3 and 2.5V 300B tubes.

Purity Audio Design

Harmonia v3.0
45/2A3 Preamp/Output Stage

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

Discontinued from
Purity Audio Design

June 2022: Starting now, Purity Audio Design is sold out of the Harmonia v2.0. We will no longer sell this product under the Purity Audio Design Name. This product will soon be available via Raven Audio