Purity Audio

Reference mk4

Balanced Class A Vacuum Tube Linestage


- Type : Class "A", Zero feedback, triode vacuum tube preamplifier
- Circuit gain: Adjustable
- Input impedance: 100K Ω
- Output impedance: <180  Ω
- Recommended output load: >2000 ohms
- Frequency response: 13Hz-35kHz -1dB
- Total harmonic distortion: 0.05% @ 1V output
- AC Power Requirements : 117/220/230/240 volts (factory wired)
- Fuse: 1.2 amp fast blow (1/4" x 1-1/4")
- Tube lineup : 6SN7 or 12AU7 ×2 / 5R4 x1
- Dimensions : 17" Wide x 114" Deep x 7.5" High
- Net Weight :
- Shipping Weight:

- High current mains transformer
- Capacitor input, choke filtered
- Multiple polypropylene capacitors make up first stage filter bank.
- High value final stage capacitor bypassed with quality film capacitor.
- Teflon tube sockets
- 5R4 rectifier.

Est. Selling Price:

Availability: Early 2019



- 0 dB negative feedback
- Pure tube design (no transistors)

- Adjustable gain switching with LED indicators
- DynamiCap capacitors
- Shortest possible signal paths
- Very low output impedance to drive any tube or solid state power amp

- 6 position adjustable gain via custom 'secondary autoformers'
- Audiophile grade passive components used in all applications
- Teflon tube sockets
- Central one-point earth grounding
- Fully hand assembled to insure the highest level of craftsmanship 
- Relay based source selector with no shared grounds
- No common ground between any inputs.
- 100% point to point wired - NO PCB
- ROHS silver solder used for the best electrical connection
- Selector switch engages relays located near RCA jacks to switch all inputs
- 2 6SN7 or 12AU7 tubes for stereo line-amplification
- Regulated DC filament supply for signal tubes
- Balanced output transformers (Custom made for Purity Audio Design)
- Balanced input transformers by Jensen Audio
- Premium internal signal cable uses Silver Plated -Copper/Teflon
- 1 set XLR balanced inputs
- 3 pair RCA single ended inputs (transformer coupled)
- 2 sets XLR balanced outputs
- 2 sets RCA single ended outputs (transformer coupled)
- All 4 sets of outputs active at all times allowing for multiple configurations for bi-amping or use of an active subwoofer(s)
- RCA high quality Teflon silver input jacks
- Neutrik/Swiss - XLR chassis connectors
- Remote Control for Volume, Balance, Mute
- Chassis material: 1/2" Acrylic
- Chassis finish: Black
- Equipped with high quality IEC AC power cord
- Made in USA
- Three years parts and labor warranty. 90 days on supplied tubes

The multi award winning Reference linestage continues to get better. We have removed all the unnecessary options and circuitry found on previous models to provide with a true, state-of-the-art 2-channel preamp. The Purity Reference mk4 is a Class A, transformer coupled balanced linestage and is the result of years of intensive research directed at attaining the most accurate reproduction of recorded music.  Unique topology and application of the most advanced technological resources and processes bring the Purity Reference to a threshold of excellence in sound reproduction.  To add to the main features, the Purity Reference utilizes transformer coupling at both the input and output. Transformer coupling output results in a low output impedance making the Purity Reference a versatile unit that is capable of driving both solid state and vacuum tube amplifiers with input impedances as low as 600 ohms. Extraordinary transparency of perceived sound which in turn assures the recreation of a three dimensional soundstage.

The Reference mk4 has a unique employment of output gain selection. rather than installed sonic purity robbing resistors in the signal path, Purity Audio Design has come up with a unique way of obtaining six output gain levels using specially design "secondary autoformers" as not to impart of the sonic integrity of the circuit or degrading impedance interactions. Our autoformer adjustable output gain allows for up to -15db of attenuation making the Reference mk4 suitable for use with virtually any amplifier. Switching duties are handled by a 6 position, relay based selector with LED indicators letting you know what level out attenuation you are at. Secondary attenuation can be adjusted while music is paying.

A new feature now found on the mk4 is the tape/monitor loop. While this feature can be used in a conventional manner, its intended use is to install the Purity Harmonia 300B buffer allowing all inputs to benefit from 300B sound. Installing the 300B buffer in this loop is identical to having a 300B tube output stage on all your source components. Please contact us for a package price on both the Reference MK4 and Harmonia 300B tube buffer.

The Reference now incorporates Dynamicap capacitors in the output stage. Enhancements in the power supply include a newly developed tube power supply using the 5R4 rectifier carried over from the mk3. Tube filament power is now supplied by a high quality, highly regulated DC supply for the quietest possible presentation.

With 1 sets of balanced inputs, 3 sets of unbalanced inputs and 2 sets each balanced and unbalanced outputs, connection possibilities are vast. When an unbalanced input is selected, the signal still passes through the input transformer maintaining a low output impedance as well as the resolution and transparency transformer coupling is known for.  Single ended outputs also benefit from transformer coupling. Balance control is selected via the remote handset.

As with all Purity Series products, the remote circuit has been granted a dedicated power supply including a separate, standalone power transformer as not to interfere at all with the analog circuit.