Longdog Audio VDT1 DAC review

There is for sure no lacking of DAC’s choices on the contemporary high-end audio/audiophile market. You can go from extremely affordable feature packed product to the most crazy exotic stuff. 

With all the 21st century impact and the exploding arise of the digital to analog converters one would expect the abundance of great sounding DAC’s. Well think twice. We came a long way with analog. Digital audio seems to just entered its evolving phase and finally we’re separating the mediocre from the “higher” meanings sound wise. 

Somehow for me as a rule with the top tier DAC’s a tube tandem comes as a must. In absence of tubes too often for some reason the involving musical factor is gone. Still, as learned over the years tubes are not magical. The problem often sits in the different zone. When implemented, right tubes should be via medium and not acting as EQ or paint desk. 

Here is where designer Nick Gotham elaborate why he choose his path with Longdog Audio VDT1 DAC converter to be different:

Most DAC’s seem to be lacking in a couple of areas:

1. Their power supplies let them down (I see this by the number of after market linear power supplies we sell to power other manufacturers DAC’s). 

2. Their analogue outputs are mainly designed with a view to cost, and often are direct copies from the DAC chip specification sheet involving a number of low quality op-amps. 

There are a number of more creative DAC designs out there, but many of them suffer because they don’t take advantage of modern production methods. I attempted to solve these issues, drawing on my experience with power supplies, valve circuit design and by combining the best of new and old. Modern DAC chips are capable of very very good performance, but they are often let down by poor power supply design. By making use of modern surface mount components in the digital parts of the design, its possible to surround each part of the digital interface with many tiny, ultra low noise voltage regulators, and by placing them as close to their load as possible, the goal of clean pure power can be attained. But just as important, is the electrical ground it all stands upon. It doesn’t matter how pure each power rail is, if the ground moves the signal will be corrupted. 

By using high speed (150Mhz) onto isolator devices between stages, it was possible to isolate both the power and ground that each part of the circuit needs. And likewise, isolating the inputs to the digital stage by using high speed transformers, its possible to avoid any contamination from the source and connecting wiring finding its way into the DAC. The digital board contains 9 individual power supplies and three isolated areas to maximize performance in the digital realm. The final stage of the digital board, the balanced analogue output from the DAC chip is taken directly via high quality resistors directly to the analogue board, where the signal is directly connected to the grids of the triodes in the output stages. The circuit used in the analogue stage can claim heritage from what was found in 1950’s and 60’s studio equipment.

It takes advantage of the balanced output from the DAC chip to drive a balanced pair of triodes. The valves used are Jan Phillips 5687 dual triodes, chosen for a number of reasons. They are the result of the end of the development history of valves, in fact they were used in the earliest valve computers, they have very long life, and good triode to triode balance. and above all they sound very very good. To power the analogue stage, just like the digital stage, a clean pure power supply is required. This is provided by a hybrid valve/mosfet design. Finally, the analogue stage is connected to the outside world by a pair of UK made nickel core output transformers. Nickel is used as it offers much lower levels of distortion than less exotic core materials. The combination of these transformers, the power supply and the output stage means that this is a valve output DAC that doesn’t just sound great, it can also hold its own against the measurement of typical solid state circuits. The valve output stage is larger, uses more power and costs more to implement, but sonically there is no comparison. 

The output stage is capable of driving any load its likely to face, and in fact will drive sensitive speakers directly if called to (though of course this is just to demonstrate its driving ability, the DAC is recommended driving a high quality pre-amp or integrated amplifier). In term of inputs, the DAC offers two conventional RCA/Phono (can optionally be BNC, XLR, or Optical) inputs and one USB input. The USB input offers asynchronous signaling and will work out of the box with Apple and Linux operating systems. For Windows a driver disk is provided for simple installation. The inputs all take up to 192k sample rates, with 16-32 bit bit length. Via USB the DAC will also accept and process DSD over USB, switching the DAC chip into its dedicated DSD processing mode. DSD up to DSD64 is supported. As standard the output of the DAC is via high quality silver plated RCA/Phono connectors. Fully balanced output via XLR is available on request. The DAC is housed in non ferrous (aluminum) casework, is available with silver and black fronts, and is available for 230v or 115v mains supplies. As standard the DAC is fitted with RDC cones to provide the best isolation and resonance control and ships with an IsoTek EVO3 Premier mains power lead to suit your country.


Simple and straightforward. 

On the front panel very nicely implemented knob selector let you change smoothly between USB and a pair of coaxial inputs. LEDs indicate many different workings from error, DSD, power, high resolution digital coaxial input etc. 

VDT1 is capable of reproducing both PCM and DSD, but only DSD 64. It seems, that DSD addition is there just for the sake. But for sure nobody will mind I’m sure.

Under the hood Longdog Audio VDT1 DAC spots JATPhilips 5687 triode balanced valve output stage followed by the nickel core output transformers. Thats for the analogue. And in the heart of the matter? Not widely implemented Asahi Kasei AK4396 DAC chip.

Now let us see how all written above sums with the most important factor…


Eric Clapton From The Cradle. My favourite Eric Clapton album. Too often overlooked and understated on all fronts. This blues cover album hits me directly in vein like no other from Eric catalogue. Here “slow hand” brings his’s best in the full real blues embrace. This is Erics best for those not being to elitist regarding their blues agenda. 

Eddie Boyd/Willie Dixon Third degree is as poignant as it gets. Quite few critics wrote how Eric’s playing is great, but the vocals lacking the real deal. I’m not really sure how anyone cannot grasp the emotional burst of this song conveyed by Mr. Clapton. Eric embraced the blues impromptu. 

With mosts DAC’s From The Cradle might spark some emotional impact. More of an intro. Only few really bring the emotions and energy as via medium. Longdog Audio VDT1 DAC is very different. And different in positive way. VDT1 showed the ability to “liquefy” blues and portrayed the aura of the time. This never happens with reserved and flat sounding DACs. 

Call me strange. I like Donald Fagen creational outputs even more then the Steely Dan. Don’t know exactly why, but for exemplary Kamakiriad album embodies this perfectly. Donald always seems to encompass the futurist post apocalyptic feeling most profoundly with his music. Its a voyage of its own. 

Snowbound slow pace kicks in with the wonderfully mastered audio accompanied across the complete album. If you’re not getting affected by the deep, focused and involving bass, matching snapping snares, groovy organs and Dystopian lyrics then something is lacking at the digital front end. Nicks philosophy comes as a practical and factual example of things done right here! No BS and instant involving sound deliverance even after few bars of the Snowbound…

Wonderful new album Into Colour by Rumer brings the best of the 70 R & B’ish feeling in a mighty palpable package. Its hard not be affected with this music. Great production and emotional deeper side. It seems like an easy going album at first. Yet, Into Colour possess many great attributes that reveals the shortcoming of digital audio converter very quickly. VDT1 shifted minutely to the Rumors aura and pace. Some more priced DAC’s might gives more colorful presentation, but for sure nowhere near the price of Longdog Audio DAC. Here

Michael Jacksons Thriller needs no introduction. Still one of the best pop albums ever recorded. Its a production masterpiece with the quality still challenging any sound and mastering engineer. Billie Jean practically slaps you with rhythm and pace. Everything about this album is on positive explosive side and it quickly reveals the ability of any device under the test. For many DACs Thriller becomes quickly a stress rather then thing of a foot tapping. Too many take this album to lightly. Its a very nice presentation of the music on highest level of the quality pop music can (should) be recorded. VDT1 followed the grip and locked firmly to the rhythm. Along other things it proved to be able to holds up to the expectations. Checked! 

Anne Bisson September In Montreal is among my favorite listening testing tracks. Anne ability to engage one into the her exploration of the jazz singing in unique. An instant relationship established. Album is expertly recorded and of the great quality and shows at once what DAC is capable of. VDT1 portrayed Anne Bisson performance very potently and with great impact. Checked!

Great surprise for me was finding Student’s Orchestra of the Moscow Conservatory Liadov: Baba Yaga. Reference Recording renowned release I’ve probably heard too many times and this came as most positive, refreshing surprise. Completely different pace and execution. Here on test is always an energy transfer and an orchestra forte. Longdog Audio DAC conveyed the bursting energy exchange with quite surprising discharge for the price. Most importantly musicality was not in second place, but followed the impact of both quiet passages and loud crescendos. Checked! 


“Gott see Dank” there are few DAC’s on the market, that are following what it can be called the right - musical path. They all come at the different prices, but have engrossed the same idea about how music should be reproduced. For this “analog” musical way of voicing them I’m all for it! 

With VDT1 DAC for a change tubes were implemented not for the sake of typical warmish tube sound, but to bring an unprecedented clarity. Tubes, when implemented right do not sound the way most people expect them to; slow, saturated and overly warm. They can be transparent medium, that carry the musical energy unabridged. And this is what’s one of the stronger points of VDT1 DAC. Longdog Audio DAC carry unexpected weight of the music, that DAC’s in this price range lacks as a rule. Along with that the ability to engage one with the music is another VDT1 stand out attribute. 

VDT1 DAC is a positive surprise. This DAC from England embodies so much of what its most important for the true high-end audio digital audio reproduction. With its harmonic richness and three dimensionality it even on the moments rival some of the highly acclaimed DAC systems costing 50k+. This is very the reality strikes.  

You can clearly hear where the money went with the VDT1 DAC. Minimalistic, stylish and utilitarian contemporary looks hide a potent digital heart, that brings natural, transparent and musical music reproduction.
We got used to listen about complexity of analog reproduction and how it operates with so many variables. Nowadays audiophiles and music lovers are slowly understanding, how digital audio needs more then off the shelf solutions in ensuring great  sounding DAC’s.  


S-PDif inputs: 2.

Galvanic isolation with high performance pulse transformers.
RCA connectors with 75 ohm impedance.
110 Ohm AES XLR inputs available on request.
Supported speeds from 16bit/44.1k to 24bit/192k
SPDiff Reciever supplied by three separate ultra low noise voltage regulators.

USB Input: 1.

Powered from Host computer, Galvanic isolation between Host PC and DAC, prevents noise from the host computer being coupled into the DAC.

USB Audio class 2.0 interface.
Driver free on Linux and OSX host systems.
Simple driver installation on windows.
Speeds from 16bit/44.1k to 24bit/192k (32bit accepted).
DSD over USB supported, 64bit DSD, automatic switching between PCM and DSD


AK4396 DAC selected for best subjective sound when used in balanced out mode.

DAC powered by two ultra low noise voltage regulators. I2S and DSD input isolated from receiver to avoid noise transfer between stages.

Analog output from DAC taken directly to output buffer, no op-amps, capacitors or additional solid state devices in the signal path once it has left the DAC chip.

Analog stage:

Fully balanced valve output stage using 5687 dual triodes, and custom Sowter output transformers, with nickel cores and balanced winding patterns. Use of balanced design ensures distortion levels equal to solid state output stages, but with the sonic qualities that only valves can deliver.     All resistors in signal path are high quality Takman carbon film types.

Output via high quality RCA sockets, fully balanced XLR output available on request.

Output signal level 2.18v RMS full scale (single ended).

Power Supply:

Digital board has 4 stages of pre regulation using low noise regulators, feeding 9 individual ultra low noise regulators mounted next to the driven device. Custom board design providing isolated ground paths between stages to reduce noise induced jitter to a minimum. High quality parts used throughout digital stage to ensure optimum performance.

Analog board contains three regulated power supplies, one for the digital board main supply, one for the output stage valve heater supply, and a valve regulated high voltage supply using high voltage mosfet and EF86 pentode design. Low noise HT supply ensures ultra low analog noise floor.

Custom UK wound toroid transformer, with oversized core, shield and hum band, supplies power to the unit.


450 x 240 x 120mm
l 16 to 24-bit, 44.1kHz to 192kHz PCM;DSD64 playback
l Asahi Kasei AK4396 DAC chip l Tube output stage with 2x Philips 5687s
l Galvanically isolated inputs


00 44 1484 540561
07908 056978