Direct Heated Triode Tube DAC by Allnic Audio Labs

The New Allnic D5000 DHT tube dac is finally available world wide. I have been a huge fan of Allnic since my introduction to them two years ago by John Wright, former engineer for Ed Meitner. I recently became familiar with Direct Heated Triode tubes with the purchase of a used Allnic L5000 Linestage (preamp) which lists for $23K. So my heart leapt like a gazelle when I heard this was in production.

I have not myself heard the D5000 yet but expect to in the near future. However, I am very impressed with Waversa Systems digital architecture design. Most of the components are custom designed for this application. I believe the designer offers a fresh perspective and addresses areas where other dac designs fall short. Most important to me is complete galvanic isolation of the USB input which eliminates noise from the switch power supply of source components. This will likely negate the sonic benefit of my custom ten-rail linear power supply designed by Paul Hynes ($5000). But this alone to me makes their dac competitively priced, given the potential front end savings. I will also perform a USB cable comparison to determine any sonic benefit between a range of cables, including my $1600 Vertere Pulse-R USB 1.5 meter cable.

The analog output uses a fully balanced circuit from input to output with no coupling capacitors, only all pure nickel permalloy cored transformers. Each channel uses twin 3A5(DCC90) DHT tubes. The DHT 3A5 amp’s frequency range is from 20 Hz to 50 kHz (-3dB) with a perfect square wave form of 20 kHz. 3A5 tubes operate at a very low temperature that ensures long tube life. The circuit displays no negative feedback, not even a partial feedback. This design has absolutely no microphonic issues, which is the biggest obstacle to DHT realization. KS Park’s design resolved this issue through a newly designed 7-pin gel damper socket. In addition, the main PCB is floated with a drum rubber specific for this application. High S/N ratio and dynamic operation is achieved through full tube designed automatic voltage regulation which protects the DHT amp from both internal and outside voltage irregularities. The front panel displays a current meter which monitors safe operation and status of the tubes.

The D5000 is very unique in today’s DAC world because most of its components are not from any routine audio market source except the DAC chips. The USB interface, SPDIF receiver and high end upsamplers are all specifically customized for this application. D5000 uses very unique technologies for audio signal processing. The clock does not directly connect to the DAC chip. Instead, the audio processor uses clock alignment algorithms that determine exact alignment for the DAC chip in a real-time manner. The ES9018K2M SABRE 32 Reference DAC chip is a high performance 32-bit, 2-channel audio D/A converter with sampling to 32/384 kHz, 128 DSD and uses a 1.5 MHz upsampler through a field-programmable gate array USB interface.

While most ES9018K based DACs use the dac chip for audio processing, the D5000 has a proprietary internal processor that performs real time PCM upsampling or upsampling and conversion to DSD. The SABRE Reference DAC chip only performs the digital to analog conversion.

Real-time PCM to DSD conversion function is implemented when “conversion” is selected. All input samples are converted to 128 DSD with an internal 5.6 MHz/32 Bit upsampler and DSD converter. When de-selected, input audio sampling is either upsampled, if selected, or bypassed to the DAC chip.

The USB interface is implemented through custom hardware by Waversa Systems and is UAC2 standard compliant. This provides very clean audio through complete galvanic isolation, thereby stripping the digital signal of any PC noise commonly created by the server’s internal power supply. Thesycon driver is provided for Windows application. Drivers are not required for Mac/Linux.

I2S input will be provided in the near future. This separate system will be connected to DAC by a proprietary method through the AES port and provide not only PCM but also DSD. This system has the capability to support extreme upsample and cross conversion between DSD and PCM. Details will be published on a future date.

Every source component has a word clock that sends an impulse to the D/A converter ‘x’ times per second triggering it to take a sample -- this becomes the sampling rate. The precision of this clock determines accuracy of the conversion process which is essential to avoid frequency drift between the internal oscillators of the device. The D5000 frame clock provides synchronization information to the outside device allowing it to precisely match the D5000 MEMS clock. If word clock input is provided then the D5000 internal system will use word clock for playback. By providing an exact data rate, data overrun or underrun are avoided and this reduced jitter creates clearer transients, pronounced attack, crisp inner detail in the higher frequencies and overall improved stereo image.

Unlike the EMM DAC2x which uses a Service USB, firmware updates are completed through the USB input designated for music data using a special interface unique to Waversa Systems.

Inputs:

2 Coax
1 Toslink
1 AES/EBU
1 USB

Output:

Balanced XLR
RCA

Analog Specifications:

1) Output RMS voltage: 2.5V
2) Output impedance: 150 ohms constant
3) Frequency range: 20 Hz-20 KHz flat
4) THD: less than 0.1%
5) Tubes: DHT: 3A5 X4; Tube-based internal power supply: 7233X1, 5654X1
6) Dimension: 430mm, 290mm, 150mm (W, D, H: 17", 7.4", 6")
7) Weight: 9.2 Kg
8) Power consumption: 23W /230/50Hz Or 23W/120V/60Hz for North America.

Digital Specifications:

1) Toslink Sampling limit 96 kHz (Note: In case of TOSLINK, some devices will work correctly with D5000 at any rate. This depends on the signal quality of the transport.)
2) AES/EBU and Coax sampling limit 192 kHz (if the source is SPDIF standard compliant). Higher sampling rates have been demonstrated with some source components.
3) USB Sampling limit 384 kHz, DSD128
4) USB Input Custom USB Audio Interface design with Cypress FX2/FPGA
5) DAC Dual Mono/Mono ES9018K-2M Reference Audio DAC
6) Word Clock: Clock Reference Output, Clock Reference Input
7) DSD Conversion FPGA Based DSD Converter: PCM to input DSD128
8) Upsampling FPGA Based Upsampler: Up to 384 KHz
9) Mac OSX 10.6, Linux OS with UAC2, Windows OS (Thesycon Driver)

List Price: $11,900 USD.

Contact your regional Allnic dealer or Allnic international distributer David Beetles at www.hammertoneaudio.com

Hammertone Audio
252 Magic Drive
Kelowna, British Columbia
Canada V1V 1N2

Contact Person: DAVID BEETLES
Office Phone: 250.862.9037

Disclaimer: I have no professional relationship or financial interest with Allnic Audio Labs.

Please post your experience with this dac or any questions regarding the summary itself.