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Digital Audio - RAKK dac

I am sure you are aware that the RAKK digital audio products offer not only great audible performance but great value for the cost. And now, it only gets better! We've completed the development of the RAKK dac Mark IV. My personal opinion of the quality of sound was so great that I removed the Mark III boards from the Sonus Veritas Modena dacs and installed the Mark IV alpha-level boards so we could use them at the 2012 Rocky Mountain AudioFest this past October. We were rewarded with many comments to the effect that the sound was detailed, but very natural, several even venturing that the reproduction resembled what they might expect from live music. Great praise, indeed!

Here is what some of our Mark IV beta testers have to say about this incredible DAC:

The detail and soundstage of this DAC is incredible and I am going to expand my music horizons...just WOW. We are listening to the HRx download now and this is completely STUNNING. B/w the DAC and the high resolution, the soundstage is straight up enormous. The sound is so big and impeccable clarity. I can appreciate every instrument. I am utterly blown away...

Robin C. in North Carolina

I was quite happy with the MKIII version (actually, entirely satisfied with it), but the new version is a truly impressive improvement. It has greatly increased detail retrieval, coherence, and an apparently lower noise floor which yields much more realistic imaging, greater dynamics, and stronger bass response. This was evident within the first 15 seconds of listening. Instruments or voices are precisely located in width and depth on the image stage, with very engaging ambience retrieval. The sound is just more real for all types of music: vocals, four-piece jazz, symphonic, rock, etc. It has a lot of the qualities of high-end vinyl now. I've listened to CDs as well as high res downloads and DVD audio up to 24/192 -- the high res content is smoother, but I'm amazed with the quality from CDs. Some that I've previously judged to be edgy or harsh now sound clean and detailed, and this is nothing like a smoothing filter effect. The MKIV just provides a cleaner and more revealing version of the digital information.

Jim V. in New Mexico

Much of the technology on the Mark IV board will be familiar to you from the Mark III. The excellent PCM1794 DAC is still there as is the equally excellent SRC4193 input receiver and sample rate converter. The sonically superior high-end opamp-based series regulators are also still in use. However, there are several important differences between the Mark III and Mark IV that contribute to a dramatic improvement in the quality of digital music reproduction. The designer, Dave Davenport of Raleigh Audio , has added another PCM1794 DAC chip so that each dac is operated in "mono mode", meaning that both DACs in each chip are serving only one channel's data stream in a differential configuration, resulting in greater linearity and higher current output. Each of these DAC chips is receiving reference current from a new reference current source that we have developed, which is responsible for a dramatic improvement in sound quality. On the digital side of the equation, the Mark IV uses a high specification low jitter oscillator to provide the lowest level of clock jitter. To complete the picture, Dave split the supply feeds to the Mark IV board into two inputs; one supplies all of the especially critical circuits, including the oscillator, and DAC chips, while the other serves the supporting functions.

From an applications standpoint the Mark IV has the same functionality as the Mark III, meaning three serial SPDIF-type inputs and one parallel I2S input. The PC board is naturally larger (6.6" x 2.8"), but uses the same mounting screw spacing as the Mark III. The power supply requirements are 8VDC-to-12VDC @ 300mA and 5VDC @ 100mA. For those of you upgrading from an earlier RAKK dac incarnation these can be potentially supplied by your existing RAKK dac supplies or we can provide suitable new power supplies.

With the RAKK dac Mark IV, our product line is now firmly established in the high-end arena.

RAKK dac Mark IV $950



RAKK dac Power Supplies

A lot of R&D activity is going on behind the scenes at Raleigh Audio and extensive effort goes into powering our products. One of the reasons that the RAKK dac Mark IV performs so well is attention to detail in the power system, including the bulk supplies powering the board. Along these lines, a new regulated power supply has been developed to power the RAKK dac Mark IV. Although the power supplies that were used to power the Mark III may be pressed into service to power the Mark IV, we recommend that the new regulated supply be used for best results.

8VDC Power supply regulator $99

5VDC Power supply regulator $99



Raleigh Audio Active Output Stage for DAC

While the RAKK dac itself is entirely new, the tube output stage, the Active Output, is a refinement of that used for the RAKK dac Mark III.

This differential class-A triode parafeed output stage is based upon the circuit, now in its fourth generation, first used in the excellent Raleigh Audio Line Stage detailed in the November 2004 issue of AudioXpress.

The input section of the Active Output Stage includes passive current-to-voltage (I/V) conversion that provides two equal signals of opposite polarity for the output section.

The output section of the Active Output Stage provides a transformer-coupled circuit in a bridged parallel feed configuration that was used by Western Electric over 60 years ago. However, it employs a cascode connected depletion mode MOSFET constant current source (CCS) that is more effective than anything available to Western Electric engineers. The amplifying device is the robust Russian 6N30P (6η30π) dual triode, one per channel. The output transformers are the superb amorphous core Lundahl LL1674.

Advanced Minimal Reactance Power Supply circuitry is incorporated into the Active Output Stage PC board, so only a Lundahl LL1683 power transformer is required to complete the picture.

The circuitry employs all top quality parts, among them: Lundahl transformers, Cardas film capacitors and tantalum resistors. The Active Output Stage provides an interface for a volume control. Either a standard 10K to 50K stereo audio potentiometer or K&K Audio's shunt attenuator can be used to control the volume. An optional volume control (not included) has also been accommodated (see Stepped Shunt Attenuator below). The Active Output Stage, as shown in the photograph, is assembled and tested. Of course, the constructor must provide an enclosure, power transformer, jacks, an input selection switch, (optional) volume potentiometer, and other minor parts.

Features, requirements, and specifications:

  • Output level: 2vRMS for 0dBfs digital input
  • Output impedance: 350 ohms
  • Frequency response: 10Hz to 20KHz , -0.3dB, -0.0dB
  • The dimensions of the PC board are 7.8" x 7.3"

A practical minimum internal height for an enclosure is about 3".

Prices

Raleigh Audio Active Output Stage for DAC (assembled and tested): $1295

Optional Stepped Attenuator: $199



Raleigh Audio Extreme RAKK dac

The evolution of the digital and analog circuitry designed by Dave Davenport at Raleigh Audio has continued, with the aim of providing ever better sound, yielding a true high-end audio digital-to-analog converter. The Extreme RAKK dac consists of an attractive enclosure containing a RAKK dac Mark IV, an Active Output Stage (described above,) various digital input circuits, together with the necessary powering.

The Extreme RAKK dac is designed for flexible configuration. Up to six digital inputs and two stereo output pairs can be accommodated on the back panel. Note that a mixture of XLR/balanced and RCA/unbalanced outputs can be chosen, but they are not isolated from each other, so you may not be able to use them simultaneously and preserve the balanced operation of amplifiers being driven from the XLR/balanced outputs.

This unit has sonics superior to all of the mid-priced DACs that we have auditioned, and challenges some of the real heavyweights in the business, as well. To facilitate your decision-making process, we have developed an auditioning program that allows you to have an Extreme RAKK dac in your audio system for 10 days to decide if it is the DAC that meets your needs. Call for details.

Specifications

  • Output voltage: 2vRMS at 0dBfs digital input
  • Output impedance: 350 ohms
  • Frequency response: 10Hz to 20KHz , -0.3dB, -0.5dB
  • Size: 18.125" wide, 13" deep, and 4" high
  • Weight: 21 lbs.
  • Enclosure finish: choice of matte black or silver metal-flake powder coat painted front panel, black aluminum knob(s) or natural aluminum knob(s); body of enclosure is finished in durable textured black paint

Features

The Extreme RAKK dac is available as a completely assembled and tested finished product, custom built with the following features/options:
  • RAKK dac Mark IV
  • State-of-the-art differential vacuum tube gain stage with integral power supply
  • Front panel switch selectable digital inputs of various types.
  • Up to six inputs can be accommodated (see below for inputs available).
  • An optional 23 step discrete resistor stepped shunt volume control for those who have only digital sources in their audio systems and, therefore, have no need for a conventional preamplifier.
  • Choice of (up to three) serial digital inputs including:
    • SPDIF (on RCA or BNC connector)
    • AES-EBU (on XLR connector)
    • TOSLINK (optical)
  • Choice of (up to three) parallel digital inputs including:
    • I2S (on HDMI connector)
    • asynchronous USB (24 bit/192KHz)
  • Both balanced (XLR) and unbalanced (RCA) outputs. There is no sonic compromise in choosing one over the other.

Call or e-mail for a price quote for your custom configuration.


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K & K Audio 1004 Olive Chapel Rd. Apex, NC 27502 USA (919) 387-0911 Mon-Fri 8 a.m. - 5 p.m. EST E-mail