Ultimate-Preamplifier Plus

Not just another 8 channel DAC but a truly no compromise scalable high-end DSP based digital preamplifier for stereo or custom multi-channel applications !

The Ultimate-Preamplifier Plus (UP+) is the first truly scalable DSP based Preamplifier aimed at high-end audiophile Stereo and Multi-Channel audio applications. At its heart It contains an Analog-Devices SHARC DSP which can easily be configured with Audio Weaver™ from DSP Concepts. For those applications which require more DSP power the UP+ can easily be connected to an external PC which hosts a USB Audio Class 2 interface. All preamp functionality remains the same and the preamp looks like a standard audio device to the PC ! 

This essentially provides scalable DSP capability without the existing hardware becoming obsolete. Because the PC is external to the UP+ and connected through our proprietary Final-Link interface the delicate electronics of the UP+ is totally isolated from the noise of a PC motherboard and switch mode power supply. 

As a result of this scalability you can now use your favorite audio apps on a PC to do your audio processing and are no longer limited by the capabilities of the on-board DSP. Along with the ESStech ES9038PRO Sabre DAC, a wide variety of digital and analog audio inputs and outputs you now have the ultimate DSP processing platform to build your next ultimate active speakers ! Stay tuned for our companion multi-channel power amp specifically tailored toward active speaker environments !

Features at a glance

  • 2 channels input and 8 channels output for 4-way stereo active speaker system.
  • 2 channels input and 10 channels output with external DAC of your choosing for a 5-way stereo active speaker system.
  • Increase channel count by cascading preamps in a one master many slave setup. 
  • Simultaneous output on both RCA unbalanced and XLR balanced output connectors.
  • Multiple Input formats supports 2-channel USB Audio, S/PDIF, Toslink, AES/EBU,  I2S on HDMI, Analog balanced in and unbalanced in, Phono-MM
  • Sampling rates from 32k to 192k
  • 32 bit lossless Master volume control
  • 12V Trigger Input/Outputs
  • DSD support on USB interface
  • 2-channel Direct DAC mode to use as a stand-alone stereo DAC
  • 2-channel Preamplifier mode
  • Multi-Channel Preamplifier mode
  • 800 MMACS DSP Processing
  • External DSP processing for added DSP power

Introducing the Loop-Thru Digital Audio Conduit


Just like a tape monitoring function in an analog preamp being re-routed to an external graphic equalizer for equalizing a system we have implemented similar functionality in the digital domain ! For the first time a digital preamp allows DSP duties to be re-routed off-board to external DSP hardware for additional processing for both stereo and multi-channel processing duties thus either augmenting or replacing the existing on-board DSP hardware. Typically, this functionality would be used when additional hardware capability above the performance of the on-board DSP capability is required.

Alternatively, computationally intensive audio processing software such as room correction or group delay correction software designed to exclusively run on a PC or Mac can be deployed and integrated with the full functionality of the preamp in a seamless and transparent way as though the hardware was built into the preamp. There is no need to run specific music playback software to take advantage of this functionality either. Any sound processing or streaming software that supports ASIO devices will work with the Audio Conduit and that means you still get to use any of your existing source equipment such as CD player, PC audio device, Tuner or turntables that work with the standalone preamp ! This opens up the Ultimate Preamplifier to running a whole host of new applications that either replace or are complementary to the standard Audioweaver application that is bundled with the Preamp.

A first with the Hybrid DSP mode !

Alternatively, with our proprietary Hybrid DSP mode, it is possible to mix on-board DSP functions using Audioweaver with DSP functionality using software running on the external DSP hardware. For example, some on-board functions such as crossover can be implemented with the on-board DSP whilst phase correction of the crossover and/or speaker can be implemented on an off-board DSP using a high tap count and high sample rate FIR filter etc. The DSP limitations now become that of the external hardware and with low cost high core count multi-threading processors the Ultimate Preamp Plus grows with your needs and does not become obsolete as new technologies become available !

Turbo charge your passive speakers with DSP correction ! 

For the first time a 2-channel Preamp coupled with your favourite room or group delay correction software running on an external PC can be used to correct the deficiencies in your passive loudspeaker system. No other hi-end stereo preamp that we know of offers this capability with all possible input sources in a seemless and transparent way that does not impart its own sound and colorations ! The improvement to your system should be astonishing ! Who said there was no free lunch ?

Key Features 

  • Esstech ES9038PRO Sabre Reference Audiophile DAC. With ESS patented 32-bit Hyperstream™ DAC architecture and Time Domain Jitter Eliminator, the SABRE32 Reference Stereo DAC delivers an unprecedented DNR of up to 135dB and THD+N of -120dB, the industry’s highest performance level that will satisfy the most demanding audio enthusiasts.
  • DAC-IV stages completely redesigned using high current differential, ultra wide bandwidth amplifiers with purpose built optimal bias servo control for each DAC output to establish the optimum operating point for each DAC,
  • Ultra low-noise analog DAC supplies using the Esstech ES9311Q regulator 
  • Femto clock with ultra-low phase noise performance, with dedicated low noise regulator circuit and clock distribution network designed to mitigate jitter by optimizing PCB layout with the shortest possible traces and keeping all peripherals on the same board,
  • Dedicated 2 channel USB class-2 interface can handle PCM processing up to 192KHz
  • Dedicated 8 channel USB class-2 interface can handle PCM processing up to 192KHz
  • A new world first with our all new Loop-Thru Audio-Conduit™ processing capability redirects DSP duties to an external PC using a single USB Audio Class-2 interface thus providing unlimited DSP capabilities well beyond the limits of the internal DSP capability. All preamp functionality functions as normal except the external DSP is used for any DSP requirements and the internal DSP is used for normal house keeping and ancillary audio functions such as phono EQ. This means that 3rd party audio processing software normally used on a PC or Apple computer can now be used with the UP+ in a transparent way. This is the digital equivalent of the old Tape-Monitor circuit featured on many older amplifiers and receivers.
  • A new world first Hybrid DSP mode combines external PC DSP capabilities with the onboard SHARC DSP to take advantage of both pieces of hardware. For example, you may have high tap count room correction or group delay correction software that runs exclusively on 2 channel audio on your PC hardware but does not do crossover duties. The crossover can then be configured with the on-board SHARC DSP thus combining the benefits of both hardware to create a fully featured high sample rate DSP solution.
  • Sabre DAC Master mode available for 2 channel and 8 channel preamp modes
  • Perfect Link is available to link and synchronize multiple preamps together for more channel and DSP capability without any additional delay between preamps. Timing delay is within one MCLK period or 20 nS.
  • Our own proprietary in-house Adaptive Intersample-Over filter makes sure that the asynchronous sample rate converter does not saturate or clip when it is dealing with differing sample rates !
  • Use of MELF resistors where appropriate for lower noise and distortion
  • Low noise LDO regulators for the main analog supplies for the quietest operation
  • Double the filter capacitance in the power supply with double pole RC filtering to reduce supply ripple noise from the mains supply
  • Mains input conditioning including DC blocker for optimum operating point of the power transformer which improves long term reliability 

Features in Detail

The Ultimate-Preamp can function as a stand-alone stereo or multi-channel preamp which can process both analog or digital signals including signals from a magnetic cartridge. Precision RIAA equalization is done in the digital domain by an Analog Devices 4th generation SHARC DSP within a 0.01dB tolerance of the inverse RIAA curve and without the problems of a passive design. Unlike analog or passive designs, multiple RIAA curves can be easily accommodated simply by changing the digital filter coefficients whilst still maintaining precise conformance with the standards. Other digital sources can be processed from any one of six galvanically isolated S/PDIF sources and one galvanically isolated I2S interface. In addition, through its galvanically isolated USB interface it can also process PCM up to 192KHz and DSD 64/128/256 source material.

Secondly with its 8 full channels of DSP processing the Ultimate Preamp can form the basis of a stereo 2/3/4 way active stereo speaker system (or 8-way mono) with precision crossover functionality using the full 80 bits fixed point precision or 40 bits floating point precision of an Analog Devices 4th generation SHARC DSP. The Ultimate-Preamp is in a class of its own. With the Link Port adaptor, it is possible to chain two or more boards together for more channels and/or processing power with no latency issues. This allows self-contained fully active speakers to be designed.

Lastly the Ultimate-Preamp can function as a high quality stand-alone stereo DAC. With the industries best DAC hardware and the ability to process digital signals in both PCM and DSD formats from a number of sources including S/PDIF, Toslink, USB-2 audio and I2S. In this case the DSP is not used to process the audio. It is only used for the house keeping functions such as programming the DAC, display information on the LCD display etc.

In all three operating modes, bit-perfect volume and channel level controls are accomplished with true 32-bit precision irrespective of the source and mode of operation. This equals or betters the performance of the best analog volume controls but with the precision, reliability and noise free operation from digital signal processing.

You’ve spent a long time and money building up your vinyl collection so you are going to want to preserve their pristine condition as early as possible. It has been said that the tip pressure of a stylus in a groove can reach as high as 14 tons per square inch which results in a contact temperature as high as 300 degrees Fahrenheit. The friction between stylus and the record can heat the vinyl locally to temperatures near the melting point so some argue that there is degradation of the vinyl after each playback. In fact, an old advert from Goldring many years ago made a point that a typical LP record is only good for 200 plays. Then compound that with wear and tear of a stylus along with air born contaminants finding their way into the grooves, it is imperative that some way of archiving the vinyl playback is needed as early as possible.

The Ultimate Preamp can not only playback vinyl with its built in precision Analog-to-Digital Converter and DSP based RIAA playback equalization but can also archive this playback via an S/PDIF or Toslink output or with the Ultimate Preamp Plus – directly to an external PC equipped with a USB interface thus allowing you to archive and preserve your vinyl collection for posterity sake.


For the first time a multi-way DSP based crossover can accept and directly process Direct Stream Digital (DSD) Audio through its own proprietary on-board DSD processing engine without any software overheads or having to convert it to an analog signal first to be resampled by an Analog to Digital converter. DSD is usually neglected on DSP board offerings simply because to do it in software by the DSP would consume a large proportion of the DSP resources or in many cases require an additional DSP ! We’ve solved this problem by building a DSD decoding engine from the ground up into the on-board custom logic hardware. From DSD-64 all the way up to DSD-256 the on-board DSP decoding engine can process it with ease whilst the DSP is free to do other processing.

The heart of any digital audio system is a precision low phase noise clock generator coupled with a clock distribution network and in this instance we didn’t disappoint. We used the best low jitter clock oscillators from NRZ along with low noise power supplies so that clock purity is maintained. The clock signal from the oscillator is then buffered through a dedicated clock distribution chip and routed to the other devices on the board using impedance controlled traces and the shortest possible trace length thus adding negligible jitter to the clock signals.

In addition to the DSP we have incorporated two large gate count custom logic devices to do tasks that would be difficult if not impossible to achieve in the DSP. Code named ‘Rubidium’ and ‘Iridium’ after their respective chemical elements. Like the use of its chemical counterpart in precision atomic clocks the Rubidium custom chip provides precision timing signals to the DSP, DAC and ADC as well as support for the processing of native DSD data streams which would otherwise consume a large portion of the DSP capacity that would no longer be available to other audio processing needs. The Iridium device performs ancillary functions such as glue logic and support for the LCD display without the need for a second microcontroller.

To communicate with the user, we didn’t just leave them in the dark with a non-existent user interface or one that exclusively relies on lugging a PC around! We’ve incorporated the necessary hardware to build an intuitive user interface. A fast pixel rendering, high resolution full color graphic LCD display coupled with navigation controls provides a context sensitive menu system. For user controls we added a rotary control which doubles as a master volume and menu adjustment control. Along with five navigation buttons the menu is both easy and intuitive to navigate. Seven dimmable status LEDS provide real time status of various conditions. Finally, an infrared remote control interface which is compatible with a standard Apple remote essentially duplicates the functionality of the navigation buttons.

We spent a lot of time perfecting the hardware and firmware for system integration applications. For the ultimate in standalone active speakers each of which would have its own DSP processing hardware we provide the means of linking speakers together so that each board operates in perfect word sync right down to the resolution of each boards on-board master reference clock period of 20 nS ! Typically, other DSP systems ignore this often-overlooked issue and run their boards asynchronously to each other so it’s not uncommon for them to drift out of sync by a few word clocks at best simply because there is no means of synchronizing them together. Worse still they can slip out of sync by up to one hundred word clocks per second depending on the tolerance of each boards master clock. To compound the issue is how to split the incoming digital audio signal from a single USB or S/PDIF connector and make it available to multiple DSP boards?

Our proprietary on board Perfect-Link hardware enables multiple DSP boards to be linked together using a simple connection whilst still being clocked from their own on-board low phase noise master clocks. This results in zero-phase shift between the DAC’s on each separate board as though all of the DAC’s were located on the one single board and being clocked from the same low phase noise master clock!

For standalone speaker applications all that is required to link the speakers is a Simple-Link cable which can be obtained in lengths of up to 5 meters! No more messy and expensive speaker cables running around the floor! Whether you are building a simple active two-way speaker system or multi-way behemoth each with its own self-contained DSP and amplifiers it is mandatory to maintain perfect synchronization otherwise there will be undesirable phase delays between the speakers and that just isn’t considered hi-end these days! Looking at it another way, would you tolerate a standalone DAC which had considerable delay between left and right channels? No you would think it had a design flaw and yet many people operate DSP hardware in this way!

For any DAC or SRC that up-samples a low rate digital audio-stream to a higher rate audio-stream, it is inevitable that some of the intermediatory samples may well exceed the numerical limits of the up-sampling hardware and hence drive the interpolator into an overloaded state. How a DAC or SRC handles these intermediatory samples may well determine the overall sound quality of the device and why one device sounds better than another.

To this end we have designed a very unique system for catching and adjusting for inter-sample overs in real time so that only the necessary amount of attenuation of the incoming signal is used to limit the SRC from being over driven. We also provide a statistics mode which can be used to observed the amount of inter-sample overs on any recording. You will be surprised at how often and the magnitude of these overs occur in standard recordings when up-sampling is being used.

Of course all of this capability would be rendered useless if it could not be customized for the application at hand. To this end we have employed the expertise of DSP Concepts of California to incorporate Audio Weaver as part of our on-board firmware. Audio Weaver from DSP Concepts is an innovative design environment for developing optimized embedded audio software. It embodies years of audio product development experience and enables algorithm and product developers to more quickly and efficiently develop products and technology.

Typically to program a DSP would require a thorough understanding of the underlying hardware and digital signal processing concepts along with years of programming experience in a high level language such as ‘C’ or C++. In other words, not shy of having a degree in electronics or computer science for starters! Audioweaver takes this skillset and wraps a simple to use graphical interface around it so that people who have never programmed a DSP before can now do it in minutes! No cryptic ‘C’ compilers and linkers, just drag-drop and then upload to the board and you can build and customize your DSP designs like you had been doing it for decades! No need to hire a team of specialized DSP engineers – hire Audioweaver for your next project.

Unlike other DSP vendors boards built with the lowest cost in mind we didn’t skimp on quality when the benefits considerably outweighed the increase in cost which is why we specced in a DAC that cost at least fifty times more than the cheap one dollar DAC’s typically found in other DSP products ! We’ve spared no expense when it comes to component selection using the best quality passive components where appropriate. Premium audio grade capacitors such as Nichicon, Roderstein, Wima and NP0/COG ceramic capacitors in both the signal path and power supply make sure signal fidelity is preserved. Other DSP vendors will hope that you don’t notice the skimp on quality and lack of attention to detail in their products but we believe you deserve better.

For the tube aficionados out there we have incorporated a number of software plugins which behave like tubes without the physical tubes installed in the system. Typically, a DAC or preamp would use tubes to add some of that classic rich tube sound and texture to the mix. Instead we have accomplished this using the DSP in the form of tube emulation and soft clipping. Using a DSP to mimic the sound of tubes is nothing new. The pro-audio industry has been using this technique in its studio mixes to emulate the sound of the great classic tube recording equipment of the past. We’ve just taken this idea one step further and applied it to the reproduction chain!

For the first time we provide classic SET (single ended triode) sound with relatively inefficient speakers and solid state amplification all without the inefficiencies of a class ‘A’ single ended tube amp of the same power rating. Now there is no need to own a pair of exotic horn speakers just to enjoy that classic SET amplifier sound! As long as your solid state amp never clips you would never know you were running solid state amplification! We also provide various tube configurations with different distortion profiles and grid bias settings so that you have total control of the sound. Gain matching between different settings means that you can actually do objective comparisons without being fooled by changes in level.


Clock Source and Timing
  • Femto-Clock specced low phase noise precision clock generator
ESSTech ES9038PRO 2nd generation Sabre Professional Audiophile DAC featuring:-
  • Hyperstream II Technology
  • 64-bit accumulator with 32-bit processing
  • Patented Time Domain Jitter Eliminator
  • -140 dB Noise
  • -120 dB THD
  • Precision 32-bit volume control on all channels in 0.5dB steps
  • Precision Gain matching between chips
  • Seven preset reconstruction filter types to suit different applications: –
    • Fast roll-off, linear phase filter
    • Slow roll-off, linear phase filter
    • Fast roll-off, minimum phase filter
    • Slow roll-off, minimum phase filter
    • Apodizing, fast roll-off, linear phase filter
    • Hybrid, fast roll-off, minimum phase filter
    • Brick wall filter
  • Master mode where the DAC determines the timing and the DPLL is not used
DAC Post Processing:-
  • DAC-IV stages completely redesigned using high current differential, ultra wide 180MHz bandwidth amplifiers
  • Purpose built optimal bias servo control for each DAC output to establish the optimum operating point for each DAC,
DSD Processing:-
  • Native onboard DSD Processing in real-time with no software pre-processing required!
  • Supports DSD from DSD64(2.8MHz) up to DSD256 (11.2MHz)
  • No DSP intervention
Advanced user interface console featuring: –
  • Full colored QVGA (320×240 pixels) LCD with backlit display and crisp fast pixel rendered graphics,
  • Stylish full colored bitmap graphics and true-type fonts for that professional appearance,
  • Smooth rotary encoder control for master volume and quick menu changes,
  • Large display of master volume,
  • Seven dimmable status LEDs for real time status reporting namely:
    • IR receiver activity status
    • DAC Lock status
    • DAC Mute status
    •  Plugin active status
    • Line Lock status
    • Sample Rate Converter status
  • Full hierarchical intuitive menus and navigation system including: –
  • Tactile buttons for menu navigation
  • Remote control navigation of menus
  • Full color display with context sensitive display
User Customization of DSP firmware using drag and drop DSP design software:-
  • Design complex DSP systems in minutes
  • No complex DSP coding necessary
  • Dynamic instantiation so no additional compilers or linkers needed
  • Precision low noise, high performance filters not limited to low sampling rates
  • Field upgradable
DSP plugins for 2/8 channel preamp modes includes: –
  • Soft-Tube emulates the rich sound of many different tube types and operating points
  • Soft-Clipping emulates the clipping characteristics of a tube amp
  • Distortion less precision 32-bit sinewave generator for test purposes
  • Image focuser adjusts stereo image width