New digital audio interface and protocol

Backwards compatible with Toslink interface and S/PDIF protocol. Our new electro-optical digital audio interface and low jitter protocol eliminates -unwanted- jitter in digital audio source, digital audio interlink, and all DAC circuits even when significant crosstalk is present. It has to be generated directly by software (UPL96ETL and U192ETL).


Discrete Fractal DAC based on custom DAPI* board with independent clock.

The DAPI board converts Toslink input to extreme low noise parallel data driving our improved** Fractal DAC. The DAPI board also reduces source influence considerably. This results in better than expected performance. The Power DAC-R has RCA output and built-in volume control (27 dB range) using bit-shifts i.c.w. 2 voltage levels without using any amplification, buffer or attenuator circuits.

* DAPI : Digital Audio Parallel Interface

** improved : PowerDAC-R has lower output impedance than DA96ETF


USB transport with ElectroTos/Toslink interface and low jitter ElectroTos protocol

Backwards compatible with Toslink interface and S/PDIF protocol. Supports asynchronous USB audio Class 2, 44.1/16 to 192/24. Based on XMOS XU208. Low jitter system and audio clocks, 24MHz, 22.5792MHz, 24.576MHz. Each oscillator has separate RF supply noise filtering. Advanced synchroniser / driver circuit for XMOS jitter attenuation. USB bus powered (5V).


Very clean USB memory stick -reference- transport with ElectroTos/Toslink interface and ElectroTos low jitter protocol.

Backwards compatible with Toslink interface and S/PDIF protocol, remote controlled by software on PC + build-in webserver for remote control using phone/pad. Our UPL remote software supports WAV files using ID3v2.3.0 metadata with jpeg/png cover-art. USB sticks and USB SSD drives are supported with upto 999 CDs with upto 99 tracks per CD. Using the UPLPlayer third party software developed by one of our customers upto 98.901 CDs are supported by using cue sheets with multi-track wav files (one CD per wav file). Supports 44.1/16 to 96/24. Based on STM32 ARM. Low jitter system and audio clocks, 24MHz, 22.5792MHz, 45.1584MHz, 24.576MHz, 49.152MHz. Each oscillator has separate RF supply noise filtering. Advanced synchroniser / driver circuit for jitter attenuation. Built-in 20 MHz bandpass, USB bus powered (5V).


Discrete, ultra low noise multi-pattern fractal DAC with ElectroTos input.

The DA96ETF pairs with U192ETL or UPL96ETL, these support the ElectroTos low jitter protocol. Note: the DA96ETF does not support standard Toslink protocol, it will only produce noise when attempting to drive it with standard Toslink sources. Sample rate support: 44.1, 48, 88.2, and 96 KHz. Bit depth: automatic (ElectroTos protocol). Standard digital audio protocols are no longer used / generated anywhere in the DA96ETF. D/A converter type: Fractal multi-pattern converter, 32 bit core / channel (this type of converter is -completely- different from all existing audio D/A converters). Fractal multi-pattern converters offer extreme long term accuracy (with given component tolerances), low output impedance (375 Ohms), and extremely low digital interface switching noise because of the parallel data interface (highest switching frequency equals the sample rate / ELE latch signal). System: unfiltered NOS (fully passive output circuit). By using 88.2 or 96 KHz, 2 x oversampling can be obtained. Included power supply: external, 5V/100mA (4.8 ... 5V5), connection USB-B (large).

Also see:


Passive stepped volume attenuator.

Manual operated 24 step volume attenuator for our DA96ETF.


Passive stepped universal volume attenuator.

Manual operated 24 step universal volume attenuator for existing DACs.


USB stick size measuring instrument for measuring if playback is (still) bit-perfect.

The Bit-Perfect tester is a USB stick size measuring instrument for measuring if playback is (still) bit-perfect. It is used together with digital audio test files.


Open baffle speaker.

The OBS100 is an open baffle spreaker with 8" full range speaker and two 15" bass units. De OBS100 delivers realistic music playback with high resolution.


Howto connect our audio components to each other, and howto connect them to existing audio components.

Our audio components are designed to perfectly complement each other. Using one of our transports in combination with our DAC, volume attenuator and headphone amplifier or our active open baffle speaker will produce music instead of sound. With this combination you can exactly hear what we hear and enjoy music like never before, just like we have for the last couple of months.
Apart from buying a whole set you could also start with improving your current setup. Our two transports can be used with any DAC equipped with a Toslink input, the UPL96ETL and the U192ETL will introduce you to ElectroTos technology and could already improve sound quality significantly. Also our SVC24U stepped volume attenuator and our SHPB10 headphone amplifier / OBS100 active open baffle speaker could also be a big improvement in sound quality with existing audio components. Check out the connection diagram below to see how to connect our audio components to each other, or howto connect them to existing audio components.

When connecting our U192ETL or UPL96ETL transports to an existing Toslink DAC make sure to disconnect all other inputs from the DAC !

Resolution and clarity

The sound quality of an audio set depends on the cumulative distortion introduced in the entire audio signal path.

It is best to avoid audio components that are not strictly required like pre amplifiers and coupling caps for example. It would be best to connect the DA96ETF directly to the power amplifier input, and use a shunt volume control like our SVC24 to control the volume. In order to get an impression of what the DA96ETF is really capable of one can directly connect high Ohmic studio headphones like the Beyerdynamic DT 990 pro to the DA96ETF outputs, if these play too loud one can add a shunt resistor of 33 ... 100 Ohms or use our SVC24 shunt volume control. This can serve as reference when attempting to get similar resolution and transparency out of the speakers. Similar applies to analogue sources like vinyl and tape, so this is by no means a DAC only problem!

The amplifier - speaker combination causes most degrading as related distortion is always very high (typically 2 ... 20%). This is mainly caused by the steering method (constant voltage steering). This steering method is not optimal to drive a speaker voice coil where the magnetic field depends on the Ampère windings. The result is both, resolution and transparency loss.

Tube amplifiers are more compatible with most speakers as tube amplifiers are usually based on quasi constant current steering, this will increase resolution and clarity compared to semiconductor amplifiers that are based on constant voltage steering. This may be one of the reasons why tube amplifiers are still popular.

If a semiconductor amplifier fails to offer similar resolution and clarity compared to the DT990 studio headphones reference, there is an easy trick to improve this. It is not the perfect solution but it can help to come closer to the studio headphones reference.

Connect a 4.7 Ohms power series resistor between the semiconductor amplifier output and an 8 Ohms speaker, or a 2.2 Ohm power series resistor for a 4 Ohm speaker. This will shift steering from constant voltage to quasi constant current steering. The optimal series resistor value equals approx. speaker impedance divided by 1.6. Use power resistors with a rating of amplifier output power divided by 2.6, so for a 40W rms output amplifier use 15W series resistor.