Resonessence Labs Herus+

Herus+: Asynchronous USB Audio 2.0, 24bit 352.8Ks/S, DXD and DSD64/128, 2.4VRMS Headphone DAC with Filters and Low Power Model

HERUS is our smallest form-factor, audiophile quality USB to Headphone DAC. It uses the USB Audio 2.0 Asynchronous protocol and supports DSD64 and DSD128 as well as high data rate PCM at 24bits up to 352.8Ks/S. It is a USB powered device that achieves more than 100dB of SNR, (typically 108dB) and is capable of driving 2.4V RMS, (ie 6.8V pk-to-pk) into headphones from 600 Ohms to 32 Ohms. The distortion in all cases is better than 0.005% (85dB): the measured THD+N is typically 89dB for 32 Ohms and 90dB (about 0.003%) for 600 Ohms.

The HERUS+ is our latest version of HERUS, it meets all the specifications of the HERUS but now includes a user selectable, on-the-fly, choice of two up-sampling filters.
The first custom up-sampling filter the Apodizing Filter, the second is the Minimum Phase IIR filter. Please refer to our note on Digital Filters for more details.

Here is how it works: just plug the HERUS+ into your music source; IPad, IPhone, Android, MSWindows etc, and HERUS+ is recognized and powered up.

• HERUS+ looks and behaves just like the HERUS at power up. But unlike the regular HERUS, HERUS+ has a slightly raised “R” logo. Gently press and release the logo and the color will switch from Blue to Magenta. You have just engaged the first alternate up-sampling Apodizing  filter. Press and release again, the logo remains Magenta, but the second up-sampling filter, the Minimum Phase IIR, is now engaged. Press and release a third time and the logo goes back to Blue, indicating you are now back to the nominal un-specialized up-sampling filter.
• In any filter setting press and hold the logo. After a few seconds the LED goes out. This does not change the filter setting, rather it puts the HERUS+ into a lower power state to help preserve your battery. Press and hold again and the LED lights, the HERUS+ has returned to normal power mode at the same filter setting that was engaged at power down
• Please note: HERUS+ needs the latest USB driver – check you downloaded the latest one

HERUS+ is designed to operate with MS Windows, MAC OS and Linux. You may download our Thesycon USB Audio 2.0 driver to enable USB Audio 2.0 on Windows. HERUS+ uses the ESS 9010-2M DAC, our custom code, and our own asynchronous algorithms that run in a generic Cypress USB interface chip.

We use Resonessence designed, advanced power line processing circuits that can reliably deliver more voltage range than the USB provided 5V, and we maintain the SNR of the power supply to a degree such that HERUS exhibits well over 100dB of SNR at the headphone output. HERUS+ also has a very low 0.2 Ohms output impedance that prevents external noise sources coupling into the output.

All Resonessence products feature upgradable firmware and hardware and despite its physically small size, HERUS+ also contains Resonessence upgradable hardware and firmware.

HERUS+ is machined from a solid block of aluminum and is 63.5mm (2.5in) long, by 31.7mm (1.25in) wide and 19mm (0.75in) high. It has just two connectors: a USB type ‘B’ socket on one end and a TRS 1/4inch Stereo Headphone connector at the other end. HERUS+, like all Resonessence products is Designed, Manufactured, Tested and Shipped in Canada.

HERUS+ will enumerate to the controlling computer and register itself as being able to handle volume control internally.

Almost all music player applications will then send control commands to the HERUS+ which it will use within the ES9010-2M DAC chip to implement high performance 32 bit volume control processing. This is significantly better than the volume control implemented in the music player software. HERUS+ is easy to use: plug HERUS+ into a USB 2.0 (ie High Speed port) [with USB+ Audio 2.0 enabled if on MS Windows] and select HERUS+ as the output device in your system control panel. That is all there is to it…

IMPORTANT Please note: some (if not all) software on the PC, MAC and Linux will, the first time HERUS+ is connected, set the volume to 0dB. That is, to the highest volume level. This may be very loud in the headphones. On subsequent connections the music player application will recall the last volume setting, but we have seen instances where plugging into a different USB port again sets the volume back to 0dB. Consequently, we strongly recommend that you plug the HERUS+ into any new port on your computer with the headphones unplugged, and set the volume to a reasonable level prior to plugging the headphones into HERUS.

Additional note: the volume level may rest to full volume if the headphones are swapped out while music is playing – please pause the music while you swap headphones when using HERUS+. For more details see this FAQ note.

You may, if you wish, use HERUS+ as other than a headphone driving DAC. For example, when driving a power amplifier you will find that HERUS+ is a capable and high performance system component. It is perhaps the optimum and lowest cost solution to accessing DSD music from your computer collection. Read our FAQ on this question for more information.

HERUS+ SPECIFICATIONS

The total distortion (THD) on any HERUS will always be better than 85dB (ie less than 0.005% distortion) and the noise (SNR) will always be better than 100db, typically 108dB. More detailed specifications are: