USB-I2S Audio-Interfaces

It is a great time to be an audio diy’er. There is currently great availability of quality boards aiming at providing the greatest fidelity with incredible VALUE.

Here are some side by side photos of the two USB-I2S interfaces I own.

Worthy of mention is the upcoming next generation Wave IO board. Mr. Lorien posted a sneak peek at his next generation board [link]

From the look of the layout, this board has electrical isolation of the outputs and flip-flop reclocking after the isolator.

TEAC USB Interface

Updated 4/30/13

The new Teac UD-501 DSD capable DAC has received good reviews everywhere. Was curious about its USB interface. Here is a photo taken from a French site, qobuz.com [link]

There is a TMS320 chip and an unidentified chip. It is possible the unidentified chip is the USB receiver or the TMS320 is doing receiver function and the unidentified chip is a microprocessor to control the TMS320 chip.

The TMS320 is a DSP chip [link]. It is a “C67″ series, an up to 1GFLOP 32-bit floating point DSP (the XMOS are rated at 500-1500 MIPS, likely equivalent performance). This family of DSP products was introduced in 1983 and new models have been introduced along the way.

The “C67″ series is a current product and an EVAL kit, in particular for the C6748 chip,  is available from TI [link], [link]. According to the documentation:

…The
TMS320C6748, a low-power dual-core applications processor based on a fixed-point C64x+™ instruction set and the floating-point C67x+™ instruction set. It provides significantly lower power than other members of the TMS320C6000™ platform of DSPs and provides both floating-point precision and fixed-point performance in the same device. With a wide variety of standard interfaces for connectivity and storage, the C6748 development kit enables developers to easily bring audio, video and other signals onto the board.

… Included in the C6748 development kit is all the hardware and software needed for two demonstrations, a fingerprint-recognition demo and a face-detection demo.

Here is the block diagram for the eval kit:

Looks like a very capable and general purpose processor for not just audio but a lot of other things not even related to audio. You can take a look at the WIKI for all the available libraries for the DSP [link]. The DSP can even implement audio decoding and filtering.

In addition, the USB-2 interface is provided by the FT232 chip (and thus the unidentified chip is  likely not the USB interface chip; however, there are no FT232 chips in 48-pin package).

Further, the DAC has an upsampling feature and is provided by the Cirrus CS8422 chip on the main taking the I2S output from the USB board.

Thus the USB board, I believe, it is just moving the bits  to the DACs. It looks kind of overkill; perhaps in some future Teac will add other capabilities such such as PCM to DSD conversion and different upsampling algorithm on the DSP chip. It is also likely that Teac is just reusing hardware from their TASCAM proline. A device such as the TASCAM US-366 is a “USB interface with DSP Mixer”

This design from TEAC gives credibility to what Musiland is doing in their upcoming “SuperDSP” chip. The good thing about the Musiland product is that the DSP is dedicated to audio, and the chip will have native support for USB 2 and USB 3 interfaces.

UPDATE

Appreciate Mr. Daussin, the reviewer of the TEAC DAC, providing additional information in the comments section. The unidentified chip is the TPS65070. Readers would recognize “TPS” being power chips. The TPS65070 is a single-chip with multiple voltage outputs. Here it provides the different voltages required by the DSP chip. It is a convenient, integrated solution to provide the power to the main chip instead of using separate regulators.

The TMS320 DSP chip has implemented USB 2.0 capability in s/w and there is no need for a FT USB receiver chip (In the block diagram the USB 2.0 receiving capability is provided by a separate chip because (I think) the DSP chip is already burdened with many different functions).

Got the XMOS 384KHz USB Interface

Updated 4.21.13

Follow the discussion of this board and XMOS technology in general in the diyaudio thread: [link].

The new board

The new chip from XMOS

Cannot tell from the chip markings what part is it. It is “missing” the part number. But it is definitely a “U” part as there is no separate USB controller chip. Here is the datasheet  of one version of the part: [link]

The previous generation XMOS devices required a separate USB interface chip (foto from here: [link]):

The audio clocks. According to the datasheet, pin 1 is the enable pin and pin 3 is the output pin. Looks like the enable pin is controlled by the XMOS chip, enabling/disabling the clocks for the corresponding sample rate.

The local ultra low noise LDO (excuse the left over cotton fibers from my cleaning ). You can bypass the USB power by removing FB1 and provide external 5V.

The 2 LC filters for filtering the output from the built in DC-DC converters. Here is place to add larger caps and increase the filtering.

Solid ground plane. CN1 is for external powering (instead of using USB power).

If you read the datasheet and compare the topology of this board you will find that the manufacturer has followed the build and layout recommendations from XMOS. In fact it is so simple, that not following the manufacturer’s recommendations is kind of hard

The new XMOS chip has several advantages over the old device

• Built-in USB receiver
• Requires much less external components and thus it has been optimized to be implemented on a 2-layer board
• Built in voltage regulators. The internally generated regulated power is further filtered by external LC filters – Here is an area to mod: add capacitance to increase the filtering
• The clocks can be positioned much closer to the device than in the previous design

Apparently 384KHz support was added by diyinhk according to this lively discussion at diyaudio [link]

FEATURES OF THE MODULE (From the manufacturer)

1. 6.5uVrms Ultralow noise LDO. -The TI LP5900 [link]
2. Solid ground plane (a must for high speed digital circuit)
3. No Via in active circuit (via inductance always create jitter problem)
4. FOX Xpresso ultra low ppm oscillators and Murata capacitors sourced from Digikey USA. -The two Xpresso 22.579 2MHz and 24.576 MHz clocks. Not the ultimate in low jitter, but pretty low jitter. See the graph below
5. Gold plated USB connector
6. Compact size 50mm x 30mm. -That is even smaller than the Amanero which is 30×70 mm approx.
7. USB powered but can be externally powered by removing FB1 and connect 5V to CN1 (warning: over-voltage or reverse-voltage can damage the XMOS chip immediately. Any modification will void item warranty)
8. Can optionally install series resistor to I2S lines (by cutting the traces)

Comparing the Xpresso clocks with Crystek.

DEVICE DRIVERS

I first checked it by plugging it to a Macintosh computer. Native MacOS supports up to 352K and 384K sample rate.

On the PC, it requires device drivers.

Version 1.63.0 is the latest driver from Thesycon.

No indication of 352K/384K capability for WASAPI shared mode. This may in fact a limitation of Windows mixer as it expects to resample every audio stream to the selected sample rate. However, in WASAPI exclusive mode, this part (the mixer) is totally bypassed and the output sample rate from the player application is passed directly to the hardware.

The driver also supports ASIO

CONNECTING TO DAC

Connected the board to my old Buffalo II DAC (80 MHz clock) and tested all sample rates from 44.1KHz all the way to 384KHz. With the 80MHz version of the Buffalo II DAC, 352.8KHz and 384KHz work fine with oversampling turned off. All sample rates work as advertised. Modern designs are pretty robust, especially this version of the XMOS chip which requires only a few external components.

The socket in the XMOS device matches the socket pin arrangement for the latest version of the $99 ES9018 board and a ribbon cable can be used. For the Buffalo simple cat-5 twisted pairs can be used.

Here is an implementation from a reader with diyinhk $99 DAC board:

The XMOS is hiding…

 

DIYINHK XMOS USB: The “DXIO”

Straight from the eBay page [link]

I have to congratulate this Mr. diyinhk. He can non only produce designs with such speed, but can somehow price them so amazingly low. This new module is priced at $59.95 -Can’t resist not getting it!

FEATURES

1. Latest XMOS chip that uses 48MHz oscillator (rather than the 13Mhz used by the older XMOS chip for the USB interface) – I believe this is the XS1-U chip with built-in USB interface [link]
2. 6.5uVrms Ultralow noise LDO. -The TI LP5900 [link]. I believe (the 6-legged chip next to the USB connector).
3. Solid ground plane (a must for high speed digital circuit)
4. No Via in active circuit (via inductance always create jitter problem)
5. FOX ultra low ppm oscillators and Murata capacitors sourced from Digikey USA. -The two Xpresso 22.579 2MHz and 24.576 MHz clocks. They are of different size which reminds me of user complaining when some of the Hiface interfaces were built with the smaller size oscillators. But the industry is moving away from 5×7 mm to 3×5 mm and there is no way back.
6. Gold plated USB connector (Molex, FCI, or other -depends on stock)
7. Compact size 50mm x 30mm. -That is even smaller than the Amanero which is 30×70 mm approx.
8. Module is USB powered but the diyer expert can remove FB1 and use an external 5V PS to CN1 (warning: over-voltage or reverse-voltage can damage the XMOS chip immediately. Any modification will void item warranty)
9. Can optionally install series resistor to I2S lines (by cutting the traces)

WINDOWS DRIVERS PROVIDED (NO DRIVER REQUIRED FOR MACS)

Looks like the first USB interface using the latest generation XMOS chip (XCORE USB) with built-in USB.

Amanero PCM and DSD (Update)

This is an update to this post on using foobar to play both PCM and DSD files [link]

Playing PCM and DSD files with foobar:

After installing foobar2000,

From the foobar2000 website, download:

• ASIO support 2.1.2 or newer

UPDATES

Get to the “Super Audio CD Decoder” repository [link]

• Download the latest file from the foo_input_sacd folder
• Download the latest file from the foo_dsd_asio folder

When you extract the zip file you will find:

• foo_input_sacd.dll
• ASIOProxyInstall-x.x.x (application). This installs foo_dsd_asio

foo_input_sacd

This plug in shows up as “Super Audio CD Decoder” and allows you to playback the following formats:

• Playback of Super Audio CD ISO images, DSDIFF files and DSF files
• Converts DSD to PCM (if your DAC cannot play native DSD)

To install or update foo_input_sacd, just drag it to the components window in foobar and click “apply”

The control panel looks like this: you can select DSD output or PCM output (when converting DSD to PCM)

More on the different options: [link]

I tested the conversion of DSD to PCM, using both DSD64 and DSD128 files. The results were as expected:

PCM Conversion	Output Sample Rate for DSD64 Input	Output Sample Rate for DSD128 Input
44.1KHz	44.1KHz	44.1KHz
88.2KHz	88.2KHz	88.2KHz
176.4	176.4	176.4
352.8KHz	352.8KHz	352.8KHz

foo_dsd_asio

foo_dsd_asio is kind of a “meta-asio” driver. It is used by the sacd plug-in above as the output device and in turn foo_dsd_asio outputs to an ASIO driver for an actual device. Apparently the sacd plugin does not output directly to an ASIO driver, it must go through the meta-asio driver. (Actually, ASIO itself is a meta-device driver because it talks to the actual device driver)

For one thing, foo_dsd_asio handles the “DSD playback method”: for example, “DoP Marker 0×05/0xFA”. “DoP” means DSD over PCM. Marker 0×05/0xFA means use the marker (for DSD) as specified in the proposed “USB Link for DSD Audio via PCM Frames” open standard [link][link]. This “marker” method is predominantly driven by the MacOS since its built-in USB2 audio driver only supports PCM. On the PC side, there is no native support for USB2 audio so people use ASIO and ASIO can support both PCM and DSD streams. The Amanero board handles “ASIO native”, but other boards may require a marker on the DSD stream.

Thus, foo_dsd_asio has the following functionality:

• Handles DSD playback method
• Converts PCM to DSD (optional)
• Outputs to DSD-capable ASIO driver

To install or update foo_dsd_asio, run the ASIOProxyInstall-0.6.x.exe program.

I tested the PCM to DSD conversion. The latest foo_dsd_asio plug-in handles all sample rates as shown in the following results:

PCM Sample Rate	DSD64 Conversion	DSD128 Conversion
44.1KHz	2.82 MHz	5.6MHz
88.2KHz	2.82 MHz	5.6MHz
352.8KHz	2.82 MHz	5.6MHz
96KHz	3.07 MHz	6.14MHz
384KHz	3.07 MHz	6.14MHz

AMANERO FIRMWARE/DRIVER UPDATE

Recall that previously ASIO4ALL was used because the Amanero lacked native ASIO support. Amanero updated the firmware and released ASIO drivers.

For instructions on enabling native ASIO playback, you can follow this excellent post:

Amanero ASIO [link]

After updating the Amanero device with ASIO support you do the following:

Fist set the output to be foo_dsd_asio (in order to support DSD output, and also PCM since this is the output device)

And then in the foo_dsd_asio configuration screen, select the Amanero board.

TIPS FOR UPDATING FIRMWARE

Erase firmware

1- Plug board into USB port

2- Short the pads as shown for at least 1 second (I used a paper clip)

3- Unplug the board

Download and Install Atmel device driver

1- Download and unzip the update tools from the Amanero web site [link]. You will get several files: a device driver for the ATMEL chip, a configuration application for updating the firmware and some other files.

2-Plug the board into a USB port. At this point the device is completely unidentified. You may get a prompt to install a driver or you may not. Following is the manual installation of the ATMEL device driver:

3- Open the Device Manger under the System control panel. The device shows up as “unknown device” as shown below

4- Right click on the unknown device and select Update Driver Software, indicating the location of the driver which is in the folder you downloaded. Your Amanero board is now a “AT91 USB to Serial Converter”

Your are ready to update firmware

1- Ensure that you have erased the firmware as shown above, and ensure that the device is identified as “AT91 USB” as a port as shown below:

C-Media CM6631A-based USB-I2S Interface

Got a hold of  DIYINHK’s C-Media based USB-I2S interface a while back, and it is just now I got around writing something about it.

This is based on the newest USB2 audio chip on the block, The C-Media chip is the CM6631A. This version in turn is the newer, the “A” version of the CM6631 chip which has been implemented in several recent products. The CM6631A differs from the more common (and older) CM6631 in that it supports 176.4KHz sample rate. All other features are the same as the CM6631.

According to the product info page [link]:

USB 2.0 Asynchronous operation (every one does this nowadays)

Up to 192KHz / 32bit

Very capable set of input/output (the implementation reviewed here only implements USB input and I2S output)

• 2 pairs I2S or Left-Justified serial audio output interface
• 2 pairs I2S or Left-Justified serial audio input interface
• Built-in 192K/176.4K/96K/88.2K/48K/44.1KHz and 16/24-bit SPDIF transmitter
• Integrated 192K/176.4K/96K/88.2K/48K/44.1K and 16/24-bit SPDIF receiver
• Supports SPDIF IN-to-OUT loop-back path for signal transforming between TOSLINK and RCA connections

I was able to find an older version of the datasheet for the CM6631 which is pin compatible with the DM6631A [CM6631_Datasheet_v0.8]

It can be seen from the specifications that a more capable system can be developed. For example, a 4-channel I2S output driving two DACs. (allowing performing digital crossover functions in the PC)

DIYINHK USB Interface: CM6631A (with the “A”)

Top

Bottom. Uses the CM6631A

DEVICE DRIVER

The vendor provides a device driver [link]

Other sources: the latest version of the driver is a unified version for the CM6631 and CM6631A devices, thus available from other manufacturers using either the 6631 or 6631A part (likely they all offer the same versions. some manufacturer may be faster than others in offering newer versions):

• Emotiva [link]
• MHDT Labs [link]
• Schiit [link]

I tried the Emotiva provided driver and it works. Here is a screen shot:

FIRMWARE

There are two versions of the firmware as discussed here [link] and here [link]. However, these versions seem to be related to the SPDIF features of the chip. For this board, which only supports I2S, I don’t think these versions of the firmware matters. Note: according the tdtsai [diyaudio], the developer for the driver s/w, the firmware for the CM6631 is not compatible for the CM6631A.

• Firmware 0101 PID 0×0319 can output to SPDIF via CMedia ASIO, but it will never passthrough DTS and AC3. I2S and SPDIF-Out work simultaneously
• Firmware 0108 PID 0×0314, using current drivers, will not output to SPDIF via ASIO, but it can passthrough DTS and AC3 correctly. I2S and SPDIF-Out are reported as different devices (so one output at a time depending on which one you choose)

SALIENT FEATURES

Two ultra low noise regulators: the TI LP5900 [link]

Uses high frequency 45.1584 MHz and 49.152 MHz oscillators to derive the audio frequencies (the manufacturer indicates that these are sourced from Digikey, thus ensuring their quality). This is unique as most devices use half that frequency or lower.

No markings? According to the datasheet, this seems normal. The product number is in the box or reel.

The oscillators output are available to be used as master clock for the DAC. The higher speed oscillator are in the “sweet spot” frequencies for ESS Sabre DACs for synchronous operation.

Since the board does not switch the clock lines, you can only select one of the clock lines to feed the ESS DAC. In this manner, with some of the sample frequencies the DAC will operate in synchronous mode and with other sample frequencies, in the normal asynchronous mode.

For example, if you chose to use the X45 line (45.1584 MHz) as the clock for the ESS DAC, then when playing 44.1K, 88.2K and 176.4K the DAC will operate in synchronous mode and when playing 48K, 96K and 192K, the DAC will operate in asynchronous mode.

You could manually switch the clock lines but this is not only impractical, but it could also upset the DAC requiring a reset.

Easy bypass of USB power. CAUTION: Maximum input voltage for the local regulators is 5.5V

According to the manufacturer, the design employs solid ground plane (a must for high speed digital circuit) and no vias in active circuit (via inductance always create jitter problem). This is apparent from the photo below and in comparison with other designs. The overall layout is very clean and compact.

Datasheet: [link]

Jitter

The datasheet for the Xpresso clocks is actually very extensive, and the jitter measurement is equally extensive. The phase noise plot is included. I have shown here the comparison with the Crystek CCHD-950-80 MHz which is the oscillator I have in my version of the Buffalo II DAC:

Using the 62,5 MHz curve, we get a phase jitter value of 6 psec RMS (10 Hz – 1 MHz). The Crystek CCHD-950-80MHz has a jitter value of about 2 psec RMS. However, at the lower offset frequencies (the ones of interest to audio performance) the phase noise is not very different from that of the Crystek clock which is a good thing.

INTERFACING WITH BII DAC

There is something “a bit odd” with this interface: According to the specifications:

DATA	LRCK	BCLK	MCLK
16/24bit	44.1kHz	5.6488Mhz	11.2896Mhz
16/24bit	48kHz	6.144Mhz	12.288Mhz
16bit	88.2kHz	5.6488Mhz	22.5792Mhz
16/24bit	96kHz	6.144Mhz	24.576Mhz
16bit	176.4kHz	11.2976Mhz	22.5792Mhz
16/24bit	192kHz	12.288Mhz	24.576Mhz

2X BITCLOCK

BLCK is the same for both 44/48K and 88/96K. This means that for 44/48K sample rate, the data is running at 128fs and for the rest of the sample rates, it is running at 64fs.

Even though the Sabre32 DAC specifies BCLK to be 64 fs, it appears that it also supports  128fs. Why? because when I play 44.1KHz material, the DAC reports 88.2KHz sample rate and it sounds perfectly fine. (The sample rate reported by the Sabre32 DAC is  based on the frequency of the bitclock, the DAC reports 88.2KHz for 44.1K material)

The sample rate for the higher sample rates are reported correctly by the ES9018 DAC.

Is this a “common” feature supported by other DACs?

The AK 4399 supports both a 64fs and a 128fs bitclock:

The Wolfson 8804 also supports 128fs Bitclock -in DSP mode (p. 44):

So it seems that a 128fs bitclock is not so strange after all. I am not sure if any other dacs support 128fs bitclock, but the Sabre32 DAC definitely does.

OTHER NOTEWORTHY IMPLEMENTATIONS

C-Media has been in the computer audio business since its inception. According to their website, their world’s first accomplishment are all related to audio. Its claim to fame is probably the ASUS XONAR series of PC audio cards and interfaces. The latest ASUS XONAR ESSENCE ONE uses the CM6631 part as shown here (There is a review of the Essence One here: [link]):

The Schiit DACs also use the CM6631 part for their USB option board. As discussed here [link] it does not support 176K material because of hardware limitations in the 6631 part. The “A” part supports 176K sample rate.

The Emotive XDA-2 reportedly also uses a CM6631 chip for the USB interface [link]

The MHDT USB Bridge also uses the CM6631 chip [link]

Have yet to see any commercial implementation using the CM6631A part.

NEW VERSION

diyinhk turns his designs very quickly. This version of the board has been replaced with a new version having isolated I2S [link]

MAC USB 2.0 COMPATIBILITY

There are some reports and fixes to ensure USB2 compatibility with Macintosh computers: [link] with certain CM6631-based implementations.

This board does not suffer from the reported problem: there are no 3-pin devices near pin 98 of the chip.

Plugin this device into a Macintosh computer shows that it is indeed a high speed USB 2.0 device as shown in this snapshot of the CMEDIA device under the USB description screen

JITTER IMMUNITY  TEST

Here is a reported test of the CM6631A (implemented in a different device) showing jitter measurements with and without processor load and comparing the asynchronous nature of the USB communication vs a device using USB adaptive communication. [link]

In his conclusion, this device (as well as other USB-asyncrhonous devices) show great immunity against processor loading:

Bottom Line: Don’t worry about jitter! It’s more than likely inaudible in a modern computer system and with decent (not necessarily expensive) audio gear. I see no evidence that high CPU/GPU load makes any difference to jitter. Isolating your DAC from electrical noise polluting the analogue output seems much more important.

Reader Contribution: Musiland Review

Here is a nice review from Sam5050 on the Musiland devices

Part 1 can be found here: [link]

Just finished my review on the following Musiland devices used as headphone amps/DACs and/or PC interfaces.

• 2012 Monitor 01 USD (as USB to SPDIF interface only)
• 2012 Monitor 02 US Dragon Edition (as USB to SPDIF interface and as a DAC and as a headphone amp)
• 2012 Monitor 03 US Dragon Edition (as a DAC and as a headphone amp) [link]
• 2012 Monitor 03 USD (as USB to SPDIF interface only)
• older Monitor 02 US (used as USB to SPDIF interface and DAC and Headphone amp).

(The “D” in USD is “digital interface only”, no analog outputs)

TEST ENVIRONMENT

Here are the computer systems used for testing:

Office system

Win 7.0 64bit/PC i5 Processor/ 8G Ram, 4 T of storage (2 -1T HDs and a USB 3.0 2-T WD external), SOtM CPU fan and PS filters, powering the USB 3.0 with a AQVOX linear USB 2.0 PS. Cardas Clear USB cable. Foobar2000 v1.1.8 – tried various output schemes, including Musliand ASIO, Musliand KS, JPlay, SoX upsampler, various bit depths and latencies. DAC – APL (6 AKM 32-bit DACs per channel, linear independent PS, ECC99 tube output).

Main System

Win Vista 64bit/Core 2 Quad Q9300 4G/ 4 Tbs – (2- 1T HD and a 2-T HD). Using a SOtM tX-USB Audiophile PCI to USB Audio Card/and a fan-less ultra high quality PC supply in my main PC music server, SOtM CPU fan filter. Stilnote USB 2.0 USB cable. Foobar2000 v1.1.8 – tried various output schemes, including Musliand ASIO, Musliand KS, JPlay, SoX up-sampler, various bit depths and latencies. DAC – Xindak DAC5 with NOS Siemens Cca (1960′s) tubes.

The rest of my system included Reference 3A Royal Masters (main), Dulcets (office), same Class A MOSFET hybrid amps (6922 pre section), Tellurium Q Ultra Blacks (main) TQ Blacks (Office), Synergistic Research Power Chords and Digital RCA cables on each.

I used my amp/speaker system and headphone system over many months and tweaks.

Music

Mostly Alt, some vocal, classical and jazz. Redbook tracks were up-sampled to 32/176k w/SoX ), native high resolution played without up-sampling. Test tracks are too numerous to list but included redbook wave files (burned using EAC), Vinyl played on a SOTA analog rig and recorded at high Res (32/176K), native DxD (32/352k)(curiosity of L2) and DsD (PCM re-sampled in foobar).

Here are a few favorites: Florence and the Machine – Dog Days, David Gray – Please Forgive Me, Joni Mitchell – Court and Spark, Brand New – Degausser, Them Crooked Vultures – No One Loves Me and Neither Do I, Wiz Khalifa – Work Hard, Play Hard, Zedd -Spectrum, BOB – So Good, David Guetta – Titanium, Joseph Haydn – String Quart in D, Op 76 (DxD), From Let Us Garlands Bring – Come Away Death (DxD) etc…

APL DAC as implemented inside a Denon 3910

The AKM 4397 DAC boards

The modded Denon 3910 with the APL DAC

Tube stage and Lundhal amorphous core transformers

SOtM-PCI to USB Audiophile Card [more here: link]

Xindac DAC 5

USED AS USB TO SPDIF INTERFACE

Bottom line – the 03 USD is an exceptional Interface. In fact, it beat out the M2Tech EVO/with Acopian Linear PS (the best I have owned so far out of many)! Which I have now sold. I bought another 03 USD for my office system. It has become my reference. Wonderful sound, great interface software! So flexible and stable – surely beats the M2Tech non-interface.

Well, to summarize the sound of the Musiland 03 USD as an interface is just plain outstanding! Incredible detail, while always supremely musical. This is THE BEST value in high end audio – never even reviewed by a major publication (sad)! The sound stage is deep and wide, with a wonderful texturing of instruments – each presenting a holographic image. Great PRAT, dynamics with excellent bass clarity. Everything you could ask for.

One note – highly sensitive (especially using headphones) to settings, for example in Foobar the simple changing of bit depth or buffer length in the output setting window has a significant effect on the sound (32 bit sounds best on most recordings, 260-1000ms buffer setting sounded the best).

It was system dependent on the ASIO vs Kernel Streaming output. On the office system ASIO; on the main system KS had the greatest clarity. Somewhat a tradeoff of clarity (KS) vs smoothness (ASIO). You really need to play around with these setting to get the right blend. It is worth it…the difference between sounding good and magical!

I can not say enough good things about the 03 USD – how great this interface is when properly tweaked.

The Musiland Monitors with digital output are the best USB to SPDIF interfaces I have heard (they are the new standard). In other words better then the M2Tech EVO, Hi-face, Audiophilleo 2, John Kenny Mk 2, etc… That I had tried before. – answer = YES! Beat the best by a hair – the EVO,with a vastly better control panel.

The 2012 Monitor 01 USD (as a PC interface) it was better then the 02 US Dragon, but not nearly as good as the 03 USD

USED AS DACS

Both as DACs not nearly as good, (as described above, they are much better as interfaces). The sound stage compressed, tone thinned, a bit of edginess, etc… One note the DxD native files (24 bit/352K) played perfectly on both using the analog DAC outputs (using Foobar, no re-sampling), and sounded really good. When compared to the down-sampled (176K) run through the tube DACs it was a push. The tubes more musical, richer in tone, the SS DACs more lively (and I mean lively with DxD files!!!).

As a DAC, these Musilands really can’t compete with a top end tubed DAC. Even a moderately priced one like the Xindak DAC5 with a high quality tube replacement (NOS), is in a whole other class. The Xindak can be had for $500-$600 bucks adding another $100 for a good NOS 6922 and maybe $150 for a good power cord, you have a really excellent DAC. THe Xindak also has a opamp based SS output and also a switchable upsampler.

Obviously for a lot more money you can get something like the APL – 6 32bit AKM DAC per channel, linear power supplies, (my older version has the ECC99 tube output stage), a pro quality SPDIF receiver chip (this can handle 192K inputs with ease, the Xindak is limited to 176K), Lundahl transformer coupling (no caps), etc… Now you are in a whole other league.
Sound and money wise.

I had a MiniMax DAC plus which used the ESS9018 and offered both a tube and opamp based output. It had some nice features like Sabre ES9018 DAC chip, Separate Power Transformers for digital and analog sections, M2Tech OEM 24bit 192KHz Async USB input. It sounded good, about were the Xindak 5 was (with NOS tube), but much more expensive. So I sold it. The APL is in a whole other league. So much for the cult of the “Sabre ES9018″ being the best DAC chip around!

There are many fine high end DACs, like the DCS, the Lampizator, MSB etc…

Musiland 02US Dragon Edition

The Musiland 03US Dragon Edition

USED AS DAC PLUS HEADPHONE AMP

On the Headphone side, my listening system is a Pair of Senn HD800s (upgraded Warren Audio cables). Woo Audio WA6SE (with upgraded caps, 6FD7 NOS tubes, NOS 1952 5u4g rec). In comparison the Musiland 02 us Dragon and the 03 US Dragon were not even close. The 03 US Dragon was better, but had the same flat sound stage, thin tonality, edginess in the upper frequencies, hollow bottom. I do use the 03 US Dragon with my laptop as a portable “on the road system” with some Phillips noise cancelers. Now it is not fair to compare $1000 tube headphone amp to a $200 one, but I wish I could say it was a closer match.

The sound from the HD800/Woo combination is incredible! The presentation is different from the amp/speaker system, a much more upfront (1st row vs 20th row) sound stage, but the level of detail retrieval is unsurpassed. I have heard sounds from recording that I have bee listening to for 20 years! Spooky good!

I tend to like the tonal richness, sound staging and musicality of the tube variety – best sound of the money.

MONITOR 02US DRAGON

I did own the older version of the Monitor 02 (the one hard AC wired), the new 02 Dragon beats it in every way.

I have to say I do like the design concept and functionality of the new 02 Dragon.  It has BOTH the SPDIF RCA output to feed an external DAC and the analog outputs (both RCA and dual Headphone jacks).  This makes it a very versatile unit.  I also liked the 02 Dragon’s built in volume control knob.  Great as a extremely portable unit.  You also have the power option of USB or 9V DC.  The Musiland Windows Control Panel, makes it  breeze to switch between digital and analogue outputs, even balance L/R channels.

I really wanted the 02 Dragon to be the winner sound-wise – I really love this design -but unfortunately it is inferior to both the USD 03 as an interface and US 03 Dragon as a DAC/Headphone amp.  It has a bit of a nasty edge to the treble, and a flattish sound stage.  The use of the Acopian linear PS did help, but not enough to my ears.

Gave the 02 Dragon to my son in college -  he loves it!  It is much better then the laptop headphone output!  It would be a great gift for someone not so obsessed with sound quality.  Add a pair of nice amped speakers (Bose) and some good headphones, and you have a really neat little audio system.

SUMMARY

Are the Musiland Monitors with digital output the best USB to SPDIF interfaces I have heard (new standard). In other words better then the M2Tech EVO, Hi-face, Audiophilleo 2, John Kenny Mk 2, etc… That I had tried before? – Answer = YES! Beat the best by a hair – the EVO, with a vastly better control panel.

Are they reasonably good as an analog-out DAC? With the huge advantage of being able to easily handle native 24/352K files, could they match some really good tubed DACs? Answer – definitely NO! And that would be asking too much – I agree!

Are they reasonably good headphone amps? Answer= YES and NO. They are in no way in the same league as say a Woo Audio WA6SE, or even the EarMax, but they are pretty good and very portable.

Amanero Reclocking: 352.8K/384K

(1/28/13) Important Update: See comments section regarding reclocking with the DACs 100 MHz clock.

Even though the Amanero USB  interface supports 352/384K sampe rates, if this high sample rate bitclock is reclocked with the original clock signal, the output is completely silent The DAC cannot see a signal to lock on. Here is the reason why:

Here is the truth table of a flip flop: the output (Q) reflects the input (D) on the rising edge of the clock (CLK) signal.

Here is a diagram illustrating the re-clocking of two signals: a 175.4 KHz sample rate signal and a 352.8 KHz sample rate signal. Keep in mind that at 352K sample rate, the frequency of the bit clock is the same as the frequency of the 22.5792 MHz on-board clock. (352.8K x 64).

Shown in red is the clock signal taken straight from the clock and fed to the flip-flop. In gray are the input signals coming from the CPLD and fed to the flip-flop. Since there is a propagation delay in the CPLD, they are shown with a delay in relation with the native clock signal. In green is the output from the flip-flop.

If we follow the truth table above, we can see that at 176.6K, the output can still follow the input but with the edges coinciding with the edges of the original clock signal. But with the 352K signal, we see that at the rising edge of the original clock signal, the input is always at the same value, hence the flat output.

At 352K, the Buffalo DAC correctly reports “No Lock”. Indeed, there is no signal to lock to.

Thus if using reclocking with the original clock signal, you will loose the ability to play 352k/384K, unless Amanero releases a new board with clocks with frequencies 2X the current values, or you manually bypass the reclocking flip-flop.

ANOTHER WAY

Rather than reclocking with the “source clock”, one can reclock with the “destination clock”. Russ has experimented with reclocking the I2S lines with the Buffalo 100 MHz clock (see comments below) with good results. Reclocking with the destination clock (the clock of the Buffalo DAC) would require reclocking all 3 I2S signal lines to ensure bit-perfectness.

“Destination clock” only applies to DACs that normally operate in asynchronous mode, generating their own clocks. I think only the ESS DACs would operate in this manner. Most other DACs require a master clock as required input.

The circuit, with Potato flip-flops would look something like this.

DSD 5.6MHz

Tested DSD 5.6Mhz with the Amanero board with the bit-clock reclocking mod and works perfectly. Got the sample track from Design W Sound (link in the Free Hi Res page or http://designwsound.com/dwsblog/2012/09/audiophile-jazz-prologue-part-04/). Design W Sound also has 384KHz sample tracks.

As with the DSD 2.8MHz tracks, the lower DPLL settings don’t work well (and I don’t know why as the bitclock for 2.8Hz DSD is the same as the bitclock for 44.1K PCM)

Notice the sample rate indicating 88.2K which is the DSD bit clock (5.6 MHz) divided by 64. I will change the code to correctly reflect the DSD frequency. The “DSD” indication confirms that the stream received by the DAC is DSD. This value is read from the status register of the DAC itself.

Also ignore the label “PC-LOW”. That is just the name of the input, and can be named anything. “70K” is the IIR filter for DSD and there are other values to choose from: 60K and 50K. “SLW” is the PCM FIR filter which probably does not do anything for the DSD stream.

Congrats to the Amanero team. Very nice board and nicely priced. Awaiting for version 2

More Tweaks on Amanero USB Board

Still striving for unlock-free behavior, I implemented what Mr. Abraxalito recommended:

Be careful with ultra-fast CMOS logic – it does require extremely good decoupling. Inside CMOS devices the transistors crowbar the supplies (quite literally) every clock transition. I discovered this with 74AC chips many years ago – even there I was using a multilayer PCB. I suspect the Potato chips are considerably faster! Get the smallest package size you can solder, decouple with 0603s and use a ferrite bead on the positive supply to reduce the bounce on the GND. Even with these precautions you’ll get some jitter from the bounce on the positive supply. Good luck! [link]

Before:

After the mods:

Basically I added a ferrite to Vcc and a capacitor to GND. Effectively, including with the previous bypass capacitor, it is a CLC filter which is symmetric from either side of the supply line (meaning it should filter noise coming into the flip flop and noise coming out of the flip flop through the power line).  I also paired the bit clock line with a ground wire to provide some shielding. Pretty standard and common sense tweaks.

Unfortunately I messed my my clean and professional looking implementation . If I were to do it again, I would put those components under the board.

(Update 12/3/12)

Based on feedback from readers, I’ve replaced the “magic red cap” ) with a much smaller ceramic cap

RESULTS

Seems very positive: I did the first interval for the unlock test, from midnight to 8:00 AM and there were Zero unlocks. It “survived” the “morning hiccup” where at the start of the day, electrical activity would cause one or more unlocks… We will see what happens in the afternoon.

Unlocks before:

Unlocks after: (8 hrs play time)

after 20 hours, the results are really good. Have never gotten this kind of performance in the past: ZERO unlocks (except, of course for the warm up time).  Here is the plot showing the full 20 hours of play time. Well, there is really nothing to show

This turned out a very effective mod, even with much less than ideal components. If done correctly (proper PCB with ground plane, proper bypass, compact layout, etc), the results would be even better (and finally beyond my “measurements” – not really, I just use higher sample rate material). Anyone wants to develop a small PCB?