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AA Audio has a new website.

Useful contents from this blog (i.e. tips on computer audio playback) will be moved over.

This is the new brand logo for AA Audio.

AA Audio is a brand name, not a company name. Products will be sold under ‘The Optimization Expert PLT’.

AA is the initial for my given name, Anwar Ali. The AA initial was drawn in slanted sinusoidal form with shadow (representing audio waves). The horizontal stroke for characters AA initial is filled by “AA Audio” text.

On second look, the slanted sinusoidal wave form can also be seen as AAVM; the V is in the middle and M is the whole wave form. AAVM is the initial to my full name, Anwar Ali Vali Mohamed.

I thought of using AVM initially. My late father used AVM for his business since my grandfather’s name started with an A (Abdul Karim). So AVM can be the short form of AAVM. Unfortunately, there is already a German audio company with AVM brand, with full business name Audio Video Manufaktur GmbH.

Yes, the show was confirmed last night. Thank you to Wilson Teoh for including a newbie hi-fi entrepreneur into the show. This short post provides a preview of what will be demonstrated during the show.

Flagship AA Music Streamers

With three USB2 Isolator prototypes in good working condition, plus the TI’s EVM board with modifications, there will be two flagship music streamers on display to feed two different DACs: FCPGA-based DSD 4x upsampling DAC (Marantz SA-10) and a newly purchased R2R-based DAC. Another flagship streamer will be used by the other exhibitor sharing the same function room.

How a reasonably good CD/SACD player sound quality compares to using its internal DAC through USB connection with AA music streamer will be demonstrated using Marantz SA-10.

Now about the new R2R DAC. There will be not enough time to get the new R2R DAC to fully break in – it needs 500 hours. It will sound better during the Gelombang show in Kuala Lumpur in early August. Picture below was sent by the seller in Hong Kong during quick check before shipment, tested while still wrapped in plastic. Any guess what DAC is this?

Experimental Entry-Level AA Music Streamer

The earlier attempts of using Fractal Design Node 202 computer case resulted in overheating issues due to undersized heatsink to fit within Node 202 case. The selection of computer case is still pending. However, for this show, an experimental two-case solution will be shown. The idea is to gauge whether there is a market for such product. The USB2 Isolator prototype will be used here.

If there is enough interest (i.e. its sound quality is good enough and acceptable), a new custom computer case will be designed and developed. It will be offered as a single-case product.

AA USB Audio Cable

I was ready to purchase another expensive USB Audio cable from UK. However, I decided to experiment building the cable myself. Tried different solid-core pure silver cable with different gauges and from different manufacturers. Also tried different USB A and B plugs – they really matters and make very big difference to the sound quality.

The characteristic impedance of the differential data lines were measured using Vector Network Analyzer. The goal is to make it as close to 90 ohm impedance by adjusting the twists for data lines.

If you bring your own USB Audio cables, I will let you compare and hear the difference with the recently developed AA USB Audio cables shown above.

The AA USB audio cable will made-to-order per length specified by customer. Please note that for USB audio cables, the shorter the better. The data lines use solid core 5N pure silver wire. Each cable will be hand-made with the characteristic impedance measured.

Price

Details on price and configuration options will be published before the show.

You can leave your comments here.

There will be a hi-fi show in Penang 11-12 June 2022 which is only 3 weeks away. Luckily, with the completion of USB2 Isolator prototypes, we are ready to demonstrate AA Music Streamer with the isolator.

Just a few days before the weekend of Eid Mubarak festive holidays, the semi-assembled prototype PCBs (with 0402 capacitors assembled) arrived. We purchased only 4 units of Texas Instrument’s XISOUSB211 pre-production samples (limited to 2 pcs per order), hence at most only 4 prototype boards can be made. The hand-assembled boards were completed last week but the troubleshooting and testing were only completed this week.

There were issues with TI’s footprint used in PCB design – the pitch was 0.66 mm (incorrect) when it’s supposed to be 0.65mm. It can be clearly seen from the above picture that not all pads were aligned correctly to the chip. With careful placement and soldering, there were no bridging. The PCIe brackets custom-made by Gompf Brackets Inc, USA were reused from the previous USB filter.

Swiss-made Audio Consulting’s 24 AWG solid-core silver wire with cotton sleeving (for data lines) and USB2 4-way IDC connectors were used to connect motherboard’s internal USB2 header to the USB2 Isolator input (left side of above picture). A dedicated 5V isolated LPSU (with floating ground) feeds the peripheral side of the isolator. This 5V supply previously powers USB cards like JCAT USB XE and also the passive USB filter.

From the rear of Streacom FC10 case, the look is very similar to the previous USB filter. Connection to USB DAC is made through the PCIe bracket of USB2 Isolator, not motherboard’s USB2 ports.

I will not comment on how it sounds. Please come and visit our booth at Penang hi-fi show on 11-12 June at Ascott Hotel, Jalan Gurney, Penang. Formal announcement of the event is coming soon.

Please note that TI has not released the ISOUSB211 chip. The pre-production sample XISOUSB211 is no longer available for purchase. I hope it will be released to production soon so that we can start selling AA Music Streamer with the USB2 Isolator.

Please leave your comments here.

This is the first time I evaluate USB2 high-speed isolators. I have evaluated USB2 Redriver and USB regen/reclocker cards. USB2 Redriver has little improvement to SQ. USB regen/reclocker PCIe cards have its own sound signature and the 5V DC supply really matters.

Most USB isolators were designed for rugged industrial use, but it works for audio as well. The isolation voltage ranges between 1kV to 5kV. Budget USB isolators like Topping HS01 only provide Ground isolation unlike the industrial ones which provide isolation for ground, power and signal lines.

The original Intona USB Isolator from Germany in crude plastic case was designed for industrial use. One person tried it with USB Audio signal path and discovered it indeed improves the sound significantly. The news spread quickly. Intona has the newer versions in metal case which can even improve Taiko Audio SGM Extreme USB Audio output.

Why the need to isolate USB

In industrial use, USB isolation was meant to protect computers from dangerous voltages in rugged environment, for example, PC-based oscilloscope used in automotive. In audio use, it’s to isolate the noisy DC ground of the computer power supply. Some high-end DACs already have USB Ground galvanic isolation inside the USB receiver. From my experience, using industrial-grade USB isolator can improve the sound further even when the DAC has USB Ground galvanic isolation.

The Need for USB2 High-Speed Isolators

High-res music in PCM and DSD requires USB2 to operate in 480Mbps high speed mode. Most of the earlier USB2 isolators provided by chip makers like Analog Devices only work in USB2 low speed (1.5Mbps) and full speed (12Mbps) modes, hence they are not suitable for USB audio use. One of the integrated circuit (IC) for USB2 Isolation with support for high speed and used in many USB Isolation products (including Uptone ISO REGEN) was Silanna ICE08USB which was introduced in 2015 but discontinued in 2019.

In 2021 Texas Instruments (TI) announced their ISOUSB211 product to be available in Q3 2022. Analog Devices recently has the ADUM4165/4166 USB2 high-speed isolators available.

USB2 High-Speed Isolators available for purchase

The list here is not comprehensive but includes the popular products. Most of the earlier products based on Silanna ICE08USB are no longer available for brand new purchase, which include:

• Uptone ISO REGEN
• iFi Nano iGalvanic3.0
• Singxer UIP-1 USB Isolator

The following are the products we can buy as of March 2022:

• Intona 7054-series USB2 and 7055-series USB2/USB3 Isolators
• ALLDAQ ADQ-USB 3.0-ISO-PS / 3.0 Isolator incl. Power Supply
• Virtins Technology VT USB-ISO-480 USB High Speed Isolator (>800 mA, comes as USB dongle)
• Topping HS01 Ground Loop Isolator

Three of the companies listed above make industrial products. As mentioned earlier, Intona (Germany) makes USB2/3 Isolators for industrial use. ALLDAQ (Germany) and Virtins Technology (Singapore) are both PC-based measurement and instrumentation companies making products like oscilloscope.

Topping HS01

The HS01 only provides USB ground isolation. It only supports 480Mbps high speed. I have done quick listening test with another friend. My recommendation – DO NOT waste your money and time with this product.

TI’s ISOUSB211EVM

I bought two of these (only 1 unit allowed per order) since modifications need to be made. My first hand experience with the default settings – I was surprised by the improvement in layering, decays and details without being too digital. The sound is less congested. I prefer the sound when using TI’s ISOUSB211EVM compared to Core Audio USB P24 OCXO and JCAT USB XE cards.

EVM Modifications

Ideally the 5V from motherboard should not be used, but the default EVM configuration uses 5V from motherboard’s USB and isolated DC-DC converter to generate 5V to the DAC side. The default configuration also uses internal LDO to generate 3V3 from VBUS1 (input side) which is suboptimal. Changes made:

• Disconnect 5V from USB A connector
• Use external LDO to generate 3V3 on the input side
• Disable 5V LDO (input voltage from DC-DC isolated converter) on the output side
• Add terminal block for separate 5V inputs on input and output sides

2-rail 5V LPSU

I build my own 2-rail 5V LPSU so that each side of the board is powered independently. Here are some pictures. The encapsulated transformer is from Nuvotem Talema 80VA with dual 9VAC outputs.

The tests were done using evaluation board with makeshift setup like shown in the pictures above. Additional modifications were done by adding Vishay bypass capacitors at the 5V terminal blocks.

Another EVM board was purchased for comparison with the modified version. In its default configuration, the sound is totally different.

Intona 7055-C USB 3.0 SuperSpeed Isolator

Daniel Staemmler of Intona Technology could not confirm this will work my XMOS-based DAC, but he heard no complaints. Choosing 7055-B versus 7055-C was a tough decision since in What’s Best Forum, some Taiko Audio SGM Extreme owners prefer 7055-B (good for vocal) while 7055-C is said to be more suitable for orchestra and complex music. 7055-C has dual LT3045 regulators with lower noise measurements and supports up to 1A without using external power supply. 7055-B supports 0.5A only (single LT3045). There is Micro USB port if the connected USB device requires more current. In the end, I bought 7055-C and luckily it works well with my Marantz SA-10 used as USB DAC.

The Intona USB3 Isolator is indeed very small in size, easy to place behind DAC or music streamer. I prefer the sound when placed near the streamer. The USB2 port used is the one with separate 5V DC, called USB filter.

Analog Devices ADuM4166

A week after online order placed, I received Analog Devices EVAL-ADuM4166. Its operation requires 2 rails of 5V DC supplies, which I have already built. This board requires no modifications. The 5V DC terminal blocks are already on each side of the PCB. The jumpers were set to 5V at each side, with the 5V at peripheral side powering VBUS.

ADuM4166 was selected instead of ADuM4165 as the external 24 MHz crystal is on the peripheral side, hence more suitable for USB Audio. The design makes it possible to use higher quality 24 MHz crystal or clock. The only surprising fact about ADuM4165/ADuM4166 family is that they are not USB2.0 certified, but per my tests it works with USB Audio.

Preliminary Listening Impression

With Intona 7055-C in my own system, the sound is very high resolution. Definitions and separations are very good. However, after long listening, it can be a bit fatiguing. The sound feels a bit unreal. With TI’s ISOUSB211, the sound is very musical but with slightly less resolution. Vocal sounds more realistic with TI’s ISOUSB211 and layering is really good. More details unheard before can now be heard, most likely due to lower noise floor. AD’s ADuM4166 surprisingly degrades the sound compared to using my own USB filter.

I also had the chance to test the USB isolators with Dr Azmel’s system in Taiping. DACs include Chord Hugo TT2 and M-Scaler combination plus Matrix Audio X-Sabre 3, mainly used for DSD. The Chords were tested with AA Streamer using USB input from JCAT USB XE but the sound was not impressive as reported by Dr Azmel. With TI’s ISOUSB211, the sound from the Chord components is good. When X-Sabre 3 is used, the sound is more musical, less fatiguing, and better layering. With Intona 7055-C, the sound is high resolution with good definitions and separations but lacks musical soul, consistent with what I heard with my own system. We also tested AA Streamer JCAT USB XE output into Denafrips GAIA then its I2S output into X-Sabre 3. We heard colored sound and we both do not like it.

Next Steps

The plan is to develop stand-alone USB2 Isolator based on TI’s ISOUSB211. It will include the required low-noise linear PSU to power each side of the USB2 Isolator and power the USB VBUS (DAC side) independently. Stay tuned.

Please leave comments here.