Combining Amp & Dac as One unit

Its been long since my last update.

Brought the headphone to my office since its very under utilised at home.

The following mod took place due to space constraint on my work desk, so the unit was to be mounted below the desk surface.

1. My idea was to mount them upside down to decrease the profile.
2. The heat sinks in each runs quite hot. So some form of cooling would be a great idea.

Its great that the Amp card has a 15V output. I could run a 12V fan with no problem.

Since i try not to buy new parts, i recycle whatever i could get my hands on. The CPU cooling fan was tested at first. The air flow is great! The only complaint was: its too noisy!

Here aluminium plates are introduced to bind the two separate units as one.

Here is the final product.

But its a tad too noisy still. My friend suggested to do without the fan, flip the unit on its side, allowing hot air to vent naturally upwards. It works.

Another mod was to protect the cables with the plastic braid sleeve which was surplus from my last trip to the audio cable shop. Now i found a good use for them!

Here you could see the unit sitting under the desk.

A final and last tweak: I updated the unit with a large fan with psychedelic colour leds. This was also from my computer parts.

The fan EXTRACTS the air from the unit. I found this to be a more efficient option. Previously i blew air into the unit. Probably choke and resonance from the air in vs air out, the CPU cooler fan was noisy. With Extraction, the unit's noise isn't really audible while listening.

The unit actually feels extremely cool to touch.

A success!

Enjoy listening ya....

Timber's RCA Interconnect

Featuring 8" / 20 cm RCA interconnectors terminated with Neutrik heads

Specification
Cable Type and gauge: Secret
Solder type: Secret
Cable burnt and tested

DIY RCA Inter-Connect (RCA IC)

Construction my own RCA IC

This is my final construct of RCA IC for my DAC and AMP.

The common solution used for RCA cable is the 22AWG Belden 1505F.
The spec sheet can be found here.

Upon encouragement from Timber, i proceeded with the order of Neutrik RCA heads.

Mfr. Part No. NYS373-2

Neutrik adapter was used on the Beyerdynamic T1 too.
So i figured it would be good enough without having to spend too much and focus on the cable itself.

Having soldering iron and solders gave me motivation to try without having to spend extra.

Construction of RCA Cable

For my cable selection, I had a length of spare marine cable around. It is 2.5 mm² cable.
It is approximately AWG 13 for this size.

Per core 2.5 mm². Solid copper core. Per core is d=0.7 mm x 6 strands.

I stripped the outer insulation, di-electric layer and steel wire braid, keeping the wire and PVC insulation.

The OD of the wire is 3.5mm with insulation PVC grade ST2.

The second layer is a flexible OD6xID4mm Polyurethane (PU) Air Tubing

The copper sheath is taken from my spare coaxial cable and it fits well on the blue PU air tubing.

Got the 2:1 shrink tube from audio store as well as extra RCA adapters as my order has not yet arrived.

The adapter is for small gauge wires only. To overcome my thick 7.5mm outer diameter, I had to remove the plastic insert.

To adjust the slack between the cable and adapter, i added another short length of shrink to beef up the thickness.

My first time soldering. Well, sacrificed two adapters while learning where to solder. The thick wire gauge is a challenge to work with.

The finished product. 10" length 13AWG interconnects. 

Yes, i know it is an over-kill with such a short & thick cable.

The freebie 1.5m RCA cable has resistance of 0.004 ohm.

The resistance of DIY cable is 0.000 ohm

Summary of Parts

13 AWG stranded copper wire with PVC insulation OD 3.5 mm

OD 6 x ID 4 mm Polyurethane (PU) Air Tubing as 2nd di-electric layer

Copper sheath of OD 7.5 mm

Shrink Tube 2:1 to finish the outer insulation

Neutrik NYS373-2 RCA adapters

On di-electric materials

http://www.pvc.org/en/p/electrical-insulation-characteristics

Foam High Density Polyethylene (HDPE) is the usual Di-electric for Belden 1505F

Grounding & Electrical shock

Whenever i touched the casing of my Amp and DAC, there is this tingling sensation which i knew was some sort of current leakage.

I did not know if this was normal since my Macbook Pro also had the same issue when it was running from the adapter. Having long hairs on my forearm, i do get electric shocks, much like shocks we get from static charges. Its an unpleasant feeling.

In this video above, the test pen lights up when it touches the bare metal casing for both units.

In this next video, a grounding cable was attached and the test pen only litted up when the ground was removed.


Hence i proceed to investigate the grounding for both units.
I realised only the DAC had no grounding. Since it was touching the AMP casing, naturally the AMP also litted up when the test pen touched it.

The earth pin is not grounded

Grounding is added onto the earth pin and connected to the casing.

Thereafter, when tested with the test pen, its all good. No more tingling sensation.

I do not know if leaky earth does affect the performance of listening, but at least it improved the handling by a great deal. No more shocks!

Iphone & External DAC Connection

First, for a DAC (Digital to Analogue Converter) to work with iPhone/iPad, the DAC must have a XMOS chip that is iDevice ready.

http://www.xmos.com/products/reference-designs/ipad

Extract from link
"The XMOS USB Audio Interface for iPad simplifies the design of products requiring USB connectivity to audio and control interfaces for Mac, PC and iPod, iPhone and iPad devices. Using High Speed USB 2.0, it allows high quality digital audio, MIDI and control data to be transferred between the host Mac, PC or iOS device and the XMOS interface."

You can find more details from the printing on the DAC chip to find out its compatibility if it is not spelled out by the product / manufacturer.

If the XMOS chip is unsuitable, a message will pop on the iPhone/iPad indicating that the DAC is drawing too much power even when some DACs have their own power.

Setup

Next, a "Lightning cable to USB Camera Adapter" is required to connect the DAC to the iPhone.

Lightning cable to USB Camera Adapter

For my case, I had the latest iOS 9.2 on the iphone 6S

(Jan 20, 2016 - iOS 9.2.1 proves to be better when it solves the clipping issue)

There are two ways to read FLAC files.

1. Reading FLAC files from NAS connected to router

2. Storing FLAC files locally in the iPhone/iPad and play directly

In both cases, I had to limit the iPhone volume to 2 bars below MAX and adjust the amplifier volume to reduce clippings.

PRO: 

1. This setup will allow max enjoyment without distraction of the macbook or bright screens.

2. No hot laptops burning tights.

CON: 

No EQ software or choice of players like VOX available to give color to the music.

Reading FLAC files from NAS 

Screenshot of QNAP's Qfile browser / player.

Depending on your NAS, most popular NAS will have an iPhone/iPad app where the FLAC file can be played and streamed onto the iDevice.

Storing FLAC files locally in the iPhone/iPad and play directly

Thankfully for mature in technology and app, we are now able to store and play FLAC locally from the iPhone & iPad.

FLAC Player+ from the App store

You need the FLAC Player+ app to be installed on the iDevice.

It is a FLAC player and also has uploading capability to transfer files from PC/MAC via IP address on the iPhone. Simply follow the instructions. Real easy.

There after, use the FLAC player+ to play the files.

In the NAS option, when the iPhone go into LOCK mode, there is a delay in playing and then clipping occurs. To remedy, i had to stop the player in the lock screen, forward and reverse the chapter and resume playing to rid the clipping.

However in the FLAC Player+ option, the playing of song is normal and there was no delay or clipping when the iPhone go into LOCK mode.

Reported & Solved.

Celine Dion's "My Heart Will Go On"

On iPhone, clipping heard later in the track > 3mins

Current iOS9.2

Today i updated to iOS9.2.1, similar to the apple discussions below, the clipping is gone.

Then, one must be careful not to update and keep the current iOS version until it is tested to be stable for DAC usage.

++++++++++++++++++++++++++

https://discussions.apple.com/thread/7371479?start=15&tstart=0

iOS 9.2 Distorted audio on Lightening to USB (garbled or skip/seek like noise)

ARB-82Dec 9, 2015 1:03 PM

As a follow up to this thread: iOS 9 lightening to USB audio clicks and pops

SITUATION
iPhone 6S Plus, iOS 9.2, Opel Ampera/Chevy Volt, Original Apple Lightning-USB cable

ISSUE
Distorted audio - stuttering and seek/skip like sounds - will occur when playing audio files over a Lightning to USB connection. 

The issue will arise anywhere between 3 and 15 minutes into a track or audio file. The issue will arise only when the phone is locked.

REPRODUCTION

1. Play a long audio file (>5 minutes) on a LOCKED iPhone running iOS 9.2 and wait for the audio to distort.

2a. Once the issue occurs, UNLOCK the phone and the issue will be resolved immediately.

2b. PAUSING the playback and waiting around 5-10 seconds until playing again will also resolve the issue temporarily.

3. Once the phone is LOCKED again (either auto-lock or manual) the issue will come back immediately.

NOTES
The issue can be predominantly heard using spoken word media. 

The issue will happen with music, but due to high dynamics certain music types can have, the issue might be less noticeable.

If you have a similair issue, please post your findings in this topic.

iPhone 6s Plus, iOS 9.2

Conclusion

Getting 24-bit files to play back through a portable DAC seems to be a challenge when using an iPhone.  There are rumors of changes in iOS, specifically the native support of hi-res playback.  If that happens, high-resolution music playback will likely get much easier, and even become a plug-and-play experience.  Until then, one can get portable DACs to play hi-res music with either careful choice of DAC or a little additional work, as I have described.  Hopefully this post will help others who are interested in exercising all of the capabilities of their high-resolution audio devices.

Do i need XLR cable or simply unbalanced cable for the headphone

Do I need a XLR cable set up headphone?
What advantage will it contribute to the listening experiences.

Summary of article
Balanced cable designs, i.e.XLR solution is all about noise isolation especially long cable runs. It addresses noise transmission from mics or instruments that have to feed to the sound board some few hundred metres away from the stage during performance or in recording studios.

But headphone cables are less than 3 metres will see minimal noise. Hence you can get XLR mods when you have extra cash to burn.

Bonus material
This web has a silent CD/track used to test equipment for noise
http://duramecho.com/Misc/SilentCd/

This is one of the sure ways to check for noise in your DAC/AMP/Headphone setup!

The zipped file 4kb can be found here as well.
https://drive.google.com/file/d/0Bx4rnFdYzy0jbms5bWE5ZkdKLTA/view?usp=sharing

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Discussion

This thought came about when i was looking for a used T1 and saw one with XLR balanced setup going for S$750 which is really affordable compared to the stock 1/4" connector going around S$800.

The hesitation for me are
1. XLR outputs are rare in non high-end headphone amplifiers.
2. An adapter for XLR to 1/4" unbalanced is required to sample other normal amps
3. Amp costs.

Most headphones are sold with an unbalanced 1/4 jack like the photo below.

The stock Beyerdynamic T1 has an unbalanced 1/4" Neutrik connector.

An additional blue wire is un-used and is said to be able to convert the connector to XLR balanced 4 pin.

AMP costs
OPPO HA-1 Headphone Amplifier, DAC & Pre-Amplifier
USD $1199

MJOLNIR 2 TUBE OR SOLID STATE BALANCED HEADPHONE AMPLIFIER
USD $849

This is the Chinese Amplifier we have
RMB 520, about S$115 or USD $80 that drives the Beyerdynamic T1 really well which we are really happy

Its all about NOISE

Screen captures from videolink #2 below

Unbalanced: 1 metre cable. Nice clean sine wave

Unbalanced: 25 metre cable. Fuzzy (noise) sine wave. Cable acts like antenna, picking up noise.

Balanced: 25 metre cable. Clean sine wave. The signal amplitude has doubled as an added benefit.

Video explaining balanced vs unbalanced cables briefly

Here is a more detailed explanation

Reference
All materials are taken from youtube
https://www.youtube.com/watch?v=BQtMFsw_3Hg
https://www.youtube.com/watch?v=KpiTGyGZqUQ

Thanks to video authors for the great explanation.