Astell & Kern AK240

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krisstack

  • Jr. Member
  • Posts: 9
Astell & Kern AK240
« on: 10 Apr 2014, 02:13 pm »
I got a chance to listen to the AK240 for a brief period at the recent NY Head-Fi meet, and I was impressed with the functionality of the device.  I'll reserve judgement on sound for now, as it was just a brief period, and they didn't have any music I was very familiar with loaded on the device- as expected though, it did seem to be an improvement over my RWA AK100 though.  I've been spending much more time listening to DSD files on my home system, and find I tend to prefer the DSD sound over PCM for many types of music.  At the very least, it is nice to have options.  So I'm thinking of purchasing one.

Vinnie, I know you mentioned somewhere that you had acquired a unit, but seem to have been quiet on your opinion of the stock sound, and how you might modify it.  So please do tell.  I know you've been busy with the Sony HAP-Z1ES mods (not to mention battling the mighty pathogens), but you must have spent some time with the AK240 by now.

I would use it as a portable player only, with CIEMs.  I currently use Ultimate Ears Reference Monitors with my RWA AK100, so would start with those running balanced, but I'm also considering getting a pair of JH Audio Roxanne's to use with it.  I don't really have an interest in carrying a stack around, so I wouldn't use an external amp.  Looking for the best sound possible, with a good UI, in a very portable device.

Any other circle participants get one yet?  I've read many opinions over on Head-Fi, but healthy discourse is always good.  If you used the device, would you primarily want to use it without an external amp?

Vinnie R.

Re: Astell & Kern AK240
« Reply #1 on: 10 Apr 2014, 03:48 pm »
Hi krisstack,

Next week I should have details about the RWAK240 posted on my website.  I wish I was feeling well last weekend because I would have been at the NY Headfi Meet and let you hear what I've done with it!  :eyebrows:   I'm feeling a lot better - finally!

Headfi.com is definitely the place where there is most interest in the Astell & Kern AK100, 120, and 240 players (and the RWA modded versions),
but I will still post about the RWAK240 here on the RWA forum. 

For starters, I will say this about the AK240 (in no particular order, and these are my opinions from listening to and exploring the internals of the AK240 for well over a month):

- The "line out" feature of the stock AK240 is NOT a true line out.  The signal still goes through the headphone output stage.  When you set the volume to max (or select "line out" in the settings menu), the output level of the SE output jack is approx. 2Vrms, but it still passes through the headphone amplification stage.  iRiver wants to call this a line-out, but I do not agree.  We can call it a pseudo-line-out (PLO).    :green:

- Feeding the PLO into a top notch portable headphone amp (e.g. SR71A or B) sounds better than the stock AK240. 

- The stock AK240 headphone outputs (SE and balanced) sound better than the stock AK100, AK100mkII, and AK120 players.

- The AK240 really shines with its native DSD playback. 

- More notes on how I find the sound of the stock player (and what I've worked on to improve it) will follow soon...


REGARDING THE RWAK240 MODIFICATIONS

- There will be two versions: The RWAK240 and the RWAK240+.  I will briefly mention them below, and then add more details in the next few days.

The RWAK240 will be modifications to the SE and BAL headphone outputs of the stock player.  This will be optimized for those who will NOT be using an external headphone amplifier.  You can still feed the output to an external headphone amp if you want to, but as mentioned above, it is still NOT a true line out.  It would be a "modded PSL."  :wink:

The RWAK240+ will be all the modifications of the RWAK240, + there will be an added line-out jack.  This jack can be either a 3.5mm TRS (for those who want a SE line out), OR a 3.5mm TRRS (for those who want a balanced line out).  Either line out option of the RWAK240+ will require that you set the volume of the player to MAX (75) for full signal (no digital attenuation), but the signal will NOT pass through the headphone output stage.  They are taken from the output stage of the dual d/a converters before the headphone amplification stage. This is the optimal signal to pass to an external headphone amplifier. 

With the RWAK240+, the SE and BAL headphone outputs are also modified identical to that of the RWAK240.  So you can still use the RWAK240+ without a external headphone amp.  In many cases, you will NOT feel like you are missing much by not using an external headphone amp when using the RWAK240/RWAK240+.  Unless you are using something like an SR71B or RX3-B+, you will probably agree that the RWAK240's balanced headphone output is better than using an external headphone amp.  :)   It's really good!

Regarding the RWAK240+ line out jack:

As usual, there is a very limited amount if space to work with inside a sophisticated portable audio player like the AK240.  There is really only one location where I am able to just barely fit a line out jack (remember, the volume control wheel location is NOT an option because we are not deleting it like was done for the RWAK100-S or RWAK120-S/B modifications).  The location is on the angled surface above the volume wheel.  Some machining of the enclosure internally is needed to take place (Very carefully!) to remove aluminum so we can fit the 3.5mm TRS or TRRS jack inside, along with drilling the hole on the angled plane to panel-mount the jack.  It's a royal PITA, but there have been some of you who have been asking me about a true line out for the AK240.  This is the only way I can do it, but unfortunately, I don't see another type of line out jack being able to fit. 

Modification details and pricing:

Coming soon!
« Last Edit: 16 Apr 2014, 04:26 pm by Vinnie R. »

krisstack

  • Jr. Member
  • Posts: 9
Re: Astell & Kern AK240
« Reply #2 on: 10 Apr 2014, 03:57 pm »
Thanks Vinnie.  I love it.  Options.  Might be interested in the +, as it doesn't take anything away (well, except more money  :)).

Vinnie R.

Re: Astell & Kern AK240
« Reply #3 on: 15 Apr 2014, 05:25 pm »
Here are the details on the RWAK240 / RWAK240+ modifications:


RWAK240

When comparing the headphone output (both the SE and BAL outputs) of the AK240 to some of the best dedicated, portable headphone amplifiers, it becomes apparent that the AK240 lacks in bass impact and extension.  While the AK240 bass is nimble, it is missing foundation and authority when called upon, especially with lower impedance headphones.  There is also some missing body.  The main reason for this has nothing to do with output voltage swing or output impedance.  It entirely has to do with the fact that the power supply rails for the headphone output stages are quite low on reservoir capacitance, so they have a hard time delivering the needed instantaneous current that high end, dedicated portable amplifiers can deliver.  Inside the AK240, space is at a premium and there isn’t the room for a respectable amount of power supply rail capacitance if it is to be installed on the board as needed for machine assembly.  Fortunately, there IS a way to hard-wire increased capacitance directly to the rails of the output stage FETs by way of the modification process, and this is exactly what is done:

Modification:  2,000uF of super-low ESR power supply rail capacitance is hard-wired directly to the headphone output stages.

Result:  With this modification installed, the AK240 delivers the bass weight and scale that is now on par with high-end portable headphone amplifiers.  It extends deeper, hits harder when called upon, and is tighter and more responsive throughout the entire volume range – but is most welcomed at medium to higher listening levels where more instantaneous current is required (especially with lower impedance headphones).  This modification also helps add more depth so certain recordings.


Another area where the AK240 headphone outputs can be improved upon is in both the midrange and top-end.  While it does a good job at keeping things neutral, the tends to sound a little dry at times – siding towards being more analytical instead of delivering the right amount of richness and musicality that makes you want to listen longer and longer.  While not “hard” or “digital” sounding in its stock form, there is still a certain lack of emotion in the midrange, and lack of naturalness in the top-end that is so important for taking this DAP’s sonic performance to the highest level possible.  After much experimentation, a solution was put in place to improve both SE and BAL headphone outputs equally:

Modification:  Pure Class-A biasing of the headphone input stages via an installed JFET cascaded constant current source (CCCS). The JFET CCCS’s are bench-tested and matched to be better than +/- 0.5% tolerance.

Result:  This greatly improves the midrange by making it sound more seductive and natural, and does not harm the transparency and micro detail retrieval of the stock player.  Treble becomes very open, extended and effortless sounding – and these improvements, along with the improvements to the bass response (mentioned above) work together to elevate the AK240’s SE and BAL headphone output performance to a level that is competitive with some of the best source + portable amp pairings!   :singing:   :drool:   :guitar:

Availability and Lead-Time:

We are accepting AK240 players for the RWAK240 modification service starting 4/21.  Lead-time is within 2-weeks from receiving your AK240. 

Price:

$495 + return shipping ($15 inside the USA, $55 outside the USA).

Payment:

Please paypal directly to: vinnie@redwineaudio.com   until we set up an RWAK240 page on our website that adds a shopping cart interface.
Be sure to confirm your email return shipping address is added to the "notes" section of the payment.


RWAK240+

- Includes the AK240 modification listed above

- Adds either a SE (3.5mm TRS jack) OR BAL (3.5mm, TRRS jack) true line output jack.  You select the line-out that you prefer.

The location is on the angled surface above the volume wheel.  Some machining of the enclosure internally is needed to take place (Very carefully!) to remove aluminum so we can fit the 3.5mm TRS or TRRS jack inside, along with drilling the hole on the angled surface to panel-mount the jack.  This is hard-wired from the output stage of the d/a converters, and completely bypasses the stock headphone output stages and gives you the cleanest possible line-out signal to feed an external portable amplifier.

NOTE: You will still need to set the volume wheel to MAX in order to get full output voltage (no digital attenuation) from the d/a converters.

Availability and Lead-Time:

We are accepting AK240 players for the RWAK240+ modification service starting 4/21.  Lead-time is within 2-weeks from receiving your AK240. 

Price:

$795 + return shipping ($15 inside the USA, $55 outside the USA).

Payment:

Please paypal directly to: vinnie@redwineaudio.com   until we set up an RWAK240+ page on our website that adds a shopping cart interface.
Be sure to confirm your email return shipping address is added to the "notes" section of the payment.

----------

We also plan to offer new, fully modified RWAK240 and RWAK240+ players. 

RWAK240 player:  $2995 + shipping ($15 inside the USA, $55 outside the USA).

RWAK240+ player: $3295 + shipping ($15 inside the USA, $55 outside the USA).


NOTES:

- Website for AK240 mods and players will be added soon to: http://redwineaudio.com/mods
- As with all our modified products, we do not offer a return policy.  See: http://redwineaudio.com/about/terms-and-conditions
- Just like the AK100/120 modifications, we warranty the RWAK240 for as long as you own it (applies only for the original owner). Note - This excludes any issues unrelated to the modification, such as the battery, LCD, etc., but we still try to offer prompt repair service for such non-warranty items.  Price depends on nature of repair.
- All stock functionality does NOT change with the RWAK240 or RWAK240+ ... these are only sonic improvements and not firmware related.

Thank you for all your interest and support!

Vinnie

Vinnie R.

Re: Astell & Kern AK240
« Reply #4 on: 17 Apr 2014, 07:35 pm »