RWAK100/S

For Astell & Kern AK100 Digital Audio Player

Best value high-end digital music player!

RWAK100

The RWAK100 is a modified version of the Astell & Kern AK100 digital audio player (DAP)

We achieve this by:

  • Bypassing the 22-ohm resistors in the headphone output stage, which results in a < 1-ohm output impedance that can drive IEMs and headphones whose impedance is as low as 8-ohms
  • Hardwiring the headphone output stage FETs directly to the pins of the headphone output jack to provide the shortest, cleanest signal path. This also bypasses the tiny circuit board traces and the header that connects the main board to the smaller headphone jack board.

The result is a very portable (smaller and lighter than an iPod) DAP that now has a clean, low-impedance headphone output stage. The RWAK100 can drive IEMs with ease, as well as most full-sized headphones to more-than-adequate volume levels. The RWAK100 unravels layers and layers of detail and nuances from your music, and is free of any audible background noise.

RWAK100 Q & A

Q: Do you warranty your modification work?
A: Yes, we warranty the RWAK100 modification 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.

Q: Besides what is listed above, does the RWAK100 modification alter features/functionality of the AK100 in any way?
A: No

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RWAK100-S

The goal of the RWAK100-S modification is to transform the stock AK100 into the finest sounding digital audio player (DAP) used exclusively to send a line level output signal to your portable headphone amplifier.

We achieve this by:

  • Replacing the stock Wolfson WM8740 dac chip with the premium WM8741
  • Configuring the WM8741 to run in “hardware mode” – eliminating the digital volume control processing
  • Configuring the WM8741 to use its “minimal phase digital filter” option
  • Hardwiring the stereo line-out signal to the 3.5mm (1/8”) stereo output jack (formerly the headphone output jack), hence completely bypassing the headphone output stage
  • Removing the unused digital volume control wheel

Digital Volume Control and Minimal Phase Digital Filter with the WM8741

The stock AK100 uses a Wolfson WM8740 dac configured in “software mode.” This means that the AK100 software configures the dac and allows for a digital volume control of the unit. We discovered that even with the volume set to MAX (setting 75), the output voltage of the WM8740’s output signal is still attenuated in the digital domain.

The premium WM8741 is not a drop-in replacement for the WM8740 in the AK100. This is because the software control of the WM8740 does not control the WM8741 in the same way. We therefore have to hardwire the WM8741 (pulling up certain pins to logic HIGH, and pulling down certain pins to logic LOW) to configure it to run in “hardware mode.” This means it is NOT controlled by software. The digital volume control is eliminated and does not alter the digital bit stream entering the dac, and we manually configure the WM8741 to use its optional minimal phase digital filter. The result is a more natural, organic sound that is lively, finely-nuanced, open and transparent, and extended – what you should expect from a true reference quality source component!

More impressive than its superior technical specifications (e.g. 8db greater SNR and Dynamic Range) compared to the WM8740, the WM8741 can be configured to use a “minimal phase digital filter” for the data prior to d/a conversion. Unlike most d/a converter chips that use a standard linear phase digital filter, the WM8741’s selectable minimal phase digital filter has no “pre-ringing” of its impulse response. Pre-ringing is an unnatural side effect of using a linear phase digital filter. Real instruments do not ring before they are excited – a guitar doesn’t produce sound before a string is plucked, a piano doesn’t not produce a sound before a key is pressed, and the impulse response of a minimal phase filter does not have prea-ringing and therefore produces a more natural sound.

Line out

The RWAK100-S modification also hardwires the analog line-output stage following the WM8741 directly to the headphone output jack. Therefore, the headphone output stage is completely bypassed and the headphone output jack is converted to a true, 2Vrms line-output.

Hardware volume control removal

Since the digital volume control functionality is completely disabled, we also remove the volume wheel that exits from the left side of the AK100, and we plug the hole so the RWAK100-S is slimmer by 5 mm – and simply looks cleaner.

RWAK100-S Q & A

Q: Can you preserve the headphone output stage with the RWAK100-S mod?
A: Unfortunately, no. Without a custom firmware update that is designed for the WM8741 and allows it to both run in software mode AND use its minimal phase digital filter, this is not possible. We therefore make the best of the situation by dedicating the RWAK100-S modification to those who exclusively use it as a source component to feed an external headphone amplifier (required) with the best possible, true-line out signal.

Q: How much better does the RWAK100-S sound compared to the RWAK100 used a source feeding a portable headphone amplifier?
A: Remarkably better! The main reasons for this are:

The WM8741 is a better sounding dac, especially when using its minimal phase digital filter to eliminate pre-ringing
The digital volume control is completely eliminated – so no attenuation of the digital signal occurs
The output is a true-line out signal taken from the analog output stage that follows the WM8741 and is hard-wired to the 1/8” (3.5mm) stereo output jack - so the headphone output stage is completely bypassed as well.

In other words, the RWAK100-S is configured like a dedicated source component such as a high-end external dac unit, where there is no digital volume control or headphone output stage.

Q: Besides requiring a headphone amplifier to drive headphones and removing the digital volume control, does the RWAK100-S modification alter features/functionality of the AK100 in any other way?
A: Due to the higher current draw of the WM8741 dac compared to the stock WM8740, the max. play time of the RWAK100-S is expected to be up to 20% shorter.

Q: Does the RWAK100-S modification alter the optical digital output feature?
A: No – the optical digital output is not altered and still works the same.

Q: What headphone amplifier do you recommend with the RWAK100-S?
A: There are many excellent portable headphone amplifiers that should all work very well with the RWAK100-S, assuming they have a line-input and input impedance of 5k ohm or greater. The RWAK100-S, headphone amplifier used, AND headphones used all work together to deliver a particular sound signature. We can only describe the sound signature of the RWAK100-S. From there, you will need to determine the amplifier and headphones that best suite your taste.

Q: What cable is recommended between the RWAK100-S and my headphone amplifier?
A: Assuming your headphone amplifier uses a 1/8” (3.5mm) stereo input jack, there are numerous “mini-to-mini” cables out there to choose from at various price points.

Q: Do you plan on offering similar modifications for the AK120?
A: When they become readily available in the USA, we do plan to explore the modification potential of the AK120 as well and determine if the results clearly surpass the performance of the RWAK100 and RWAK100-S. If they do, we most likely will be offering such modifications to the AK120.

Q: Can I use the RWAK100-S to feed a home audio stereo preamplifier or integrated amplifier?
A: Absolutely – we have tested the RWAK100-S modification to achieve remarkable high-resolution playback performance in home audio systems as well as portable audio systems, so go for it! Note - you’ll probably require a 1/8” stereo mini to RCA cable for this application.

Q: What about using the RWAK100-S in the car?
A: As long as your car has an AUX input jack AND can handle a 2Vrms line-out signal, it should work without any trouble in your automotive stereo.

Q: Do you warranty your modification work?
A: Yes, we warranty both our RWAK100 and RWAK100-S modifications for as long as you own them (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.

Purchase

RWAK100 (modification only)

Pricing for the Modification Service only. Customer must supply AK100 for upgrade. See Terms & Conditions for additional information.

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Price: $250

RWAK100-S (modification only)

Pricing for the Modification Service only. Customer must supply AK100 for upgrade. See Terms & Conditions for additional information.

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Price: $495

RWAK100 player

Brand new AK100 unit with RWAK100 modification.  See Terms & Conditions for additional information.

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Price: $895

RWAK100-S player

Brand new AK100 unit with RWAK100-S modification.  See Terms & Conditions for additional information.

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Price: $1145