Don't those problems occur when the device is running on battery power?

Matsuzaki:
No, they don't. The power circuit structure for running on battery power at normal gain is very simple, so there's nothing in the power supply that can become a source of noise. However, in high-gain mode, which is used with high-impedance headphones, the voltage is increased. This means that even when the device is in battery power mode and isn't being powered by the AC adaptor, the power supply can still be a source of noise to a lesser extent. But to counter that we use high-grade switching controllers—the kind that are used in measuring instruments—so that the effects are minimal.

Tomo (S): 
This power source structure means that the optimum setting for the DMP-Z1 in terms of audio quality is battery-power mode at normal-gain. In this mode, the audio circuit with positive and negative power sources is driven by clean, noiseless power from the batteries, without using a DC/DC converter. This power-circuit arrangement, unique to the DMP-Z1, enables this special operation mode. Amongst audiophiles there's an urban legend that high gain gives a better sound even with ordinary headphones, but that's certainly not the case with this product, at least.

Does that mean the DMP-Z1 isn't recommended for use with high-impedance headphones?

Tomo (S):
It does not mean that it is not recommended. Normal gain has output high enough to get the most out of ordinary headphones anyway, and with high-impedance headphones both driver efficiency and noise sensitivity are low, so you won't hear noise even in high gain. You can try listening in normal gain with your headphones and then switching to the high-gain setting if you feel the volume isn’t loud enough. Changing the gain setting to suit your headphones' efficiency and sensitivity in this way is an important point when trialling high-quality audio.

What kind of features does the analogue amplifier have?

Hiro (S):
We use the TPA6120A2 analogue amplifier made by Texas Instruments. We considered using various amplifier types and devices, including ones that were discrete and had an internal negative power supply, but the TPA6120A2 provided sufficient performance, both balanced and unbalanced, and we'd grown used to using it after several years of testing. From the point of view of its power consumption, and of course its sound quality compared with other options, it seemed like the perfect IC for this model.

What's more, to get close to the sound quality of digital amps, which have superior separation, we went with a dual DAC structure. Although size reduction was also a focus, it was important to use a dual structure with a certain degree of size and area to it. If you opted for circuit boards or a device that was too small, the distance between the L and R channels would be too narrow and would degrade the stereo separation, which would negate the choice of a dual structure. In other words, it would defeat the purpose of the product.

A full digital amplifier uses final stage Pulse Height Volume to convert the output audio signal amplitude to voltage. However, as the DMP-Z1 needs a volume control instead, the performance of the volume control device we used was extremely important.

Nowadays, you would normally use an electronic volume control. However, it takes a lot of power supply to make proper use of the low-noise performance suited to headphone audio, so this was an aspect that didn't fit the concept of high-quality, battery-driven audio that we were aiming for with the DMP-Z1. After weighing up various options, we came to the natural conclusion that analogue volume was the way to go for this product.

Hiro (S): 
Audio signals travel directly through the volume control, so it plays an essential role. We tested lots of different volume control parts for the DMP-Z1 and were really surprised just how much of a difference volume control makes to sound quality. After trialling various analogue volume controls, we chose the Alps Electric RK501, which is highly regarded among audiophiles. Its sound quality was hugely impressive.

Tomo (S): 
I'd heard of it, naturally. But as you can see just by looking at it, it's somewhat on the large side, so I didn't think we'd ever get to use it!

Hiro (S):
When we requested a sample from Alps Electric for use in a prototype, I think they found it strange that the Walkman® development team wanted a volume control as giant as the RK501!

Has the RK501 used in the DMP-Z1 been modified at all?

Tomo (S):
We worked together with Alps Electric on the customised version built into the DMP-Z1. The first thing we tried was swapping the brass casing to aluminium to reduce the weight of the device. In theory this shouldn't have had any effect on the sound, but when we actually listened, we found that the sound had become very light.

Hiro (S): 
The team from Alps Electric also did listening tests and looked at the internal structure of the volume control with us, to help figure out why sound quality was being affected by the material used in the volume control casing.

Tomo (S): 
As is always the way when testing audio quality, we had to produce prototypes and actually listen to them in order to get to the bottom of it. And so we kept trying out lots of different variations and kept requesting prototypes, without a thought for mass production. We customised it with all kinds of different specifications to try and improve the sound quality, like aluminium casing with gold plating, almite processing, changing part of it back to brass, etc. But for all our trial and error, we couldn't make the sound any better. Eventually we thought the sound quality would improve if we customised the original and gave up on trying to reduce the weight, so we changed the base metal used in the casing back to brass. At long last, when trialling the prototype with a combination of brass plating and gold plating, which is used in the NW-WM1Z from the first part of the Signature Series, we were finally able to create a customised volume control that surpassed the original RK501 in terms of sound quality.

Hiro (S): 
As we'd only asked the Alps Electric team for prototypes up to that point, we weren't sure whether they'd allow us to mass produce it. But when we all listened and compared the sound quality together, they agreed that the sound was indeed different and gave us the green light to take it to mass production. With this customisation, the device is able to reproduce a clearer and more transparent high end than the original RK501, as well as incredibly deep and powerful bass in the low end.

Finally, is there anything you would all like to say to people reading this article?

Tanaka:
We designed this product with the goal of providing a headphone listening environment unrivalled by conventional desktop audio devices. And so, as I've been saying throughout, I'm proud that we've managed to achieve that, thanks to the passion of our engineers. I know this device can deliver a sound to your favourite headphones the likes of which you've never heard before, so I'd like to invite you all to bring your headphones to a Sony store and give it a try. I'd like everyone to come and experience for themselves just how different the sound is.

What's more, it has a lot to offer in terms of signal processing technology, which is something Sony excels at, including the newly developed DSEE HX™, Vinyl Processor, and DSD Remastering Engine. With a combination of these functions, it's a product you can enjoy for a long time.

Tomo (S):
At first glance, the DMP-Z1 may look like a desktop device, but it's actually made by the Walkman® team. I think many people will be interested in hearing what kind of sound we have pursued with an analogue amplifier, given that the Walkman® team have been a proponent of full digital amplifiers until now.

Analogue amplifiers are sometimes said to have a warm, soft tone, but characteristics like these are heavily reliant on the design of the power circuits and audio circuits. In fact, an analogue amplifier with a properly made power source won't result in a warm or soft tone. One of the causes of the soft tone on an analogue amplifier is not enough power being supplied to the amplifier due to a poor power source, or it may be the case that it has been designed specifically to produce that tone quality. We wanted to bring out the finer sounds in the same way as the S-Master HX, but through an analogue amplifier that can offer large output and added punch beyond that of a digital amplifier. I think that by achieving this, we've managed to give the product a touch of its character.

Matsuzaki: 
This product is a culmination of all the techniques and expertise I've built up since joining the Walkman® team many years ago. I can safely say that I've put my all into it. So please, take a trusted pair of headphones and give your favourite music a fresh new listen. If you listen to the DMP-Z1 using headphones with the potential for high-quality sound, it's easy to understand. It creates a spatial audio effect never heard in headphones before now, by reproducing not only a wide horizontal sound field, but also a high vertical field, allowing you to feel the spatial audio effect in front of you and behind you as well. I'm certain you'll discover something new.

Hiro (S): 
These past 30 years, every time a new product has come out there's a CD that I've tested it against, and this time I truly did discover something new. In fact, this product places importance not only on high resolution, but also on accurately bringing out the sound of an audio CD. Through technology that has been honed over many years, the DMP-Z1 is a portable player that lets you hear all the audio packed onto a CD in the most incredible detail. I'm repeating what was said before, but I would encourage you to visit a shop and experience that sound for yourself.