HeadAmp will be releasing a new portable amp, the Pico Slim. For now, please visit HeadAmp Audio Electronics for postings & updates on the Pico Slim design, or continue to check this thread. Any questions or discussion about the Pico Slim can be posted here.
We will begin accepting pre-orders for the Pico Slim soon. See here for the latest update: http://www.head-fi.org/forums/6188343-post899.html
Please see here for pictures of the latest prototype of the Pico Slim: http://www.head-fi.org/forums/6089974-post615.html
Here is a "Q&A" about the Pico Slim that I will update. I'll start with a few of my own questions and how they are answered by the Pico Slim.
Q: Who will want a Pico Slim?
A: The Pico Slim is for anyone interested in a portable headphone amp. But more importantly, it's also for people who have said they will not use a portable amp for reasons such as size (too thick), or that they offer little improvement over the headphone outputs of DAPs. The Pico Slim will be thinner than an iPod/iPhone, and offer multiple features never found in portable amps that will improve the listening experience especially with IEMs.
Q: What are the basic specifications of the Pico Slim?
A: The dimensions will be about 3.15 x 1.5 x 0.37" (80 x 38.1 x 9.4mm), a battery life of ~70 hours, and output of up to 4.2V @ 250mA per channel. The noise floor has been tested with the Westone ES3X custom IEM, with a sensitivity of 125dB/mW is tied for the most sensitive IEM available according to published specs. At any possible listening level, its not possible to hear any hiss or even tell the difference between the amp being 'on' or 'off'
Q: What are the new features offered in the Pico Slim?
A: The most important feature in the Pico Slim is the use of a new digital volume control. To be clear here, only the interface for changing the volume is digital, and it still uses a volume knob. The audio & actual volume control is and always will be analog. There is no question about it, the Pico Slim uses the best and probably most expensive digital volume control chip available. It offers more attenuation and better channel matching than a $500 Alps RK50 volume control, which is as round as a soda can and has only been used for the most exotic home audio & studio equipment.
Q: How much attenuation is there and what does this mean?
A: The spec. for amount of attenuation is how quiet the volume can be set. A typical volume control found in a portable amp only has about 70dB of maximum attenuation. This is why with sensitive IEMs, you can still hear the music even with the volume knob all the way down. Worse, as you turn the knob, you have to go several degrees until the left/right channels seem to be matched in volume. At this point you may only have 40 to 60dB attenuation, and the sound can already be too loud. The Pico Slim has up to 110dB of attenuation.
Q: How closely are the left/right channels matched?
A: The left/right channels are matched better than 0.1dB. The threshold for human hearing is said to be 1dB. Small potentiometer volume controls are only specified for +/-3dB matching, and can be much worse at the quiet range of their volume. It's far from 'high-end' to be listening to something with this much left/right imbalance, especially when the imbalances from your source, amp, and headphones can all add up to something you can easily hear. You never have to worry about this with the Pico Slim.
Combine the attenuation and channel matching of the Pico Slim, and try it with IEMs. It's very relaxing & reassuring to be able to slowly turn up the volume, listen at quiet levels if you want to, and the left/right channels are always perfectly balanced.
Q: How many steps does the volume control have?
A: A popular DACT stepped attenuator in home amps only has 23 volume steps. Most digital volume controls offer 16, 32, or 64 volume steps. A potentiometer technically has infinite steps, but there are the problems described above that limit its use. The Pico Slim has 255 volume steps, which will be completely seamless so it will sound and feel like there are no steps at all.
Q: Besides the size differences and new features, how is the Pico Slim different from the 'original' Pico amp?
A: The Pico Slim is an entirely new design under the 'Pico' family of portable amps & DACs. It will only be offered as an amp. The 'original' Pico will remain the most powerful amp of its size, the only one with a 2-cell (8.4V) battery.