Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: Does it have a 110-220 v switch? an it be used in countries with 220v ?
Document: It has what I consider to be two design flaws. (1) The power switch is located on the rear of the unit, right above the power cord input. If you run this unit with a 170i stacked on top, as I assume most will, you will find it to be awkward to turn the amp on an off.
Here's where I think they fouled up:1. Why is there no power switch on the front? I leave mine on all the time now.2. This would be PERFECT for an office setting if it had a headphone amp! During the day you listen to your headphones. On weekends (yes I work weekends) you listen to your speakers. It is super small and compact. It would be perfect for your desk. Try doing that with a PeachTree 65? Guess what?
Wow, good weight, good control no bloat. Nice midrange. Smooth highs. You get some of that signature Wadia sound.This thing is $800. My cables cost more than this. It's a bargain for the money. Hook up an old mac mini, airport express, sonos or transport and you're done.I imagine the DAC section is better than the amp section.
With the Wadia, the Polks are really punchy and you feel the music. Wadia has terrific customer service. I had an issue and they simply swapped my unit for another one at no charge, no questions.There is an achilles heel with the Wadia and it is what happens when engineers don't listen to the market and know their customer. They put their head down and develop products that miss the real market need.
Wadia 151 PowerDac Mini AmplifierJohn Schaffer / President of Wadia demonstrated their new 151 at Rocky Mountain Audio Festival October 2009. Set up with a 170i and a pair of Dynaudio Excite x16's, the sound was quite incredible for such a simple and affordable system. I immediately contacted my local dealer and put one on order. Initial shipment was delayed, but it was well worth the wait. Perfect combo....excellent for a office setup. Mine is setup with Wilson Benesch ARC speakers.
This little baby needs no introduction. Web is already flooded with excellent reviews. I paired it with Dynaudio exite x16. And still breaking in. Both amp and speakers need at least 160 hrs of breaking. I am half way there but this pair is already touching that level. I also paired it with wadia i170 transport and all of sudden iPhone/iPad started producing excellent music. I am a happy customer.
This is exactly what in was looking for at a price I could afford. I bought and returned some other equipment you'll see listed as alterntives, they were really just not the whole package.What's it like? After a somewhat extended break in (60 hours? ), I find a very nice soundstage, great clarity, surprisingly solid bass, and at any reasonable listening level plenty of depth and control. I haven't tried the USB input, maybe someday.Premium construction /build quality.
This is a seriously good piece of gear for the money.Sure, there are some ergonomic issues. No outputs except speaker outs. If you want analogue out or headphone out, Wadia makes the 121, which has both. No volume knob. You won't want to use this at your desk using the remote to change the volume all the time.
There are billions of people like me who have all of their music on their computer, iDevices, or apple tv's. Guess what? They are all digital! Anyone who is using CDs or even analog sources today is really a dinosaur. This unit was not made for them. Wadia got close with this, but no cigar.
The Wadia 151 Power DAC is a 25 watt per channel integrated amplifier with a DAC. I am using it in conjunction with a Wadia 170i transport and a pair of high quality Opera speakers, in a desktop configuration--supposedly the set up for which this amplifier is optimized. I found the sound quality to be unremarkable.
Answer: It accepts autovolt input of 110v to 220v AC. It works in 220v country, like in my case SG.