Instruction: Answer the given question using the supporting document.

Input:
Question: Can I plug in a cd player,  or do use a digital out from a cd player or transport?
Document: Could you imagine having to use the remote to turn up or down the volume from 12 inches away? Stupid4. Why does it take Wadia forever to engineer and launch products? They are super duper digital engineers, but their lineup is too paltry.5. The whole "transport" idea seems weird to me. Who pays 700 bucks to plug in their iPhone? Get a 99 dollar 13 inch LCD and an apple tv and you are set!
How about activating it and calling it "power"??? (2) The amplifier only accepts digital coax, TOSLINK optical, and USB B inputs. It strikes me as unlikely that many users will run multiple sources into this amp that are all digital. Given the preponderance of audio devices with RCA phono outs, you have to wonder why this unit was designed with four digital inputs, but no analog inputs. If all you want to do is plug your 170i into it, this is no big deal.
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.
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.
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.
Not quite as refined as the dCS rig or the better Meridian digital stuff, but it doesn't embarrass itself. It's quite remarkable for $800.If you can tone down the audiophile neurosis, the 151 can be quite satisfying. I recommend it.
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.
But, it won't drive an 8 ohm speaker unless you're pushing 90+ output, which, will kill the unit in short order. The digital performance as a DAC is the finest I have heard - just what I'd expect from Wadia.I'm bummed to say the least. I rated it one start due to false disclosure. Perhaps not fair, but, in my book, misrepresentation is far worse than poor execution.
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.
Finally, Wadia has a reputation for making excellent, perhaps the best, digital audio equipment from their facilities in Wisconsin and now Michigan. Be advised that this unit is "assembled in China." It is still well-built, but not on par with Wadia's legendary digital audio devices. In fairness, though, this unit is also priced at about 10% of the cost of those units. Also note that there are comparable integrated amps with DACs on the market by Cambridge, Peachtree Audio, and Teac.
Answer: All inputs are digital, you may take the digital signal out of your CD player using either a TOSlink (optical) or coaxial cable.