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Practical Devices XM5 review

post #1 of 8
Thread Starter 
I got a Practical Devices XM5 to be reviewed.
This is a feature packed nice sounding amp with a compact package.

Click pictures to enlarge.


1. Look, feel

http://vaiopocket.up.seesaa.net/imag...thumbnail2.jpg http://vaiopocket.up.seesaa.net/imag...thumbnail2.jpg


At first glance, XM5 looks like another hammond case amp. However, in a closer look, build quality is nice and XM5 is fairly built.
The input plug is located lower position of the front end panel. This offset plug position is very useful to form U-shape with ipod LOD.


XM5 comes with complete package so you can start without anything, but iPod Line out dock is recommended to get a better sound.
The package including a bonus mini-mini cable , a charger(optional), a printed manual and a hex key to open enclosure.

2. Features

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As stated in their home page, XM5 is a feature packed amp.
First, XM5 has five function switches on the front end panel.
From the left, "Crossfeed", "Bass boost", "Treble Boost", "add gain" and "increase 75 ohm impedance".
Crossfeed function is a common feature can be seen in other amp. But XM5 employs a variable control volume on the rear panel.
"Bass boost" add 6dB in the lower register and "Treble boost" add 3dB in the highs.
"75 Ohm" feature increase impedance by 75 ohm.This is similar to ER-4P adapter that add 75 ohm to their impedance.
XM5 amplifies 12dB at normal. This is almost mid gain. "Gain" button add further 8dB for higher impedance cans like HD650.
XM5 also has additional feature to test battery and "FLASH LIGHT" feature to brighten two LEDs.
XM5 is controlled by microprocessor to manage these rich features.

Next, Practical devices stated the XM5 is a mono-block amp. I am not sure the technical detail but I guess this is similar to dual mono topology that means left signal and right signal are amplified via well separated circuit.

Lastly, XM5 employs a decent USB DAC.
According to their web site, the USB DAC chip has been upgraded with TI PCM2702.

3. Ordering options

To order XM5, follow the link.
Practical Devices Corporation

You will have some options.
First you have selections of buffer.
Copper busbar means a bypass wire for the buffer. That means no-buffer and current is limited.
I recommend to take BUF634 option, this is a popular buffer, powerful enough to improve current that means high performance.
AD8397 is another good alternative, this is a dual opamp and powerful buffer at the same time. I will cover the opamp rolling later.

You can add Lithium ion battery package option that include a universal charger at $25 plus.
You also have a color option, black or blue/silver.

My XM5 has following options has set
*Color: Blue/Silver
*Buffer : BUF634
*Battery: Lithium Ion package with an universal charger


4. Sonic impression

I hooked it up iMod 5.5G with ATH-ESW10JPN, UE11, YUIN G1 and ATH-W2002.
I prefer ALO super cotton dock as I think the silver cabling brings out the crispness and openness of the XM5 well. The ALO super cotton is a forgiving cable for the silver, this could be useful on sibilant setup. Though I do not think XM5 is so harsh, it would be a good match to XM5.
I use Jazz, Classical and New age music as well as Rock disks.

At the first listen, I noticed sound stage is fairly expansive and surrounding. As if I were in a large hall. Most amps have a 2D stage like soundscape that is wide in a horizontal axis. The 3D like spaciousness of XM5 is exceptional. I found this is something similar to 4ch advantage of Xin SM4. XM5 has a good focus on imaging as well. Performers and music instruments are well localized.
I'd say that the mono-block topology works as designed here, it delivers a great channel separation for this unique soundstaging.

Next, XM5 is a fairly transparent amp, yet the sound imaging is very much sharp and crisp. Vocal is fairly articulate and resolved, that makes the music very realistic.
XM5 is also a high speed amp with a good attack. The XM5 deliver solid, fast and good transient on the sound without being analytical. XM5 is not a warm nor colored amp. I'd say the sound is neutral and flat. Highs could be a bit pronounced, but no sibilant in my setup. Bass have a good impact but not pronounced nor bloated.

Thanks to the flat frequency response, I think XM5 is completed without bass boost or treble boost.
However, those features will work on some specific headphone combinations. Gain boost is the same.
For example, YUIN G1 is a great mate with XM5, the spaciousness with the G1 is really striking. However, G1 needs gain boost and bass boost to shine.

Speaking about gain, I think the standard gain is a bit too high for IEMs. Especially for my sensitive UE11. I think lower gain mode is desirable for IEMs, if possible. Around 3dB would be fine.

As for USB DAC, I am not a heavy USB DAC user. I simply use home amp at home. So I can not say much about here, however I think USB DAC ability of XM5 is very good. I guess improved TI 2888 surely work well. If I can listen music in my office, I want to use this at work.

5. Opamp rolling

XM5 is socketed and easy for rolling opamps.
I tried AD8397 that is supplied from Practical devices. AD 8397 is a dual opamp but it comes with adapter so you can install them easier.

http://vaiopocket.up.seesaa.net/imag...thumbnail2.jpg http://vaiopocket.up.seesaa.net/imag...thumbnail2.jpg

AD8397 does not need a buffer as it has adequate current output, To bypassing the buffer, you will need a copper wiring.
I left the BUF634s in the buffer sockets as just I am lazy.
Follow the manual to disassemble and to re-assemble.


Left: OPA134, Right: AD8397

http://vaiopocket.up.seesaa.net/imag...thumbnail2.jpg http://vaiopocket.up.seesaa.net/imag...thumbnail2.jpg

With the AD8397 attached, the overall sound signature is almost same, however XM5 is now less bright, a bit warmer and more forward sounding. I also feel bassy and punchy. I think those are AD8397 characters.
This is good for Rock, Pop music, and if your setup being harsh, 8397 can be more forgiving.

However, I felt original OPA134 has a better channel separation, sharper and better articulation. But can be a bit bright.
The 134 configuration is good for Acoustical music, Jazz trio, so it depends.


For $200 - $300 mid price range, I think XM5 is a good choice. Sharp, transparent and enveloping.
I strongly recommend to take XM5 with BUF634 option. Though I never hear Copper Bus version but I think good buffers are mandatory for such a good
amp. The buffer option costs more, but at $315, XM5 worth more than that. XM5 is that good.


Ah, I forgot to mention about the flash-light mode.
I guess you doubt the effectiveness of the flash-light mode for portable audio gear.
If so, have a look here
- Reuters news 2008 December
post #2 of 8
Good review - I agree with you, and it is a very good amp. The Japanese PCM2702 DAC is the same as the 3MOVE and on the same quality level as the Predator, and I think it does a good job. But, the Pico's ASRC upsampling to Wolfson WM8740 DAC is still better. In all, I think the amp deserves to be on the same level as those I mentioned above.
post #3 of 8
Thanks for your time on the review. I've been enjoying my XM5 very much. I feel that the XM5 has very good detail and is not colored. I've found use for all of the features which is what caught my attention in the first place. It is a great feature packed amp with a fair price tag. I recommend it.
post #4 of 8
Thread Starter 
Hi HeadphoneAddict, GreatDane,
Thank you for the comments!
post #5 of 8
Hey there Sasaki, I ordered a set of Sennheiser HD650's and for some reason I didn't think to order an amp for them(I just didn't think about it, I'm new to this whole audiophile thing), do you think this little amp will be able to pump out enough power for those 650's? I also have Etymotic ER4P's, do you think this will be good for these as well?...Great review BTW
post #6 of 8
FWIW, I've used my XM5 with both the HD 650 and ER4P. I often use the treble boost with HD 650 for a brighter sound and bass boost with ER4P. For some recordings, the 75 Ohm feature also gets used with ER4P.

My XM5 has TI BUF634(buffers) and AD8065 op-amps. I've rarely felt that the amp lacked power with HD 650.
post #7 of 8
WOW...thank you so much GreatDane, that's EXACTLY the info I was looking for(and more), because you already answered my next question. Thanks again
post #8 of 8
Hey! You're welcome. I'm glad I could help.
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