SQ Impact Report: NDX2 Stacked on NAC552

Purpose: To test my NDX2/XPSDR’s impact to signal quality being stacked on top of my NAC552/552PS.

TL;DR: Putting the NDX2 into standby while playing a LP is more significant a sonic performance bump (+5% v. baseline) than removing it from the system altogether (+7% v. baseline); a net 2% improvement in perceived performance that I don’t really trust I actually heard is not enough to convince me to unstack my components or change furniture. A giant nothing burger but feel free to waste your time reading the rest of this, you may find it entertaining…

System: LP12/ARO/NAPSA/Hana ML, Superline / SCDR (SNAIC 4 to 5), NAC552/NAP300DR (Stock Cables including Powerline), NDX2/XPSDR (SuperLumina 5pin, Chord Ground Arary), Harbeth C7ES3 (Blue Jeans Custom Octoquad 3m Cables w/ ultrasonically welded locking bananas), power delivery via two, dedicated 20amp mains circuits, hospital-grade isolated ground outlets, and a trusty wiremould strip.

Background: I don’t own a FRAIM and I don’t want one. The bookcase I use necessitates stacking my NDX2/XPSDR on top of my NAC552/552PS (gasp!). Don’t worry, I didn’t pay full price for most of this stuff and have a casual, irreverent attitude toward the equipment anyway: I care about records and how things look much more. I’ve heard a lot of hifi (probably sold a few of you components in a prior life as a hifi shop ace) and feel confident that I can hear as well as the next guy or gal (despite a bit of a shift in my right ear… 10-years a Sapper hooah)…

My system is installed on a solid, furniture-grade, cherry-veneered, MDF/plywood core, 6-foot-wide console bookcase with a welded steel base (“Copenhagen Console Bookcase” from Room & Board if you want to google it). It’s a proverbial ‘unit’ at ~400lbs:’mass-loaded’ with about 350 LPs in the storage shelfs. The unit’s base is aligned on-center with the floor joists under my diagonally laid, old-growth cedar sub-floors, and quite lovely oak floors. My speakers sit atop custom Gig Harbor Audio stands, equidistant both sidewalls, approx. 1m from the rear wall, with a slight tow-in towards the listening position at about the same distance per Harbeth’s advice on the triangle thing.

As shown in the photos below, my system components are mostly separated using the ‘brains & brawn’ methodology employed in many Naim systems. My NAP300/300PS, Supercap, and NAPSA sit on the floor under the bookcase which allow for careful dressing of power cords and Bundys - no cables touch the floor and there is free space for air flow around components. All speaker cables are carefully routed, suspended by foam pipe insulation of my own manufacture. Signal cables do not touch power cables or Bundys. Where unavoidable, cable crossing is done at 90 degrees (I think that’s 32 C).

On the top level, the PSs are stacked on the far left, the streamer is atop the 552 in the center, and the Superline and Cartridge are given the most separation from the transformers sitting on the far-right end. I employ a high-quality wifi connection with my NDX2 (gigabit fiber into a top-notch mesh, spray-the-pixies-into-the-air router thinger); I don’t really think a wired connection delivers better performance in my case (yes, I’ve tested it and it’s out of scope for this particular folly anyway).

Methodology: Spin Ry Cooder’s Boomer’s Story - a mint original pressing that’s been run through a Degritter and sounds super dynamic revealing the best the Harbeths have to offer - and make some notes about performance in four different system configurations. 1) Control, NDX2 streaming Qobuz via Roon (listen to the stream) 2) Digital Interference, NDX2 Streaming while the record plays (listen to the record), 3) NDX on standby while the record plays (listen to the record), 4) NDX2/XPS removed from the system completely (listen to the record). I used an iPhone SPL app to ensure the stream and LP we’re volume matched within +/- .5 dB: Avg. 70 dB w/ Max Peaks @ 80dB (I told you this record is dynamic!).

Note: Keep in mind that I really only care about sonic performance with regards to my vinyl playback chain; digital streaming and my fm tuner (Fanfare FT1 if you care) are convenience items for me so whatever blah blah.

Findings: This is all malarkey so believe nothing and trust no one except for your own ears. These notes are what my ears told me in words at the time, so, daddy chill (*if you get that reference please send me a friend request and we can ride off into the sunset together)….

Test 1 - Digital Stream.
Top - Articulate, a little dry and metallic.
Mid - Clear, detailed, a little bit hollow and distant.
Bass - Tight.
Stage - Forward, present, 3D.
Image - Very Centered, anchored
PRAT - Snappy and toe tapping; pretty nice.
One-Word Summary - Exciting.

Test 2: NDX still streaming, but LP actual listening source.
Top - Articulate, organic.
Mid - Warmer, smoother, sweeter.
Bass - Not as tight but open and tuneful.
Stage - More diffused but still centered.
Image - Rounder, deeper, wider.
PRAT - Easy and natural.
One-Word Summary - Easeful.

Test 3: NDX in standby, LP actual listening source.
Top - Dynamic, refined.
Mid - Focused and cohesive.
Bass - Balanced and tuneful.
Stage - Wider and forward again, bigger 3D effect.
Image - Centered and defined.
PRAT - Snappier again.
One-Word Summary - Cohesive.

Test 4: NDX/XPS completely removed from the system.
Top -Really dynamic and sparkling.
Mid - Very focused and natural.
Bass - Tuneful and detailed, more powerful.
Stage - Wider, deeper, open, more expansive.
Image - A bit more presence.
PRAT - Quite noticeable.
One-Word Summary - Presence.

Conclusion and Next Steps: The biggest impact to sonic performance was Test 2 to Test 3, putting the NDX2 into standby whilst playing an LP. I noticed that doing this had a bigger impact sonically than removing the NDX2/XPSDR from the system entirely. Still, I did notice a bit ‘more’ magic running the NAC552 bare on the console with the LP12 & Superline. I do wonder if that’s due to a) wanting to hear that improvement, and/or b) having less stuff in the actual soundstage space between the speakers, akin to pulling the speakers out from the wall… or, c) stacking something on the NAC552 does in-fact sacrifice a bit of performance. How much performance? Well, I would say that Test 2 to Test 3 gave me “5%” performance bump - on par with taking the lid off my LP12 but not as big as ultrasonically cleaning a record. Going from Test 3 to Test 4 was barely perceivable and I’m not sure I trust my judgement here - certainly not enough to pass an A/B blind test 8 / 10 times… let’s call this an extra 2-3% bump in performance.

So the question is: do I get rid of my NDX2/XPSDR for an extra 2-3% bump in LP playback performance? No. Will I put the NDX2 in standby when I listen to LPs? Yes. Will I take the lid off my LP12 when critically listening and make sure to clean my records with an ultrasonic cleaner? Yes… both those yield more performance benefits in my system than unstacking the components. Do whatever you want, I’m keeping things as they are over here for the time being. Then again, selling the NDX/XPS would buy a lot of records, which I’d still need new furniture to accommodate.



Wow ,comprehensive write up !
I would first of all remove the big furniture and the system, so they don’t stand in between the speakers.

1.3% sound quality improvement.



I’m bored, I tested it, it all sounds fine and I’m doing nothing and going back to listening to records now :smiley:


Beautiful room


Slight side issue. When we talk about stacking what sort of distance are we thinking about for separation? My NDS and 552 are seperated by about 5cm plus a wooden Quadraspire shelf. Not sure I have any ways of changing this easily but just curious.


Mine is on top of the 552. See photo.

Nice room and set up, have you tried dropping your NDX2 and XPSDR onto the shelves below and rearranging or losing some books etc ?

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I can tell you’re a thinking man… You call out the only real, feasible, and acceptable move I can make given what I’ve got. I’ve thought about it.

Two issues: 1) to use the shelves, I’d have to cut out a rather large portion of the console’s back, and 2) either side is not large enough to accommodate the NDX2/XPSDR side by side… I’d either have to stack (this time on top of the PSU :-1: ) or relocate my FM Tuner (which so nicely fits with a rather diminutive 3" D hole cut into the console’s back to accommodate its cords.

You call out the only real, feasible, and acceptable move I can make given what I’ve got.

I’ll walk that :point_up_2: back a bit, another creative solution I’ve thought about is adding a couple wall shelves above/behind the console.

That would work, I was only looking at what you already have. Another idea in relation to shelving is to get a wall bracket shelf for your deck and free up space, meaning space needed for only one box below ?

All true. Thanks for the thoughtful response, @glasnaim :pray: :smiling_face:

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There are some good wall turntable shelf solutions from the likes of Quadraspire etc

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Fellow ex-Sapper here… UK version! Great read and I hear the Sapper common sense coming through! :joy:

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I loved this. Thanks for writing it.


Thanks @Igel. I’m not keen to do or try it because our room setup just feels “right” atm, but if I got longer speaker cables I could move the whole rig to a side wall. But then the whole feng shui changes :man_shrugging:

Okay I see,but it is an fantastic upgrade in sound 23,3 %:wink:

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Put it all on a Fraim rack and it will be even better, a lot better. I originally had my system on a TV unit and when i got a Fraim the difference was quite startling, almost black box territory, especially when one cranks the wick up.:cowboy_hat_face:


For nearly the same cost I would sell my ndx2, xpsdr, and nap300drs to buy a nap500dr. I’d put it on the same furniture and really have a black box bump :metal: