LXminiLXstudio LX521
PowerBoxes and more
Impressum, Recht



The PowerBox is all you need

between CD-player and LX-speakers



The PowerBox is a High-End DSP with ultra linear Poweramplifiers

Being quite sceptical on using digital filtering for high-end listening, only a top-notch DSP solution was acceptable as "brain" of the PowerBox:

Expertly designed digital and analogue sections of the Hypex DSP platform (Netherlands) combined with only finest ingredients allows DSP design without compromise.

The PowerBox provides not only precise filtering, but also ultra linear amplification.

Enjoy the effortless musical presentation by four Hypex UcD amplifiers, well known for their neutrality and very low distortion figures. They are arranged as optimized and fully balanced internal system layout, allowing shortest signal traces and minimizing losses as well as artefacts.

The PowerBox is a preamp with volume control, a 6-ch DSP with 6ch-DAC , feeding a 4-channel power amplifier in one slim but massive powder-coated aluminum top with brushed stainless steel frontplate. Alltogether a perfect match for Linkwitz speakers:

Sound is only "colored" by the artist, not by the amplifier!  >>>>Not just sound. But music.


It's hassle free... no error-prone "spaghetti cabling" necessary.

1) Connect LX speakers to PowerBox with professional Neutrik SpeakON® 1-click connectors.

2) Connect CD-player to the PowerBox ....and enjoy!


How does it sound compared to standard solutions?

Siegfried Linkwitz on http://www.linkwitzlab.com/What_is_new_at_linkwitzlab.htm

I just spent several hours listening to the LXmini when driven by the first production sample of the PowerBox from magicLX521. Together with Dr. Frank Brenner, and an Academy Awards nominated audio producer, we three compared the Hypex DSP and UcD amplifier based PowerBox in my listening room to my typical LXmini setup with miniDSP 4x10 Hd and AT1806 amplifiers. I am just astounded how much more is in the LXmini system in terms of low end definition and overall refinement of sound when connected to the PowerBox. We all heard the remarkable ease, openness and neutrality. And I had thought all along that I had a pretty decent setup and that it would be difficult to get even more out of the LXmini! While I can still proudly demo and listen to my LXmini system even with the miniDSP 2x4 and Emotiva amps, it is difficult to forget this comparison session.


Samuli K with PowerBox4180 :

....Powerbox arrived, everything was professionally packaged and device in one piece. I was very happy to notice that now i can get rid of separate bulky Nad power amps, minidsp, cable jungle etc. mess. Very neat, clean and visually satisfying package. .........

When i got Powerbox the sound improvement was not marginal, it was huge! I was in fall assumption that D-class amplification is kind of thin, artificial and trebly. Sound became very balanced, just correctly warm (still not too warm or ”warm", but compared to Nad system) but very detailed and just coherent........ Sound is even detailed with correct material and Lxminis create that ”sound wall” and disappear!


Jeffrey H with PowerBox 4400Analogue pro on LX521:

Hi Frank,  ....... The detail, clarity, and soundstage are all extraordinary. I don't really believe in magic, but this is the closest I've heard to real music from a recording.  Thank you for all your help making this possible.  Regards, Jeffrey 


Technical Data:



·        analogue:                    2x true balanced XLR ( RCA sources connect via our adaptor cable)

·        digital:                        AES/EBU, SPDIF, optical, USB(program and update)

·        mains:                         220V or 110V version available


·        Front push-buttons (volume control, input selection),

·        LCD display

·        IR remote volume control ability




·        6ch high-end Hypex DLCP, carefully designed digital and analogue(!) sections         http://www.hypex.nl/product/2012-11-23-14-16-32/dlcp.html

·        LXmini filters

·        the DSP may be programmed and updated via USB

·        15 filters, gain, invert and delay may be individually set for Ch1 to Ch6




·        4x Hypex UcD180OEM ultra linear and neutral amplification  (PowerBox 4180)


·       4x Hypex UcD400OEM ultra linear and neutral amplification  (PowerBox 4400pro)



·        1x SpeakON8               DSP Ch1 through Ch4 amplified loudspeaker output

·        2x XLR                        DSP Ch5 & Ch6 balanced line output

·        RJ45                            command output, able to contol chained PowerBoxes

·        AES/EBU                      unfiltered digital output for eg. chained PowerBoxes


 Specifications may vary without prior notice



Going beyond LXmini ?

Use the PowerBox as a basis for your upgrade path in the Linkwitz speaker family.

With additional woofer amplification, the 6-way DSP of the PowerBox will be able to feed your future LXstudio or LX521 speaker system.

The 8-channel system LX521.4 is run by 2 PowerBoxes.

Several PowerBoxes may be chained, allowing a combination of several LX521s and LXmini speakers in larger rooms or home theaters.

Interested in applying individual filters? The HYPEX FILTER DESIGN PC-software makes the PowerBox future proof and allows you to realize own projects. 15 programmable filters per each of the six channels guarantees precise XO definition and a wide spectrum of use.


Preloaded DSP filters for LXmini or LXstudio or LX521.4 owners:

PowerBox 4180, 4x180W: €1890.- (2249€, incl 19%VAT).

PowerBox 4400 pro, 4x400W: €2190.- (2606€, incl 19%VAT).For LX521.4  use two PowerBoxes 4400pro,  one MASTER & one FOLLOWER.

PowerBox 4400A pro analogue, 4x400W; 1 ASP board, for classic LX521 speaker: €2390.- (2844€, incl 19%VAT). Each woofer driver is supplied by its own 400W module!


Orders by email to: info@magicLX521.com

110V and 220V versions available. Please specify when ordering.



Analog Signal Processor (ASP)

To be placed between CD Player and your multichannel Amplifier

ASP boards (tested) with case. Pcbs come with their ARTA test protocols.

The critical components are selected for same or better tolerances as specified (R 1%, PP caps 1 or 2%):

ASP pbcs are enclosed by a very cool and precious custom- made case with a 3mm thick (!) aluminium body, that provides good shielding. Finished with dark graphite  powder-coating.

Inox steel front


The subcut switch multifold parallel switching reduced contact resistance in the signal path. Silver plated, PTFE insulated high quality wires are used in the signal path.

Lasered "magicLX521" logo with several backlight options. This ASP can handle balanced and unbalanced inputs.

Tweeter and woofer level adjustements (see pink noise test in the construction manual) can be easily performed from outside (small openings at the top for the screwdriver).

ca 44x36x5,5 cm.   990€ (no VAT) /1178,10 (incl VAT).

ASP: Order your stuffed and tested pcbs with case by e-mail info@magicLX521.com

Same or better tolerances as specified (R 1%, PP caps 1 or 2%) ,or limited ASP select (PP caps 0,5%)


Standard Power Supply +/-12V for ASP.  €69 no VAT / €82,11 incl VAT




Manually selected Resistors and PPcaps with Tol <= 0,5% are used in the limited ASPselect edition for tighter L/R channel channel matching (add €199 (noVAT)/236,81(inclVAT)



Ultra Stable +/- voltage regulators

These are recommended  by the reviewer in "Linear Audio" Vol.4 Regulator Test:


Sjöström SSR01 positive ultra low noise voltage regulator, stuffed and tested pcb,  €94 no VAT/ €111,86 incl.VAT

Vin:  +14V to +24V;   Vout : adjust by 10x multi-turn trimpot +11V to +20V 

(pictures used with permission from Sjöström Audio)


Sjöström SSR02 negative ultra low noise voltage regulator, stuffed and tested pcb, €94 no VAT/ €111,86


Vin: -14V to -24V;   Vout : adjust by 10x multi-turn trimpot -11V to -21V




What is the difference between ASP and standard DSP?

DSP: after receiving this nice miniDSP 4x10 hd, install the plugin and load Daveys filter configuration (great work from Davey -thanks!) to the machine. Then, adapt the routing for analogue inputs, if necessary.

The miniDSP 4x10Hd worked nicely from scratch, just found a little bit more 50Hz hum, than with the ASP. The easy handling (if you are not afraid of loading filter config files into the miniDSP and configuring the input/output routing), the internal volume control and IR remote capability make the miniDSP a very nice integrated machine.


The ASP was fed by dual mono Sjöström superregulators close to the pcb supply rails, delivering stable +/-16Volts with lowest rest ripple.

The setup was followed by listening tests. The playlist:

-Jazz at the Pawnshop (WAV24bit/88.2kHz)  Limehouse Blues, Lady Be Good

The beginning of those two Jazz at the Pawnshop tracks contain several acoustical aspects (applause, background auditorium talks,..), that may contribute to the illusion of "beiing there".

-Anhaltinische Philharmonie Dessau, Chabrier, Espana (WAV24bit/192kHz)

The Anhaltinische Philharmonie recording has the potential to show the instruments well placed, with dynamics and clarity.

-Chesky Ultimate Demonstration Disc 2 #7 Valerie Joyce, Little Wing (WAV24bit/96kHz) Midrange Purity
-Roger Waters , Amused to death, (WAV24bit/44.1kHz) , Q sound

-Barb Jungr, Sara (WAV24bit/192kHz), vocals, articulation

The LX 521 performed well with the miniDSP, e.g. tonal balance as well as Q sound were fine.
After some time spent with the DSP, I switched back to the ASP. What was the difference between DSP and ASP performance?

OK, it would be just too much expectation, looking for high high-end D/A conversion in a economic DSP machine.

Top-end sources like streamers/DACs meanwhile deliver outstanding, "close to ideal" analogue signals. A huge progress since the metallic/digital sound in the early days of the CD. Sending this "close to ideal" analogue signal through another AD DA in the DSP conversion adds jitter to the signal. Reduced clarity and hiss in sibilants/ harshness may be signs of jitter.

The listening experience showed, that the DSPs high mids seem sharper (a reported effect of jitter) and the acceptable/comfortable listening volume level with DSP is lower than with ASP.

The ASP finally felt more comfortable, cleaner soundstage, silbilants less fizzing and an overall more relaxed listening experience. More defined and dynamic. Easier listening at the higher frequencies. More impulsive bass, instruments show clearer positioned, and well separated from each other.

Nevertherless, the DSP is an economic and versatile entry level device, satisfying up to certain performance levels of signal sources.

For the tight budget, the DSP is a great machine!

However, if you plan to feed your LX521 with a high end source/DAC or analogue phono , I would definitely prefer the ASP. No matter, if listening to studio master recordings, internet radio stations 128 to320kbps or vinyl.

To get the best out of a pair of LX521, I would recommend the ASP (super regulated by Sjöström SSR), the player/DAC/phono show their full capabilities. Dynamics, and soundstage clarity are unmatched leading to a magic and relaxing listening experience.


As ASP is not available for LX521.4:

The best LX521.4 sound heard so far was when fed by 2 PowerBoxes 4400pro.






 -Cables (8x2,5mm²) from amplifier to the Speakon plugs at the woofer V frame and the bridge. 2 X 5m. 349€ (no VAT / 415,31€ incl. VAT)  per addional meter add 12€ (no VAT/14,28€ incl. VAT).


-Cables (8x4,0mm²) from amplifier to the Speakon plugs at the woofer V frame and the bridge. 2 X 5m. 449€ (no VAT/ 534,31€ incl. VAT)  per addional meter add 19€ (no VAT/22,61€ incl. VAT).


Cables LXmini

on LXmini side: SpeakOn connectors

on amplifier side: either SpeakOn connectors (PowerBox) or

4 gold plated Bananas for DIY mounting, please specify this with your order.


4x 2,5mm² cable with  Neutrik SpeakOn 4 (2,5m 24€ no VAT , 5m 38€ no VAT). Order 2 cables , one per side.

PRO cables:4x 2,5mm² OFC with extra robust shell and UV protection. Metal Neutrik SpeakOn NLT4FX-BAG (2,5m 44€ no VAT , 5m 59€ no VAT). Order 2 cables, one per side.




Cables per meter

If you perform your own cabling from LX to the amp, you might consider


the award winning 4 conductor wire Audioquest 14/4:


Audioquest 14/4    €5,80 (no VAT)/ €6,90(incl.VAT) per meter.



these stage approved Sommer Cables

Sommer Elephant 840 8x4mm² 16€ (no VAT)/ €19,04 (incl.VAT) per meter

Sommer Elepant 825 8x2,5mm² 11€ (no VAT)/ €13,09 (incl.VAT) per meter




Passive XO Components 

for LX521 classic, used together with ASP or PowerBox4400pro analogue

2 Clarity Caps ESA 12uF (matched pair) and 2 MUNDORF backlack (top quality, baked varnish) inductors 4mH, 2%


Set of 4 pieces, not inserted/connected . Add 89€ (noVAT) / 105,91€ with VAT.




Anthracite Foam Covers for Baffle Support



covering the cabling in the baffle support. 14€ p.pc (no VAT/16,66€ incl VAT)



Vibration Absorbers (multilayer Sorbothane)


to effectively dampen the vibration transmission from the V frame woofer to the floor.

These ones are rather flat (7mm)  and fit easily below the woofer cabinet.



For the plywood or MDF V frame woofer, use a set of LS3 pads per woofer.

LS3 set for up to 48kg (4pc):  37,81€ (no VAT/ 45,00€ incl VAT)