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Matrix HPA-3U based remote preamp / crossover

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Item Condition: Great
Shipping Options: Pickup available but audition is not available.,Shipping is available at agreed cost.
Suburb or Town: Brisbane Northside
State: QLD
Payment Method: Paypal as a friend
Reason for selling: no longer needed

Further Information


This product has not been manufactured by a qualified individual or company, therefore contains electrical circuits that do not necessarily comply with Australian Standards. I understand that as the seller, I may be liable to repercussions in the event of equipment failure. By advertising and selling this product, as the seller I also agree that I am solely liable, and the publisher of this website takes no responsibility for any injury or death resulting from, whether directly or indirectly, any accident that may happen as a result of the failure of the product being sold. If in doubt, seek the services of a qualified electrician to inspect the product to ensure it is safe for use.



This is design based on the Matrix HPA-3U which is a very fine sounding unit. Operates in Class A. It's loosely based on the Lehmann black cube but it's design has been refined by Matrix and IMHO a more dynamic sounding unit (based on direct comparison as a preamp in a high quality 2 channel system).


I used very high quality parts throughout this project. Just the caps in the Matrix are about $120 all up. They consist of 2X Jantzen Superior Caps and 2X Aluminium Foil Weet caps (a bit like the Janzten Alumens but more detailed).


The enclosure features an inbuilt electronic relay based volume control and remote. The inputs drive the Matrix and the volume pot in the Matrix was replaced by the one in the enclosure.


There are then dual crossover boards in the enclosure. They are 12dB/ octave high/low pass unbalanced unit that is low noise and uses dual op-amps. The parts used were very high quality too.  There are some spare crossover point boards that allow you to solder in some resistors to change the highpass / lowpass points. https://www.ebay.com.au/itm/124534690758 There is a dedicated power supply unit that taps of the mains.

The Matrix has it's own PSU already.


I have included 5 dual op-amps - OPA213PA - The unit requires 2 op-amps per channel on the crossovers. And 1 dual op-amp for the Matrix. The op-amps are untested. I'd probably use something better such as the Burson ones in the Matrix to extract the best sound out of it.


Jantzen silver plated OFC / teflon wiring internally.


Comes with a remote. 


There is a fancy HIFI Tuning silver star 5X20mm slow blow fuse in the Matrix (you need to pull the unit out to replace it). Worth about $45 each. There are fuses in the main input, the crossover PSU and as mentioned above, the Matrix preamp board.




Chassis / PSU and remote stepped relay is similar to this - https://www.ebay.com.au/itm/353464357239


Note that the unit has 7 sets of RCAs at the rear which allows you to configure this different ways. 4 are inputs but it only accepts 1 input at the moment. Not sure if you can wire it up to accept multiple switchable inputs. I also ran it for a good while just using it as a preamp running from my DAC to my preamp. It's good a really clean sound and great warmth and dynamics.

The very last time I used this unit, I actually had the Matrix "out of circuit" and wired it so that the inputs went straight into the crossover boards and then the other 2 sets of RCAs had low pass output and high pass output. (refer to the closeup of the wiring next to the crossover boards). It's all ready to be re-wired as required if you want to bring the Matrix and volume control back into the equation.


Plenty of scope for adjustments. I only feel confident selling to someone who is aware of the potential dangers of working internally in a mains powered unit.


I can post at cost. Paypal as a friend only please.



Left is input selector

Right in volume.

LED display is blue from memory.
Enclosure is in good condition with only 1 small scratch on the rear of the top of the chassis. 


Crossover boards and dedicated PSU:




Matrix unit. ALPS volume pop removed and wired to the relay volume control.



Opamps and spare crossover modules:



Edited by Deepthought
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