Alto + Sub-Chassis

Stack Audio is pleased to announce the launch of our new Alto+ Sub-chassis, designed specifically to work with standard wooden arm boards. Traditional laminated arm boards can be a weak point on the LP12 with the three screw connections becoming loose and over time and potentially warping. The Alto + has 4 extra screw fixings for laminated arm boards, and it covers most of the Arm board surface keeping laminated boards flat and rigid to the sub-chassis.

Maintaining a consistent centre of gravity for the LP12 platform is critical. The Alto Sub-chassis has varying hexagonal pocket depths, spreading the weight perfectly to maintain the correct centre of gravity. Located in the pockets are AVDC inserts which trap masking vibrations quickly, dispersing this energy as heat.

Useful duty and shipping information can be found here.


  • Machined from solid aluminium, providing a truly rigid structure
  • Varying hexagonal pocket depths, maintaining the centre of balance
  • Precision cut AVDC inserts to trap masking vibrations
  • Tight tolerances ensure a perfect fit with the bearing housing and armboard
  • Precision location rods included when purchased with the Alto Armboard
  • Compatible with Cirkus and Karousel bearings
  • Comes with necessary fixings and grounding wire, which is compatible with all existing LP12s with separate sub-chassis and armboards
  • 4 additional screw points to hold wooden arm board flat and in place
Alun R - Purchased with Alto Arm Board and Cross-Brace


“Well, the Stack Audio “wizardry is now complete, along with a bit of fitting magic from my trusty local Linn Dealer.

New Stack Alto Sub-Chassis, Arm-board and Cross-brace. I was very impressed with the quality of the new parts and I was very impressed in how it now sounded. My local LINN dealer also felt exactly the same way as I did. He also said that the new Alto parts were of exceptional quality, excellent to work with and to fit.

These new Stack Audio Alto parts replace what were previously very early Stack Audio Serene parts made out of Solid Surface material apart from the cross-brace, which was acrylic. those earlier parts were also of very good quality, by the way.

I am extremely happy with how these new Stack Audio Alto parts compliment many other key components of my LINN Sondek LP12. I have also retained the Stack Audio Ultimate Baseboard, fitted in 2017. Together these Stack Audio components provide a very solid foundation to my LP12. This allows the Karousel bearing, Audio Origami PU7 tonearm and Dynavector DV 20x2L cartridge to extract the musicality from the grooves of the record more than I had experienced before.

So how does it sound now? Quite superb to be honest. The bass seems a little deeper, a little more defined and the whole soundstage just seems a little bit cleared too. Trebles are that bit brighter. Vocals are clear, warm and very engaging. Overall the deck sounds very musical indeed. It just feels as if all the artists are in the room.

“The music sounds just like it really ought to”

I can most certainly highly recommend these new Stack Audio components, which I feel offer super quality and performance and extremely good value for money.”

Adrian G - Purchased with Cross-brace and Armboard


“Hi Theo, just some feedback: I have finished rebuilding my LP12 and it includes an Alto Sub-Chassis, cross brace and Serene arm board and the results are amazing. I have to say my wife and I run a precision engineering company in Southampton and specialised in machining aluminium and titanium, so I think I am a good judge of your products and they are well made and very competitive, the LINN keel is just ridiculous, there’s no more than two hours machine time. Keep up the good work and allow us to keep those vintage decks sounding great.”

Paul S - Purchased with Alto Arm-board


“A couple of weeks ago I took delivery of the new Alto sub-chassis and Armboard and duly installed it over the weekend. I had been eagerly awaiting this, since Theo informed me last year that he was upgrading the design from the existing Serene chassis and Armboard available at the time. I had previously upgraded my LP12 with a Serene top-plate, cross brace and ultimate baseboard, and was very impressed with the improvement in sonics (cleaned up midrange, deeper, tighter bass and clearer treible) but nothing could have prepared me for the depth of imrpovement that the new Alto Chassis and Armboard have brought to my LP12.


What really struck me is the bass is now incredibly tight – it’s almost as though it’s going an octave lower, with a phenomenal impact and solidity. Any percussive instrument has a heightened sense of attack, and in rhythmically complex passages I can hear the individual elements of rhythm more clearly, and the sense of timing now seems incredibly precise.


Overall an unqualified success I would say and incredible value for money – a big step up from the standard Majik Chassis (for less dosh than a LINN kore)”

Patrick B - France


“My first impressions: greater clarity, better extinction of notes: better signal to noise ratio.. “the iconic LP12 sound with more transparency”: that’s right!”





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Sub-chassis machined from aluminium to a honeycomb shape with AVDC technology

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