"What a refreshingly honest blog about listening to music through hi-fi. So happy to see views based upon the enjoyment of music rather than so-called sound 'quality'." - Peter Comeau, Director of Acoustic Design at Mission / Wharfedale

Sunday 11 February 2024

A "New" Retro Streamer - Pushing the LK Envelope

For information only: this post is not a set of instructions nor is it intended to encourage any kind of modification of electrical products. As they say: "Do not try this at home".

Some of you may have read through the first "episode" of what has now started to be a theme - modernise a Linn LK enclosure with a streamer, or, from the other perspective, taking a modern streamer down the retro route.

That little excursion is available here. It covers off the history of the LK boxes and describes the Sneaky Music DS also used in this project.

A quick recap - that story covers converting an example of the iconic Linn "LK" enclosure into a streamer as purely a source component, using a Linn Sneaky Music DS in "source only" mode.  That's possible in a non-ventilated case, but to use the full features of a Sneaky, including the power amplifiers, that needs a ventilated case, so something from the all-in-one or the power amp sections of the LK range of products.

The other difference is that in the previous project I wanted to present only the source component connections to the outside World, but with this project the intent is to provide all of the Sneaky's connectivity so all of its functions can be enjoyed. Let's see how it panned out..

Basics

Ingredients this time:

- Linn Sneaky Music DS

- Linn LK85 Power Amplifier (with dead mainboard)

- Lots of M3 fasteners

Plan

- Strip the interior out of the LK85

- Trial fit the Sneaky MDS board and PSU

- Work out all the fittings etc., similar to the previous project

Did That Happen?

No. And, yes.

Starting with the LK85, which had a dead mainboard, all the innards were removed - as it happens the LK85 toroidal transformer was repurposed into an LK140 power amp that had a healthy mainboard but a dead transformer.  So the LK140 won't produce the power it used to, but its back up and running and can be used again.

The LK85 chassis stripped bare looks like this:


The back connector panel is at the top of the image, the toroidal transformer mounting hole is midway down on the right then the ventilation and substantial heatsinks.

The ventilation and heatsinking on the LK85 and give confidence that the comparatively low power amps in the Sneaky Music DS will be adequately cooled.  Next it was time to remove the heatsink from the base of the LK chassis - this involves drilling out the securing rivets.

Drilling out the heatsink rivets

This left lots of space to work in side the chassis but also a base plate that wasn't particularly secure.  So once the heatsink was out its mounting holes, that also mate to a centre strengthening plate, were replaced with M3 nuts and countersunk bolts.


Countersunk bolts replacing the heatsink rivets


So that's the basic starting point.  Time to have a look at how to layout the Sneaky boards inside the LK chassis, which is likely to be different to the previous project because there's now the need to look after the power amp and it's heat production.

And then something struck me - once the Sneaky MDS is relieved of its clamshell outer panels, the remaining chassis looked very similar in width to the LK.  If all went well, perhaps the whole Sneaky chassis would slide down into the LK with no modification? A quick check and I found that it is EXACTLY the same width as the LK - so no, it won't slide in easily.  Because the LK box has a chassis with sides and then the top / side panels are a slide over clamshell, the internal side walls are not visible on a fully assembled product. A few measurements told me that it would be possible to cut away sections of the chassis side panels and integrate the entire Sneaky MDS into the LK rear panel - so no need to strip the Sneaky boards / PSU and no need to use jumper cables from those boards to a custom back panel.


Cutting away the side and rear panels ready to accept the Sneaky MDS chassis in its entirety. Around 3/4 of the length of the side panel has been removed.

Trial fitting of the whole Sneaky MDS chassis into the newly cutaway LK inner panels.

In the above picture you can see that the external width of the Sneak MDS is exactly the same width as the LK chassis and in this trial fit, this was confirmed.  The 4x threaded bosses in the top of Sneaky chassis are the mountings for the external clamshell panel.  They are replicated on the underside and their positioning means that only 4x standoffs can be mated to them to supply support and fixing in to the LK. Plus the height up from the LK base means no need to powerfile away the LK's old threaded bosses, so one less job to do.
I didn't have standoffs of quite the right length to screw directly into the Sneaky chassis, but adding an nut to the threaded section before mating them up gave exactly the right clearance.

Making the standoffs in stock a couple of millimetres taller

Threaded standoffs fitted into the Sneaky threaded bosses that normally provide a fixing point for the outer clamshell panels

Underside of the Sneaky chassis with standoffs in place


4x holes were drilled to align in the LK chassis and another trial fitting undertaken. Note that the front to back location of the Sneaky chassis aligned the original back panels of both products.

Alignment of the remains of the LK rear panel (along the bottom of the picture) with the entirety of the unmodified Sneaky rear panel. Together they don't vertically add up to the same total of the old LK back panel, leaving a gap across the whole width

The only modifications needed to the Sneaky are two fold.  First, and easiest to describe, is swapping the original front blue panel LED to the green "power" LED next to the on-off switch of the LK.  This just involved a swap of the connector (as per the previous project) and re-routing of the cable.  The second part was to accommodate using the front power switch.  This required a slight tweak - the brown positive cable from the IEC rear panel socket that goes directly to the PSU was unsoldered and effectively routed round to the power switch on the front before going back to the PSU. Handily, by fitting a rubber grommet around the Sneaky's front LED mounting hole, it was possible to route this cable without and modifications to the Sneaky chassis.

The LK power switch assembly as removed from the amp.  The IEC socket is cut off leaving the 2x brown cables going to the switch

This is the Sneaky front LED mounting point.  A rubber grommet protects cables passing through - this was used for the mains switch cable and the LK green front panel LED

Front panel switch fitted with a 2 pin connector

The redirected brown cable is sleeved and makes its way neatly under the PSU output cable off to the front panel power switch


Passing out of the Sneaky chassis to the front panel

Adding a 2 pin connector to mate up with the connector added to the front panel switch leads



And that's about it. Except for that gap across the top of the rear panel.  The material for this was taken from the top of the original LK back panel, but mounting needed to be resolved.  Handily some offcuts of aluminium panel from the last project were just the right width to create a pair of mounting brackets.  These were cut to length, bent to shape and bonded to the back panel gap filler. They then sit neatly onto the Sneaky's upper clamshell mounting points.

Offcuts cut to size for their new role

Offcuts bent into brackets

Bonding the newly fabricated brackets to the newly created back panel filler panel. Note use of universal clamping equipment

And that was largely that.  Some primer and matt black spray paints finished off the exposed LK chassis edges and spruced up the rear panel.  I used satin black on the first of these projects and gave matt black a try here.  I will keep to the satin for future project.


So here it is, the second of the LK streamer projects.  This was a simpler build than the previous one and is probably the route I'd use again in the future.  It has the benefit of exposing all the functions of the Sneaky but it has the downsides of needing a vented enclosure (harder to get hold of because the amps are probably mostly still in use) and it doesn't have that more bespoke feel to it. There is one further advantage - the Sneaky needs the absolute minimum of changes, so could be converted back to standard in about 15 minutes.

Rear filler panel mounts



Finished
LED and mains switch cables pass through the grommeted LED hole of the Sneaky. Connector of the power switch cable

A neat final result

Base panel labelled up with the new information.  LK mains transformer mounting hole plugged with a rubber bung

As per the plan - absolutely no clue that this is anything other than an LK power amplifier

Until you turn it around and find a whole bunch of unexpected connectors.  As you can see in this picture the top filler panel, the unmodified Sneaky back panel and the remaining lower edge of the LK back panel marry up well to make an (almost) seamless result.

And finally...

Here is the Sneaky going through its boot up sequence, using the original green LK LED rather than its own blue LED.



Monday 29 January 2024

A Retro Streamer, Is That A Thing? Linn's Iconic LK Series Brought Up To Date

For information only: this post is not a set of instructions nor is it intended to encourage any kind of modification of electrical products. As they say: "Do not try this at home".

Boxing Clever?

Back in 2007, Linn introduced the Klimax DS streamer and told the World that they believed streaming to be the future and that it outperformed their best CD player at that time (the CD12).  They also cemented the format of the new Klimax casework introduced earlier with the Klimax Solo power amp and the Klimax Kontrol pre-amp.

Klimax DS

With the full rollout of the lower Akurate and Majik ranges, Linn's iconic LK casework from the 1980s into the 2000s was fully retired.

Akurate DS

The LK range really span the whole of Linn's electronics product line with its origins in 1985 with the first pre-amp and power amp, the LK1 and LK2, right up to the 2000s.  The casework for those early components were product specific but they set the basic blueprint for what became the "standard" LK box - a 2/3rds width box when compared to most hifi of the time.

Some LK product examples:

LK2 and LK1


Linn Classik all-in-one system

Linn Klout power amplifier

To complete the history lesson in the context of this post, all streamers after the 2007 Klimax DS have been in Klimax, Akurate or Majik casework, plus some more specialist products such as the Sneaky MDS for multi-room installs and the "lifestyle" Kiko all-in-one product.

Some Linnies lamented the end of the LK casework, seeing it as a simple iconic design which embodied musicality over bling.

So, is there a way of building a streamer that will give that "retro" LK style but updated with more recent internals?

Basics?

Linn's later range of cases are, generally speaking, larger than the LK range.  Although the internals of the Klimax casework, which is machined from a solid billet of aluminum, is not very spacious.  Maybe there is a later project on that topic...
This means that something more compact needs to be sourced to form the basis of a streamer inside an LK case.  LK cases need to be sourced too, which is easy if you want to dismantle a working product (and pay the prices of working products), but very much harder when you look for dead products to use - Linn's equipment being so reliable, even many 30 year old products are still working well. Sources of cases are very welcome - please add to the comments below!

As mentioned above, there is the Linn range of streamers that are built primarily for multi-room installations.  The intro level is the Sneaky Music DS (now discontinued in favour of the multi-zone Kustom DSM product) which is a streamer and amplifier in one (it is not an all-in-one product as it does not have the ability to accept other sources into its pre-amp).  It is housed in a very simple clamshell style case around a rigid chassis.  8x screws open up the case and reveal the innards.



I already use a Sneaky Music DS in the workshop system, lightly customised (or kustomised?).

Workshop Music DS



A Good Fit?

So, does a Sneaky Music DS fit inside a standard Linn LK box?
No, the basic chassis is too wide.

What might've been a day's project therefore become more involved.  It started with stripping the internals of the existing LK box and removing the main circuit board and PSU from the Sneaky (the IR board came later). 

Inside of Sneaky Music DS before dismantling

The empty Sneaky Music DS chassis (IR board still in place, top right)


Then, several orientations / positions of the circuit board and PSU were considered - primary focus being on ensuring existing mains electrical safety is maintained, the second on minimising change.  Several things needed to be taken into account on the orientation decision:
  • Electrical safety
  • Ease of extending the connections from the board to the back panel
  • Closeness of audio circuits to the power supply
  • Where mounting points need to be drilled into the LK chassis
  • Room for the first stage heatsink
  • Minimising cable changes for the power supply
  • Ensuring the power supply heatsink makes good contact with the enclosure




You can see the final orientation chosen in the later pictures.

I also wanted this first project to be purely a DS, rather than the full Sneaky Music DS with an amplifier - to think about this as a source, rather than an amplified room solution. It would therefore fit better into a existing LK based system as a new source format.
The Sneaky case has slots in the top and bottom to allow cooling of the power amplifier modules which have their own heatsink.  That would mean the LK case would need to be a vented version too - I didn't want to go down that route on this project.
A search through the settings options on Linndocs - and the impact of those settings - established that the "volume control off" setting also disabled the power amplifier - resulting in minimal heat production.  So this solution has to be configured that way in Konfig or in the online Manage Systems tool - I left the most immediate heatsink attached to the power amplifier chips and it is connected to the casing using metallic mounts, so if there is any residual heat it will be dealt with.

So a DS it would be then.  This had another couple of implications - a need for a new, custom, back connector panel (omitting the speaker terminals and the old skool Linn multi-room system connections) and the ability to leave the donor Sneaky Music DS chassis in one piece - enabling the boards and PSU to be transferred back there if required in the future.

Quick Build?

In general terms, this process lead to a fairly straightforward build.  Mechanically the existing LK rear panel needed to be cut away and replaced by a custom version, but electrically I needed to find a way to transfer the required ports (ethernet, audio out, SPDIF out, Toslink out etc.) to the rear panel, in addition to a "fallback" facility.  In previous projects I've attempted to remove an external connector (such as audio out) from a circuit board to be replaced by cables, I found it far too easy to damage the delicate tracks on the circuit board this way.  So "jumper" cables looked to be the best option. Although this looked simple enough, sourcing suitable cables took a while to find and then to be delivered. Then some needed some further modification...
  • For Toslink I found a "pass through" panel connector that has mounts and female connectors on both sides - combine this with a short optical cable (one end having a swivel 90 deg mount) solved that one.  (in the later pictures this is the braided silvery grey cable)
  • I wanted to be a bit flexible on the route for audio out so chose a pair of standard interconnects with 90 deg connectors each end - then cut off one end of this cable so it can be soldered to a panel mount pair of phono sockets on the back panel.
  • Mains was easy - the existing LK rear panel socket remains as does the front panel switch and the existing connector is directly compatible with the Sneaky power supply.  The front panel LED "on" indicator we'll get to soon.
  • SPDIF - I chose a panel mount single phono socket.  However, in the Sneaky its outer connection has no electrical connection to the Sneaky chassis - so I needed to find a nylon external washer and a nylon "stepped" T washer internally where the leg of the T goes around the phono socket and through the back panel to create electrical isolation.  The correct depth of T couldn't be found anywhere so I purchased something too long then filed it down to size.  The connection from the Sneaky board SPDIF to the new external connector was a simple shortened phono cable.
  • Fallback - this is a tiny microswitch on the circuit board. Fortunately it has dual orientation mounting which means there are 2x tabs on the top of the switch that replicate the bottom connections.  Cables soldered to these tabs are taken to a stainless steel push switch - another component that had to be ordered specifically for the project.
  • Finally - ethernet.  After much searching I found a very short cable that has a normal RJ45 plug on one end (to plug into the Sneaky board) and a chassis mount socket on the other end.
So with all the connections sorted, the build got underway, trial fits and test power-ups continue throughout the project:


The first modification was to remove all the existing threaded mounting bosses in the LK chassis that would not be used and would be hidden under the circuit board - short circuits are not a good idea.  I left the bosses in other areas in case they could be used for cable tidying clips.  A power file made light work of this job.  The positions of all the original Sneaky circuit board mounting points were also marked up and 4mm holes drilled through (the screws are 3mm, but 4mm allows a little "tolerance").

LK bare chassis - black dots are for 4mm holes, arrows for bosses that need to be filed away.


LK chassis with bosses removed and Sneaky board mounting holes drilled

Closer view of removed bosses.

The power supply location was then addressed - drilling through the side of the LK chassis and countersinking to allow the top sleeve to still slide over the main chassis without fouling on screw heads.  Also, because the power supply unit is in a different orientation with more space around it, a angle strip of aluminium was bonded to the side wall to ensure good locating.  

A small amount of countersinking on the underside - note the need to relocate one of the feet by about 2mm

Countersunk hole in side panel for PSU mounting

I didn't want to drill the front panel of the LK box, keeping it as clean and traditional as possible.  So a hole is cut into the front edge of the base panel for the IR receiver - not sure how well this will receive a signal, so will see how that goes.  Also to keep the front panel clean, the existing green "power on" LED is re-purposed to function as the original blue status LED that's provided on the Sneaky.  The connectors used by Linn are not branded and I have not been able to track down the correct product.  However, an existing common industry connector has the correct pin spacing and a little work with the powerfile on the outer dimensions of the plug ensures a good fit.

Modified connector

Connecting the green "power" LED to the Sneaky LED port

Hole for IR sensor - it sits on its own very small daughter board

Additionally M3 10mm standoffs are added to the underside of the Sneaky circuit board. These align to the new holes in the base of the LK chassis and are secured using black dome headed M3 allen bolts from underneath.

M3x 10mm standoffs. This is an early trial fit - completed project has shakeproof washers between the nut and the circuit board

The final element is to address the rear panel.  A connector layout was sorted on paper then the plan for cutting out the existing rear panel marked up - for strength of the existing chassis and to support the new rear panel, cutting is kept to a minimum.  The rear panel is formed from a new sheet of aluminium then the holes drilled or cut out with a jigsaw, checking dimensions and fit iteratively.

Rear panel cutaway, retaining as much as possible for strength and to support new rear panel

One of the many trial fittings of the new rear panel. In this photo you can also see the aluminium angle strip bonded to the side panel - this helps with locating the PSU.
Random selection of isolating plastic washers on hand.  Of course, as usual, the exact size of washer for the SPDIF connector was not available, until Amazon delivered the solution...


And Finally?

Finally? Well, these things are often revisited later. But for now we have a fully working DS as a source in an LK box, so mission accomplished.  Finishing touches included several coats of spray satin black paint for the rear panel and labelling from a Brother label printer.

There may be follow ups, perhaps a fully functioning Sneaky Music DS with the amplifier in play too.  Perhaps something completely different!

Please leave any comments / questions below, and thanks for reading.