Linn Exakt and PMC Twenty.26. World First Review Part Two - Converting The Speaker

Part Two Of A Three Part Review

Part One of the Review Is Here

EDITED 30 September 2016:  The official Linn conversion kit for the PMCs are now available from Linn dealers - there's now no need to convert DIY as per the described below - although the official kit still requires much of the same actions :)  Note that the PMC warranty will still be voided by the Linn kit.

After conversations with Linn about the timing of the conversion kit launch which is still not clear, back in April it was time to take the plunge.  So here's what is involved in the conversion from standard Twenty.26 to an Exakt compatible version. To be fair, this conversion could be done for any project to convert the PMCs to any form of active operation, it is not specific to Exakt.

FIRST AND MOST IMPORTANT: THIS CONVERSION WAS DIY AND IS NOT APPROVED BY LINN NOR BY PMC. THIS CONVERSION WILL INVALIDATE THE WARRANTY ON THE SPEAKERS. THIS IS NOT A COMPREHENSIVE GUIDE, IT IS NOT INTENDED AS A SET OF INSTRUCTIONS.  ANY FOLLOWING OF THESE STEPS IS ENTIRELY AT THE RISK OF THE PERSON MAKING THE CONVERSION. THERE MAY BE ERRORS OR STEPS MISSING. NO ACCURACY NOR COMPLETENESS CAN BE IMPLIED. YOU HAVE BEEN WARNED!

The basic principle here is to remove all electronics that sit between the rear terminals and the drive units in the speaker. Fortunately, PMC have provided the .26 with pairs of terminals for each individual driver unit within the speakers. This is intended for bi-amp or tri-amp operation of the speakers, still in passive mode.  Exakt needs a direct connection to each drive unit within the speaker, so the 3x pairs helps considerably in this conversion. The latest Twenty5.26 from PMC has reverted to a single pair of terminals and uses a metal panel, so would be considerably more work to convert. The plan was to make the conversion reversible, so making as few modifications as possible whilst still achieving the objective.

Dismantling and Removing The Passive Crossover

The back panel with the vertical terminal links already removed - this is how the speaker would be used in a tri-amp passive arrangement.  Note the textured paint finish on the back panel shows every bit of dust and finger mark, but these are easily removed with a lightly dampened cloth, as you will see in the finished article pictures at the end of the post.

The panel is held in place by multiple allen headed countersunk machine screws.  They're not particularly tight as they're threaded directly into the MDF of the main cabinet.

Once all the allen head screws are removed, the panel can be lifted out.  Here, a cloth has been used to support the panel on the speaker's stand without damaging the finish of the stand.  The panel is a fairly straightforward piece of machined MDF.  The crossover is very substantial and looks to be populated with good quality components. Along the top of the picture the cables go out to the individual drive units - these will need to be connected directly to the speaker's rear terminals to enable Exakt operation.  At this point they are kept connected until they can be correctly identified.
Here the damping foam for the Advanced Transmission Line can be seen.

Fortunately, the drive units for each cable are clearly identified and each cable has a clear + side marker on the cable itsself.  Before disconnecting the cables, the treble cable was given a single cable tie as a marker, the mid-range cable 2 cable ties and the bass cable 3 cable ties.  This makes them identifiable once they are removed from the passive crossover.  Note different gauges of cables used

The crossover circuit board is attached to the back panel by 4 crosshead corner screws and the mounting bolts for the 6 terminal posts.  Here an 8mm spanner is being used to loosen the terminal post nuts.  There are 6 nuts, washers and shakeproof washers to be removed.  Note these were only nipped up and not tight - presumably to avoid damage to the circuit board.

Once the 6 terminal nuts were removed, the corner crosshead screws were removed

The crossover board then just lifts off the terminals.  Here the plastic spacers that keep the crossover board supported away from the back panel can be seen.  This is all the dismantling completed - the posts and spacers all remain in place as this is where the cables that go to the individual drive units will need to be connected

Conversion

At this point, all the passive crossover components have been removed.  The speaker cables that go from the passive crossover to the drivers have female spade terminals, but they now need to be connected to the back of the cylindrical terminal posts.  It would be easy enough to just cut off the female spades and solder on some loop terminals, but that would make the conversion back to standard passive more complex and that was something that was to be kept as straightforward and as standard as possible.  This maintains the future resale value of the speakers as there is a much bigger market for standard passive speakers than there is for Linn Exakt compatible speakers.

So a conversion from cylindrical terminal posts to male spades is required.

Parts required are 5mm gold plated loop terminals (its hard to find any of these. So here, 8mm are used ones and they're a little larger than ideal so stanless steel 5mm washers were also used to help with the fit), male gold plated 6mm spade terminals, some solder and tubes of insulation

On the left the 6mm male spade, on the right the 8mm loop.  Using pliers, the cable grip part of the male spade was gently squeezed together to the point at which it was a tight push fit into the cable tube on the loop terminal

Here the male spade has been push fitted into the loop terminal

Working through the 12 connectors - 6 for each speaker

Using a 45W soldering iron, heat was applied to the interface between the loop terminal and the spade terminal at this end of the loop terminal's cable tube.  Only once the flux would melt on the outside top of the loop terminal tube was the solder applied to the joint - this makes sure that all the surfaces are hot enough to receive the solder at the same time and eliminates the chances of dry joints.  Soldering is being carried out on a ceramic tile work surface

After cooling the male spade on each terminal was bent upwards to approx 45 degrees to assist with connecting to the speakers' internal cables.  Later, after fitting the loop terminal to the speaker terminal posts, the loop terminal was also bent upwards by about 20 degrees as other wise it would have been easy to trap the cables between the back panel and the speaker carcass

The terminals are then attached to each of the terminals on the inside of the speaker back panel using the stainless steel washers and the shake proof washers and nuts that originally held the crossover to the terminal posts

Then insulating soft plastic tubes were added over the male spades.  Probably not necessary.  Additional pencil markings show which way up the panel goes and which column of terminals is +ve

Here the panel is offered back up to the cabinet and the cables connected.  You can see the extra bend put into each of the loop terminals to move the cables away from the cabinet.  Tweeter to the top pair, mid to the middle pair and bass cables to the lowest pair, using the previously fitted cable ties to ensure correct connection order.  Note, the cables are only just long enough to reach the terminals.

Once the panel was refitted, a 1.5V AAA battery was used to ensure that the speaker cones all moved in the correct direction.  Put the positive of the battery onto the positive of the speaker and negative to negative and the speaker cone should move outwards,  Just a brief touch is enough to check but doesn't damage the drivers

The back panel was then masked up to create guides for adding a set of old Linn active system labels

Labels installed

So that was it, all done.  Checked, checked and checked again.  The connection sequence was as follows:

- Connect bass amp to bass terminals
- Play music quietly and ensure only bass info was coming out of bass drivers.
- Switch off amps
- Connect mid amp to mid terminals
- Play music quietly and ensure mid information is coming out of mid drivers
- Switch off amps
- Connect treble amp to treble terminals
- Play music quietly and ensure treble information is coming out of treble drivers

Enjoy the music.  Pack the passive crossovers carefully in bubble wrap and a strong box and store in cool dry place.

Part Three Of The Review Is Here 

EDITED 30 September 2016:  The official Linn conversion kit for the PMCs are now available from Linn dealers - there's now no need to convert DIY as per the instructions below - although the official kit still requires much of the same actions :)  Note that the PMC warranty will still be voided by the Linn kit.

Acitvating Katans With AV5125

In this post there's a pictorial explanation of changing Linn's 2-way Katan speaker from passive operation to bi-active using stereo active cards inside a Linn AV5125 power amp.  They're in sequence order.

NOTE:  IF YOU ARE AT ALL UNSURE OR LACK CONFIDENCE, TAKE THE SPEAKERS AND AMP TO A LINN DEALER TO HAVE THIS WORK DONE.

THE SEQUENCE BELOW ARE THE STEPS I TOOK TO SUCCESSFULLY MAKE THIS CONVERSION.  IT WAS SUCCESSFUL FOR ME, BUT NO RESPONSIBILITY IS TAKEN FOR THE ACCURACY, OR OTHERWISE, OF THIS INFORMATION.

In original single wired passive form.  By removing all the collars on the terminals, the configuration cards that are recessed into the back of the speaker cabinet can be lifted out

Collars removed - each side of the configuration card there is a recess in the speaker cabinet, allowing for access to lift the cards out

There are 2 configuration cards.  Each one has a different configuration on each side - in this case 'single wire passive' is on one side of both cards.  Put the unwanted configurations back onto the connection terminals first, then the card you require with the required configuration facing outwards, then refit the terminal collars.

This is the reverse side of the 2 cards shown in the picture above.  Choices here are 'Katan active' and 'Katan bi-wire passive'

The 'Katan bi-wire passive' card has been fitted onto the terminals, then this 'Katan active' card has been laid on top

Collars are fastened back on and tightened.  Any blanking plugs inside the terminals need to be moved to new positions, freeing up the appropriate connections for active use.  Here I've used red = bass +ve; black = bass -ve; yellow = treble +ve, grey = treble -ve

Now to the amp.  Switch off and unplug the amp and disconnect the mains cable! Laying on a firm but covered surface (to protect the finish) top downwards, the amp looks like this.  There are 4 self tapping screws along the silver section which need to be removed.

The cover of the amp can then be slid off - the amp chassis slides out of the back of the cover.  Once removed, place the cover out of the way and somewhere where it won't get damaged.  Place the amp chassis on your work surface, base side down.

BEFORE PROCEEDING FURTHER, YOU MUST TAKE ANTI-STATIC PRECAUTIONS BY EARTHING THE AMP CHASSIS AND WEARING AN EARTHED ANTI-STATIC STRAP.  IF YOU DON'T KNOW WHAT THESE ARE OR HOW TO USE THEM, STOP NOW AND TAKE YOUR KIT TO A DEALER.  STATIC ELECTRICITY CAN DAMAGE THE CIRCUITRY!

This is the amp chassis without any active cards or support fittings.  The stereo active cards are going to be fitted top left in this picture - across the back of the amp

To fit the cards, the plastic circuit board stand-offs and screw are required.  These are usually inside the amplifier.  However, many amps will not have these installed as they have gone missing over the lifetime of the amp.  If your amp is missing these, or the ones for the mono card, please get in touch as I have complete sets available for purchase.
In the full kit there are long, medium and short stand-offs with a protruding thread at one end and a recessed thread at the other.  There is also one very small stand-off with recessed threads at each end.  The tall stand-off and the very small stand-off with recessed threads at both ends are used only for the mono card.  Fitting the stereo cards as described here uses the medium and short stand-offs that have a protruding thread at one end and recessed thread at the other, along with a short screw.  These are the stand-offs shown above

Fit the medium stand-off as shown above, into the threaded hole at the rear left of the amp.  Finger tight is enough - the threads are only plastic, so please take care.  A second picture of the medium stand-off is shown below.

ALSO NOTE THAT I HAVE FITTED THE BASS CARD INTO THE LOWER SLOT AND THE TREBLE CARD INTO THE UPPER SLOT.  ALL THE STEPS DESCRIBE THE SEQUENCE I USED FOR FITTING THE CARDS THIS WAY AROUND.  THEY CAN BE FITTED THE OTHER WAY AROUND, BUT CONNECTIONS WILL BE DIFFERENT, SO TAKE CARE.

A stereo active card.  This is the bass card for a Tukan (or a Katan, or a Sekrit)

For the first card being fitted, fit the short connection cable as shown above

Now slide the card into the lower set of slots in the back of the amp (you can see the green tabs of the card peeping through the amp's back panel).  The slots are the same height in the amp as the top of the medium stand-off fitted earlier

Another view of the first card sitting in situ.  Note that the card sits neatly on top of the medium stand-off fitted earlier

Now connect the connecting cable into the amp board as shown - channels 4 & 5.  In my install this is the bass card, so now Channels 4 and 5 will output bass information

Now fit the short standoff by feeding it through the installed card and then tightening into the thread of the medium stand-off.  Again, finger tight only - take it gently!

Now, repeat the last few steps with the top card, fitting the longer cable and sliding the card into the top slots in the back panel of the amp.  Connect the cable into the port on the amp labelled Channel 2 & 3.  In my install this is the treble card, so now Channels 2 and 3 will output treble information

If the card is fitted with the treble adjustment control, push out the black blanking plug to allow the control to protrude through the back panel.  Here the cards are both installed, the green tabs can be seen through the back panel, as can be the white treble control knob

Now fit the short screw through the top card and into the short stand-off.  Again, tighten enough just to hold the card in place - don't strip the thread or put the card under any pressure

Put the case back on the amp and refit the 4 screws in the bottom of the amp casing

NOW FOR CABLING.  AGAIN NOTE THAT THE SEQUENCE SHOWN BELOW IS CORRECT FOR THE WAY THAT I INSTALLED THE CARDS - BASS ON THE LOWER SLOT, TREBLE ON THE TOP SLOT.  IF YOU HAVE PUT THE CARDS IN THE OTHER WAY AROUND, THIS CABLING SEQUENCE IS NOT APPROPRIATE!

The way I installed the cards means:

Channels 2 and 3 are Treble

Channels 4 and 5 are Bass

If you have the labels that come with the active cards, now is the time to label up each channel on the back panel!

Connect an interconnect from Channel 2 output (in this case, this is Treble right) to Channel 4 input (in this case, Bass right).  If your interconnect claims to be directional, the arrows should point from Channel 2 to Channel 4

Repeat this with an interconnect from Channel 3 output (in this case, this is Treble left) to Channel 5 input (in this case, Bass left).  If your interconnect claims to be directional, the arrows should point from Channel 3 to Channel 5 

Now fit the interconnects from the pre-amplifier.  Here, Channels 2 and 4 serve the right speaker and so the right interconnect is connected to the input on Channel 2.
Channels 3 and 5 serve the left speaker so the left interconnect from the pre-amp is connected to the input on Channel 3.

Now connect up the speaker cables.  Note that they must match the outputs from the amp:  treble to treble, bass to bass.  Following through the colour coding I connected to the Katans, here Channel 2 yellow / grey go to the right Katan treble input, Channel 3 yellow / grey go to the left Katan treble, Channel 4 red / black go to right Katan bass; Channel 5 red / black go to left Katan bass.  Be careful to observe the correct polarity of connection throughout.

And thats the job done.

NOW CHECK ALL YOUR WIRING FROM END TO END, AT LEAST TWICE!   IF YOU ARE NOT SURE, GO TO YOUR DEALER!

Now disconnect your anti-static strap and refit the cover (by reversing the removal procedure).

Before you switch on your system, ensure the volume control is set to zero.  Now, play a track very very very quietly.  Check each speaker - make sure treble sounds are coming out of the tweeter and bass sounds are coming out of the bass driver on both speakers.  If not, immediately switch off and re-check all the connection paths.

Once you're sure that you're hearing the right sounds from the right drivers, turn up a little and re-check.  If its still all OK, enjoy your music!