In the end, I built one of these turntables.
As stated before, the whole thing just became too expensive
and time consuming to make into a sellable product.
The plinth
This was built from 25mm MDF profiles, one
edge of these
being angled at 30° and
bonded to an extra 12mm layer to form the inner part of the
plinth. The base was made from 25mm and lap jointed into the
sides with all sides mitred and lined up, polyurethane
adhesive applied to all joints and the whole thing securely
clamped together until dry. The resulting plinth is strong,
heavy and very rigid.
Before the
plinth was assembled, the original hinges were fitted back
in. To make this work, they had to be inserted between the
two profiles.
Much like the original turntable, I retained
the sprung base suspension because when installed in a
sturdier plinth it worked very well, stopping a very
surprising amount of vibration from reaching the sprung
chassis - I'd go as far as saying that when installed in a
proper plinth and sat on the same audio unit as my other
turntables, the PL-12's simple spring suspension is more
effective against acoustic feedback than any other higher
end Pioneer, Technics, Thorens or Lenco I've ever owned, and
some of these are very good turntables.
A small strip of timber was added around the
inside of the plinth to act as a stop for the chassis.
The posts which locate the springs were cut
from standard softwood 2.5"x1.5" timber profiles, the
locating recesses drilled in from a template (they need to
be exactly in the right place to work correctly) and with
the profiles then securely bonded to the base and sides of
the plinth in their correct positions.
When the plinth was finished, it was given
several coats of matt black paint to cover all edges which
would not be covered by veneer. the outside edges were
then sanded flat, with car body filler used to square up any
small inaccuracies in the corners and the whole thing then
sanded one final time.
View of the plinth, showing internal structure. Simple
but rigid.
Veneering
Finally, the plinth could be veneered. I've
tried many different veneers over time, but on this I
settled for white Ash finished with a deep grey stained
finish as it seemed that it would compliment the black and
silver on the rest of the turntable well. Veneering is
something which you need to take your time with, not only do
you need to plan the order you work in (to make sure cut
edges don't end up facing the wrong directions), you also
need to work out beforehand which part of the veneer you
will use where. the Ash sheet I used had one area with a
very detailed grain on it and I decided that this would be
used for the most visible parts on the front, with the least
detailed parts of the grain on the rear.
The veneering process took me around 4
hours. Planning the cuts beforehand, I started on the lower
part - rear first, then sides, then front - this was sanded
flush and square as I went (sanding the edges neatly takes
longer than applying the veneer). Next was the chamfered
surface - again, rear, sides then front, then finally the
most difficult part which was the top edge. The key to a
neat finish here is to take your time and have a couple of
steel rulers and a very sharp knife handy to make the neat
45° cuts so that the pieces
line up without gaps.
The final
result was a near perfect veneered plinth with barely any
sign of cut edges (and a poorly lit 2am photo):
The finished plinth in bare Ash veneer
For the colouring coat I used a 2:1 mixture
of turpentine based wax and Ebony dye, 2-3 fairly thick
coats of this applied by brush and then buffed smooth. I
realise this is a pretty strange way of colouring the veneer
but the dye by itself had issues colouring the hard veneer
dark enough and through experimentation I found this method
to work well and give the grain the 'depth' I was looking
for.
Close-up of veneer after colouring
Finally, once it was all assembled I applied
a couple of coats of dark Briwax to seal the finish and give
it a sheen and added an aluminium Pioneer logo sourced from
another turntable.
The chassis
The actual turntable assembly was stripped
down with everything removed from the metal chassis. The
chassis was then stripped back to bare metal and primed and
painted and finally hand polished - the results you can see
in the final images at the end of this page.
The arm was re-wired with copper litz
twisted into shielded pairs, although this is probably not
something I'd attempt again as the PL-12 arm inserts are almost
impossible to remove without damage - that part alone took
me over two hours. The audio interconnects were replaced
with something better, I used 6mm OFC cable and metal bodied
plugs - anything more expensive than this and you're onto
quickly diminishing returns. The internal wiring on all
vintage Pioneers is very solid and to my knowledge doesn't
degrade so was left original and just neatened slightly with
a modern twin core mains lead soldered on.
Everything was cleaned and polished,
bearings were oiled and the whole thing reassembled and
tested before fitting to the plinth. I changed the wiring
layout slightly to keep mains and audio as far apart as
possible - I toyed with adding a shielding can over the
audio section but in reality this just wasn't necessary.
The raised lettering on the switch surrounds
was tricky to do. After trying a few finishes, I settled on
airbrushing them alloy silver with the lettering picked out
in black (the lettering first sanded to sharpen its edges),
with the result covered with a few coats of satin lacquer to
help make it durable.
Finally, I added some soundproofing material
underneath to help lower the chassis' resonant frequency and
further help prevent acoustic feedback reach the arm.
Fitting it together
The plinth had holes cut on the rear for the
cables to exit, these being chamfered on the outside
slightly to create a crude but quite effective strain
relief. As mentioned above, I exited audio and mains cables
as far apart as possible to prevent hum pickup, each set of
cables twisted slightly and securely fixed to the bottom of
the plinth using cable saddles (just like the ones you get
in mains plugs). The chassis could now be lowered in to the
plinth, locating the springs and getting them seated
correctly was tricky but when it was all together the
chassis fitted nice and squarely.
The final touch was fitting a new dust
cover, a few of which I had had made to order in the US a
few years before. These covers were not cheap (around £80
each imported) but are a huge improvement on the original
flimsy item. Not only do they look better, they also have a
functional use as they too help cut acoustic feedback.
The end result
This wasn't something which I completed over
a weekend, overall it took probably 4 years - I'd spend a
few hours and then it would sit on a shelf in my workshop
for months before being touched again.
The improvement in sound quality surprised
me a great deal, especially when compared side by side with
a standard, unmodified PL-12. Gone was the slightly hollow
upper midrange I'd come to know when I'd repaired them for
other people, gone was the boxy resonance in the 150Hz
region, completely gone was the audible feedback and
resulting distortion when playing at higher sound levels in
my vintage system (in a room with wooden floors on a
rosewood hi-fi unit, enough acoustic feedback to actually
make a stock PL-12 skip at those volume levels).
I'm not going to argue it was true high end
- somebody with 'golden ears' would've shot holes in it,
just by knowing its heritage - but in the time that I owned
that turntable it did surprise me how much it had been
possible to improve the way it sounded. I've been in audio
for long enough to know that a modified PL-12 would never
get me any respect in the vinyl community, but that's never
been what motivated me and to say I was happy with the way
it turned out would be an understatement.
It spent the next couple of years in my
vintage system, sitting above one of my few remaining pieces
of vintage Pioneer - my old SX-1250 receiver - and used to
attract more attention than the receiver. Eventually I sold
it to a customer for pretty much cost price - I hope he will
be happy with it.
- After final finishing (pictured with restored Quad 303)
(Click for larger version)
- After final finishing (pictured with restored Quad 303)
(Click for larger version)
- Deck paintwork
(Click for larger version)
- Front view
(Click for larger version)
- Close-up of raised lettering
(Click for larger version)
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