Over the years I've tried
various upgrades for vintage
audio gear...
Over the years I've tried various
upgrades for vintage audio gear, including upgraded
components and various types of wiring and sockets.
Here I'm really talking about vintage silver
Pioneers as these have always been my first love
as far as vintage audio goes.
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Pioneer SA-9800, gold phono sockets |
I went through a period where I was
changing all the input sockets with gold plated PTFE
ones on every amp I restored, but really apart from visual
effect it was a great deal of work for very little,
if any, audible improvement; the original phono
sockets are actually very good quality, even if they
don't look as pretty as nice gold plated ones.
Of
course, if you were committed to a ground up
restoration or were building a piece of audio
equipment from scratch, it would make sense to use
the best you can get hold of. Here however, the
original sockets do the job fine and there are
plenty of limitations elsewhere which would be more
deserving of upgrading or which would just limit the
amount of improvement which you could make.
Wiring and sockets
One of the first things I tried was
changing both the loudspeaker sockets, and, if
possible, the associated wiring. The original wiring
was the same type/gauge as that used in the rest of
the amplifier, usually flimsy single core and in the
case of the smaller amps, the thinnest core 'bell
wire' which Pioneer used anywhere.
This is fine for
carrying low level supply voltages but for high
current audio signals you really want to aim for
something better, especially when there's nearly a
metre of wiring on the speaker circuits snaking
around to the speaker switches on the front panel
and back again. The same situation goes for the
actual loudspeaker sockets, the original spring
loaded connectors aren't really up to the task of
transmitting high current audio signals, aside from
the limitation they have regarding the gauge of
cable you can use with them.
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New sockets in place on a Pioneer
amplifier |
The best workaround are high quality
metal bodied audio binding posts which are almost
universally used on high end audio, these will work
with even the largest gauge of cable and are built
to accept 4mm 'banana' plugs which, again, are the
most common connector used on higher grade
loudspeaker cables, you can buy them almost
anywhere.
As for gauge of cable used inside
the amp, you do reach a limit with regard to being
able to actually connect to the switches and circuit
boards and also by how much you can actually cram in
there. 1.5mm is a good choice, 2.0mm can be used but
you're beginning to push it here, it depends on how
much space is available and even thinner wiring may
cause major problems when you try to connect it to
the original loudspeaker switches or PCBs.
On most of the amplifiers, the
speaker wiring is connected to the amplifier PCB by
Pioneer's ubiquitous tie-wrap pins, you can uncoil
the original wiring and solder the new cable onto
these but thick, stranded cable soldered to pins
isn't ideal and in places where the wiring is packed
tightly together you need to be wary of anything
which could possibly cause a short circuit (heavier,
thicker wiring may risk bending the pins).
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Screw terminals replaced with binding
posts |
Some amplifiers had screw terminals
instead, these are actually better than the later
spring terminals - you can crimp or solder spades to
your speaker cables and they will work quite well.
However, with some ingenuity the bases of these can
be converted to take binding posts - much easier
than making new bases from aluminium sheet and they
still fit perfectly.
Originally the PCBs were drilled to
around 0.8mm to take the pins, you can carefully
drill the holes larger to around 1.5mm most of the
time but this is about the limit you can safely go
to without risking lifting the copper pads. The
loudspeaker switches can also be tricky, most
integrated amps use wafer switches where the wiring
attaches directly; these can be fragile and if you
snap one of the wafers you're going to be in
trouble, you need to be careful if you try to attach
heavy, thick cable to these. Usually I make wire
loops out of 1.2mm tinned copper wire and solder
these to the switch, then solder the thicker cable
to the loops.
This is fine on some amplifiers,
however on a few models you do run into problems
where the wiring is run through spaces in the
chassis - in this case it's better to leave the
original wiring in place and just upgrade the
sockets; luckily the wiring runs on most of the
earlier integrated amps are fairly short so any
voltage drop across them would be minimal.
Sometimes the mains circuits can
also be upgraded; models built for some markets have
obscure type 2 pin power take-off sockets fitted to
the rear panel to power other separates, with some
metalwork these can be replaced with standard IEC
sockets although if you're like me, you wouldn't
find them that useful anyway.
Signal purity
As time goes on, one thing which
really bothers me about vintage audio is the amount
and quality of signal wiring they often contain -
especially on the larger amplifiers and receivers,
there can be up to a meter of this stuff which your
sound has to pass through on its journey to your
speakers, not to mention all the switches and PCB
tracks along the way. This signal wire is often
extremely thin single core - although it is
screened, the capacitance is often through the roof
as far as interconnect cables are concerned and I'd
bet that cross-channel interference wouldn't be much
better either.
The major problem with upgrading
this wiring is finding the required amount of space
inside the amplifier - good quality interconnect
cables tend to be thick and you'll run into problems
if you need to fit several of these into a small
space in place of the originals. There's also the
argument that the designers may have originally
allowed for the loading that all of this wiring
would cause (capacitive/inductive loading such as
long lengths of screened wiring will cause high
frequency roll-off) and compensated for it, taking
away a portion of this loading by adding better
wiring might actually brighten the sound too much.
Then you have the sheer amount of
circuitry which these units often contain - on one
hand, compared
to a modern consumer grade mid-fi system, the signal
line in most vintage gear is quite pure - most
modern equipment contains dozens of processors and
op amps and very dubious components, placed with
little or no regard for their negative effect on
audio quality, all of which
distort and add huge amounts of coloration to the
sound, NOT something you want for good audio.
However, even in vintage gear, there
are often still a number of components placed in the
signal lines. For example, running a phono
signal through the average Pioneer integrated you
will probably have two amplifier stages for the phono stage, then a line amp,
then perhaps two or even four amplifier stages for
the tone controls, another
line amp and only then will the signal get into the
amplifier - with many switches, PCB tracks and lengths of
screened wiring in between.
In addition you also
have a lot of extra components placed around these
stages, for example electrolytics used for DC coupling
between most stages - these were bipolar (essentially two
capacitors connected end to end) on most of the
later amps, making things much worse. Earlier amps
made a lot of use of ceramic capacitors doing
bandwidth filtering on the transistors, these all
add their own resonances to the sound, one reason
why Pioneer's earlier integrated amps tend to have a
brighter, more projected sound to the later ones.
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Home brew passive pre-amp - things don't get
much simpler than this. |
Higher end Pioneers were fitted with
'Pre Out' and 'Power In' sockets on the rear panel,
often connected with a metal jumper link. Signals into the
'Power In' sockets often only need to travel through a
short length of screened wire running straight to the
amplifier PCB and then with only the loudspeaker wiring
and switches remaining between it and your speakers -
the vast majority of the signal wiring, components and
switches, are in the pre-amp section of the amplifier,
situated before the 'Pre Out' socket.
Removing this link and plugging a CD player
and passive volume control (see image to the left) straight
into the power amplifier section and sitting down and really
listening to the sound might shock you.
You might notice a lack of bass if you're
addicted to loudness and tone controls and have smaller
speakers but you're effectively bypassing 80% of the signal
circuitry and you should notice a huge improvement in sound
quality and imaging, so much so that if you're the type of
person who listens for detail and transients, it may be
difficult to go back and listen to music through equalisers
and loudness controls ever again.
Components
The original components tend to be
surprisingly good, a far cry from most modern consumer audio
equipment. Back in the 1970's, high end 'audio grade'
components weren't widely available, at least not at a price
low enough to see them fitted to mainstream audio gear;
however, the quality of what Pioneer used was still high.
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Volume control from SA-9500 - this kind
of quality costs nowadays |
Speaking for Pioneer at least, the
higher end did see some nice components used; very
high grade Alps brand switches and pots, high grade
polystyrene capacitors doing low value precision
stuff such as phono stage equalisation (you
definitely DON'T want to use ceramics in places like
this). The lower end equipment didn't get the same
amount of love when it came to component choice,
some undesirable components did get into the audio
circuits at the lower end of the range - tantalums
doing DC coupling between stages, those dreaded
ceramics doing equalisation on the tone controls and
phono circuits.
Again, if you're serious about audio
quality, you really don't want to be putting your
sound through these kinds of components. However, it
can be a two edged sword; some people do actually
prefer the brighter sound of the lower end gear over
the high end ones and these components do go quite a
way to creating that characteristic sound.
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Restored SA-8500 with some upgrades |
Any tantalums in the signal lines
are easily replaced with electrolytics - poly
capacitors are ideal for anything under 1µF but they
are more expensive and much larger than electrolytics. The ceramics
pose more of a problem, these are used where
extremely small values were needed, in places like phono
stages and tone controls; these often have values in
the tens of picofarads (pF) and changing these values will alter the response of those
circuits greatly so you'd need an exact match.
The
only suitable replacements which can do these tiny
values are polystyrene; polystyrene are excellent,
there's no doubt that they're better than ceramics
by order of magnitude; indeed, they're often the
first choice for higher end audio these days. Again
the problem is in their cost (often £1 - £2 per
component - you might need a couple of dozen or
more) - many people wouldn't see the point of
spending those amounts of money on what's
essentially a low value piece of audio gear.
Resistors were almost all carbon
film unless they were anything special (high power
or fusible etc); carbon film resistors are fine and
rarely cause any problems for me except in the small
number of cases where they run hot in a design and
eventually go high in value or even open circuit,
causing a myriad of problems which sometimes seem to
point elsewhere (SA-8800 and SX-880 spring to mind
here). In my experience, the only component caused
noise problems come from leaky transistors or dry
electrolytics, I have far more problems with bad solder
joints on a seemingly troublesome component than any
of the components themselves; I leave the resistors
alone unless I have good reason to do otherwise.
Active components and sound quality
Often overlooked by people who modify audio
equipment, active components (that's transistors and diodes,
through to op-amps and the like in later gear) also have a huge bearing
on the resulting sound - after all, it's the transistors
which amplify the sound in each stage in the first place.
Op-amps are usually a cheap and easy way to
improve the sound of audio gear, especially CD players and
pre-amps. That said, I've never experimented a
great deal with transistors. Many times I've had to replace
transistors for different types - for example substituting the originals for modern low noise audio
transistors when repairing cassette head
and phono amplifiers and fitting substitute outputs in amplifiers
where the originals are
virtually unobtainable. Often this is a large undertaking but
resulting sound is always excellent if modern audio grade
transistors are used, logic tells me that there IS
definitely a sonic improvement to be had. That said, I've never really sat down
and done a thorough comparison test, also I lack the huge
amount of expensive laboratory grade test equipment
necessary to accurately measure parameters such as harmonic
distortion - this is equipment which I'd love to own but is priced
way beyond the budget of any small scale audio restorer.
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