Vintage sound
Many people have a
romantic idea of vintage audio sound
as all warm and fuzzy, soft deep
bass with a smooth lower midrange
and a slight roll-off at the top end
of the treble - much like how
classic valves often sound. In
reality, the sound of vintage audio
gear varies greatly, depending on
brand, relative price and era.
For example,
Technics tend to have a very heavy,
almost 'glassy' sound with strong
mid bass and projected treble and a
lean midrange, this trend gets
stronger after about 1980 as ICs
became more widely used by them. Quad are very
understated in a typical English way
- pure, uncoloured, almost 'soft'
sounding, imaging can be superb -
especially on vocals - but the
overall sound might be too reserved
for some people. Pioneer vary more than
most (perhaps I've just heard too
many), but most have a deep sound
with strong midrange and good bass
dynamics - the higher end receivers
sounding 'warmer' than their
integrated amps, the earlier amps in
particular sounding brighter than
the later ones or the receivers.
Also, these days
people will often run vintage
equipment on either modern speakers,
modern music formats, or both -
vintage speakers and older music
have a completely different sound to
anything modern.
Brightness
Vintage audio gear
(and even a lot of modern transistor
audio gear) gets a reputation for
being 'bright', I don't know whether
I just have exceptionally sensitive
hearing but I find a lot of lower
end modern audio equipment literally
painful to listen to because of
this.
Many people perceive
this 'brightness' as being an issue
in the treble region - actually,
what I perceive as 'brightness' is
rooted in the midrange, usually
around 2-4kHz. I tried using mild notch filters to remove
this brightness but then you're
removing portions of the 'presence'
frequency band of the music.
Resonances play
their part, but sometimes this
brightness is present in the
original recording and some
equipment and room acoustic
combinations just brings it out more
than others - load a portion of the
offending song into a sound editor
like
Audacity and plot a spectrum
graph, most likely you'll see peaks
in the midrange region. Try applying
a mild notch filter in this region
and then replay the sample and it
will probably sound much softer and
easier on your ears at higher
volumes.
Some people blame
modern metal tweeter drivers, but
these aren't solely the culprit for
brightness - having soft dome
tweeters may make the sound more
'warm' and less fatiguing to some
people but will just nudge any
apparent brightness firmly into the
midrange. Metal tweeters are there
to project dynamics and 'sparkle' in
a way that a soft domed tweeter just
can't, they do that well - but
inevitably that will give the sound
a different character that people
may, or may not, like.
Dynamic range and compression
Most 'better' vintage audio
equipment used discrete transistors
in the low level signal stages -
while not as 'perfect' as modern op-amps, a
discrete transistor circuit can take
a much higher supply voltage (on
vintage Pioneers, often somewhere
between +/-25v to +/-40v opposed to
around +/-15v for most op-amps).
This higher supply voltage means
that the voltage output on peaks can swing much higher in relation to
the rest of the sound signal,
meaning better dynamic range and
'headroom'. This all depends on the
magnitude of the input signal and
the gain of the amp though, so you
can't just assume that an amp stage
with a +/-30v supply will sound
better than one with a +/-15v one.
The same goes for power
amplifiers - to a trained ear, an
amplifier which is being pushed hard
and running out of power reserve
will noticeably compress the sound
long before it's driven into
clipping (clipping = audible distortion). This
is the reason that a great deal of
higher end audio equipment has high
power ratings, it has more to do
with dynamics and compression than
it has with outright loudness. Hence
the reason why a good high powered
amplifier will always sound more
dynamic than a smaller one, even at
low volume levels - there's more
room for the peaks of the signal to
expand without being compressed, so
the resulting sound is more dynamic
and powerful.
This is the same as the
compression which you'll get with
cheaper loudspeakers - when asked to
provide higher sound pressure levels
(SPLs), a loudspeaker which has a
lower capability will compress the
peaks of the resulting sound, partly
because of the mechanics of the
suspension and cone but mainly
because the voice coil heats up and
increases in resistance during
musical peaks, which means less
force gets to the cone - resistivity
of conductive materials such as
copper increases in proportion with
temperature, and higher resistance
means less current passed and hence
less power and less SPL.
Magnetics also play a part - this
is one reason why more expensive
loudspeaker drivers tend to be
heavier and have larger magnets than
cheaper ones (although control of
resonant frequencies also plays a
large part in the need for large
magnets).
On power amplifiers (and, to an
extent for signal stages), the two
factors which are the most important
for good dynamics at high power
levels are the voltage and current
capability of the power supply.
Input levels
This really leads on from the
section above. Back in my early days
in audio, I used to wonder why some
companies sold 'input attenuators'
which would sit inline with the
audio outputs of a CD player etc and
reduce the volume level of signal
getting into the pre-amp - surely,
if a CD player could output a higher
signal than most (vintage) audio
gear was designed for, that was a
good thing for noise levels?
Most modern CD players will
output around a volt of signal, many
pre-amps (especially older ones
designed before the CD era), will be
designed for half of this or under.
Putting a really high signal into an
amplifier doesn't necessarily mean
you'll get distortion, but it will
have an effect on the dynamics and
linearity of the sound output.
Effect of components on sound
Yes, components do have their own
sound. At the extreme, you have
op-amps which contain complete
amplifier circuits complete with
dozens of miniature transistors
etched into their silicon, many IC
devices such as op-amps are designed
to be 'modular' - for example, the
ubiquitous 4558 dual op-amp used in
huge amounts of audio gear could
often be directly replaced by many
more modern, higher quality chips
with little or no modification -
with the result of much better sound
quality, especially on high gain
circuits such as phono stages.
Discrete semiconductors such as
transistors also have an effect on
sound - capacitances, resonances and
linearity of a device (well, its
linearity at the point it's being
operated at) all factor in here.
When you get to small signal
transistors, things such as noise
levels become important (think
'white' or 'thermal' noise), a
modern audio grade transistor will
easily outperform a vintage one,
although the difference that will
make in a well-designed circuit
might not be anywhere near as large
as you'd think.
Then you get passive components.
Capacitors in audio equipment are of
varying types, depending on their
size, the job that they're meant to
do, and their cost. Many capacitors
in transistor audio gear will be
electrolytic (for more information
on electrolytics, see
this page) - these capacitors
are, by their nature, imperfect, but
a necessary evil when you consider
their size advantage over 'better'
types. Electrolytics vary widely,
with frequency related changes in
inductance, ESR and overall
differences in value altering their
performance and hence the response
of the circuit that they're part of.
The golden rules with electrolytics
are to use good quality ones which
are suited for the job you want them
to do, make sure they don't get
reverse biased, keep well below
their voltage rating, keep them
cool, and finally aim to renew them
every 10-15 years.
Inductors don't see much use in
audio gear outside of tuners,
speaker output networks and
crossovers, so don't really factor
in here. Some people talk about DC
resistance, but that might well have
been factored in by whoever designed
the circuit in the first place.
Personally, I leave them alone
unless I have a really good reason
to do otherwise.
Resistors in most audio gear tend
to be pretty good, purists talk
about certain types of resistor
colouring the sound of amplifiers
and I wouldn't argue against this,
but as long as they're of good
quality, they're not a major issue.
Wire wound resistors might be
another issue because of inductance
in the coil, but you're only going
to meet those inside power supplies,
amp output stages and loudspeaker
crossovers, they don't really have
much use elsewhere - most resistors
used in small signal circuits are
going to be metal or carbon film,
hopefully with good tolerances and
low temperature coefficients.
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