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How we test
People often ask if
we really can test equipment. The answer is "yes we can!" Our parent company
'Timestep' is engaged in Satellite Meteorology and has an awful
lot of test equipment. We are able to test to a specific
parameter or advise manufacturers of potential problems. We
can provide pre-review testing before a magazine tests your unit. We can provide expert advice in
customer/manufacturer disputes, or we can just provide
consultancy.
We are working with
Noel Keywood on turntable flutter measurement. This often
forgotten parameter is quite possibly the secret to a good
sounding turntable, and without doubt one of the main reasons
turntables sound different to each other (that and their
suspension). It was us who found Noel's Kenwood FL-180A
and brought it back from the USA by hand.
In 2008 we advised
two major turntable manufactures on how to use Jelco tonearms
and match them with OEM Shelter cartridges.
in January 2012 a leading turntable manufacturer asked for
help in measuring speed and wow & flutter, we were able
to provide test methods and sources of test equipment for them.
In late January
2012 we looked at a
€26K
turntable with electrical noise problems.
All these
photographs are of our individual items, not library images!
Below is just some
of our equipment:
Recently some have
asked about our owner, so here is a very short biog. Our MD Dave
Cawley served his apprenticeship in the 60's designing magnetic
tape recording heads and is now one of the leading experts on
Weather Satellite technology. He and his company Timestep have
presented several papers to world audiences and did so to
the US Department of Commerce on 11 December 2008 (paper 5.3
click here to see it). In fact Dave
Cawley lectured to the United States Department of Commerce in 2000,
2002, 2004, 2008 and also in 2011. The
audience always includes more than a dozen N.A.S.A. scientists. But what has this do
with Audio? It was once believed that to receive a certain
satellite you had to use a 2.0M dish, very big in fact!, however
Dave worked on a solution using an antenna the size of a
paperback book, to this day no one has achieved anything
similar! The challenge of getting a 5 watt satellite 24,000
miles away to give 60dB signal to noise on a hand sized antenna
is extraordinarily difficult. It is this low noise experience
that rubs off onto audio. In his early days Dave was a senior
electronic design engineer at Philips and remembers it well!
Some manufacturers
claim association with a local university to prove the
legitimacy of their work, and why not? However Dave Cawley
is a renowned engineer in his own right who has lectured at both
Universities and to N.A.S.A. scientists.
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The 'fast
test' area where we use the Leader Low Distortion Audio
Generator to feed the equipment under test. The
results are displayed on two ShibaSoku Automatic
Distortion Analysers and two Kenwood scopes. This
is a very fast and easy first test. |
We can
measure gain, level, frequency response and distortion
in a flash! |
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This is the
'main area' a few feet to the right of the 'fast area'.
Starting at the top we have the Leader LJM-1851 CD
Jitter meter, and that is exactly what it measures!
Below are
three HP 8903B Audio Analysers. Why three?
Well, we use the bottom one 'second functioned' to be
just a signal generator, and the top two display level
and distortion on each channel simultaneously.
They will allow measurement of delta functions so that
frequency response can be measured easily. For
phono stages we use a precision 'inverse RIAA' box that
also has the Neumann 3.18uS curve added. This way
we routinely measure phono stages up to 32Khz.
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We have
precision 8, 4 and 2 ohm loads, using the HP 8903B
special functions, they will read power and distortion
directly. |
At the
bottom is the HP8568B RF spectrum analyser. With
this we can easily see amplifier instability that often
occurs well outside of the audio spectrum. Also it
has over 30dB more dynamic range than the lower cost
audio analysers, it's a thing of pure joy! |
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Here we
have the Kenwood FL-180A Wow and Flutter meter.
Using the reference disc from Clearaudio we can measure
turntables. Unlike most, we prefer to measure the
peak which gives somewhat worse results. We
believe comparisons are easier this way. We can
also measure speed, the test record is cut at 3.1500Khz
and the built in frequency counter should reflect that.
However, if the turntable is using an AC synchronous
motor running straight of the mains power, we are left
with the unstable 50/60hz, but the FL-180A can be
switched to synchronise from the same 50/60Hz mains,
giving a true 'geared' speed value. |
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The HP
3312A Function Generator allows us to 'pulse' power
amplifiers to get their maximum dynamic RMS power. |
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A trio of Kenwood power supplies. Here used to check the
legendary Technics SP-10 turntable in 'safe mode'.
We actually have seven of these lovely units, used from
esoteric phono stages to charging motorcycle batteries! |
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The
Tektronix TDS 210 show us waveforms as they really are,
and makes a good stab at measuring them too. RMS,
peak-to-peak, DC and frequency, all at the same time,
simply brilliant! Now why don't we have the colour
version? |
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For really
accurate voltage measurement we use the HP 34401A, a
really cool DVM don't you think? Legendary
accuracy and not made in China! |
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We use this
special 'F' version of the HP 400 voltmeter to
measure power supply noise. The noise floor on the 100uV
range is about 2.5uV, remember that most equipment
rejects power supply noise by about 60dB, so this is a
very small level. But we have plans to go further!
The nature of noise is important, flicker noise is
especially annoying. An average reading meter like
this one, shows you in real time the nature of the
noise. True RMS voltmeters actually suppress
flicker, and do not have the essential 100uV range.
Every power supply made by us is tested on full load and
no load before despatch. |
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We use
Hewlett Packard 3400A True RMS Meter when specifications
call for RMS measurements. |
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The
Meguro MN-446 Noise Meter is a joy, with its average,
quasi peak and RMS readings it does what no other meter
does. Even in wide band mode as shown its noise
floor is 0.8uV and in weighted less than 0.4UV |
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The B&K
4517 accelerometer bought new in July 2009 at the
recommendation of Noel Keywood. |
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The
infamous HP 3561A FFT Dynamic Signal Analyser, although not
really as 'dynamic' as they could be. This unit
fully meets it's makers specification and is loaded with
options. Using a the accelerometer above we are able to
accurately measure resonance in turntable pick-up arms.
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Thanks to
Noel Keywood of Hi Fi World for telling us how
to do this. |
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As well as
this pile, we have RF generators, more scopes, Fluke
handhelds, AVO's, and
almost another two test benches. Collectors?
us?? |
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Sunday, 29 January 2012 |
