How we test 

People often ask if we really can test equipment.  The answer is "yes we can!"  Our parent company 'Timestep' were engaged in Satellite Meteorology and consulted to Inmarsat and BT and have 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. 

All these photographs below are of our individual items here in Dartmouth, not library images!   Some people have questioned the age of some of our test equipment. And this is interesting! Some of it is brand new as you can see, and some older. To be honest we prefer equipment that is analogue in feel, some of the new digital test equipment is Windows CE derived and it isn't appropriate to what we actually do. We aren't the only ones as HP/Agilent are desperately trying to get all owners of the HP8903B Audio Analyser to upgrade by offering huge part exchange values, they will then probably crush them to keep them off the market. Why ? well they work so well and once you have one, or three in our case, you simply don't want to upgrade, and the majority of users haven't, hence the big incentives. The 8903B Audio Analysers are so good that there is just one newer model, so we don't think that one model out is too bad!! If we were to replace all our test equipment with brand new, including our RF bench, we would be looking at 1/4 M or more. Most magazines have far less than we do, and only a very few manufacturers have any more!

We are working long term 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.

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, 2011 and April 2013.  In 2013 Dave was presented with a Long Service Award by the US Dept. of Commerce. 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, he needs no such references.  These are some of the more notable achievements taken from a long list:-

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.

March 2012 we looked at a 9,500 phonostage, diagnosed a problem and suggested a solution.  The manufacturer had not noticed and has now incorporated our suggestion into the design.

"if it measures well and sounds good, then it is good" : "if it measures badly and sounds bad then it is bad" : "if it measures badly and sounds good, then it could be improved" : "if it measures well but sounds bad then it is bad" Dave Cawley
 

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!

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 an optional Neumann 3.18uS curve added.  This way we routinely measure phono stages up to 32Khz.



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!


Here we have the Kenwood FL-180A Wow and Flutter meter.     

Like HiFi World we only use the DIN 45 545 test record, we have tried all others and they are all flawed.  We have three of them including the rare metal centre one shown here.

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.

Crystal  controlled direct drive PLL turntables rarely have any speed error.

We can get a numeric value for wow and flutter and assess the demodulated spectrum using the HP 3561A below.


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!
Bought new in 2012 this Agilent DSO-X 2004 real time 4 channel oscilloscope with built in function generator and DVM has revolutionised the way we work.

We can store settings and front panel set ups and even give them names by plugging in a USB keyboard.

The really cool thing is the real time four channel display, with each channel colour coded. The lets us look at all three phases of a direct drive turntable and the PLL error signal all at the same time. Brilliant!
 
Leader 5835 Stereo Audio Vector Scope.  This remarkable instrument uses a 6" CRT and gives immediate visualisation of the stereo width, balance, phase and more.  It is especially useful for looking at mono signals and shows clearly the effect of properly configured mono switches and mono cartridges.  Yes you can use a PC, but this has zero latency and just gets on with the job.

What is interesting is looking at the Beatles LP "With the Beatles" where the stereo version shows the poor stereo and the mono version how it should be done.  We are looking forward to evaluating the new Beatles mono vinyl taken directly from the master tapes later in 2014.  We expect to use the Miyajima-lab Zero African Blackwood mono cartridge for our tests.

The 2013 Agilent 33220A Function / Arbitrary Waveform Generator, allows us to 'pulse' power amplifiers to get their maximum dynamic RMS power. But more importantly to simulate waveforms for the Technics SP-10 development.
For really accurate voltage measurement we use the HP 34401A, a really cool DVM don't you think?  6 1/2 digit accuracy says it all.  Legendary accuracy and not made in China!

Bought new in 2016 the Keysight 34450A isn't as accurate as the HP 34401A but has huge digits you can see out of the corner of your eye.
Bought new in 2012.  Agilent 5131A high stability frequency counter with high stability oven oscillator option.  Remarkably this is used to check the speed of turntables.  Over the top ?  Yes ! but why not ?
The HP 58503A GPS locked frequency standard is more accurate than a Rubidium standard  and is rated as a "secondary standard" just one below the world's very best.  This is the genuine HP version not the "clone" re-boxed Chinese one !

The unit has a 8011 oven oscillator locked to the GPS satellites. Total lock in stable format can take over 4 hours.
 

This is one of our Rubidium atomic frequency standards.  This is a secondary frequency standard that only takes about half an hour to warm up anywhere.  For a quick measurement nothing beats it this side of many, many tens of thousands of pounds.  But given time, the GPS clock will outperform it.

Bought new in 2011. Fluke i30s high sensitivity, wide bandwidth current probe.  Used to see the actual current draw of turntable motors, the waveform and stability with the storage scope above.

There is another use, and that's to look at the current waveform of HiFi components and what they kick back into the mains and hence into everything else.  No one has done this and we can see why............

Bought new in 2012.  Fluke 6200 advanced PAT and appliance tester.  Absolutely essential to test electrical safety.
Bought new in 2011 and 'cos we liked it so much we added a second one in 2015!.  Easy and accurate, that's how you would describe the Fluke 115 True RMS DVM.  It's handy, always by our side and remarkably accurate.  It's shown here measuring a Vishay 100 ohm MC input loading resistor.  2015, we liked this so much we bought a second new one for the other bench !

The HP 34401A above is better, but the Fluke is so simple to use.

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.

We use Hewlett Packard 3400A True RMS Meter when specifications call for RMS measurements.

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

The B&K 4517 accelerometer bought new in July 2009 at the recommendation of Noel Keywood.

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.  We also use it look at the flutter specrum from the FL-180A

Thanks to Noel Keywood of Hi Fi World for telling us how to do this.

Aeroflex/IFR/Marconi 2031 RF 2.7Ghz signal generator with dual audio signal generator option, bought new in 1993.  We use this a a reference.
HP 11848A Phase Noise Interface.  This is an on going project to really  test jitter in clock oscillators.  This is a minefield as some replacement clocks are worse than the original, and some much better.  We plan to use this with custom software and using the National Instruments GPIB-USB-HS adaptor.
As well as this pile, we have RF generators, more scopes,  AVO's, and almost another two test benches.  Collectors?  us??

Membership



Full Member of AES Audio Engineering Society) click here
Institutional member of iasa (International Association of Sound and Audiovisual Archives ) click here

Member of The City of London Phonograph and Gramophone Society click here
Institutional member ARSC (Association for Recorded Sound Collections) click here


 

Saturday, 04 June 2016

Sound Hi Fi

PO Box 2001  Dartmouth Devon  TQ6 9QN  Great Britain

Telephone 01803 833366  Fax 01803 839498  e-mail sales@SoundHiFi.com