It’s almost ironic to consider using digital equipment to manufacture good old analog tube gear!  Nevertheless I’ve seen it happen in my own shop over the years for a variety of reasons.  The picture above is my test bench where everything we build is tested and or troubleshot during the Quality Control process.  This bench is in the QC room adjacent and open to our large reference room where everything is listened to in a real environment as it is being tested.

A guy came in my shop the other day, new to Decware, and after looking around made a comment that he expected to see a massive amount of test equipment and was frankly puzzled at how we design gear without any.  I smiled and tried to explain that the bench over there was it (pointing to the bench pictured above).   In the past 10 years computers have reached the speed and power where they can be used as highly sophisticated test equipment.  The bottom line is that you save money, time and space.  One of the things the “bench” above has replaced is my Bruel&Kjar frequency response recorder, plotter, and microphone preamps.  An item that weighed at least 200 lbs and cost some 30 grand back in the 80’s.  Some of the other 95 things it replaced I’ll touch on below.

The brainchild behind the system is a hardware interface and dedicated computer making it possible to plug test leads and microphones into the computer and test not only amplifiers and loudspeakers but even room acoustics.  It helps to have been a computer hacker in the 1980’s (grin) but frankly anyone can now have the equivalent of about$500,000.00 worth of test gear at 1980’s prices for a few grand if they are highly motivated and willing to subject themselves to staggering learning curves brought on by the shear number of different test devices to learn how to use.

The interface can be seen built into the wall in the picture above where it is labeled I.  I keep a good meter, frequency generator and small scope at my soldering bench, but if any serious troubleshooting or measurement needs to be done it gets hooked to the interface.  The display for the interface is maked B.  A color LCD display that presents a variety of dual trace color scopes with data logging, a VOM,  several frequency generators, waveform analysis, frequency response and distortion analysis, automated testing cycles, noise analysis, and a collection of design logs, schematics and build photos of every prototype and production unit designed here.   It also is used to measure inductance, capacitance, phase angles and theil & small driver parameters.  It also measures acoustics and early time reflections for 3D waterfall plots of any loudspeaker or the reference room.  Separating the two is as easy as using a time gate.  Computers are now so fast they can measure and analyze a sound wave before it travels past the microphone and reflects of the walls making it possible to get close to anechoic results without the 1.2 million dollar chamber.   In addition to the above, this machine is connected to the internet making it possible to do quick lookups, scan in work orders, and in it’s static mode it displays a real time build sheet so we can see at a glance what is being built, what the status of it is,  what’s been shipped and what’s coming in.

To supplement all this fancy technology, item B on the wall is a good old school tube preamp/headphone amplifier.  It’s primary purpose it to test souces, like CD players and phono stages for noise and sound quality.  This way you have a reference set of phones on a reference grade audiophile OTL headphone amp, and can pipe it to the listening room at the same time.  It has enough gain that a listening level on the phones would be about 1/8th volume on the control.  This way when you unhook your source and want to hear background noise you just turn it all the way up.  Now you can hear noise and hum of whatever is under test at 10 times it’s normal level.  An excellent tool for fine tuning layouts and testing.

Item D is the dedicated music server.  It feed a highly modified set of 16 external firewire DACs, item E, with music from the hard drive or the Internet.  Believe it or not, there are 1.2 meg uncompressed audio feeds on the net if you have the bandwidth to play them.  Some great radio.  The music server is never silent.  It is either fed into an amplifier under test or to the reference amp on the wall, item A.  The music server is also a video server and is piped into the listening room with both HD video to a projector and it sends 6 channels of audio in there as well.  Tuesday nights we watch movies on it using a listening room full of tube amps - it’s great fun.

Item G is a Thornes turntable with a Fidelity Research arm and various cartridges to do final listening tests on the phono stages even though there is an inverted RIAA output on the music server that is used for initial testing and burn in.

Item H is an old school analog tube tester built into the bench.  It too could be replaced by digital testers but I like the personality of the real thing since it lets me watch the tube come to life and foreshadows any glitches the tube might have in a way not possible with anything else.

What I’ve described above is a brief portion of the actual list of things this bench can do. Had someone told me 20 years ago I would have this much power at my disposal without wining the lotto first I would have just laughed.  What’s neat about it is that the D.I.Y. hobbyists , both electronics and loudspeaker designers, can now take their passion to as serious a level as their passion pushes them, something that only 20 years ago would have been impossible by all except large well funded corporations and government agencies.

So with that, I think I’ll pull up a satellite view of the earth on my test bench and see if there are any clouds out tonight before I take the dogs for a walk.