Zed Audio Draconia Instruction & Installation Manual - page 4
Our design philosophies have been influenced by both the professional and home audio markets. Traditionally the
professional market has been driven by reliability with sound quality as second. The home market was the reverse. Today
however both reliability and sound quality carry equal weight in both sectors. Cosmetics for obvious reasons are important in
any sector. My experience in designing and building professional amplifiers has helped me in taking a similar approach in the
design of mobile audio amplifiers. No matter how pretty or good sounding an amplifier may be, if it fails then it is a bad
amplifier. The lesson learned many years ago was “silicon”, and use lots of it. All things being equal, if an amplifier drive
circuit is stable, then adding an output stage (itself stable as well) with enough power devices will make the amplifier reliable.
This assumes of course that mechanical issues are taken care of. Zed has always been a proponent of using a generous
amount of power transistors in the output stages of our amplifiers. In addition we design at temperatures of 80 degrees
Celsius. All semiconductors must be derated at these elevated temperatures and we use enough power devices for safe
operation into the lowest load impedance the particular amplifier has been designed to drive.
Our personal opinion about “fancy” cables and exotic passive components may shock some of you. I have never been able to
hear the difference between a cheap or an expensive RCA patch cord. My listening has been done using double blind A-B
comparisons. Electrons are not very clever things and they have no knowledge of the type of material through which they are
flowing at the speed of light (312,000 Km/second). The ONLY reason we recommend high quality double shielded RCA patch
cords in mobile installations is to reject noise. My opinion about speaker cables is the same. As long as the wire is thick
enough, it’s construction makes no difference. As long as the amplifier is stable into reactive loads with phase angles of up to
60 degrees, the amplifier is none the wiser what type of speaker cable is used.
The use of teflon, polypropylene, tantalum or other capacitors does not make a good sounding amplifier. There are too many
other variables in the audio chain that one capacitor can make a difference. The use of metal film resistors is only of use in
low noise circuits and where tolerance is of an issue. Never forget what the music signal had to go through to get onto your
CD or vinyl.. The signal began as a micro volt specimen at the microphone, sent through a high gain pre-amplifier, passed
through equalization circuits, possible compressors, limiters or other processing gear and then mixed with all the other tracks.
In analog days and today still, this signal was sent to a 24 track tape recorder again through a multitude of transformers, pre-
amplifiers, equalizers and yikes the tape heads themselves. Then the signals were passed back through the tape deck’s
playback circuits including the equalizer for playback, then back into the mixing console for mix-down to two track and then
this was repeated again onto a two track tape recorder, then sent to the cutting head amplifier where the masters were then
cut. A torturous journey one could say for this fragile audio signal. Semiconductors have more tolerance in their specifications
than any capacitor or resistor. A well known fact is that different types of capacitors work better at certain jobs than others.
Example, disc ceramic capacitors are better in high frequency compensation circuits than film types. Film types work better in
audio frequency selective circuits than ceramics. So we at Zed choose our components to suit the application.
Our quality control (QC) program and testing procedures work well for us. Over the years we have refined these processes to
what we have today. Our philosophy is to design around potential or real problems. If we feel that a particular item could
cause a problem now or in the future, we either change the design or improve upon it. The goal is ZERO defects.
QC begins with the initial design. The electronic design goes through as many prototype iterations as is necessary to make
sure it is working the way we want. These prototypes are bench tested, put in to vehicles, listened to both in the vehicle and at
home then retested on the bench. We bake them in ovens and retest again. Heat is the enemy and we want to make sure that
it will not hurt our products. Mechanicals of course do not have to be put in an oven (we do anyway). Fit and finish must be to
our standard. Samples are minutely inspected for fit and finish. Once we approve them only then can the hard tooling be
done.
Each and every product manufactured at Zed is tested using Audio Precision test equipment. Software is written for each type
of amplifier and then on final test the amplifier must pass these rigorous tests. If not it is rejected and returned the production
line for repair. Samples are pulled from the line for further testing.
Mechanical inspection is done throughout the manufacturing process. Before each amplifier is packed it is fully inspected
again for any cosmetic flaws. Any damaged or any part which is out of specification is replaced.
Zed takes pride in what we design and manufacture and we trust that this shows in the final product.
Stephen Mantz
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