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WHY TUBES?
A COMMENT ON TUBES VERSUS
TRANSISTORS FOR REPRODUCTION OF RECORDED MUSIC
By Jud Barber
President, Joule Electra
....I first
became interested in Audio in the early fifties, well before transistors
and other high tech materials became available to the Audio Industry.
We were constantly looking for ways to improve in the quality
of sound production, even before the development of stereo vinyl.
Stereo tapes were available, but the program material was so limited
that few people had invested in two channel systems,
....Instead
some of us went to great extremes to try to improve the realism
of our playback system, I remember well my first three channel,
monaural system which used passive high level crossovers to divide
the music spectrum into three audio bands. The crossovers were
at 500 hertz and 5000 hertz and separate amplifiers were used
for each of the three frequency ranges. The results were not particularly
good, but we thought it was great, being driven more by the quantity
of hardware in the system than by sonic splendor.
....
Then came the first stereo vinyl recordings which were really
very good even today, when played with state of the art turntable
cartridge systems. The problem was the transducers, both at the
beginning and the end of the playback system. Compliance without
excessive resonance was an elusive goal for the cartridge designers
at the time. The first cartridge I bought, a Grado, was probably
the first they ever designed. It weighed several ounces and really
made a great sinker for fishing line. As a retriever of the nuances
of audio from fragile vinyl it was a disaster.
....
The tube technology used for amplification was very mature by
this time and probably much better than we realized. It was the
transducers that were limiting the quality of reproduced sound.
A good phono cartridge was extremely difficult to make and when
the design was good it was very difficult to make them in quantity
with the same level of performance. Later, in the fifties and
early sixties, transistor equipment became available and everyone
was entranced by the absence of noise and ease with which good
specifications could be achieved for a modest cost.
....
In fact, it was the transistor that prompted me to quit designing
and building tube-based equipment. Even very simple solid state
circuits performed better on the workbench than
my most sophisticated tube designs. At the time I decided that
it was the answer to the quest for the grail
in amplification and I began to look for the pot of gold at the
rainbow's end. Oddly enough, it was not to be found and sound
reproduction seemed to have reached a plateau that was good, but
not great. By the mid seventies virtually all space-age technology
had seeped into the audio world and transducers were steadily
improving.
....
By the early eighties the advent of the CD player (unfortunately
transistor based) was revolutionizing the beginning of the audio
reproduction chain and the new materials available were allowing
designers to develop phono cartridges and speakers with dramatically
improved characteristics. But there was still something missing
in most music reproduction. No one really understood why, even
with hardware that measured magnitudes better than that available
in the fifties and sixties, recorded music still did not sound
very good let alone create an illusion of the real thing.
....
I should have been able to make the discovery that turned this
thing around, but being an engineer, I was convinced that what
measured the best, sounded the best! For fifteen agonizing years
the audio community struggled with the realization that tube hardware
used judiciously in a playback system almost always produced a
more enjoyable sound and a better illusions of live music.
....
The engineers laughed at this and continued
to bash anything that did not measure perfectly. In fact they
were so sure that ordinary copper wire measured so perfect, the
developing high end cable industry was thought to be a bad joke.
In fact you still hear some engineers say that the best amplifier
is a straight wire with gain. Wow, how wrong can you be!
To put it simply, tubes have a sonic
signature that mimics acoustic music and transistors do not. Now
I'm going to lay low while the cannon shots pass over my head.
It is certainly true that good, let's say average, performance
is easier to obtain with solid state hardware than with tube designs.
However, well designed tube equipment coupled with a good output
transformer will sound more musical and is more satisfying to
listen to than solid state at any price. It does take a little
maintenance, but it will warm your feet on a cold winter night.
The next level of sonic achievement can be obtained by use of
an all tube OTL - but that's another story.
....
The real improvement in audio reproduction in the last forty years
has taken place at the ends of the chain - namely good transducers.
These are the devices that change acoustic energy to electrical
energy and back again. Even the CD player, which begins its life
with solid state technology, is a major advancement in transducer
technology. Better analogue circuitry has resulted in very good
sounding digital information recovery, but it still lies in the
realm of the vacuum tube to produce the recorded sound musically
and with realism.
....
You will notice that I don't use the term
accuracy. This throws us back into the engineer's argument with
the artisans that the most accurate is the best. The answer to
that is a flat no.
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DESIGN GOALS
By
Jud Barber
President, Joule Electra
Why does a preamp costing less than half
the price of other high end products have sonics judged to be
as good as (some say better than) these marks? Let's look at the
details of the design and build quality of the Joule Electra LA-100.
There is where the secret is; but it's really no secret. All you
need to do is pull the cover and start looking.
POWER SUPPLY ISOLATION - The
first thing you will notice is two separate construction boards.
The larger one contains the power supply, and the smaller one
is the "Signal Board". The power supply board uses broad
copper traces to connect the major components, but some of the
heavy current is direct connected With separate insulated conductors.
HIGH ENERGY STORAGE - The next thing you
will be aware of is the large number of capacitors, over
150,000 microfarads of energy storage. They are used in the two
regulated filament power supplies and two separate tube regulated
B+ supplies. HIGH COST TUBE REGULATION is usually found
in very expensive hardware like that mentioned above.
POINT-TO-POINT WIRING - Then
you will notice that the smaller board, the "Signal
Board" is unique in that it has NO traces.
That's right all the connections are point to point with the component's
lead wire being the only wire on the board. Each connection point
is a large copper pad on the board where all the leads are
sealed together with silver bearing solder. This construction
technique is unique to Joule Electra.
PREMIUM QUALITY PARTS - Further
examination will reveal that all the resistors are of the
expensive Holco brand. We auditioned several different
brands of metal film resistors and the Holcos were head and shoulders
above the rest. The prominent white caps are MITs, the
best available at any cost. And cost they do; triple the cost
of other high quality caps. Cardas jacks and Cardas wire are used
in point to point configuration to avoid lost definition and detail
in the signal.
WE LISTEN - The LA-100 has
a stereo/mono switch by popular demand. To prevent this feature
from causing crosstalk between channels a triple pole switch is
used with the center contacts grounded. Channel crosstalk
is -80db.
PURE DC - Now you will notice something
funny. At the bottom of the signal boards there are two batteries
(yes the batteries are included). They are part of the adjustable
bias circuit and insure that pure DC is on the signal grids of
the gain stage. Critical listening has shown this to be significant
in producing the sonic signature of the LA-100. The result is
clear, open treble; rich, full upper midrange; warm balanced lower
midrange; and a solid deep bass presentation. Again unique to
Joule Electra.
MAXIMUM CHANNEL SEPARATION - The next funny
(read innovative) thing you will notice is the brass
shaft that connects the selector switch to the front panel. You
will see this on a lot of preamps but the switch won't have multiple
decks and wide spacing like the one found on the Joule. It shortens
the length of the signal inputs and reduces cross talk between
the channels. The multiple decks allow paralleling of the contacts
which reduce the lack of transparency caused by the single contact
arrangements found on most preamps, even the Joules' competition.
SIMPLICITY - The second duty
this switch performs is to allow all switching functions to be
done with one switch. The tape monitor loop is available between
each of the selector points eliminating the need for another switch.
Each input is "virtual direct".
SONIC EXCELLENCE - You will now note the
unique shunt to ground input block, using custom made pots to
our specifications. This volume/balance system is completely passive
and functions outside of the signal path.The signal passes through
two high quality resistors and then directly to the input tube
grid.
HIGH-TECH CHASSIS - Now for the icing on
the cake, and you may argue that it was the first thing you noticed.
The signal board is mounted on an exotic tri-flex suspension
system to isolate it from the cruel world of vibrations and feedback.
State of the art materials are used for this including EAR vibration
bushings and ISO-DAMP sheets. Where have you seen this
before? Probably nowhere!
TUBES ONLY - And now the last
straw--six, yes 6 tubes in a line stage only preamp. A carefully
selected Sylvania 5751 for the Gain Stage and a RCA 5751 for the
Mu Follower, and the 6EM7 regulator tube and 0A2 voltage reference
tube, industry standards since the fifties.
....
None of this is snake oil--all of it is what makes the )oule Electra
a giant killer. Audition one in your home today.
GIANT KILLER? YOU BE THE JUDGE!
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