LC >
Thor Audio is a new name in the game of tubes HiFi equipment. When
did you start this project?
PM >
Thor officially opened the doors in January of 1996, but we were
working full time on this for three years before then just designing the
line. Two ideas were to govern everything we did during that time.
One -
If we were make "just another" tube line, then what's the point! And Two
- You only get ONE shot in this business. With these two thoughts in
mind, we had to do our homework.
The line had to be the very best we
could possibly make. I must say that surviving with no real income for
three years in the nineties and exhausting the savings, while at the
same time saying no to two investors along the way, was indeed a "leap
of faith".
LC >
Thor Audio makes some pretty original and revolutionary components
using good 'ol days technology (tubes, that is).
Why did you choose
tubes and which are, according to you, the main pluses of this
technology when compared with the traditional solid state one?
PM >
Our first component was actually a solid state line/phono preamp. It
was very good, and could have competed well in the market, but again,
"well" was not what we were after.
I must point out that at my age, I was raised on tubes with McIntosh,
Fisher, and Eico/Heath amp/preamp kits, etc. With the beginning of the
tube resurgence in high end audio, I was only too happy to begin designs
using them.
I could combine my most favorite sound together with the active and
passive components available today, thus eliminating some of the
drawbacks of the "over-warm/no-bass" tube sound, while at the same time
being one of the first companies in the tube "wave" hitting then.
There
was now no reason to believe that we couldn't make a tube based product
that was as fast and detailed as solid state, that would also inherently
negate all of the "in-your-face" type of detail of some solid state
components of that time, while remaining truly musical in it's delivery.
I didn't know then that it would take as long as it did to develop the
line, and we were certainly not one of that first wave, but I knew we
had made the right decision after I started listening to what we had
with even our first circuits.
LC >
Form follows function. This seems to be your credo. Can you explain
why a toroidal cabinet works better than a traditional one?
PM >
Eliminating one of the inherent problems of replacing tubes frequently
was the first thing we took on after some of the basic circuits were
realized. A three minute timed "ramp" of the B+ and filaments would give
the tubes a nice soft start after turn-on, but what about the other
inherent problem AFTER turn on - heat!
Vertical mounting with as much free air around the tubes as possible
was an obvious answer, but what about totally free air! That would mean
NO chassis on top to trap the heat.
It also would mean that the tubes
would have to be shielded on all sides to prevent any AC/RF fields from
getting to them - maybe in a circle around the tubes. This done, we then
had tube sockets coming through the bottom of a flat 6 1/2" circular
piece of aluminum (with enough % of copper in it to do good RF
rejection).
The tubes were then placed sitting upright within a circular
tube of the same material shielding it on the bottom and now on all
sides. Once these two pieces were welded together for a reliable
contiguous shield, it became the tube "chimney" that we have used since.
What chassis would accept this unusual design? A rectangular chassis
with a 6 1/2" circle cut out on the top? Interestingly enough as I did
more research on circles, I found that from a purely physics standpoint,
anything round would be inherently non resonant as all vibrations would
inevitably go to the center and begin canceling themselves out.
This
eliminated the last large inherent problem with tubes - vibration. It
also made the rest of our chassis obvious. It also had to be round.
The first chassis made was essentially what we ended up with in
production but we added one more element.
We placed over 10 pounds of
damping material affixed to the inside of the top of the chassis,
forcing everything down. Not only did it do a better job of vibration
rejection throughout the entire chassis, but it solidified the acoustic
image and helped bring the bass to the deep, tight and controlled sound
we are known for.
Curious to see what this type of chassis was doing for
the sound, I removed the entire guts from the toroid chassis, and put
them into a rectangle chassis, complete with the same amount of damping,
feet, etc., and the difference was astonishing. 10-15% of our sound is
based upon our toroid chassis!
LC >
Many modern tubes amps and preamps are designed around old schemes
(Williamson and others) and many HiFi designers swear these old schemes
are better than anything else...new.
Do you believe is there some room
for new schemes and unconventional designs with tubes? Can you tell us
something about the schemes you use?
PM >
While the answer to our layered soundstage, imaging and focus, lies in
a new and somewhat unorthodox circuit proprietary to Thor Audio and used
throughout our line, I will say that the basic circuits used in the
"golden age" of tubes, were my first choice.
Use of noise cancellation
via differential circuits, low output impedance via cathode followers,
etc. have been used for years and I saw no reason to "re-invent the
wheel".
However, in my opinion, the overall sound, using these circuits,
is something more closely linked as an answer to your next question.
LC >
There are many things that can affect (or improve) the performance of
a tube equipped component: passive components, cabling, quality of the
tubes, layout, mechanical construction etc.
Which are, in your opinion,
the most relevant ones?
PM >
I believe that absolutely EVERYTHING is audible. Although one of
countless things we went through at the beginning, one of more
interesting stories happened after we completed the first line stage.
To save the considerable time and expense having a PC board house make,
and then change the prototype boards every week or so during the
development stage, we did them ourselves.
They were of the "home brew"
kind made with photographic film positives exposed to a sun lamp, then
etched and drilled. We then used an electro-less plating process to keep
the copper from oxidizing. After a dozen or so changes to the board, we
finally had the sound we were looking for!
When the last change was made, we had the boards done at the outside
vender - complete with solder re-flowed traces, and a great looking
solder mask. Before I go on, I must point out that our entire line is
essentially hard wired. Any audio carrying signal paths are connected
using separate individually shielded wires, and all capacitors are
soldered tube pin to tube pin, leaving less than one inch total pc board
trace that actually carries signal.
Therefore, we were not expecting any
significant sonic differences using the new "pro" boards. Unfortunately
with the new board, it was immediately obvious that ALL of the magic had
left!
I must also point out that the components used on the new board
were not new components, from another batch of caps, etc., they were the
SAME ones taken from our home brew board. This was a true A/B test.
Fascinated by this, we then had the vendor make more boards in two
different ways. The first had the solder re-flow but no solder mask.
Surprisingly, the air returned immediately, but the sense of delicacy
was still not there at all.
In fact it sounded smeared, veiled and
lifeless, with a muddy upper mid-range and somewhat strident high end.
It wasn't until we had them make a totally bare board and put the same
electro less plating on it that we had on our home brew one that the
magic returned!
Whether or not this would show itself in another less
revealing circuit I have not taken the time to research, but from the
start we have had our PC boards shipped to us with bare copper and put
them through our electro-less plating process.
We also have many boxes full of very expensive and extremely good
capacitors, wire, switches, solder, connectors, etc. that did not make
the cut. The final selection of our custom made input switch alone was
over eight times the cost of most used today in very pricey and well
established lines, and took over two years to find. (Once again, it was
nice to have the time in the beginning!)
I believe therefore, that it is a cumulative effect of active/passive
component choices going through the design process that makes or breaks
a circuit, not just the circuit schematic itself. You could change only
one component, (a coupling or pi filter cap maybe) and have a totally
different sounding preamp or amp.
LC >
Any advice for tubes lovers willing to get the best out of their
equipment (tweaks, tips to extend tubes' life etc.)?
PM >
One of the few sonic liabilities of using tubes is the vibration
problem. Our tube sockets are mechanically coupled to the chassis, and
do not move.
If you notice that when you replace tubes in your component
that the pc board moves when you push down or pull up, the use something
like "Top Hats" would reduce the inevitable vibration that an approach
like that gives. I have seen them work very well
As far as my tweak/opinions - Two things I have spent enough time with
in enough rooms/systems to comment on are:
1) Use of Black Diamond shelves and racks. They have been the most
significant and beneficial to our sound that we have come across so far.
So much so that while we use "Audio Points" tiptoes instead of rubber
feet on our chassis, we have a reverse triangle of 1/4-20 threads
drilled on the bottom to accommodate the Black Diamonds (and any others
a customer wishes to experiment with).
The Audio Point feet are slightly
shorter than most other tiptoes/feet, so they do not have to be removed
to experiment with other cones - another reason to use them stock.
2) The second is AC cords. They have a great deal to do with the
overall sound of a system. Experimenting with a few of them is the only
way to find out what works in your particular system. We ship a
"Discovery" power cord with each unit. This is not to say that our
products will sound the best using only this one, and we would not want
to be accused of "pre tweaking" anyone, but with all the R&D we did, we
felt that sending an inexpensive bargain brand with our components would
compromise those efforts.
On the technical side for those building from scratch, or able to do
some serious changes to an existing component - If you run a heater on a
12.6V tube at 12.3V, you can expect to double the life of the tube. That
is what we did throughout the line.
LC >
Could you tell us something about new products from Thor Audio?
PM >
There are quite a few items that are new and are best served by going
to our web site, they are the TPA-30 (30W mono blocks), the TPA-150
(150W mono blocks) and the "100" series of front end electronics (line,
line/phono, phono only, and DAC).
Our TPA-30 made their debut at the CES (Consumer Electronics Show) show
in Las Vegas this last January and are in production now. They are built
around the EL34s, and are designed into our "preamp" size toroid chassis
with all transformers, etc. mounted inside the chassis. Features include
fuse replacement, bias adjust controls, and a built-in bias meter. All
controls are accessed from the top of the unit for safe, user friendly
operation.
The TPA-150 mono blocks are designed into a large 22 inch round chassis
weighing about 100 lbs. each. Scheduled release time is mid to late summer
of 99'. Unique to the TPA-150 is the use of a cumulative hour counter.
This meter measures the total time the amp has been on for accurately
tracking the normal 2000 hours of expected output tube life. Also unique
to these amps are something we are very excited about.
We are calling it
"Compu-Bias". Once the customer finds out the overall sound that they
like (under biased/over biased, etc.), they program the amp for that
particular setting. Once the bias switch is thrown, the input gets
shunted to ground, and all bias controls automatically clean themselves
be turning all the way left, then all the way right. Each control then
automatically biases it's own tube in turn (to the user preset), and
repeats the process, going around and around until all tubes are
perfectly biased!
This biases the amp in a fraction of the time it would
take by hand, and is far more accurate! You can bias the amp easily
anytime "on-the-fly" without turning the amp off, unplugging it, putting
shorting plugs in, etc.
The new "100" series are the first price pointed components in our
line. We still use exactly the same circuits and component
manufacturers, but use their second best components as our choice for
active and passive components. The thought was to make our line
available in the more conventional rectangular chassis, and at the same
time, making it more affordable. They are 75% of the sound of the
Signature "1000" series for about 1/2 the retail price. Release time is
staggered over the next few months, again seen in full on our web site.
Thank you for taking the time to read this, and a big thanks to Lucio for asking us to be a part of his wonderful web site!
Courtesy Paul Marks for TNT-Audio.
Copyright © 1999 Lucio Cadeddu