● Digital inputs: 2 RCA, 1 BNC, 1 AES/EBU, 2 optical (1 Toslink, 1 optional
● Analog Inputs: 1 stereo pair on single-ended RCA jacks, 1 stereo pair on balanced XLR jacks
● Input Impedance: 10 K ohms
● Frequency response: DC - 20 KHZ
● THD+Noise: <0.0005% @3VRMS in and out, balanced
● Dynamic Range: 125dB ref 18VRMS Bal
● Signal to Noise Ratio: 125dB ref 18VRMS Bal
● All DSP processing is 24-bit with 56-bit accumulator
● D/A Conversion: 24-bit Ladder (8x oversampling); 2 DACs per channel for
● Volume Control: Proprietary switched resistor network in the analog domain
● Digital Filter: 8x oversampling proprietary FIR filter running on Motorola
● Size: 17 5/8” W x 5” H x 17 3/4” D
● Weight: 29 lbs
● MSRP: $10,000 USA
Equipment reviews ordinarily begin with an introduction, proceed with
discussions of design, functions and technical specs, and then move onto
time-honored listening assessments. At one extreme, those assessments read
“When I played my favorite recording of Mahler’s Eighth Symphony, otherwise
known as the Symphony of a Thousand, I heard orchestral details I had never
heard before. Due to the infamous squeaky chair under the extremely animated
eighth violinist in the orchestra’s second row - a squeak that has made this
recording a cult favorite among audiophiles inhabiting the outer islands of
Japan - I was never able to locate the sound of the third row of violinists
within the recording’s massive soundstage. But with this new preamp, I could
not only hear the resin on the bow of the sixteenth violinist in the third
row, but could also identify the exact moment when she, in a fit of rage,
momentarily lifted her bow from her instrument and jabbed it into the back of
the eighth violinist. The thrill of actually feeling this outburst of anger in
the middle of Mahler’s greatest expression of spiritual exaltation makes the
asking price of $49,798 seem most reasonable.”
This, however, is no ordinary equipment review. While it will undoubtedly
include some listening assessments, I prefer to proceed in less formulaic
fashion. My rationale? To paraphrase an oft-quoted axiom, extraordinary
equipment calls for extraordinary measures.
Gen. X - The Experience
Have you ever spent years fantasizing your ideal relationship, even passing
the person on the street from time to time, yet finding yourself unable to
make an actual connection? Have you ever carried on an internet relationship
with someone living a great distance from yourself, but had to wait years
before meeting face-to-face? Are you someone who, assuming marriage was a
legal option from day one, was forced to wait many years before popping the
question? Are you a person who had to search many years before finding the
house of your dreams?
If you have ever had an experience that even remotely parallels any of the
above, you can begin to understand what it was like for me to wait well over
four years before receiving the Theta Gen. VIII.
Theta was the first audiophile company to produce separate outboard DACs. They
continue to honor their long-standing policy of producing fully upgradable
Theta's ambitious plans for the Gen. VIII ultimately
required designing an entirely new unit, a combined DAC preamp that features
both single-ended and fully balanced inputs and outputs. Theta claims that
this new design brings the performance specs of its single-ended outputs
close to the same level of excellence as its balanced outputs. This is
important factor for those like myself whose amps only feature single-ended
When the Theta Gen. V first came on the market in 1994, a number of reviewers
who had previously pledged total allegiance to analogue hailed it as the first
two-channel DAC to render digital recordings not only listenable but also
distinctly musical. The unit came in two configurations: for a hair less than
$4000, you got a single-ended DAC equipped with coaxial outputs; several
thousand dollars more got you a purportedly quieter and superior fully
balanced unit with XLR outputs.
I first obtained my Theta Gen. V single-ended DAC in January 1996. While I did
not have a decent analogue set-up with which to compare it, I certainly found
the Gen. V rewardingly musical when compared to live acoustic music
presentations. It didn’t sound remotely the same, of course, but it was
musically satisfying. The unit in fact proved so satisfying that, besides
upgrading it to V status within the year, it remained a constant in my system
until two months ago.
As we all know, digital technology has made great strides since 1994. First
came 24-bit chips. Then arrived separate bit interpolating and upsampling
devices, external DACs that performed the same functions, and 24/96 one-piece
CD players. All claimed to make 16-bit/44.1 khz sampling rate redbook CDs seem
as though they had been recorded and issued in 24-bit/96 khz or higher
I probably first began contacting Theta about such upgrades to the V sometime
in 1999. I was immediately assured that the next generation product was in the
Every three or six months I would check in. Sometimes I was told that the Gen.
VI was only six months away. At one point the Gen. VI was listed on Theta’s
website; then it disappeared. Six months became a year, a year became two. By
whose calendar did Theta operate, I began to wonder.
At first the reason I was given for Theta’s seeming intransigence was that the
company was unable to find a 24-bit chip that sounded as good as what they had
accomplished with the V’s outdated 20-bit chip. When that story could no
longer hold water, it became clear that, in the face of changing listening
preferences and economic downturns, Theta Digital had chosen to insure its
survival by building a strong presence in the multi-channel home theater
market. The Casablanca, mega amps, and various other audio and home theater
products debuted to great acclaim while the company’s two-channel DAC
Over two years ago, a Bay Area Audiophile Society member who had spoken with
Theta President Neil Sinclair reported that the Gen. VI was no more than six
months away. Hardly. I even saw the empty shell of the “expected shortly” Gen.
VIII at CEDIA 2002. But the wait continued.
After 9/11, the economic downturn reduced Theta’s ability to put their main
focus on a product that, given the state of the audiophile market, they now
considered (to quote Theta’s Mary Cardas) “a bit of a ‘vanity product.’”
Happily, the designer of the original V remained with the company. Yet, each
time he proceeded to design an upgrade, another state-of-the-art chip came on
the market that tempted him to experiment anew. The combination of continued
experimentation and development and low priority added a good year and a half
to the final release date.
Finally, the decision was made to proceed no matter what new developments
might occur. (To paraphrase a Buddhist phrase, there’s always another chip).
Given the arrival of new DVD-A and SACD formats, Theta also chose to rethink
its design in order to provide a DAC that could also decode those formats’
In the end, it all boiled to the company’s long-standing motto, “Digital Done
Right.” Theta took as long as it felt necessary to get it right.
Theta’s ambitious plans for the Gen. VIII ultimately required designing an
entirely new unit, one that offers both single-ended and fully balanced
outputs as well as an internal preamp. (Theta claims that its new design
closes the gap between the unit’s single-ended and balanced outputs for those
like myself whose amps only accommodate single-ended inputs). Though such
fundamental design changes mean that the Gen. VIII shares only a small number
of parts with the Gen. V, and is housed in an entirely different chassis,
Theta continues to honor its long-standing “fully upgradeable” policy for
original owners of all versions of the Generation DAC. In this instance,
however, the “upgrade” means that you receive an entirely new unit.
After the Gen. VIII’s design was completed and beta tested, the first units
were released in late spring of 2003. A few went to print reviewers, a few
more to dealers, and a few to buyers. But while the first units seemed to
function smoothly, the need to integrate a two-channel DAC with all of today’s
electronics (including satellite and various limited-use digital devices) took
Theta many, many additional months.
I had originally hoped to obtain a demo Gen. VIII after CEDIA 2003. Alas, all
the CEDIA demo units returned to the company arrived too beatup to refurbish.
Then more problems arose with the next round of units. The wait became longer
I must confess that, in the face of yet more delays, I was sorely tempted to
throw in the towel and obtain another company’s DAC. Not only was I frustrated
on a personal level, but I also felt a responsibility to Secrets readers to
review with state-of-the-art equipment. Yet even in my most exasperated
moments, a strong belief that the company was doing all it could to honor
their promise to me, combined with my faith that the Gen. VIII would turn out
to be something else entirely, kept me hanging in there by a thread.
By CES 2004, a few exhibitors, notably Genesis and Thiel, had rooms equipped
with correctly functioning Gen. VIIIs. (Theta’s own exhibit in the Las Vegas
Convention Center only offered a static display). It is one of those CES demo
units that, after a round of tests and retests, made it to Oakland on Friday,
February 13, 2004. Given that was the same day I became Jason Victor
Bellecci-Serinus, I am happy to report that my feelings about Friday the 13th
have forever changed.
What is the Gen. VIII?
The Generation VIII is a full differential balanced two-channel DAC featuring
custom-designed software-programmable digital filters feeding into two
digital-to-analog converters per channel, one for each phase angle. Several
Gen. VIIs can be strung together and connected to the Theta Casablanca or Casa
Nova for multi-channel operation. While this represents a considerable
investment, Theta assures me that as good as its current multi-channel
processors are, the Gen. VIII takes digital-audio conversion to another level.
Since my set-up is strictly two-channel, I am not in a position to evaluate
Theta has posted a host of technical information about the Gen. VIII on their
site. I refer you to same. The site includes a white paper that discusses the
truths and myths of upsampling vs. oversampling. The Reader’s Digest version
is that the Gen. VIII’s multi-stage digital filter brings the signal up to a
sampling rate of 384 kHz.
The unit also offers the option of Theta’s proprietary
“Jitter Jail” which the company claims reduces jitter (time alignment
distortions which are a major factor in the degradation of digital signals and
cloudy sound) to almost zero.
Notes by Colin Miller: The rest of the industry calls
this a Phase Lock Loop (assuming it is similar), operating with a healthy FIFO buffer to reclock the
data, or simply reclock it completely without the PLL (a la Meridian) and
attenuate if not eliminate jitter, but 'Jitter Jail' is a snazzier name. It
may be that the Theta can alternate between these two methods, but it all
boils down to a FIFO buffer on the input, and a new clock feeding
information to the DAC process.
Jitter is a timing error, an error in data rate,
either over a very short time, or a very long time. Short periods of data
rate error (too close together for a few samples, too far for a few more,
etc.) are high-frequency jitter. Long periods of data rate error (too close
for very many samples, gradually shifting to too far for many more, and so
forth) are low frequency jitter. The only way to correct the error is to
correct the timing. The only way to correct the timing is to space the data
evenly at either a derived rate, or a known rate. The only way to do this is
with some working room, which requires an input buffer, and then you can do
what needs to be done, reclock it to the most uniform (evenly spaced) and
preferably correct data rate.
In a perfect world, jitter would be no issue at all.
In a next to perfect world, the DAC device would control the transport
device's servo-controller that determines the data rate, and the only clock
would be the master clock that times the DAC process, and so jitter would be
very easily avoided with a small FIFO. That has yet to happen, to my
In a world almost as perfect as that, you have a FIFO buffer at the input,
the DAC device figures out the rate by looking at the data, and reclocks the
data completely independently of the incoming rate that would be carrying
the jitter. In this scenario, the only jitter possible is that of the DAC's
own clock itself, and any jitter prior to that is completely and utterly
irrelevant, with one exception. If the error is of low frequency, i.e., goes
too fast for awhile, then slows down for awhile, or as a most extreme
example of the lowest frequency jitter, spits CD information out at 44,003
samples/second instead of 44,100 samples per second, you'll have buffer
over- or underrun, in which case you either get dropouts, no sound, or a
really nasty mess of a sound when the DAC tries to resynchronize with the
rate. From the comment that your DVD player doesn't work with the "Jitter
Jail," I'd guess that they're going this route for higher quality digital
sources and that your DVD player is a particularly poor one. Stacey
had this problem with his Meridian anti-jitter reclocking circuitry when he
used a particular DVD player with the AC power, but it worked fine with the
onboard battery power supply or when he used his Power Plant. He had to set
his unit to operate in the more standard PLL with that source.
The above illustrates why most of the industry resorts to a PLL, or Phase
Lock Loop. This uses the same FIFO buffer, and attempts to smooth the data
rate. It'd be like having a bunch of unruly school kids come in clumps
through the gates at Disney Land, and the teacher assistant tries to get
everyone evenly spaced before the turnstile and going through at a constant
rate. He can't hold people up so that they're standing in the parking lot,
nor can he get people to run to the parking lot, but if the average flow is
steady, he can provide an even stream of screaming children. Every
off-the-shelf DAC has a PLL, though some are better than others, and it's
quite possible that Theta's is better than most. A better PLL requires
a larger FIFO buffer, so to accommodate larger swings in the tide, so to
speak, without having to compromise the new clock. For instance, if a CD was
fed at 44,003 samples per second, a PLL would simply shift the master clock
to 44,003 samples per second, not underrun the buffer, and still be able to
attenuate the higher frequency jitter. This extreme example would result in
a slight pitch shift, but where it gets really difficult is when it's
shifting fast enough to cause modulation problems in the DAC, but slow
enough to cause the FIFO buffer problems, an area where better jitter
reduction schemes really shine.
This extreme example would result in a slight pitch
shift, but where it gets really difficult is when it's shifting fast enough
to cause modulation problems in the DAC, but slow enough to cause the FIFO
buffer problems. Although the PLL circuit is the best way to attenuate
jitter while managing the FIFO buffer with poor sources, the strength of the
PLL's continuity is also its weakness in jitter reduction. In order to avoid
buffer overflows or underflow with low frequency variations, the PLL will
adjust the clock to match the data rate over a particular period, and if
that jitter period is large enough (low in frequency) to make the PLL
circuit adopt the change in data rate, the clock essentially tracks the
jitter, passing the same timing errors on, even if slightly attenuated.
It is here that we see that all PLL circuits are not created equal. A larger
FIFO buffer, and possibly better buffer management in terms of how the clock
adjusts to the amount of data in the buffer, mean that different PLL
circuits have differing amounts of jitter attenuation, particularly in terms
of low frequency jitter.
With better jitter reduction methods, the input buffer and the PLL can
manage more low-frequency jitter while still attenuating the lower frequency
jitter, whereas a poorer PLL circuit will simply begin to let the clock
follow the lower frequency jitter, essentially passing it right onto the DAC.
Since it is the lower frequency jitter that's the most audible, this is
where the better jitter reduction schemes really shine. They still follow
the rate of the incoming data, but their clocks remain more stable and
jitter free in the presence of a less desirable source.
- CM -
As noted above, the Gen. VIII’s rear panel features:
Six digital inputs (two RCA, one BNC, one AES/EBU, one toslink, and one
One set single-ended (RCA) analog inputs
One set balanced analog inputs
One set single-ended (RCA) analog outputs
One set balanced analog outputs
● Options for remote extensions and
external volume data inputs for owners of the Theta Casablanca or Casa Nova
A main on/off switch
The front panel offers:
24 character by 2 row vacuum florescent display
Standby/on button LED
Five programmable input select buttons
A setup button used to access setup menus that choose all user parameters
A lock light
A mute button that mutes all audio outputs. The mute button is not active when
optional fixed volume cards are installed.
Level left and right buttons as well as level up and down buttons, designed to
appear and work like four pieces of a pie. These buttons perform such
functions as balance, editing, master volume and setup menu adjustment
All of the above features are controlled by an easy-to-use remote control
powered by three AAA batteries. The remote control, which operates up to 20
feet from the unit, includes:
Standby button that puts the unit in Standby mode or initializes it for
playing or programming
Input Select buttons (1-5)
Display button to control brightness
Mute button (not active with fixed volume card installed - see below)
Setup button to enter/exit setup menus and set all user parameters
Level up/level down buttons for master volume and setup menu values
Level left/Level right buttons that shift the balance and adjust master volume
Phase button to shift between 0 and 180 degrees at speaker outputs
Purchasers can order the Theta set to either adjustable volume (ideal when
using it as both a DAC and preamp) or fixed volume (which those who use an
external preamp may prefer). Since this adjustment must be made at the
factory, those considering purchasing a Gen. VIII would be wise to read this
entire review before making the decision.
The heart of the Theta is a
sophisticated internal computer that can be reprogrammed by linking it to an
external PC and downloading data from either an upgrade CR-ROM supplied by
the company or from the Theta website. The unit’s
computer-based circuitry requires that it be grounded via a three-prong AC
Power cord. If your outlet is not grounded, before you connect the unit,
ground your outlet via a grounding wire to your cold water pipe or a
grounding pipe driven into the earth before you connect the unit. Be sure not
plug the unit into a line conditioner that defeats the ground. (Some units,
such as PS Audio Power Plants, do not read as grounded when tested with a
Radio Shack polarity tester. Rest assured that the Power Plant is a fully
When I first received my Gen. VIII and discovered a 29-page binder filled with
instructions on how to use and program the unit, I held my breath. No need.
Programming the Gen. VIII is pretty simple. Within a short amount of time, I
had labeled the four inputs I am using as phono, tuner, CD, and DVD; chosen
the form of jitter reduction I wished to use for CD and DVD; and made sure all
other features (such as balance and startup volume) were set as I wished.
Features such as the built-in burn-in signal option that provides white noise
to burn in the Theta as well as cables and other electronic devices, remote
trigger, RS232 protocol interaction, baud rate, IR remote jack, and
screensaver time did not require adjustment on my part. If they do in the
future, adjustment is easily accomplished. The only thing that confused me was
exactly which buttons to push to choose the form of jitter reduction. But
since I could do no harm by pushing the wrong button, I just pushed away until
I figured it out.
The Theta requires a good week of constant signal playing through it to break
in. Either music or the built-in break-in signal may be used. Since your amp
need not be on, you don’t have to listen 24 hours a day.
Any already broken-in Gen. VIII started up cold needs 72 hours warm-up to
sound its best. The first 24 hours are most significant, with increasing
levels of refinement obtained in the next 48. Those needing to turn the unit
off completely via the power switch at the back would be wise to do so for not
more than 1 or 2 minutes to avoid having to go through this extended warm-up
I have experienced only one problem with the Gen. VIII. Within a week of its
arrival, the unit began to freeze up. I would initialize it and start to play,
only to discover that I couldn’t adjust the volume or switch inputs. Sometimes
the problem would self-rectify, but most of the time I would need to put the
unit in standby mode, turn it off in back for two minutes, turn it back on,
reinitialize and play.
When the freezing became more common, I contact Theta’s technical expert, John
Baloff. He suggested that the software had become corrupted, and I needed to
hook the Gen. VIII to a PC and reinstall. When I couldn’t find the Theta
Digital Downloader CD that had been sent with the unit - I am a music
reviewer as well, and there are piles of CDs and boxes of review equipment
scattered around chez Serinus - John was good enough to send me another. (I
now know exactly where I’ve put it). This Mac user then called upon John and
Mary Cardas to help walk me through the inner recesses of David’s PC laptop.
Once we were able to locate where the appropriate upgrade file had been
stored, reinstalling the software was accomplished in no more than 30 seconds.
Since then, the Gen. VIII has sounded significantly different and far more
impressive than what I heard after the initial 72-hour settling in period.
What Mary, John and I have surmised as the cause of the problem lay in the way
I changed frequencies on my Power Plant. We think that changing my P600’s
frequency back and forth between SIN, TubeWave, and P-1 while the Gen. VIII was
on had corrupted its software; hence the need to reinstall.
I now keep my PS Audio Power Plant set to P-1 (the setting I like best with my
reference system) unless I am playing LPs. (The motors in most turntables do
not function properly if fed other than a standard Sin wave.) When switching
frequencies, I first put the Gen. VIII in standby mode, then scurry around one
of my speakers and two racks, turn the Gen. VIII off completely via the rear
on-off switch, scurry back in front and reset the P600’s frequency, zip to the
back and turn the Gen. VIII back on, and finally come back to the front of the
Theta and reinitialize. I may not enjoy doing this at age 80, but at 58 3/4,
it’s fine. Following this procedure will hopefully insure that I won’t need to
re-download the software anytime soon. But I do expect, given that I need to
reinstall programs in my Mac from time to time, that I will eventually have to
reconnect the PC and perform the procedure again.
The good thing about this experience is that I not only have learned the best
protocol for Power Plant users to follow, but have also discovered how easy it
will be for Gen. VIII users to upgrade the unit’s software when and if new
software and/or codes become available.
Click Here to Go to Part II
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