AUDIO EXPERIMENT SYMPHONIES TUBE PREAMP (LINE STAGE)
As I write this in July 2005, I have owned my Audio Experiment Symphonies preamp for over four and
one-half years. I purchased it on eBay in January 2001 and it cost $438 with shipping. I would like to
note that it is still being sold on eBay but it has come down to $420, shipping included (although
there are some variations in how it is being priced). The current item appears to be exactly the same
unit as I have. The specifications are identical.
I have wanted to write about this component for some time. I think it is an absolutely wonderful
preamp. The sound quality, imaging, and reliability have been outstanding. I have had no problems
of any kind with it. It is simple, quiet, and, unlike a passive preamp, has the improved dynamics that
are present with an active unit.
A History of My Preamps
(Feel free to skip ahead. This got a lot longer than I intended.)
I have owned a number of receivers and even a few integrated amps over the years. The first
“preamp” that I owned as a separate component was the Adcom SLC 505. I bought it in the late
1980s. The 505 was a passive switching box with volume control. I loved it. It worked great,
sounded good, and was inexpensive. It was paired initially with a modified Adcom 545 amp and
served me for quite a few years. When the VTL 50-50 replaced the Adcom 545 in late 1994, I
continued to use the 505 and it still worked great, which frankly surprised me. From what I had read
regarding tube amps, I did not expect this passive unit to be compatible with it, but it seemed to work
fine.
Some time in late spring 1995, I saw an ad in the paper for a Dahlquist crossover. I called the seller
and a couple of evenings later, I met him at his house. He was selling a Dahlquist DQ-LP1 stereo
low-pass crossover. It was exactly what I needed for running the woofers in my now bi-amped
system and could replace the summing box that I was using. I bought it for $50. While I was there I
asked the seller if he had any other stuff he was selling. He said he did, he had a broken preamp he
wanted to sell. Evidently, it had decided one day to start smoking. I looked at it and noted two things:
it had tubes and the manufacturer’s name was Theta. I bought it for another $50.
I didn’t know what I had in the preamp as I was only familiar with the Theta name in regard to digital
equipment but it sure looked hi-end compared to anything I had ever owned.
I knew my friend, Tom Boffa, could fix the Theta for me if I could find a schematic for it. I started by
calling Theta digital. I didn’t even have to finish my question before I was interrupted and given the
name and phone number of the person to call. I ended up speaking with the man who had actually
built my preamp. Theta started out in Florida with the preamp as their first product. It was built until
about 1980 when it was discontinued. The company then moved to California and started building
digital products.
I learned that my preamp was one of the last ones built, 471 of, I think, about 475 total. (I am
operating off of memory here, as I no longer have the notes I took.) It was a Theta B Revised. As one
of the last units built it had all of the upgrades that were made during its production run. My contact
was very nice on the telephone but made it clear that he was getting tired of supporting a product,
essentially for free, which had been discontinued for nearly 15 years. I can empathize with that. No
doubt the curse of the high end is that if the product is any good, it never goes away. Like the child
who never moves out of the house, or moves back after college, it never stops making demands
upon its creators.
It took a while but the schematic eventually came and Tom got my trick tube preamp working. It was a
power supply problem. During the years I owned the Theta, I never had any further problems with it of
any kind.
While I was waiting on the preamp repairs, I spent some time researching my find. I found some
reviews in the Abso!ute Sound (www.theabsolutesound.com). These reviews are in issues Number
16, 24, and 45. I discovered I had a preamp that sold for $1295(!) new in late 1979. The review is in
Issue 24, December 1981. In a later article called “Olden-Golden Components” in Issue 45,
January/February 1987, the Theta is summarized as follows:
“All tube. Delicate, light and airy, almost thin, a whisp [sic] of a preamp, but still finely musical and
detailed without being the least bit hard. Would probably like mating with a darkish sounding power
amp.”
Of course, then, the primary concern was the phono section. My interest was only in its line section. I
never heard the phono section.
I replaced the Adcom box with the Theta and there were substantial improvements in every aspect of
the sound. The imaging was better; dynamics were better. While the Theta was undoubtedly noisier,
it was pretty much a theoretical matter. No noise was evident in actual usage. It was exciting to listen
to a component of this quality. I was actually listening to a whole system now that qualified as a high-
end—Muse, Theta, VTL, and Maggies. WOO! WOO!
My Theta B Revised had six 6922 (E88CC, 6DJ8) tubes, the original Tungsrams. Four were in the
phono section and two in the line stage. I removed the phono tubes and “hot-rodded” it running just
the line tubes. I later replaced the Tungsrams with Philips JAN tubes and they made a small but
worthwhile improvement in the sound. Due entirely, I suspect, to being new.
It was a great sounding preamp. It was hard-core purist, no tone controls, which greatly appealed to
me (and still does) while it still had some nice switching functions. The sole drawback, for me, was
the use of two volume sliders as both volume and balance controls. I found that while making small
changes in volume, I couldn’t tell if I was shifting the balance as well. Most of my volume changes
occurred over a one-eighth inch long segment of the volume control’s travel. I just never felt like I had
moved both controls exactly the same amount, which left me wondering if the imaging was being
affected. But for this, I never had any complaints. It worked perfectly all the years, 1995-2001, that I
owned it. I did replace the power supply capacitors in 1998. They were the original electrolytic
capacitors and were beginning to show signs of seeping. No real noticeable change in the sound
resulted. The Theta never exhibited any noise, hiss, buzzes, or other distractions, ever; it was dead
silent.
I could read a CD review and hear, in my very own system, the same width, depth, low level detail,
and nuances the reviewer described. It was wonderful.
Here Endeth the History
At the time, the Audio Experiment Symphonies preamp was added in 2001, my system looked like
this:
Transport: Philips Laser Disc Player (What else was it good for?)
DAC: Muse 2 with Bessel Filter Mod
Preamp: Theta B Revised
Main Amp: VTL 50-50
Main Speakers: Magnepan MG 10/QR
Bass Amp: Hafler 9270
Bass Boxes: Home made with Vifa 10 inch drivers
Interconnects: DH Labs BL-1 with Canare F-10 RCA plugs, home made. Illuminati D60 digital cable.
Speaker Wire: Alpha Core Goertz MI2
In the fall of 2000, I was seriously thinking about replacing the Theta for two reasons: First, was the
hassle with the volume/balance controls. I was tired of them and wanted separate controls. Second,
I wasn’t using the phono section, which was one of the unit’s real strengths. It seemed like kind of a
waste to not be taking advantage of its intended capability. With vinyl reviving, it also seemed like a
good time to consider selling it.
It looked like the Theta was worth about $300-400. I started looking around the web to see what I
could find to replace it new, used, or as a kit in that price range with tubes. It turns out there is
actually quite a lot of stuff. If you want a balance control, though, the choices diminish drastically and I
wanted a balance control.
I found some really interesting kits that appealed to me but none of them had a balance control. The
used preamps I found came in two varieties--not the least bit interesting or nowhere near my price
range. It was then I found the Audio Experiment Symphonies on eBay. (www.ebay.com)
It was perfect. It had the features I wanted, used good parts, looked nice, and had great specs.
Additionally, it used 12AX7 tubes, which meant that playing with tubes would be easy and cheap. The
drawback was that the designer, Mr. Chui Sat Sang, was in Hong Kong. There was no way to hear it
until I owned it. I hadn’t found anything else that fit my wants and needs so I decided to go for it.
When the preamp arrived I was pleased with its build quality and appearance. True, it wasn’t quite
as substantial as the pictures made it appear but it was by no means poorly made either. The build
quality reflects its price: good enough without wasting money by being overbuilt. The aluminum front
plate is 4 millimeters thick and the case is of reasonable quality steel. Fit and finish are good but do
not come at the expense of the parts reproducing the sound. The female RCA jacks are good quality
while not being as good as those on the Theta. There is an IEC AC plug on the back; the on/off
switch is on its right side. The controls consist of Volume, Balance, and Selector for 4 line level
inputs. These are marked CD, Tuner, Aux 1 and Aux 2. They are all identical. There are two sets of
preamp out jacks. It measures 16 X 12.5 X 3 inches approximately and weighs just under 10
pounds. It does not invert phase. (Visit www.ys-audio.com for all the specs.)
Upon unpacking it, I noticed was that the volume control was binding when I tried to turn it. The
faceplate had shifted slightly during transport. When I readjusted the face place, I took off the orange
decorative trim pieces that make the unit, to my eye, pretty garish. I like it a lot better without them.
(The current version still has these trim pieces.)
I also removed the top cover and made sure the tubes were in their sockets and undamaged.
Standard tubes are a Raytheon 6X4 rectifier and three Chinese 12AX7s. The middle 12AX7 is
common to both channels the other two serve the right and left channels. Technically, I’m stretching
it to say that much. The parts inside were as advertised. There is an Alps volume control, Dale
resistors, ERO and Philips capacitors. It is point-to-point wired with silver coated copper wire. The
wiring is a lot neater than I could do but not flawless. One thought I had at the time I bought it was
that it might be an ideal unit for modifying, maybe adding a stepped attenuator. I haven’t done that,
and am pretty sure I won’t, but it might be a very appealing possibility for the right person; there is a
fair amount of room inside the chassis.
Prior to installing it in my system, I got everything warmed up and did some listening to those
recordings I have used as references. With the sound of the Theta fresh in my mind, I replaced it with
the Audio Experiment Symphonies.
What I heard was what I had been hearing. The new $448 line stage sounded essentially identical to
my $1300 15-year-old preamplifier. The soundstage width and depth were excellent, voices were
excellent, low level details were clear, and the bass was deep with good definition. My investment in
Ray Brown CDs was intact. The Symphonies sounded great. It did nothing to draw any attention to
itself. I really couldn’t detect any change in my system, which was a very good thing. This was right
out of the box; after breaking in, the sound quality of the AES improved further.
I have used this preamp for over four years. I have listened to different tubes in it and have settled on
some NOS GE JAN 5751s. (NOS means new old stock, i.e. manufactured years ago but never used.
JAN refers to joint army navy, essentially military tubes. And 5751 is the military designation for
12AX7 tubes.) I think the 5751s are subtly quieter than the other tubes I have tried but all the tubes
have sounded very good, even the original Chinese. The 5751s have cost me about $5 each on eBay.
SO HOW DOES IT SOUND, ALREADY?
I could take up yet more space detailing how various CDs sound through this preamp, but I think the
best way to describe how this preamp sounds it to describe what it has let me hear. I have listened
to tubes, digital cables, interconnects, RCA plugs, AC cables, and all kinds of tweaks and this
preamp has let me hear whatever differences, if any, exist. It reveals the music. If the recording has
dynamics that go from silent to deafening, they will be reproduced as silent to deafening. I don’t think
this component has any describable sound of its own.
I took this preamp to Colorado with me the summer of 2002 so my friend, Tim Green, could hear it.
We put it in his system, which consisted of a McCormick solid-state passive preamp and amp and
Alon speakers. What stunned me was that I could hear no change in the sound of his system after
exchanging preamps. I expected that going from a solid state passive preamp to a tubed unit would
be about as big a change as could be made but the sound was identical. If I had had more time to
listen, I am sure I might have begun to hear some differences but in the hour or so we had the
chance to listen, I couldn’t detect any differences. I couldn’t even hear any change in the noise level
of the system. This means I am either deaf or the Audio Symphonies is extraordinarily neutral and
silent. I hope it’s obvious that I’m inclined to the latter explanation but feel free to draw your own
conclusion.
So, Kent, are you saying this is the world’s best preamp?
Obviously not, but for the money it’s an incredible bargain, great sounding and fun at the same time. I
really have no idea what someone would have to spend before they obtained any noticeable
improvement in sound quality, except that it would probably be substantial. I would really like to hear
the Symphonies + and see how it compares. It is identical except for the power supply. Maybe I can
talk Y-S Audio into a loaner.
KJ July 2005
As I write this in July 2005, I have owned my Audio Experiment Symphonies preamp for over four and
one-half years. I purchased it on eBay in January 2001 and it cost $438 with shipping. I would like to
note that it is still being sold on eBay but it has come down to $420, shipping included (although
there are some variations in how it is being priced). The current item appears to be exactly the same
unit as I have. The specifications are identical.
I have wanted to write about this component for some time. I think it is an absolutely wonderful
preamp. The sound quality, imaging, and reliability have been outstanding. I have had no problems
of any kind with it. It is simple, quiet, and, unlike a passive preamp, has the improved dynamics that
are present with an active unit.
A History of My Preamps
(Feel free to skip ahead. This got a lot longer than I intended.)
I have owned a number of receivers and even a few integrated amps over the years. The first
“preamp” that I owned as a separate component was the Adcom SLC 505. I bought it in the late
1980s. The 505 was a passive switching box with volume control. I loved it. It worked great,
sounded good, and was inexpensive. It was paired initially with a modified Adcom 545 amp and
served me for quite a few years. When the VTL 50-50 replaced the Adcom 545 in late 1994, I
continued to use the 505 and it still worked great, which frankly surprised me. From what I had read
regarding tube amps, I did not expect this passive unit to be compatible with it, but it seemed to work
fine.
Some time in late spring 1995, I saw an ad in the paper for a Dahlquist crossover. I called the seller
and a couple of evenings later, I met him at his house. He was selling a Dahlquist DQ-LP1 stereo
low-pass crossover. It was exactly what I needed for running the woofers in my now bi-amped
system and could replace the summing box that I was using. I bought it for $50. While I was there I
asked the seller if he had any other stuff he was selling. He said he did, he had a broken preamp he
wanted to sell. Evidently, it had decided one day to start smoking. I looked at it and noted two things:
it had tubes and the manufacturer’s name was Theta. I bought it for another $50.
I didn’t know what I had in the preamp as I was only familiar with the Theta name in regard to digital
equipment but it sure looked hi-end compared to anything I had ever owned.
I knew my friend, Tom Boffa, could fix the Theta for me if I could find a schematic for it. I started by
calling Theta digital. I didn’t even have to finish my question before I was interrupted and given the
name and phone number of the person to call. I ended up speaking with the man who had actually
built my preamp. Theta started out in Florida with the preamp as their first product. It was built until
about 1980 when it was discontinued. The company then moved to California and started building
digital products.
I learned that my preamp was one of the last ones built, 471 of, I think, about 475 total. (I am
operating off of memory here, as I no longer have the notes I took.) It was a Theta B Revised. As one
of the last units built it had all of the upgrades that were made during its production run. My contact
was very nice on the telephone but made it clear that he was getting tired of supporting a product,
essentially for free, which had been discontinued for nearly 15 years. I can empathize with that. No
doubt the curse of the high end is that if the product is any good, it never goes away. Like the child
who never moves out of the house, or moves back after college, it never stops making demands
upon its creators.
It took a while but the schematic eventually came and Tom got my trick tube preamp working. It was a
power supply problem. During the years I owned the Theta, I never had any further problems with it of
any kind.
While I was waiting on the preamp repairs, I spent some time researching my find. I found some
reviews in the Abso!ute Sound (www.theabsolutesound.com). These reviews are in issues Number
16, 24, and 45. I discovered I had a preamp that sold for $1295(!) new in late 1979. The review is in
Issue 24, December 1981. In a later article called “Olden-Golden Components” in Issue 45,
January/February 1987, the Theta is summarized as follows:
“All tube. Delicate, light and airy, almost thin, a whisp [sic] of a preamp, but still finely musical and
detailed without being the least bit hard. Would probably like mating with a darkish sounding power
amp.”
Of course, then, the primary concern was the phono section. My interest was only in its line section. I
never heard the phono section.
I replaced the Adcom box with the Theta and there were substantial improvements in every aspect of
the sound. The imaging was better; dynamics were better. While the Theta was undoubtedly noisier,
it was pretty much a theoretical matter. No noise was evident in actual usage. It was exciting to listen
to a component of this quality. I was actually listening to a whole system now that qualified as a high-
end—Muse, Theta, VTL, and Maggies. WOO! WOO!
My Theta B Revised had six 6922 (E88CC, 6DJ8) tubes, the original Tungsrams. Four were in the
phono section and two in the line stage. I removed the phono tubes and “hot-rodded” it running just
the line tubes. I later replaced the Tungsrams with Philips JAN tubes and they made a small but
worthwhile improvement in the sound. Due entirely, I suspect, to being new.
It was a great sounding preamp. It was hard-core purist, no tone controls, which greatly appealed to
me (and still does) while it still had some nice switching functions. The sole drawback, for me, was
the use of two volume sliders as both volume and balance controls. I found that while making small
changes in volume, I couldn’t tell if I was shifting the balance as well. Most of my volume changes
occurred over a one-eighth inch long segment of the volume control’s travel. I just never felt like I had
moved both controls exactly the same amount, which left me wondering if the imaging was being
affected. But for this, I never had any complaints. It worked perfectly all the years, 1995-2001, that I
owned it. I did replace the power supply capacitors in 1998. They were the original electrolytic
capacitors and were beginning to show signs of seeping. No real noticeable change in the sound
resulted. The Theta never exhibited any noise, hiss, buzzes, or other distractions, ever; it was dead
silent.
I could read a CD review and hear, in my very own system, the same width, depth, low level detail,
and nuances the reviewer described. It was wonderful.
Here Endeth the History
At the time, the Audio Experiment Symphonies preamp was added in 2001, my system looked like
this:
Transport: Philips Laser Disc Player (What else was it good for?)
DAC: Muse 2 with Bessel Filter Mod
Preamp: Theta B Revised
Main Amp: VTL 50-50
Main Speakers: Magnepan MG 10/QR
Bass Amp: Hafler 9270
Bass Boxes: Home made with Vifa 10 inch drivers
Interconnects: DH Labs BL-1 with Canare F-10 RCA plugs, home made. Illuminati D60 digital cable.
Speaker Wire: Alpha Core Goertz MI2
In the fall of 2000, I was seriously thinking about replacing the Theta for two reasons: First, was the
hassle with the volume/balance controls. I was tired of them and wanted separate controls. Second,
I wasn’t using the phono section, which was one of the unit’s real strengths. It seemed like kind of a
waste to not be taking advantage of its intended capability. With vinyl reviving, it also seemed like a
good time to consider selling it.
It looked like the Theta was worth about $300-400. I started looking around the web to see what I
could find to replace it new, used, or as a kit in that price range with tubes. It turns out there is
actually quite a lot of stuff. If you want a balance control, though, the choices diminish drastically and I
wanted a balance control.
I found some really interesting kits that appealed to me but none of them had a balance control. The
used preamps I found came in two varieties--not the least bit interesting or nowhere near my price
range. It was then I found the Audio Experiment Symphonies on eBay. (www.ebay.com)
It was perfect. It had the features I wanted, used good parts, looked nice, and had great specs.
Additionally, it used 12AX7 tubes, which meant that playing with tubes would be easy and cheap. The
drawback was that the designer, Mr. Chui Sat Sang, was in Hong Kong. There was no way to hear it
until I owned it. I hadn’t found anything else that fit my wants and needs so I decided to go for it.
When the preamp arrived I was pleased with its build quality and appearance. True, it wasn’t quite
as substantial as the pictures made it appear but it was by no means poorly made either. The build
quality reflects its price: good enough without wasting money by being overbuilt. The aluminum front
plate is 4 millimeters thick and the case is of reasonable quality steel. Fit and finish are good but do
not come at the expense of the parts reproducing the sound. The female RCA jacks are good quality
while not being as good as those on the Theta. There is an IEC AC plug on the back; the on/off
switch is on its right side. The controls consist of Volume, Balance, and Selector for 4 line level
inputs. These are marked CD, Tuner, Aux 1 and Aux 2. They are all identical. There are two sets of
preamp out jacks. It measures 16 X 12.5 X 3 inches approximately and weighs just under 10
pounds. It does not invert phase. (Visit www.ys-audio.com for all the specs.)
Upon unpacking it, I noticed was that the volume control was binding when I tried to turn it. The
faceplate had shifted slightly during transport. When I readjusted the face place, I took off the orange
decorative trim pieces that make the unit, to my eye, pretty garish. I like it a lot better without them.
(The current version still has these trim pieces.)
I also removed the top cover and made sure the tubes were in their sockets and undamaged.
Standard tubes are a Raytheon 6X4 rectifier and three Chinese 12AX7s. The middle 12AX7 is
common to both channels the other two serve the right and left channels. Technically, I’m stretching
it to say that much. The parts inside were as advertised. There is an Alps volume control, Dale
resistors, ERO and Philips capacitors. It is point-to-point wired with silver coated copper wire. The
wiring is a lot neater than I could do but not flawless. One thought I had at the time I bought it was
that it might be an ideal unit for modifying, maybe adding a stepped attenuator. I haven’t done that,
and am pretty sure I won’t, but it might be a very appealing possibility for the right person; there is a
fair amount of room inside the chassis.
Prior to installing it in my system, I got everything warmed up and did some listening to those
recordings I have used as references. With the sound of the Theta fresh in my mind, I replaced it with
the Audio Experiment Symphonies.
What I heard was what I had been hearing. The new $448 line stage sounded essentially identical to
my $1300 15-year-old preamplifier. The soundstage width and depth were excellent, voices were
excellent, low level details were clear, and the bass was deep with good definition. My investment in
Ray Brown CDs was intact. The Symphonies sounded great. It did nothing to draw any attention to
itself. I really couldn’t detect any change in my system, which was a very good thing. This was right
out of the box; after breaking in, the sound quality of the AES improved further.
I have used this preamp for over four years. I have listened to different tubes in it and have settled on
some NOS GE JAN 5751s. (NOS means new old stock, i.e. manufactured years ago but never used.
JAN refers to joint army navy, essentially military tubes. And 5751 is the military designation for
12AX7 tubes.) I think the 5751s are subtly quieter than the other tubes I have tried but all the tubes
have sounded very good, even the original Chinese. The 5751s have cost me about $5 each on eBay.
SO HOW DOES IT SOUND, ALREADY?
I could take up yet more space detailing how various CDs sound through this preamp, but I think the
best way to describe how this preamp sounds it to describe what it has let me hear. I have listened
to tubes, digital cables, interconnects, RCA plugs, AC cables, and all kinds of tweaks and this
preamp has let me hear whatever differences, if any, exist. It reveals the music. If the recording has
dynamics that go from silent to deafening, they will be reproduced as silent to deafening. I don’t think
this component has any describable sound of its own.
I took this preamp to Colorado with me the summer of 2002 so my friend, Tim Green, could hear it.
We put it in his system, which consisted of a McCormick solid-state passive preamp and amp and
Alon speakers. What stunned me was that I could hear no change in the sound of his system after
exchanging preamps. I expected that going from a solid state passive preamp to a tubed unit would
be about as big a change as could be made but the sound was identical. If I had had more time to
listen, I am sure I might have begun to hear some differences but in the hour or so we had the
chance to listen, I couldn’t detect any differences. I couldn’t even hear any change in the noise level
of the system. This means I am either deaf or the Audio Symphonies is extraordinarily neutral and
silent. I hope it’s obvious that I’m inclined to the latter explanation but feel free to draw your own
conclusion.
So, Kent, are you saying this is the world’s best preamp?
Obviously not, but for the money it’s an incredible bargain, great sounding and fun at the same time. I
really have no idea what someone would have to spend before they obtained any noticeable
improvement in sound quality, except that it would probably be substantial. I would really like to hear
the Symphonies + and see how it compares. It is identical except for the power supply. Maybe I can
talk Y-S Audio into a loaner.
KJ July 2005
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