Review of the Assemblage L-1 Preamp Kit
Fred Whitlock
A Study in the Law of Diminishing Returns
A Review of the Assemblage L-1 Preamplifier
By Fred Whitlock
As an audio enthusiast you have to be aware of the law of diminishing
returns. You've been there, I'm sure. You hear a subtle improvement that
some wonderful component can make to your system only to realize that the
cost of the improvement is completely out of proportion to perceived
benefit. It's a cruel fact of life in high end audio.
Background.
Not long ago I upgraded my home theater by replacing a good quality Dolby
Pro Logic Receiver with a Marantz AV 550 preamp and some separate power
amps. Although I do most of my music listening in a dedicated listening
room with the requisite high end audio system, I also wanted to be able to
enjoy CD's through my home theater system. The Marantz preamp does a
competent job with DVD and DSS audio but when I want to play some serious
music, alas, the unit sounds much like a $300 mid fi receiver. The amps
were capable of high end sound and so were the speakers, so I went looking
for a preamp that I could switch into the system to play CD's. It had to
be fairly inexpensive and still provide high end sound. My search ended
when I saw an ad for the Assemblage L-1 tube preamplifier kit from Sonic
Frontiers' Parts Connection subsidiary. I had already built the Assemblage
DAC 1 and DAC 2 digital processors and was quite impressed with them as
amazing values. The L-1 preamp kit was only $599. The Parts Connection
already had a good reputation with me. So, I ordered one.
The Kit.
According to the literature, the L-1 is based on the circuit of the old
Sonic Frontiers SFL-1 preamp. It features a single Sovtek 6922 dual triode
tube as the main feature in a hybrid gain stage. Parts quality is high as
I expected from the Parts Connection (metal film 1% resistors, Multicaps, a
beefy power transformer designed specifically for the unit-that sort of
thing.) For an additional charge a selection of even higher quality parts
is available to upgrade the preamp to "Signature" status. I built the
basic unit.
I would describe the kit as an "intermediate" level kit for experienced
electronic kit builders. The DAC-1 and DAC-2 are beginners kits with
preassembled PC boards that can be finished in about an hour. The L-1
requires you to stuff and complete the main and secondary circuit boards
yourself. It took me three longish evenings and one call to the Parts
Connection to complete the kit. The step by step instructions were decent
and fairly well illustrated. They weren't as good as the Heathkits of
yore, but good enough to get the job done. There are some sections of the
main PC board which aren't used and not documented in the instructions.
There were some parts which were identified in a confusing manner. I had
to refer to the schematics to ensure that the transistors in the gain stage
were properly oriented. Some of the resistors in the power supply section
were bagged improperly so it would have been easy to install some of them
incorrectly. In all, I would rate the instructions and parts
identification as fine for someone that can read schematics and not good
enough for a beginner. You can complete the kit successfully, though,
without much trouble if you're careful and have a modicum of experience at
electronic circuit assembly. The Parts Connection will build and test your
unit for you if you like. The service adds $200 to the price of the
preamp. So you can roll your own or buy it as a finished product-your
choice.
The Preamplifier
Physically the completed preamp is 14" wide, 10 1/2" deep and 3 1/4" high.
The front panel is dominated by large controls for volume, balance and
input selection. There are five push buttons as well. From right to left
they are power, mute, normal/direct, stereo/mono, and source/tape. These
should be self explanatory except for the normal/direct. One might think
that this is a passive bypass of the gain stage but it isn't. It switches
in a pair of input jacks on the back of the unit which send the signal
around the input selector and balance controls directly to the gain stage.
A more direct path, if you will.
The back panel is equipped with excellent gold plated, widely spaced RCA
inputs and outputs. There are a total of four line level inputs connected
to the selector switch, a tape input and the aforementioned "direct" jacks.
One very nice feature is the inclusion of two parallel preamp outputs.
This allows you to biamp your speakers easily or to run a subwoofer
independently of the main speakers. I really like having two sets of
output jacks so the Parts Connection gets a brownie point from me. Of
course, there is a pair of tape output jacks as well to complete the tape
loop.
The published specifications indicate a frequency response of 10hz to 120hz
-1/3 db with .02% THD unweighted. Input impedance is 47K ohms and output
is 525 ohms. Rated output is 1 volt so this preamp will drive all but the
most insensitive power amps to full output. It weighs 13 1/2 lbs thanks to
its beefy power transformer and heavy steel chassis.
The Sound
Let me get right to the point and tell you that the Assemblage L-1, at $599
for the kit, is capable of true high end sound. It solved the music
reproduction problem in my home theater in spades. Teamed with the
Assemblage DAC-2, a Classe CA 100 power amp and B&W Matrix 805 speakers, I
now enjoy high end sound in my home theater. When I want to operate as a
home theater I can simply switch the Classe and the main speakers back to
the AV preamp.
I also connected the unit to my dedicated high end audio system in place of
the CAT SL-1 preamp that usually resides there for purposes of comparison.
That system uses an Audio Research CD2 as a digital front end, an Audio
Research VT-50 power amp and a pair of B&W Matrix 802 speakers. Since I
use the CAT itself as a phono preamp, I didn't have the facilities to test
the L-1 with an analog front end. It is line level only.
In the home theater my CD listening moved from mid fi to high fi sound as
soon as I connected the L-1. It fairly glowed with a honey sweetness
similar to that of the Sonic Frontiers SFL-1 that inspired it. The B&W
speakers are fairly neutral (a little bright if anything) and the L-1
represents a good match for these speakers. The L-1 also immediately
showed its ability to deliver a lot of bass. While the 805's are lean in
the bass like all mini monitors, the L-1 convinced them to generate as much
bass as they could. The bass lines in "Things ain't What They Used to Be"
from Dave Grusin's "Homage to Duke" CD were powerful and I didn't even have
the home theater subwoofer connected. As warm as the sound presentation
was, I didn't feel robbed of high frequency musical content. Pinchas
Zuckerman's violin retained every overtone on Beethoven's Sonata #10 (RCA
09026-61219-2.) The L-1 can play soft or loud and keep excellent pace with
the music.
The lesson in diminishing returns hit home when I moved the L-1 to the
dedicated listening room. You need to understand that I consider the CAT
SL-1 to be a magical preamplifier. It projects a soundstage like no other
preamp I've ever heard. Every time I substitute another preamp the
soundstage fairly collapses. It is so detailed in its presentation that
the most subtle elements of the recorded music and the hardware system are
revealed for all to hear. The CAT is really exceptional. Please excuse my
gushing. So, my expectations for the L1 were fairly modest. After all, a
new CAT will set you back about 10 times the price of an Assemblage L1 kit.
So is the L1 a giant killer? No, but it teaches a hard lesson in the law
of diminishing returns.
The L1's bass is strong but a smidgen soft and tubby compared to the CAT's.
It has less ability to resolve middle and high frequency detail than the
CAT. And, of course, it can't project the CAT's magical soundstage. Why
would I expect it to? It's a tenth of the price, after all. Well, I
didn't expect it to but I also didn't expect it to come so close. The L1
represents over 90% of the performance of the CAT SL-1 for a minor fraction
of its cost. I was amazed at how little sound quality one really had to
give up by substituting the L-1 for a preamp ten times its price. If I
hadn't experienced the CAT's magic for so long a time, I could live with
the L-1 in my dedicated listening room and be satisfied.
Recommendation.
I'd like to hear the Signature model with the parts upgrade but mine is the
only L1 I know about. In it's basic form, it is a very competent
preamplifier and it's as good as anything I've heard for under $1000. I
would caution the prospective buyer to be prepared for a warm and somewhat
classical tube sound. If the rest of your system is honey sweet, the L1
will drip a little more honey onto the mix. If your system is neutral to
bright, the L1 should complement your system admirably. If you're looking
for a great tube/solid state hybrid preamp for under $1000 (way under
$1000,) you'd be hard pressed to find a better one that the Assemblage L-1.
Good listening.
Fred