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REVIEW: Marchand Electronics XM126 Active Crossover Preamplifier (Tube) Review by WT at Audio Asylum

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Introduction
------------
Current System:
Front End: Oracle Mk V + VPI JMW Memorial Tonearm + Dynavector 10x4
Audiomat solid state Phono Preamp
Preamp:Sonic Frontiers Anthem Pre 1L - tube preamp
Amp:2 Sonic Frontiers Anthem AMP1 - 40watt push pull tube amp - EL34
Other Front End;Sonic Frontiers Anthem CD1 - tube CD player
Speakers:Magnepan Tympani IVa
Misc:Silver interconnects and speaker cable

As you can guess, 40 watts is not enough to drive the Magnepans.
However, I have two Anthem AMP1's which previously were quite
successful at driving PSB Stratus Golds in bi-amp mode.
To use two amps however, I needed an active crossover to do the
same thing with the Tympani's.

My search ended up with Marchand Electronics, who specializes
in active crossovers. They have a new product, XM126 which
is a tube crossover. After hearing Harvey Rosenburg rave about
the XM26, I decided to take the plunge and order the 3 way kit
from Phil Marchand.

For a full description of the product, see the website:
www.marchandelec.com.

As an aside, I should mention that I have never worked on
electronics before let alone build something that works. However,
I was assured by Phil that as long as I can solder, identify the various
parts and follow the instructions, I will be ok.

The kit arrived about 6 weeks later - being in Canada has
some disadvantages in shipping times. But as later
experience showed, the wait was well worth it. The parts packaging,
parts quality and instruction manual exceeded my expectations.

When ordering the kit - make sure that you have the crossover
points and slopes handy from your speakers. I choose an arbitrary
crossover point at a much higher slope and this resulted in a bright
sound that was not eliminated until I used the speaker's recommended
crossover point and milder slopes.

Building the XM126
------------------
I followed the instructions explicitly. The detailed construction
manual is available on the website to those who are interested
in finding out what the project entails.

I received updated instructions by mail 3 weeks after receiving
the kit.

Questions to Phil Marchand.
* what is a jumper ?
(ans. a piece of wire that connects the two ends)
* there was a conflict between the picture and the instructions
in C4a, C4b, C8a, C8b as to which two are jumpered and
which two are unused ?
(ans. it doesn't matter whether you follow the instruction
or picture - just choose one)
* which way do the Mosfet transistors install ?
(ans. the white band on the circuit board matches to
the metal heat sink and the pins are offset to one side)
* what is that small tube of tooth paste doing in the kit ?
(ans. its a heat transfer compound for the externally mounted
mosfet)
* where is pin#1 in the IC chip ?
(where the little divot is on the chip)
* clarification of diode installation - do color of the bands
matter ? (ans. no - it's the band oriention in the circuit that counts,
simply match the orientation to the diagram or circuit board)
* how come the volumn controls don't fit in the panel ?
(ans. you have to break the little tabs off before installation)
* two toroid transformers are different - how do I tell them apart ?
(ans. somewhere on the large label, it says sec:240v which is
the 120v + 120v as described in the instructions)
* why does the transistor mounted on the back panel get so
hot during operation - is this normal ?
(ans. Phil says that if you touch it and you don't get a blister,
then it is operating normally)
* when I measure the filament voltage, I get 10 volts instead of
12.6 volts. What is wrong ?
(ans. the instructions to mount the voltage selector switch
is backwards, looking at the switch from the front of the power
unit, the 115 volt label on the switch should be on the right
towards the power transistor mounted externally on the back
panel with the switch moved to the left towards the fuse.
* when I plug in the unit, the fuse blows !
(ans. if the supplied fuse is 1 amp, it is incorrect - it should be
4 amps - I used a spare 3.5 amp fuse without any problems so
far)

Some Construction Pointers:
---------------------------
* there is not enough heat shrink tubing - maybe I am just wasteful
* there is not enough brown, orange wires to maintain color coding
* make sure to *assemble* the terminal blocks before soldering. The
blocks have these tiny slots and tabs that lock together. Ignore this
at your peril.
* the bolts that mount the two toroid transformers need to be swapped
with a separately included bolt. Otherwise, the included bolt is too short.
* study the color pictures really closely. Use Adobe Acrobat to read
the downloadable instruction manual and really magnify the color
pictures. For instance, it is not clear which one of the holes the two
transformers mount into until you look at the picture. Note also that
the kit designer took the trouble to use different diameter bolt holes
so that it is harder to screw up. Printing the pictures out in black
and white just won't work.
* get a good wire stripper - there are over 100 wires to cut and strip
in one of the boxes.
* sometimes the information needed to perform a step requires
studying the written instructions, the tables and the picture all
at the same time before you can figure out exactly how to assemble
a single item.
* I can only get hold of Phil Marchand in the evenings - I made my
calls for help in a polite fashion and to the point ensuring that future
assistance is provided without wasting his goodwill and time.
* I used WBT 4% silver solder with good results.

Suggestions for Improvement
----------------------------
* See the questions and construction pointers above.
* Option for a more attractive enclosure. This is as much
a high end product as from any esoteric manufacturer.
* The testing procedure for measuring the various
voltages while the unit is in operation is somewhat vague.
Although an experienced builder would know how to perform
the testing, a novice builder like myself needs a description of
where the test leads should go to measure a voltage or current
along with what setting to use in the multimeter.
* The cooling fan for the crossover box is somewhat noisy - it is
comparable to the noise coming from a fan typically found in a
computer. So far I have not used it although the case gets
hot to the touch. I hope this level of heat is not damaging to
the components.

Setup of XM126
--------------
I bypassed my preamp - simply running the source into the
XM126 and from there to the amps. There was more than
enough gain (6db) provided to drive the power amps even
when using the vinyl front end. This was an unexpected
but pleasant surprise - to reduce the need for a component.

The XM126 in a 3 way version contains 17 tubes inside one
Box - so runs very hot. Space is required for cooling. Since
the cooling fan can be noisy, location of the unit as far away
from the listener is recommended. The unit does have a
convenient switch to turn off the fan.


Listening to XM126
------------------
Vinyl
After 3 months of listening, I was quite impressed with the results.
The level of neutrality was beyond what I was expecting with tubes.
There was no grain nor any euphonic sweetener - just very neutral.
This unit is much more transparent then the Anthem preamp I am
used to and is close to other high end preamps I have listened
to in my local audio salons. Other than a greater dynamics,
I cannot readily identify a sonic signature.

The immediacy and the macro/micro dynamics was the most impressive
aspect of this unit - I often found myself looking to turn the volume
down when loud passages of the music were playing. This probably
has as much to do with the fact that the old passive crossovers are no
longer in the signal path as the preamp section of the unit.

Most important of all, I found the unit to be very musical - except to write this
review, I no longer listen to how my system sounds as I am far too involved
in the music to care.


Conclusion
----------
The construction of the XM126 was fun and challenging. When I ran
into a problem or did not understand a step, I called Phil Marchand
who was very helpful and patient. The included instructions are
complete and clear.

For the price of an average preamp, I constructed a 3 way active
crossover that also can function as a preamp. The level of performance
offered is very good even if this was only a tube preamp - instead
you get a state of the art tube active crossover designed by a company
that specializes in crossovers. I am now looking for a useful place for
my now unused Anthem Pre1.




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Topic - REVIEW: Marchand Electronics XM126 Active Crossover Preamplifier (Tube) Review by WT at Audio Asylum - WT 15:41:44 04/29/00 ( 0)