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Astute readers already noticed the dual-use frontal VU meters. Not only do they track output voltage, they are also used to bias the pentodes. The knob on the front panel selects either power monitoring (its 12:00 position) or four other positions, each of which is dedicated to one output tube. Using the meter needle's deflection, you'll turn the corresponding set screw beneath the selector knob with a suitable screw driver until it reads 40mA. Plan on spending between 60 and 90 seconds biasing each amplifier. Eastern Electric advises to check the bias on your new amp but that it won't require additional adjustments until you replace tubes. Still, it's so easy to check for bias drift that you'll probably want to do it periodically just for the hell of it. Eastern Electric partner and US importer Bill O'Connell of Morningstar Audio tells me that the amps can be completely retubed for about $200. Since the amps are manually biased (which is called fixed bias, believe it or not), replacement pentodes can be purchased individually. No matched quartets are required.
Some folks hate power meters. I admit to quite liking them and those on the M156s glow a beautiful amber that doesn't get too bright with the room lights dimmed. Aside from the meters and bias controls, the only other front panel accoutrements are the velvety smooth power switch and its soft blue pilot light. Around back are the tubes and an apron bursting with connectivity options. The M150s feature both RCA and XLR inputs
with a selector toggle between them. Another toggle selects between US or EU wiring configuration for the balanced input. Then follow four shrouded WBT-type binding posts at 0, 4, 8 and 16 Ohms. Finally, there are the voltage selection switch (230V/115V) and fused IEC power inlet.


Build quality is very good. The amps are solidly put together but not accessorized to jewel-like status like mega-buck amps - which is fine by me. They remain quite handsome. At its thickest center, the brushed aluminum faceplate is .5 inches thick, tapering back to about .25 inches at both sides. The face plate does not exceed the width of the chassis proper which is a nicely applied glossy grey metallic lacquer. All connective hardware looks and feels solid.

With regard to the balanced inputs, I asked designer Alex Yeung if the M156s were fully balanced. He told me that to achieve fully balanced operation, the amplifier would require double the amount of tubes. Instead, he uses a Permalloy-core input transformer as a phase splitter. Those familiar with the MiniMax phono stage may recall its excellent performance with low output moving coil cartridges which has been very widely praised. This is largely due to its expensive Permalloy step-up transformer. With the M156, a similar transformer is used to match impedance and create the anti-phase signal necessary for a push/pull circuit without the added expense and complexity of extra tubes. I then asked Yeung if the M156 incorporated any new twists or tricks. He told me no, that it was a straightforward, tried and true design where most of the development time had been spent refining it.
My review samples use the premium Mundorf Silver & Oil caps which command a $700 surcharge for the pair beyond the reasonable $5000 stock sticker. Without getting too deeply ahead and into the subjective portion of the review, I can tell you that Morningstar's Bill O'Connell describes the EL-156 as a highly refined cousin of the KT88. My initial impression is that he's correct. Right out of the box, the M156s sound fully extended at both frequency extremes, a little forward and slightly aggressive but that faded completely after less than 50 hours. Given where they started and where they
are now, if you're looking for a warm chocolaty midrange and a honey-sweet euphonic treble, I can pretty much venture a guess that these won't be for you. They're far too linear for that. I've used them into a series of monitor speakers including the Genesis Advanced Technologies G7.1p, the Thiel SCS4 and the Triangle Trio and as far down as those go in the bass, the M156 keeps it nice and taut, with as much power and control as you'd expect from a 160-watt tube amplifier. Indeed, the general character is definitely in line with a premium KT88 or 6550 amplifier.

The amps are still breaking in and I've got other projects ahead in the queue but because they're the new statements of a designer who has demonstrated considerable skills already with widely praised affordable electronics, it seemed timely to introduce them sooner than later. Plus, they do take pretty pictures. More in due time.
Eastern Electric website