January 2008

Markhill Audio MC-100B Integrated Amplifier
High-end sound and looks at a low price.
Review By Ron Nagle
Click here to e-mail reviewer

  Let us take a little trip back; There was a time when you could find want ads for tube equipment tucked in the classified section of audio magazines? These ads were offering, "top dollar" to purchase your old outmoded tube audio equipment. Usually included was a list of company names that included Marantz, McIntosh, Fisher, and Scott. Those were the days when transistors dominated home Hi-Fi and replaced high distortion, tube powered components. Back then I must have read hundreds of reviews toting "solid-state" sound with amazing Specifications. Reviews of these fabulous components were written like ads: One hundred watts of music power with only a tenth of one percent total harmonic distortion. If you can remember that than you might also recall the gospel of the audio guru Julian Hirsch?  What was actually going on was that some very hip individuals were buying American tube audio equipment and selling it on the other side of the Pacific for two or three times what they paid.

When the source began to peter out the prices just kept climbing and ultimately the supply never actually met the demand. Meanwhile the American public was scoffing up Japanese transistorized Hi-Fi like there was no tomorrow at the same time as some great American audio companies were driven out of business. Ironically what goes around comes around and now poor cash strapped yanks are finding that the very same prevailing wage structure that once drove American manufacturers backs to the wall are turning to our advantage. The music loving Chinese never actually found enough tube-powered audio to quench their desire so they set about making their own. At this point I would like to jog your little gray cells just a wee bit longer. Many years ago there was a debate as to which technology was more musically accurate   tubes or transistors? In time it gradually faded from print as technology improved, the differences in sound became smaller as tube components became more articulate and solid state became less grainy and cold.

Before I go any farther let me set this up by clarifying where we are now in High-End audio.

There are still tube people and solid-state people but there are many more classes and sub classifications when you consider tube audio components. I recognize the allure of Class A operation and I understand the wonderful mid range qualities of directly heated triodes. I can even understand preferring one brand or type of tube to some others. However I believe that a modern ultralinear tube amplifier can combine the virtues of solid-state power and control and still deliver more true to life sound. Well audiopals the fat lady still hasn't sung and tubes still do things the best of solid state can only intimate.

Where And What?

Cruising the bustling corridors at the Rocky Mountain Audio Fest in October 2007 I stopped in room 570, The Tube Amp Store.  As is my habit along the way I had compiled a self-flagellating wish list of things I knew I could never afford to own. Confession time, yes I do love music but at the same time the other half of my brain is an avowed equipment junkie. Just gazing at the gorgeous golden chassis of the MC100B precipitated a rush of audiophile lust I knew I had to get my hot little hands on it. The asking price of this 60 watt per channel integrated amplifier is, $1299.

This is an unequivocal price breakthrough on a full-featured tube amplifier that you really should know about. At The Tube Amp Store the President Gregory Hockman has obtained exclusive distribution rights to Markhill Audio a new line of remarkably cost effective Chinese audio components. The main reason I fly my ole bones to audio shows is to search for something that is in some way unique has value and is relatively unknown. Let me posit a little story. It was in May of 2005 when I reviewed a PrimaLuna Prologue 2. This is a 40 WPC integrated amplifier. Every one who reviewed this little amp just loved it. They agreed that for the original price of $1345 it was a true audiophile bargain. At the time I echoed their praise and I bought the review sample. As of right now the MSRP of the PLP 2 has increased to $1675. Even so considering a ratio of tube watts per dollar this amplifier can still deliver good value for the money. Why mention the PLP-2? It is to set the stage for a very interesting comparison between these two ultralinear amplifiers. If you are at all familiar with the PrimaLuna than it will serve as a real world reference point.

What Is Ultralinear?

It is an amplifier circuit patented in 1937 by Alan Blumlein and popularized by David Hafler and Herbert Keroes in the early 1950's. Basically it is the application of a portion of the audio output signal (typically 20 percent) returned to the tube screen grid, which alters the behavior of the electron stream passing through the tube from cathode to anode. Very basically it is a form of distortion lowering feedback applied to the KT88 pentode output tubes. It has the additional benefit of lowering the output impedance of the tube for increased power.

Comparison

Both are Chinese manufactured integrated amplifiers using KT88 pentodes and both are designed with push/pull ultralinear circuits and both amplifiers are built to a very specific price point. Both the PrimaLuna PLP-2 and the MC100B gradually come up to operating temperature and do not use a time delay relay. Both amplifiers use very nice ceramic tube sockets. Each amplifier has four pairs of line level RCA inputs for components and provisions for 8- or 4-Ohm speaker connections, which is the end of the similarities.

Yes there are differences, besides 20 watts of additional power the MC100B has manual tube bias meaning you will need to set output tube bias with a voltmeter. The PLP-2 has an automatic tube bias circuit said to be able to accommodate almost all types of pentode power tubes. The PrimaLuna 2 has a more expensive choke filtered power supply and the Mark Hill power supply uses the usual capacitors and diodes. The MC100B has two switches for right and left channels on the top of the chassis. They are used to switch the amplifier into either the triode or pentode mode of operation. On the rear of the MC100B are four RCA inputs marked, TAPE, DVD, CD, and TUNER. Left side rear there is a fused IEC style power cord receptacle and in the center are three each left and right speaker binding posts marked 8 Ohms, 4 Ohms and GND.  On the front panel of the amplifier there are a pair of RCA connectors designated left and right channels. And directly between them is a toggle switch marked INPUT 0.6V for the up position and INPUT 0.25V in the down position. On the left side is a four-position source selection knob and on the right side is the volume control knob.

Picking Some Nits

There are, as you should expect some cost cutting involved keeping the Markhill price low. Inside the amplifier the board-mounted components are fairly standard the boards themselves and the wiring are good quality. Additionally I was impressed by the fact that I couldn't see any sign of chip style components. If I had to characterize the construction overall I guess I would say it is expensive and high-priced consumer quality. By contrast the PrimaLuna circuit boards have a few very nice quality components like French and American film caps. Also the PLP2 internal wiring is bundled and squared off and tied mil-spec neat the MC100B is not. Neat wiring is a good thing especially if you ever have to trouble shoot problems but in of itself it does not mean better sound. Another Nit-Pick observation, The Markhill transformer covers sound hollow if you tap on them. Again that doesn't necessarily mean the transformers are poor quality but I would feel better if they were potted. Last nit, the Golden colored Markhill aluminum chassis is anodized and lacquered and I wonder if the finish is durable.

A Clever Endeavor

When the Markhill amplifier arrived it came in a triple walled cardboard box and apparently straight from the rack at the RMAF show. I had received the demo unit and it needed a little dusting. The very first thing after placing the tubes into the positions shown in the owner's manual was to turn it on and make sure it was not damaged. Next step, allowing the amplifier time to reach operating temperature I readjusted each of the four KT88 tubes bias points using two non-inductive 100 watt 4 Ohm load resistors and a digital voltmeter. As it turns out each of the tubes were on the low side of the specified 0.55 bias Volts. After I received an e-mail copy of the schematic diagram I discovered a very clever straightforward and innovative circuit design. First and most importantly the MC100 is a true dual mono amplifier sharing one chassis. There are a total of four transformers each stereo channel has its own signal transformer and power transformer.

Note: The following description is for one channel only the left side and right side circuits are the same.

The first gain stage is a single dual triode 12AX7 configured so that one half of the tube amplifies the positive portion of the signal and the other half amplifies the negative signal transition. This is handed off to a workhorse 6SN7 dual triode driver configured as a phase inverter; the positive and negative signals output from this tube are handed off to another 6SN7 driver. This tube is connected as a cathode follower, which amplifies the control grid, signals that varies the output of the KT88 power pentodes. There are still more clever aspects of this design.

The front panel toggle switch in the 0.6mV position provides a lower resistance direct path to the first gain stage via: the front panel RCA plugs. This direct path bypasses the four input connections on the rear chassis and the source selection control and an internal dropping resistor. Also note that the front panel switch serves as an adjustment for input sensitivity. This circuit routs the front panel components signals direct to the first stage 12AX7 tube.

Most of the tube sections are direct coupled tube to tube and there are only two interstage coupling capacitors in the signal path. These are labeled C7 and C6 and I would love to replace them with the best Teflon film caps I could find. By now you can tell I really like the way this circuit is laid out.

System Options

During the time I had this amplifier I was able to slot it into my system in different ways. For example: with every source component remaining plugged into my Audio Research SP 9 Mk3 preamplifier I initially connected its output to one of the four inputs on the rear of the MC100B. Next the preamp connection went to the front panel bypass direct into the amplifier first stage. Using this hookup you can use the component input connections on the back of the MC100B as well as those of the SP 9 preamp to connect additional components. However it doesn't take a rocket scientist to figure out that the use of a separate preamp is redundant and it is far better to plug your source components directly into the Markhill amplifier. Another option would be to connect your system components direct as shown in the owner's manual than use the front panel bypass connection for a separate high quality Phono preamp. And as you might expect the front panel direct connection sounds best it elicits many more small details buried within the performance.

Evaluation

Lets get to that part were we talk about what goes in and then what comes out. I always have a problem when we get to this part of the story. The fact is that with most audio magazines you get very ethereal near poetic descriptions of the sound coming through a system you don't own and references to recordings you may not have. Just after writing that sentence I was leafing through a big circulation print Mag and I came upon some of these descriptive phrases: "Sonic decay, lush lower level midrange, my ears could touch, vivid aural blackness". Still on the basis of very long-term familiarity with my system I can pick out, a loser, a common mediocrity, a good thing, a very good thing and tell you using every day American.  Employing a protesting lower back I quickly swapped these two amplifiers in and out of my system. Using only a single reference recording as the source and my Marantz DV 8400 CD/SACD/DVD player. This recording is a CD compilation of many differing musical selections by the Audio Society of New York: about 60 copies were made.

Cut to the chase, The Markhill MC100B and the Prima Luna 2 have very similar top to bottom tonal inflections/personalities. At moderate/normal listening levels the differences in power between these two amplifiers are not audible. At much higher levels the MC100B has the edge in bass drive. The PLP-2 by a slight margin is more detailed and better defines the space between my speakers. The direct input on the front panel of the MC100B improves the performance to the extent that the differences between these amps are barely detectable. But even in this hook up the PLP-2 has by the very slightest margin better micro imaging.

I must not fail to mention one of the key features of the MC100B. It is the optional triode operation of this amplifier. This part of the evaluation taught me something new. I have noted that with other push/pull pentode non-ultralinear amplifiers when they are switched into a lower power 30 watts triode mode there is a very pronounced change in sound. The effect is to lose detail and become midrange dominant because the upper and lower frequency extremes are not as extended. By comparison when the ultralinear MC100B amplifier is switched to triode operation the sound is not changed to the same degree, the bass frequencies and inner detailing remain mostly intact. What is more in your face obvious is the loss of extension and details in the treble range. For critical listening I much prefer to listen to my music while operating the MC100B in pentode mode.

Summery

Based on a balance of performance, features, flexibility, and price I can easily recommend the Markhill MC100B. The quality of music produced by this amp can be equaled or surpassed only by a healthy expenditure of many more dollars. The ample power rating means you can match this amplifier to a broader range of speakers. The combination of features and flexibility means you can adapt the sound as well as the component function to fit into a broad range of systems. The MC100B is a breakthrough product and is superior to anything with comparable specifications at anything near to its price. Let me rephrase that statement, I don't know of any integrated tube Amplifier at this price that can equal the Markhill MC100B. Audiopals this is a no brainer.

Associated Equipment

Marantz DV 8400 Universal CD player, Cambridge Audio Discmagic-1 CD transport, Cambridge S-700 Isomagic HDCD D/A Converter, ART DI/O Up sampling D/A and A/D processor, Magnum Dynalab FT 101a tuner and Dynalab Signal Sleuth.
Audio Research SP-9 MK 3 Preamplifier
StrataMini Hybrid speakers, Aurum Cantus Leisure 2 SE two-way monitors on 24-inch stands

System connections
Kimber Kable 8tc 11ft. speaker cables
Wire World Eclipse-2, 3meters
Audio Research Litzlink 2 pairs, 1 1/2 meter
Chord Silver Siren, 1 meter and
Wire World 10 gauge IEC power cord
Audiobhan 0.5-meter digital

System Power conditioning:
Richard Gray 20 Ampere Substation
Islatrol Industrial 20 Ampere AC line conditioner
Alpha Core Balanced Transformer Power Supply
Audio Power PE-1 power enhancer
Triad 2-Ampere isolation transformer

Accessories:
VPI Magic bricks
Ferrite RFI cable blocks 
Room Tunes Panels
Argent Roomlens
Gryphon diffusion wall panels

Specifications

Type: Stereo integrated tube amplifier

Tube Compliment: Four KT88, four 6SN7 and two 12AX7

Output Power: 60 Watts @ 8 Ohms Ultralinear or 30 Watts @ 8 Ohms Triode

Frequency Response: 5Hz to 80kHz (-2dB)

Distortion: <1.5%

Signal to Noise Ratio: >90dB

Input Sensitivity Switchable: Normal 0.25Volts, Bypass 0.6 Volts

Weight: 57 lbs

Dimensions: 15.5 x 18 x 8.5 (WxDxH in inches)

Warranty: One year for parts and labor and 90 days on tubes.

Price: $1,299

Company Information

The Tube Amp Store
16835 Algonquin Street
Suite 185
Huntington Beach, CA 92649

Voice: (866) 895-3178
Website: www.thetubeampstore.com