Review / Mark Levinson ML-2
Dual mono amplifiers
The ML-2 monaural Class A poweramplifier was the first amplifier from Mark Levinson Audio Systems (MLAS). This was Levinson’s statement on how a reference amp should be built. At the time (1976) it simply had no peer. Prototyped by John Curl, one of the technical consultants Levinson often used for its company, as a JC-3, and finalized by Thomas P. Colangelo the chief technical officer at MLAS. It is considered as the archetype American high-end solid state audio poweramplifier. Graced with a thick 19 inch wide black anodized frontplate, beautiful sculpted handles and white lacquer filled engravings it has a certain style that would never go out of fashion and formed the mold for a lot of derivates from competing companies. Not only could it supply Class A power to almost any load but it also had a fully regulated powersupply and a modular construction.
The six vertically stacked heatsinks (powermodules) with the attached driver and powertransistors, the inputsection (AP-1) and regulatorcard were all connected to the mainboard by golden edge connectors. Even the power-transistors could be removed from their sockets without soldering. The powersupply consisted of a huge Western Electric ‘E’-Core transformer in the early versions – later to be replaced by a Avel Lindberg 1200 VA toroid – two large 41,000 uF Sprague caps and two smaller 5,700 uF for the unregulated supply and two 10,000 uF caps for the regulator.
The regulator must be seen as an additional amplifier delivering regulated voltage to the audioamplifier. The regulator in the ML-2 delivers 27/28 Volts to the amplifying stages even if the AC voltage drops to fifty percent of its nominal value. This fully regulated powersupply makes the ML-2 almost immune for AC variations.
A regulated powersupply and Class A amplifying mode come at a price. Class A biasing is still considered as the most preferable way to get a linear response from a output device but wastes power especially when no input signal is present. A well-constructed Class A poweramplifier needs a heavy powersupply and lots of cooling surface to drop of the large amounts of heat generated by the large quiescent current to keep the outputtransistors in their linear region.
The two opposite powermodules closest to the front of the amp are the regulator-outputs that feed 27/28 railvoltage to the Class A outputsections, the next four powermodules. The middle sections also have the driverpair FT-317/417 later MJE 15030/31 (#1500 onwards) and the last two powermodules left and right are the biassections. All the output powermodules use 2N5884/5886 – 30A outputtransistors that were later substituded by MJE-15024/25025 pairs when the original failed. There is some debate if the orginal 2N5884/5886 should be used because they can deliver more current but they’re not as fast as the Motorola’s MJE-15024/25025. Output-transistors must be matched for optimal performance.
The ML-2 possesses all the hardware necessary but could only boast a maximum of 17 Volts outputvoltage resulting in a 36 Watts powerrating at a 8 Ohm load. But due to the very stiff powersupply it also supplied this outputvoltage at 1 Ohm generating almost 300 Watts at that low load. First offerings by MLAS in 1976/1977 would cost around 3,600 USD per pair which was at that time a huge amount of money for a 25 Watt amplifier and that fact alone aroused quite a lot of turmoil in the audio-community and that was just what Mark Levinson was all about.
Sonical highlights are its pinpoint precision of voices and musical instruments, super clean sound and I do not mean cold analytical but compared to other poweramps from that era and later concepts this amp sounded less grainy but glasslike palpable.
Marketvalue of these amps is depending on cosmetics, version and restoration level. A complete restored, mint looking and pair of late model ML-2’s (Toroidal transformer, Fisher outputs) could go as high as its newprice that is around 5000 USD. An early still working version with no
refurbishing at all and with dings on the front should not be worth much more as 3000 USD per pair.
– Type: 25 Watt class-A mono power amplifier
– Introduction: 1976
– Discontinued: 1986, Succeeded by the No. 20
– Designer: John Curl/Tom Colangelo
– Power rating (manufacturer)
8 Ohms 25 Watt
4 Ohms 50 Watt
2 Ohms 100 Watt
Aditional technical infomation
We still highly recommend this amplifier although it’s not trouble free. Like the old Thresholds, recapping of all the electrolytics on both the PC Cards is probably necessary as replacing the trimmers for bias, DC and regulatorvoltage on them. Complete overhaul including the blue large cans and outputtransistors is pretty costly. Be aware that new TO3 encased outputtransistors can have smaller leads then the ones originally fitted so that they do not fit tight enough to make a proper connection.
© Copyright HighendClassics.com
- Year 2019
- R.H.F.G. Sabelis