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Paris, France, May 2014.

Wednesday, April 17, 2013

ML-2 | Monophonic Class A Power Amplifier | 25 W | 1977 - 1986

The ML-2 is a massive class A mono amplifier. It's output power is often advertised to be 25 watts but it's actually more than that, maybe up to 100W.
With its class A design that means it's large, heavy, it runs hot and it's power hungry (even when idle). It'll happily suck 400W from mains (double that if your system is stereo !).

The ML-2 was used in the HQD system. Since the HQD is based on Quad ESL-57 panels, the power of the amplifier had to be low but it should be able to drive low impedance speakers (e.g. be able to output a lot of Amperes).


    The correlation between published specifications and sonic quality is usually very poor. A list of numbers reveals virtually nothing. All technical measurements must be subject to qualitative as well as quantitative interpretation.
    Measurements of the ML-2 yield excellent results by any standards. However, only those specifications that apply to the actual operation of the amplifier are included here. 
Rated Power: 25 watts minimum continuous sine-wave power into 8 ohms from 20Hz to 20kHz with no more than 0.1% total harmonic distortion.
Input impedance: 100,000 ohms
Power Requirement: 400 watts nominal, 50-400 Hz
Overall Dimensions: 19 in. Wide X 8.5 in.High X 21.5 in. Deep (48.3cm Wide X 21.6cm High X 54.6cm Deep)
Weight: 65 pounds (29.6 kilograms)
Connector Complement:
2 Lemo coaxial connectors 
1 3-pin audio connector 
5 Binding posts 
1 AC receptacle/line voltage selector 
(from the owners manual).



The Audio Critic [download]
La Nouvelle Revue du Son N°25 Feb. 1979 [download]


ML-2 schematics [download] (partial)
ML-2 Service Manual [download]
Technical Information (voltage adjustements) [download]
The power switch is an AIRPAX reference 203-222-4984-1.

Other resources

Illustrated restoration story by Raymond:


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