Revival !

I'm glad to announce that the website hosted under the name "" since 1999, which I had to shutdown a few years ago, will slowly come back to life here.

The structure of the website will be simple : each equipment will have its own blog entry, pages will be used for categories.

Please do not hesitate to leave comments!

The IMF Electronics (loudspeakers) website which used to be hosted under is at, check it out please !

You can contact me through this form.

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:


ML 3 | 2 x 200W amplifier | 1979 - 1987

The ML-3 is a hell of a beast ! With its weight of 52 Kg (116lbs) and its depth of 62cm (20½") the only place where it can fit is... the ground. Hopefully, working in class AB, it doesn't need that much electricity most of the time. The only question is, what kind of loudspeakers may need this POWER amplifier?

This amplifier is made of exactly 2 mono amplifiers, each on each side, with the two big (1,2 KVA) toroidal transformers put in the middle of the chassis next to some 36,000µF capacitors (100V). It can output 45 Volts at 30 Amperes: you'd better use fat speakers cable cables.

Pro and Cons

Pro Cons
Stereo, high power. Large and heavy. 
Can drive any speaker. Lots (20) output transistors which can be expensive to replace.
An engineer delight :-) Specific (non standard) connectors used.


Power Output: 200 Watts per channel into 8 Ohms, 20 Hz - 20 Khz, < 0.2% THD.
Input Sensitivity: 1 Volt RMS for 200 Watts into 8 Ohms.
Input Impedance : 20 K Ohm shunted by 250 pf.
Max Power Consumption: 2 Ohm load, both channels just below clipping, 2.5 kW, 200 W at idle.
Weight: 52 Kg (~120 lbs).
Dimensions:   483mm (19")  266mm (10½")  620mm (20½")


ML-3 Stereophonic Power Amplifier [download]
ML-2 class A/B power amplifier [download]


La Nouvelle Revue du Son [download]

Technical information

Warning and cabling [download]


Monday, April 15, 2013

ML-9 | 2 x 100W stereo amplifier | 1981 - 1988

The ML-9 is a perfect all-purpose amplifier. Not that heavy, not that big, plenty of power, this ML-3 little brother will suit most home hi-fi needs. It comes with the ML-10 preamplifier.


Power output: 100W per channel into 8 Ohms.
Input Impedance: 50 Kohms.
Weight: 25Kg (56 lbs).
Dimensions: 8" 19"  13⅜"


ML-9 brochure [download]


La Nouvelle Revue du Son [download]


ML-9 Owners manual [download]