Music BOX A1 Hdam - looks interesting ?

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Ian Finch

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2010-04-11 4:22 am
Coffs Harbour, NSW
Height 55 width 160 depth 240
Power 50WX2 8 ohm
Impedance matching range 2-16ohm

Transformer 120 VA maybe?

Unless bias is very low for the EF output stage, this is so small, yet has no significant heatsinking apart from the case, that it must get stinking hot. Are they serious?
I think there is plenty of DIY incentive to redesign and add proper heatsinks and case there. The price then, wouldn't be so attractive. The boards or board kit would be sensible and IIRC, the basic PCB kits are out there.

Edit: Well how 'bout that, talk about cut and paste marketing. The schematic posted for this 150W version is the same (Ahem): http://www.aliexpress.com/store/pro...969-Amplifier-Circuit/802369_32355305690.html
 
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Hi Ian,
You would run each pair around 40mA, so with 40V rails (I am assuming, can't find the figure) I would say the two channels would dissipate around 6.4W from outputs, around 3W from the input, VAS and driver stages.
The size of the box, and it's solid Al, would be OK for idling and quiet listening, particularly in a cool climate. But not good for tropical climates, your Australian sensibilities are reasonably suspicious....
However, my concern would always be the output devices - they probably are fakes, although I have found the metal work and build quality of most of the Chinese module amps quite OK. If you bought one, I would expect you would quickly blow out the outputs, but replacing them would not be expensive.
I'm a amused how they make the input and VAS circuits to be like the JLH! This is nothing like the JLH at all; it is a Marantz modded version of the original 1972 Hitachi lateral mosfet design, which is very stable and robust and often used in pro-audio.