Sure 50watt Cass-D Mini-amp

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I just got one of these to see how the TDA7294 chip it is based on performs and I have to say I'm really impressed by the quality of item you get for £28 delivered!

The case is aluminium extrusion with a thick solid aluminium face plate. Vol knob is metal too and it has binding posts on the back not cheap clips as one finds on the original 'T-amp'.

Whats-more the PSU is nicely overrated at 120watts! Since the amp IC is rated 50watts at 10% THD it is more realistically a 30watt amp for proper hi-fi use. So the PSU is rated double.

Inside the case there is extensive filtering for the power lines and a digitally controlled analog volume control IC (not a plain potentiometer). The amp IC is heatsinked with a plate of aluminium and faces to the bottom of the extruded case and it looks as though they are meant to touch but they didn't use a thick enough piece of metal. So I stuck a few craft-knife blades stacked together in the gap to flesh it out and get the whole case acting as heatsink.

 
How does this Sure amp fair in a listening test against (say) a Quad 303 or other low power quality amp?
 
I've not compared using high quality speakers against a known good amp. I'd like to when I get the chance.

It should sound good, the distortion is low, here is a plot of 1KHz disto vs. output power on a 25V supply. If there is an achilles heel it is the distortion around 3-6KHz which is higher than the rest of the range (something to do with multiples of the PWM freq I wonder) peaking around 0.2% within sensible power outputs. Whether this adds a slight sound will depend on what sort of harmonic content it is. I'd like to find out. It's certainly not going to sound 'bad' though!


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That's a sightly odd plot (the manufacturer's?); flat up to c.20w is deeply unlikely. And what's the bandwidth of the THD measurement..?
 
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