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replacing old amplifier electronics with new class D amplifier board/s

Helen Bach

if it ain't Baroque ...
I am thinking of gutting a Rogers Ravensbrook amplifier and replacing the board with a class D amplifier or two. The case and fascia of the Rogers fit in with the kitchen decor, but the sound is behind a class D amplifier I'm using (with JPW Sonata 'speakers). The problem is that the (several) low power class D amplifiers I have used seem to run out of steam quite quickly. Looking at the data sheets for the amplifier chips, I notice output is usually quoted at 10% distortion, yes 10% distortion! The Sonatas are rated at 60 watts (not that I play loudly while cooking!) but getting a class D amplifier to produce a genuine 50 watts (at <0.1% distortion) is going to need an advertised output around 300 watts!

Has anyone gutted an amplifier and replaced the board/s with class D amplifiers?
 
No, but I have a muse 200 amp that'd be a shoe in for a pair of ncores. Got me thinking....
 
I've just shoved a B&O icepower module into an old Musical Fidelity X-Can V3 case. Very simple with the icepower module as the power supply and everything is on the one small pcb. You just need cables for your inputs, outputs, mains and the status leds if you want them. It even has a small balanced 25v aux power out should you want to run a pre-amp.

It works, I haven't had a proper listen yet, but they are worth a look, profusion sell them, mine was second hand off ebay.
 
I have an original Rogers A100 amp in my second system which I bought new in the 70s and it still sounds superb now, sweet as a nut and better than the A&R A60 as it had more clout, wondering why you would would you want to replace the amps with class D ???
Alan
 
The Rogers Ravensbrook amplifier is a very old design, it even has interstage transformers in the power section, which generates distortion. I think they look good, and I have two amplifiers and a tuner, two of them with teak cases. The one I'm gutting was once owned by people who lived in Brighton, and I think the sea air got to the electronics, as most of the component leads are very rusty.

I have used small class D amplifiers with the JPW Sonata 'speakers, and obtained very good results (bettering £1800 worth of amplifier/loudspeakers). The problem with cheap class D amplifiers is their output power, grossly exaggerated, like in-car amplifier specs.
 
Have a look at the icepowers on Profusion, they have datasheets with proper graphs of power vs distortion at different impedances etc. The Icepower200AS2 would probably be more than enough, the 100AS2 may not be quite enough. The graphs in the datasheet will reveal all. My Icepower50AS2 is 2x50w into 4ohm, and does 26w into 8ohm at 0.1% THD (from memory).
 
thanks. The objective is to have sound in the kitchen when I'm cooking. There is a Virgin TiVo box there, so source material can be quite good. The speakers are quite high up, so imaging etc is not an issue (meaning I'm not bothered) I just like clear even sound! I won't be spending much on the class D amplifiers, just enough to get the sound I want.

Amplifiers in the listening room are two Cambridge Audio 640Av2 (one per side) providing a possible 480 watts, and no discernible distortion. These feed floor-standing Usher 604 speakers, and sound good together with the CA's.

It's not a 'high end' system (how I dislike that term!) but I have what I want, and I'm a music lover, NOT an audiophile. :?)
 
And what would people suggest for a power supply? Go with the tried and tested 'linear' type, or a more modern SMPS? Some offerings even have P/s on board (linear type). With the class D's I've played with, I've used an in-line SMPS, and have been impressed by the lack of hum/hiss from the amplifiers, even with the volume control turned right up! I might see what voltage the Ravensbrook runs at, and use that, if compatible.
 
Just as a reference, this is my icepower50AS2, stuffed into a cut down Musical Fidelity X-CANv3 case.

Front, will get an on off switch shortly.



And rear, better speaker connectors and a lock of paint next:


And internals, just to show how little there is:


Finally, connectors, very simple to wire up:

upload pic

It really was very straight forward, just the sockets and a 20k alps pot for the volume, all mounted on a plate to fit. Power will go through the front switch directly when it arrives. Only issue so far is it needs about 3v to clip, so I may have to poke a small pre-amp of sorts in there.
 


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