The new M50A

The M50A is biased to 35W Class sliding to A/B.
The heatsink is the chassis and temperature controlled not to go above 40C (unless you are already at 40C), So in a home at 25C the max temp was 37.8C
On start up the idle current is set to be twice the running current so the M50A quickly get to it running temp this took about 15mins.
It also has balance and non balance input were as the standard M50 has only non balance input.
The single 300VA transformer runs two bridge rectifiers with each channel having a total of 94,000uF a total capacitance of 188,000uF or 0.188 Farads. These high ripple rated capacitor should last over 20 years on all the time.
The balance input is set to run on 600 Ohms.
The RCA non balance is set for 22K Ohms.
The one I tested today gave 50W RMs into 8R and 100W RMS into 4R.
The press button ON/OFF switch operates a 16A relay with spark suppression, and maximum isolation for a safe operation. This PCB also has the mains fuse rated at 3.15A, and a added trick when plug in to draw less than 1W.

https://seca.freeforums.net/attachment/download/518

In the above photo you can see the back with the RCA,s and the XLR,s , speaker binding post and the IEC power lead. The tiny toggle switch in the up position is RC and in the down position is XLR.

https://seca.freeforums.net/attachment/download/519



In this photo on the side you can just see the power amp modules, in side at the back is the Balance to Non balance converter PCB and to it right the power On/OFF control PCB.
The front long PCB has the two DC power supplies and the on LED drive plus the 18V power supply for the balance converter PCB.
What you can't see is the six output device mounted on ceramic insulator, each power transistor can be used up to 28A and is 150W Pd. Each output transistor is driven power a 15W transistor with a BW of 140MHz this allow us to have great control on stability when driving silly loads.
The BW of the power amp is flat from 2Hz to over 400KHz crazy yes, NO this give a extremely fast rise and fall time and no phase change in the audio range and beyond. Presenting the music as it was recorded as closely as possible, sadly this mean if it was crap to start with then you get the crap out.

These are now on back order via Alan on www.abcaudio.biz/

Price TBA



Comments

  • Another Wonfor amp!
  • Audiochews demands an audition!
  • edited January 18
    Looks like another superb amp in the ever expanding EWA catalogue. Going to need to expand the shed as well Col  :)
    I suspect the answer to this is no, but can you convert a M50 to a M50 A ? 

  • 29mile said:
    Looks like another superb amp in the ever expanding EWA catalogue. Going to need to expand the shed as well Col  :)
    I suspect the answer to this is no, but can you convert a M50 to a M50 A ? 

    Sorry not possible, the cct is very different, the temperature control is designed not to burn wee hands unless the outside environment is above 40C then it has no control on that.  But is will still shut down the bias current from 1.5Amps per device (6 Off) to 150mA in extreme cases. And at 55C desert operation down to just 15mA.
    On standby the massive PSU caps are still being charged to 3V to keep them formed correctly. Thus giving a long life and reduce the peak inrush current.

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