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    Building, troubleshooting and testing of these amplifiers should only be
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Wanted Radford MA-15

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Wanted Radford Ma-15

hello,

i'm looking for 1 Radford MA-15 serie 3 to close as possible serial number : A0099
the same on the picture
mine is orphan :bawling:

in good or not condition,

i'm in France, of course i accepted to pay the expedition,
please help 😀

didier
 
A company called Woodside Electronics could once make you a set of Radford transformers. I don't know if they still can, but I recall phoning them and being told that it was the same lady with the same winding machine...

If so, you could DIY a second MA15.

PS. Welcome to the forum.
 
That's a pity about Woodside. You're right, a stereo amplifier with identical components in each channel has a much better chance with your LS3/5a. If I remember correctly, the STA15 was cathode bias, and the STA25 was grid bias. My LS3/5a appreciate a grid bias amplifier - it cleans up the bass.
 
EC8010
Just found your thread - interesting...

I have two Woodside MA100's.
The bias (grid adjusted) is set for 120ma across a 1.2R (2.5W) cathode resistor, which equates to -59v on the grids. If I grounded the cathodes and brought back the grids to -59v, am I likely to improve the bass resolution, or am I missing something?

Regards
 
m1ke said:
EC8010
Just found your thread - interesting...

I have two Woodside MA100's.
The bias (grid adjusted) is set for 120ma across a 1.2R (2.5W) cathode resistor, which equates to -59v on the grids. If I grounded the cathodes and brought back the grids to -59v, am I likely to improve the bass resolution, or am I missing something?

Regards

This resistor is just a current sampling resistor, cathode bias's big shortcoming is the cathode bypass capacitor and a tendency to head towards class b operation when pushed hard. Neither of these issues are a problem with a 1.2 ohm resistor and your fixed (grid) biased amplifiers. I'd leave them alone as it is a convenient way to measure and set the bias and its value is low enough that it is extremely unlikely to have an audible effect.
 
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