Wanted Radford MA-15

[spoke]

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

in good or not condition,

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

didier

 

[spoke]

it's me again,

my picture is delete in the first message,

a new,
good one

Did you already see or heard a Radford, what do you think about ?

didier

 

[EC8010]

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.

 

[spoke]

hi EC8010,
and thanx for your welcome,

i know woodside
I already asked them , but nothing.

make a new one : i don't believe found the same sound .

if i build a amplifier, i choose the STA-15, it's like the Ma-15 but Stereo.

and for the transfo, here is a good adress

that's for drive
this little thing

regards,
didier

 

[EC8010]

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.

 

[m1ke]

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

 

[kevinkr]

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.