Scott AW 23 modified to play through modern speaker

[Phil Lackland]

I've owned my AW23 for forty years and it is in constant use as an amplifier because of its utter clarity.  It was probably a model sold originally without a cabinet, and the speaker was already going when I got it. 

When the speaker finally disintegrated, I chose to modify the power supply to work independently of the field coil and feed the audio output to a modern high fidelity speaker.  It involved excising the output transformer from the old speaker, fitting it into the power supply chassis, and making a resistive-capacitive network to provide the required voltages (which I measured before starting out, of course). 

Naturally, this is not the purist approach, but the receiver really sounds much better using a modern speaker than it did with the original, and I've found this to be true with other receivers, the speakers were always the weakest link back then. 

Phil

[Ron Ramirez]

Hi Phil -

As much as I hate to admit it, I have done the same thing with my McMurdo Silver Masterpiece VI.

It came with everything but the original 18 inch Jensen Super-Giant when I bought it last summer. And I'm not going to pay $8K+ for a speaker. Period. End of story. So I've bought a 18 inch woofer with a frequency range of 20 to 6000 Hz, a tweeter with a range of 3000-20000 Hz, and a 2-way crossover. The tweeter is mounted coaxially in front of the woofer's cone using strips of steel similar to the Scott 800B speaker setup, and both are now in my Clifton cabinet. I can't report on how it sounds at this time, as I have not yet restored my McMurdo.

As the old saying goes, "sometimes ya gotta do what ya gotta do"...I would prefer to keep it 100% original, but when the original speaker alone is selling for $8K and up, I think you have to draw the line somewhere on originality vs. a working set at a more reasonable price.

[Phil Lackland]

I measured the voltage drop across the field coil and the current.  This gave me enough to calculate a correct value  and wattage of a resistor that would duplicate the effect of the field coil.  I also cheated by padding up the values of the filter network generally, none of this can be seen of course.  Because you don't have the field coil, you will need another McMurdo Silver owner to take a few simple measurements for you.  I think these systems are generally tolerant, but you don't want to make unnecessary changes.  Good Luck

Phil

[Ron Ramirez]

Phil

I have voltage readings, and field coil resistances. I've already calculated voltage drop across the series field, and came up with the current. So I'm ready to go. I need to have the power supply rechromed, though, plus it's finally warming up so I will be working on cabinets this summer. That means the McMurdo probably won't get touched until fall/winter.