Replacement XFMRs For Magnavox AMP148?

[kconnor]

When I decided to build my bucket list amplifiers I bought two Magnavox 150 for that purpose with the intention of transplanting them into custom chassis. However I’m thinking about changing direction and I’ve been looking at the possibility of building clones of the Magnavox 148. They look so cool with those 6 6V6 output tubes, (I know its shallow…what can I say?)
Can anyone give me some direction as far as replacement transformers for the Magnavox 148 amplifier? The best that I can tell is that the Hammond 1650K output transformer and either the 370LX or 370MX power transformers would might work. Anyone have other suggestions? Confirmation of my selections? Thanks in advance.

 

[GordonW]

I see no reason the 1650K shouldn't work for an OPT. 50 watts rated down to 30 Hz, should go lower than that before saturation, at only 40 watts.

With that much output transformer (more than the original, from what I can tell, in terms of power at low frequencies), you could up the B+ a bit. I'd be thinking about a 300-0-300v secondary transformer, if you wanted to use two 5U4 rectifiers per amp- B+ would wind up around 335v. If you went with the power transformers specified (275-0-275), a pair of 5V4 rectifiers per amp would be good- B+ would wind up around 315v. Or, the 275-0-275 transformer and two 5AR4 rectifiers per amp would give about 345v (you could use Chinese or Russian 5AR4s- they'd have no problems)... with cathode bias, that'd be about 320v across the plate to cathode of the output tubes. That'd be really good...

BTW: This might be a good, less expensive, option compared to the Hammond 1650K output:

https://www.edcorusa.com/p/454/cxpp70-ms-3_5k

Rated at 70 watts (!), it should really do some bottom end! I'd guess flat power response down to 20 Hz easy, with triple paralleled 6V6s...

Regards,
Gordon.

 

[kconnor]

Wow, thanks Gordon. You answered my questions and then some. It’s like you read my mind as far as increasing the B+ on these. Good advice on the Edcor CXPP70-MS-3.5K too. I’ll definitely build these 148 clones and start getting parts as soon as I pass the 150s on. Can’t thank you enough.