Opinions on this military amp..Redboy!
- Thread starter WhiteSE
- Start date
s-petersen
Scott
I don't see anything bad about it,caps not restuffed,but not important
Maybe i was over critical. The radial caps don't look secured well, the orange drops look like they could be supported on one end only, and the binding posts don't look to be in an absolutely straight line. Maybe sloppy is a better word than hack.
savatage1973
Addicted Member
My only concern with these old military and other old tube PA amps is the +/- db fluctuation across the entire frequency response range. Something designed to reproduce only human voice for announcements, etc. is not likely to be "flat" 20Hz to 20KHz.
primosounds
Powered with pure tube sounds.
One thing fer sure is you got some good transformers. What is the output impedance of the speaker taps? It may give you an insight into the use of this amp. And i would agree that the rebuild job looks fairly standard not really all out but more like a stock rebuild.
Hey Jack, I just found this thread...
Did you buy it?
I'd been watching that one, too! Neat old amp, and there's a chance that it might sound amazing.
A couple things that have been said already are what kept me from snapping it up (well, aside from the $1K that I don't have quite handy at the moment, but there are ways around that... ):
Output transformer bandwidth - this is the big question mark, I think. Freed made some fantastic transformers and I'm sure they're of incredible quality for their spec, but they've got an awful lot of secondary taps and most of their size can probably be attributed to what it took to wind the 250 and 500 ohm taps. They're spec'd 50 ~ 10KC but they might drop off pretty steeply after that 10K mark. Hopefully not.
The modifications that had been made to it - I wish they were a little neater. Actually, I wish it were still original, but wish in one hand, as they say... *sigh*
Did you buy it?
I'd been watching that one, too! Neat old amp, and there's a chance that it might sound amazing.
A couple things that have been said already are what kept me from snapping it up (well, aside from the $1K that I don't have quite handy at the moment, but there are ways around that... ):
Output transformer bandwidth - this is the big question mark, I think. Freed made some fantastic transformers and I'm sure they're of incredible quality for their spec, but they've got an awful lot of secondary taps and most of their size can probably be attributed to what it took to wind the 250 and 500 ohm taps. They're spec'd 50 ~ 10KC but they might drop off pretty steeply after that 10K mark. Hopefully not.
The modifications that had been made to it - I wish they were a little neater. Actually, I wish it were still original, but wish in one hand, as they say... *sigh*
Holy crap. What's the Freed part number on those output transformers? Would they happen to be 12406??
If so, I just tweaked one of my own design amps (with lots of help from Dave Gillespie, who provided invaluable guidance) with that OPT. It's possible to get response that's flat, plus or minus 1dB, up to 40KHz on the top end... it takes some pretty "aggressive" phase advance caps on the feedback resistor, a HF step network on the driver tube, and a Zobel on the output- but we got it to where it made pretty decent square waves open-load, and didn't oscillate to up to a .033uf cap across the open output. Not too shabby!
Regards,
Gordon.
If so, I just tweaked one of my own design amps (with lots of help from Dave Gillespie, who provided invaluable guidance) with that OPT. It's possible to get response that's flat, plus or minus 1dB, up to 40KHz on the top end... it takes some pretty "aggressive" phase advance caps on the feedback resistor, a HF step network on the driver tube, and a Zobel on the output- but we got it to where it made pretty decent square waves open-load, and didn't oscillate to up to a .033uf cap across the open output. Not too shabby!
Regards,
Gordon.
