MikeS
01-14-2006, 03:55 PM
I bought a little RCA record player console a couple years back or so.
50C5 power tubes, with a 12AX7 driver.
It was just a console with a record player(no radio) and rather cheap at that. I kinda paid too much for it......
When I tore into the console, I found out the amp has no power transformer.
Kinda like the "The all american five" tube radio tabletop topology.
Where the five tube's heaters strung in series comes out to 115/117/120 volts or whatever.
Except this amp just has three tubes. Some 50C5 amps had a 35W4 half wave tube rectifier, but this one just has a diode.
Straight 120 volts into the amp with a half-wave rectifier. Only the input jacks are chassis grounded, with a capacitor for safety.
All grounds are more or less on the neutral side of line, 0 VAC.
Kind of a dangerous little fucker if that capacitor leaks and puts 120 VAC on the chassis.
It's one reason why I never really messed with it. But I swallowed my balls today and tried it.
I just made sure not to touch the chassis under any circumstances.
Checked over the resistors, and reformed the black multicapacitor.
Threw in a strong 12AX7 driver tube and the RCA 50C5's tested strong.
The little amp doesn't sound really that bad. In fact it sounds rather good for a 80 milliwatt to a 1 watt amp. It actually kinda boogies for the low power.
Suprised me......
It is a wee bit on the sharp sounding side, I assume that's a trait of the 50C5.
(Maybe I can soften it up with some oil coupling caps.....)
It does have quite a bit of hum, and for obvious reasons.
The hum isn't too bad on these junk midrange speakers, but it would probably be way too noisy and unacceptable on the Klipsch Cornwalls.
50 volt heaters on the 50C5's.
I burnt the shit out of my fingers grabbing one out of the tube tester without letting it cool down.
It is a rather small amp.....dunno what I'll do with it, maybe bi-amp and use it for the tweeters.
If I do, I better use my isolation transformer........
50C5 power tubes, with a 12AX7 driver.
It was just a console with a record player(no radio) and rather cheap at that. I kinda paid too much for it......
When I tore into the console, I found out the amp has no power transformer.
Kinda like the "The all american five" tube radio tabletop topology.
Where the five tube's heaters strung in series comes out to 115/117/120 volts or whatever.
Except this amp just has three tubes. Some 50C5 amps had a 35W4 half wave tube rectifier, but this one just has a diode.
Straight 120 volts into the amp with a half-wave rectifier. Only the input jacks are chassis grounded, with a capacitor for safety.
All grounds are more or less on the neutral side of line, 0 VAC.
Kind of a dangerous little fucker if that capacitor leaks and puts 120 VAC on the chassis.
It's one reason why I never really messed with it. But I swallowed my balls today and tried it.
I just made sure not to touch the chassis under any circumstances.
Checked over the resistors, and reformed the black multicapacitor.
Threw in a strong 12AX7 driver tube and the RCA 50C5's tested strong.
The little amp doesn't sound really that bad. In fact it sounds rather good for a 80 milliwatt to a 1 watt amp. It actually kinda boogies for the low power.
Suprised me......
It is a wee bit on the sharp sounding side, I assume that's a trait of the 50C5.
(Maybe I can soften it up with some oil coupling caps.....)
It does have quite a bit of hum, and for obvious reasons.
The hum isn't too bad on these junk midrange speakers, but it would probably be way too noisy and unacceptable on the Klipsch Cornwalls.
50 volt heaters on the 50C5's.
I burnt the shit out of my fingers grabbing one out of the tube tester without letting it cool down.
It is a rather small amp.....dunno what I'll do with it, maybe bi-amp and use it for the tweeters.
If I do, I better use my isolation transformer........