Tube question

[TommyJ]

I have a old supro amp,The tubes are,
50L6 and a 12ax7.is the 50L6 the same as a 6v6?
Thank you..

[Kap'n]

Is the 50L6 the same as a 6v6?

No it's not.

50L6 tubes are pretty inexpensive. A good place to buy them is Antique Electronic Supply.

Your amp probably has series-string tubes, and does not have a power transformer. This is potentially deadly, if you don't know what you're doing. Have your tech look at it, and he might be able to suggest an isolation transformer.

[ziess]

Assuming the 50L6 follows standard tube nomenclature, does it use a 50V heater? Jeez.
Were they specifically developed for use in applications where there is no power transformer?

Tommy.

[Kap'n]

Assuming the 50L6 follows standard tube nomenclature, does it use a 50V heater? Jeez.
Were they specifically developed for use in applications where there is no power transformer?

Tommy.

Yes and yes.

They derive from power-transformerless 5-tube radios, which were extremely common. These radios were popular because, not only did you not have to pay for a transformer, they worked on both AC and DC line current. Way back when, Manhattan, and other places wired by Edison ran on DC. Plug a regular amp into 120VDC, and you get nothing - a transformer requires AC current to operate.

If you look at a 5 tube radio, all of the cases are made of plastic. This was to keep people from touching the chassis, which could be 120V over ground, delivering a nasty shock.

There's a whole number of tubes for radios like this.

The rectifier was usually 35V
The power tube was usually 50V
The remaining tubes were 12V (3x12 = 36V)

35 + 50 +36 = 111V, or close enough to line voltage.

Tube amps usually ran three tubes (rectifier, preamp tube power tube) and use a resistor to eat up the rest of the voltage.

Unfortunately, this concept doesn't work on a guitar amp, because the strings are grounded to reduce noise. Play one of these amps, and you have a 50% chance of getting a potentially lethal shock if you touch something else.

[Plugger]

So how did cryo treated versions sound?

-Mark

[stratcat55]

So how did cryo treated versions sound?

-Mark

Cold

[TommyJ]

Thanks Kap'n,you are correct it is a direct powered amp.
how hard would a conversion be and would it cost alot?

[Kap'n]

You really can't convert the amp itself without cutting metal.

I've never really considered how one handles grounding, etc. with one of these amps. You would definately need an isolation transformer.

I'd have to defer to somebody with actual experience with one of these.

[cdw2000]

I went looking for a schematic for a direct powered unit to see if I could help, but I came up empty.

[TommyJ]

Thanks guy's for the input,I really do appreciate it..
I think I'll just leave it alone and just play it in my bedroom,
and keep it unplugged while not in use..
Oh,Thanks for the tip on finding the old tube Kap'n.