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View Full Version : A call to JimmyJ and other light bulb amp lovers...



IDSkoT
02-11-2009, 12:58 AM
I recently bought a vintage record player. It has a tube amp running a single 4" speaker at .5 ohms. My mouth dropped when u measured it. Do tube amps normally nominal that low? Second, the tubes themselves have a black burnt part on the top of each one. Should they be replaced? (if possible.) after a few minutes of play, the tubes are too hot to touch. this unit was made in 49. It boasts 45 watts. But idk If that's including the turntable motor. But something tells me this is a replacement amp because of it's situation inside the box and there's a black sort of burn mark where the amp was. Pix can be posted if you want.

One tube says 35w4 then what looks like 5-04, and under that it says 188-20

The other says 50c5. And also 5448

I would look it up myself but the only Internet I have is my iPhone, and looking for information on it takes a huge chunk of patience.

Also, should I replace this speaker with one with more resistance? This amp gets really hot. Or is that normal for light bulb amps?

PaulThompson229
02-11-2009, 01:01 AM
Some heat is normal, I doubt I would be able to help but I would like pics, tubes are ****.

Side Show
02-11-2009, 01:07 AM
yeah, tubes rock...... if they have black burn marks on them i'd look into replacing them.

Cravingbass123
02-11-2009, 01:12 AM
i have a 300 watt all-tube bass guitar amp head that does 300 at 2, 4 or 8 ohms

it has 2 ecc83 preamp tubes, 2 ecc99 tubes, and 6 kt88 power tubes,

i love it,,,,,, too bad i don't play that much bass anymore. (no more band)




LOL at light bulb amps LOLOLOL

heat is natural with tubes btw, just not to the point where you can put a drop of water on one tube and watch it boil away instantly

IDSkoT
02-11-2009, 02:52 AM
i have a 300 watt all-tube bass guitar amp head that does 300 at 2, 4 or 8 ohms

it has 2 ecc83 preamp tubes, 2 ecc99 tubes, and 6 kt88 power tubes,

i love it,,,,,, too bad i don't play that much bass anymore. (no more band)




LOL at light bulb amps LOLOLOL

heat is natural with tubes btw, just not to the point where you can put a drop of water on one tube and watch it boil away instantly

I don't see the relevance... But I'll post pics tomorrow. I looked up the tubes and they're 25&6 dollars.

Also, there's a sort of hum, which is normal, so I hear. But it's really loud, to the point where you can't play it at low volumes due to the loudness

Z-Ro
02-11-2009, 02:54 AM
I recently bought a vintage record player. It has a tube amp running a single 4" speaker at .5 ohms. My mouth dropped when u measured it. Do tube amps normally nominal that low? Second, the tubes themselves have a black burnt part on the top of each one. Should they be replaced? (if possible.) after a few minutes of play, the tubes are too hot to touch. this unit was made in 49. It boasts 45 watts. But idk If that's including the turntable motor. But something tells me this is a replacement amp because of it's situation inside the box and there's a black sort of burn mark where the amp was. Pix can be posted if you want.

One tube says 35w4 then what looks like 5-04, and under that it says 188-20

The other says 50c5. And also 5448

I would look it up myself but the only Internet I have is my iPhone, and looking for information on it takes a huge chunk of patience.

Also, should I replace this speaker with one with more resistance? This amp gets really hot. Or is that normal for light bulb amps?

you have a iphone but no internet? what???????

IDSkoT
02-11-2009, 10:03 AM
you have a iphone but no internet? what???????


My modem died.

IDSkoT
02-11-2009, 11:53 AM
PIKCHUH TYME!

I kind of want to make my ava the tube amp... but that's JimJ's thing.

http://img.photobucket.com/albums/v714/TwistedShot/IMG_0226.jpg

http://img.photobucket.com/albums/v714/TwistedShot/Picture010-1.jpg

The burnage:
http://img.photobucket.com/albums/v714/TwistedShot/Picture014.jpg

The layout:
http://img.photobucket.com/albums/v714/TwistedShot/Picture016.jpg

Look at this magnet... modern speakers ain't got ish on that.
http://img.photobucket.com/albums/v714/TwistedShot/Picture015.jpg

The actual unit:
http://img.photobucket.com/albums/v714/TwistedShot/Picture011.jpg

It looks like someone put two switches... but I can't figure out what kind of switches... or for what, and why they took them out but left the screws.


And one of my favorite parts... the plug.
Can someone tell me if that's how they did it for every electronic back in the 40's?
http://img.photobucket.com/albums/v714/TwistedShot/Picture012.jpg

If you can't see well, it's the two wires, like normal... the ends are stripped then wrapped around screws and the screws are screwed down and connected to the plugs.
It's amazing.


These were taken with my phone... I can't find the plug for my camera and I don't feel like looking for it.


I'm thinking... should I rebuild the whole thing? I was thinking of making it deeper, and wider and what not and putting better ventilation, and maybe even a fan or two. Then, maybe replace the amp with something else. I definitely want to replace that speaker. Running that amp at .5 ohms is RIDICULOUS. But, my brother thinks I should keep it how it is.

JimJ
02-11-2009, 12:45 PM
Had to go back and do some research on this, I wasn't familiar with those tubes :)

First of all, if you're talking about the "flash" on the top of the tube, that's not burning, it's called the "getter" - it's made out of barium, and is inserted in the tube before it's sealed, it removes impurities left over from the vacuum process. Getters can be all different shades of silver, gray, or almost black - as long as it's not white, you're fine. White means the tube has developed a leak and is useless.

What you have sounds basically like a typical '40s-'50s console amp. It's a single-ended amp, which means you only have one output tube that's in Class A, all the time. The 35W4 is a rectifier, the 50C5 is the output tube, and the 5448 is a driver. Per the specs, power under typical conditions would be 2.3W @ 10% THD, with a plate voltage of 120V.

http://frank.pocnet.net/sheets/127/5/50C5.pdf

The low impedance isn't surprising, probably a cost tradeoff they made allowing for cheaper output transformers. Since it was a dedicated amp and speaker for the record player, making it a more standard impedance wasn't a concern. You see a lot of console stuff like that.

The hum you're hearing is probably a combination of the fact it uses AC heaters, and after 60 years the electrolytic caps in it need to be replaced. Sure, you can rebuild it, good caps like Sprague Orange Drops would probably tame some of its quirks, but I'm not sure I'd put a lot of money into something like this. If you're going to rebuild an amp, why not do something stereo and separate from any other components :)


I kind of want to make my ava the tube amp...

Go for it :)

IDSkoT
02-11-2009, 02:52 PM
Had to go back and do some research on this, I wasn't familiar with those tubes :)

First of all, if you're talking about the "flash" on the top of the tube, that's not burning, it's called the "getter" - it's made out of barium, and is inserted in the tube before it's sealed, it removes impurities left over from the vacuum process. Getters can be all different shades of silver, gray, or almost black - as long as it's not white, you're fine. White means the tube has developed a leak and is useless.

What you have sounds basically like a typical '40s-'50s console amp. It's a single-ended amp, which means you only have one output tube that's in Class A, all the time. The 35W4 is a rectifier, the 50C5 is the output tube, and the 5448 is a driver. Per the specs, power under typical conditions would be 2.3W @ 10% THD, with a plate voltage of 120V.

http://frank.pocnet.net/sheets/127/5/50C5.pdf

The low impedance isn't surprising, probably a cost tradeoff they made allowing for cheaper output transformers. Since it was a dedicated amp and speaker for the record player, making it a more standard impedance wasn't a concern. You see a lot of console stuff like that.

The hum you're hearing is probably a combination of the fact it uses AC heaters, and after 60 years the electrolytic caps in it need to be replaced. Sure, you can rebuild it, good caps like Sprague Orange Drops would probably tame some of its quirks, but I'm not sure I'd put a lot of money into something like this. If you're going to rebuild an amp, why not do something stereo and separate from any other components :)



Go for it :)

Thanks. Do you think I could replace it with a 4 or 2-ohm load with out much loss in output? Or should I just keep the speaker in there now? It doesn't sound too bad, to be honest. It could use some definite improvements, though. The only thing I'm really worried about is the amp getting too hot and burning out.

And as for the re-building of the amp, what I want to do is get a new arm, or turn this arm so it has the same connectors as guitars do, then have the amp dual as a phono and guitar amplifier.
I looked on the arm earlier, and it seems to just have 2 cables, much like the guitar does. I'm not sure if it has the same range, though. I doubt it.

Also, since I believe you would know, for record players, does one needle fit all? Or are they different as per the head?

JimJ
02-11-2009, 03:44 PM
It should be fine, although I don't think you'd have a lot in usable output.

I'm not very familiar with guitar amps, but I imagine it's a much higher line-level signal with a different input impedance than a phono signal with only 5mV or so. Also, most guitar amps are biased very differently along the tube's curve...you want more distortion out of it than any hi-fi amp, that's the attraction.

Edit - this is a 78 player, yes? You'll need a specific 78rpm cartridge, it's made for wider grooves than the standard MC or MM cartridge that's been around since the '50s. And knowing that I definitely wouldn't put too much into it, there are some people that get nuts into 78s, but if this is your first venture into vinyl, a 33/45rpm player and an RIAA-standard preamp is a much better solution.

IDSkoT
02-11-2009, 06:12 PM
It should be fine, although I don't think you'd have a lot in usable output.

I'm not very familiar with guitar amps, but I imagine it's a much higher line-level signal with a different input impedance than a phono signal with only 5mV or so. Also, most guitar amps are biased very differently along the tube's curve...you want more distortion out of it than any hi-fi amp, that's the attraction.

Edit - this is a 78 player, yes? You'll need a specific 78rpm cartridge, it's made for wider grooves than the standard MC or MM cartridge that's been around since the '50s. And knowing that I definitely wouldn't put too much into it, there are some people that get nuts into 78s, but if this is your first venture into vinyl, a 33/45rpm player and an RIAA-standard preamp is a much better solution.


It's 3 speed... which surprised me for the year. I thought they started making 33-1/3 RPMs in the 60's...? I guess not.

IDSkoT
02-13-2009, 12:50 AM
So I was listening to my vinyl player... and the hum stopped. Completely. I don't want to turn it off because it might start again. :x

Any idea what could've happened? It's only been playing for around an hour. I played it nearly all of today, though.

ngsm13
02-13-2009, 01:03 AM
lolebay...

nG

IDSkoT
02-13-2009, 01:08 AM
lolebay...

nG

For reaal. Haha. It works, though. So, I can't complain. Especially for $6 bucks. :\

FarrisAudio
02-13-2009, 01:19 AM
you should just keep it how it is man. i think tube amps rule.

heres mine(being on the subject of them), my dad built it for me. its a jtm 45 clone
http://i658.photobucket.com/albums/uu309/farrisaudio/amp2.jpg

http://i658.photobucket.com/albums/uu309/farrisaudio/amp1.jpg

IDSkoT
02-13-2009, 01:20 AM
you should just keep it how it is man. i think tube amps rule.

heres mine(being on the subject of them), my dad built it for me. its a jtm 45 clone
http://i658.photobucket.com/albums/uu309/farrisaudio/amp2.jpg

http://i658.photobucket.com/albums/uu309/farrisaudio/amp1.jpg

Yeah, I was thinking about cloning my friend's head, since he paid like $3K on it. I figure I could reproduce it for half the price, if that.

But, I'd rebuild the ampe and what nots. I wouldn't throw it away.

FarrisAudio
02-13-2009, 01:24 AM
Yeah, I was thinking about cloning my friend's head, since he paid like $3K on it. I figure I could reproduce it for half the price, if that.

But, I'd rebuild the ampe and what nots. I wouldn't throw it away.


what kind does your friend have?

IDSkoT
02-13-2009, 12:33 PM
what kind does your friend have?

It's a Marshall. I'm not sure of the model # or anything.