Turning an old tube record player into a guitar amp.

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helstab
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Turning an old tube record player into a guitar amp.

Post by helstab » Wed Nov 02, 2005 4:41 pm

So I got this old zenith tube record player from 1961. A friend suggested that I try to turn it into a guitar amp becuase it looked like a similar circuit to an old vox amp.

I replaced the cartridge with a 1/4" jack, plugged in my guitar and it sounds pretty great. I'm still trying to fix some previous problems with volume not getting up so much anymore.. New tubes are on the way and hopfully that will fix it. I'm getting ready to wire in a 3 prong power chord and a new on/off toggle, and then all I will have to do is buid a house for it.

It's a 15 watt amp and I was thinking about setting it up with 1 10" speaker. Right now the old player has a very early kind of stereo and has 2 10" speaks each with a 6" for high-mids whatever that really suck. I wan't to build a case for this thing, but I'm not sure about the speaker arrangement and kind of wood. I know it's all up to personal taste, but I was just wondering what other people thought out it.

-matt
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NewYorkDave
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Post by NewYorkDave » Wed Nov 02, 2005 5:58 pm

Before you go any further, make sure it has a power transformer. Many consumer electronics of the tube era (radios, phonographs, etc.) did not use a power transformer, so one side of the chassis is connected to the AC line. This is VERY unsafe.

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helstab
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Post by helstab » Wed Nov 02, 2005 7:06 pm

it does.
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helstab
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Post by helstab » Wed Nov 02, 2005 7:21 pm

I forgot the main thing that I wanted to ask.. Like I was saying, I'm going to build a house for this little bitch.. most likely 1 10" or something.. where can I find some recommended cabinet demensions for different size speakers? I think I remember most of the speaker sites giving giving specs for the speakers.. and I'm going to google it in 5 seconds and I'm sure I'll find out.
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Post by mlaargh » Wed Nov 02, 2005 7:54 pm

ooohhh... Check this out.

This program is pretty useful for understanding speaker enclosure airspaces/response.

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Post by winky dinglehoffer » Wed Nov 02, 2005 9:55 pm

I happened to be reading about this in a loudspeaker design book the other day. The author basically said cabinet dimensions are not that crucial for guitar amps. He did note that for closed back designs allowing about a cubic foot for each speaker was a good rule of thumb. Measuring other guitar amps/cabs is a good way to go too.


Tom

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Post by Flight Feathers » Wed Nov 09, 2005 10:09 pm

helstab wrote:I forgot the main thing that I wanted to ask.. Like I was saying, I'm going to build a house for this little bitch.. most likely 1 10" or something.. where can I find some recommended cabinet demensions for different size speakers? I think I remember most of the speaker sites giving giving specs for the speakers.. and I'm going to google it in 5 seconds and I'm sure I'll find out.
hey matt

i've been doing similar things with old tube amps. are you trying to build the head into a combo? i've just been leaving the amp chasis sitting on top of the speaker cabinents, makes it easy to mix and match heads to cabs. a basic rule of thumb i made up based on nothing at all is, the speaker baffle should be 2 inches wide at it's narrowest point, so a 10" speaker should be mounted in a 14 inch square. otherwise the wood feels too flimsy.

another neat trick is to put a a panel on a hinge on the back of the speaker cabinet to go between open and closed back. here are some picture of one of my cabs (12" jensen speaker").


Image

Image

Image




btw, http://www.mojotone.com/ is a good place to find premade amp stuff
5D Studios <-- my OLD studio
Flight Feathers <-- my band

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I'm Painting Again
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Post by I'm Painting Again » Fri Nov 11, 2005 8:22 am

hey that really f*(&#in cool ayan!!

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helstab
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Post by helstab » Mon Nov 14, 2005 5:39 am

hey there you go! Looks great. Mine should look something like that.
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Post by Antero » Thu Nov 17, 2005 8:06 pm

Dude, that looks awesome. How hard was it to mod?
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Post by Randy » Thu Nov 17, 2005 9:11 pm

NewYorkDave wrote:Before you go any further, make sure it has a power transformer. Many consumer electronics of the tube era (radios, phonographs, etc.) did not use a power transformer, so one side of the chassis is connected to the AC line. This is VERY unsafe.
Yeah, a friend of mine bought a Supro amp and plugged it into the wall and got shocked from the guitar. He thought it had a power transformer because it had some transformer-looking thing in it. It wasn't. He was lucky- no permanent damage. I double Dave's concern. Make sure it's not an output transformer.
not to worry, just keep tracking....

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Post by Scodiddly » Fri Nov 18, 2005 5:16 pm

I've got a couple old turntables I've been meaning to convert. One thing to look out for is how the bass knob is wired - in both of mine the bass knob only affects the phono signal, not the mic input.

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