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Old 21st April 2008, 05:47 PM   #1
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Default DIY Jukebox!!

Alright so heres a cool project for you guys to think about!

Fathers day is coming up and I am planning on building my dad a juke box- and what is a juke box without TUBES!?

I have a lot of 3/4" Oak plywood left over in the garage, as well as a 15" magnavox woofer , a sansui s-2002 midrange, and various tweeters.

I just won an auction on ebay for an old Admiral tube tuner from a console that looks really retro. It looks to be in pretty nice shape and has a built in SE 6v6 amp that I can use for the midrange/HF drivers.


The cabinet will be wurlitzer style without the bubblers, so it will look more like a 1930's version, more like an old console radio from the era only with an arched top. The top section will have plexiglass and will be lit inside so that he can display his model cars in it, as there will be no need for a record player.

I am going to use a trick that a computer friend of mine taught me for the CD player.
Take an old cd rom ( the ones with the play/pause/stop controls on the front) and build a simple +5v and +12v supply using LM7805 and LM7812 respectivley. Then all that is needed is to run the audio output cable ( not the IDE ) that normally runs to your motherboard's on board sound or your external sound card to RCA terminals.
Wire that into the phono input ( provided proper modification is done to remove the RIAA network if there is any, as it may be an AUX input anyway.)



So far I only have a few questions for you guys, and will be posting pictures of the process.

My first question:
How should I combine Left/right channels from the CD out into mono? I know this should be a simple question. Should I just use two 100 ohm resistors?

Second question:

This one might get a little complicated. Since I already have a 6v6 to use I might as well use it for something. If I use it for the high frequency drivers, how do I create a simple high pass filter for it?
I want to send frequencies below ~800hz to the woofer. Maybe adjustable so that I can tweak it to different drivers? Nothing hi-fi, I just need tubey sounding vintage jukebox sound

Third question:

I've got a strong matched pair of 7868's, novar sockets, a hammond 1650f 7.6k OT, and a 272FX 275v-0-275v @ 150ma PT.

I need a simple PI to drive the 7868's. I am planning on using cathode bias and UL mode, since it just makes the power supply easier and less parts count, and has the added benefit of better sound. Ill be using SS rectfication as well.
I only need about 20-30 watts since that is about the max the woofer can take, and about the limits of my OT.


So... Should I use a cathodyne or paraphase? If the 7868/7591's are as easy to drive as 6v6's and EL84's then it should work fine with either correct?

Like I said, I don't need anything ultra Hi-Fi, just not really bad sounding. I think it should be pretty easy to accomplish this goal.
Also, as one last note, should I use NFB or not? I know that I probably should, but don't know how I should calculate how much I need.

So here it is guys! Answers? Ideas? Sugguestions?


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Old 21st April 2008, 05:59 PM   #2
peufeu is offline peufeu  France
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Put a computer and a harddisk in the damn thing
You can get Celeron micro-ATX mobo's for fifty bucks, install Linux, Amarok, and a harddisk, this will make a hell of a jukebox !

Anyway if you want Mono, no problem, just sum the outputs, I wouldn't use 100R resistors, that will be a bit too low for the poor opamp in the CD drive. Instead, look at the input impedance of your amplifier, and use a value quite lwoer than that. For instance if your amplifier has a 20 Kohm input impedance, you can safely use 1K to sum the outputs.

For your highpass (active crossover ! wow) you can use a simple opamp circuit like a linkwitz-riley second order crossover. You'll find schematics all over the net. You'll need one or two opamps per channel, you can easily breadboard that. If you want simpler, you can use a passive RC crossover but you'll have to account for the various impedances in the circuit.
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Old 21st April 2008, 06:55 PM   #3
Variac is offline Variac  United States
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Yes, the computer idea is a good one, and will give you a true jukebox.
Since your cabinet is so big, you could probably just use an older computer that you have laying around. Probably replace the Hard Drive with a 500 gig for $100. (I'm not sure all older operating systems can handle this capacity) Then find a small LCD screen or CRT monitor and a track ball mouse. Run iTunes and you are done. I do this with an old iMac with CRT and it is great for background music.I just use the audio out from the computer hooked to a small amp. Haven't tried a huge drive on it since it is background music I use evil MP3's instead of something decent like Apple Lossless files..

I'm sure that others can suggest more sophisticated solutions.

I suppose that you could have a cover plate over the screen when not in use if you didn't like the look...but Ithink that it could probably be cleverly integrated...
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Old 21st April 2008, 08:09 PM   #4
peufeu is offline peufeu  France
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Linux/Amarok !!!!!!!!!

You aren't going to pay a Windoze license for this thing, are you ?
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Old 21st April 2008, 08:50 PM   #5
Variac is offline Variac  United States
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He already has windows or Mac OS on the imaginary computer I claim that he has!!!
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Old 23rd April 2008, 02:09 AM   #6
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Sorry guys, not so hot on the computer idea. I would, but it won't look like an old jukebox anymore. As soon as I get the pics up I will post them.

The goal here is KISS- keep it stupid simple. My dad doesn't have many CD's, and what he does have can be stored in the top in a cd rack along side his models. The goal here is to make something thats easy for him to use. Not that he doesn't know how to operate a computer at all, but there are so many problems associated with it. I just want him to be able to go out to it during the day when hes working on his mustang and turn it on, let the tubes warm up, and play some tunes from the radio ( which he uses the most) or a CD occasionally.

Right now, I have some sound problems nagging at me!
I've got the 15" installed in the cabinet. The cabinet diminsions are : 41" high ( at least until I put in the shelf for the radio, then the actual speaker space will be less) 17" deep, and 27" wide. The front peices are solid oak, the frame is 2x4 pine, and the side panels are 3/4" oak plywood. I don't get too much flex out of it, I still plan on bracing it though. The woofer definatly has excursion enough and can move some air, however it is not working as well as I would think. In the back of the cabinet the woofer goes down very low ( 30hz or so) but when standing in front of it, not much is going on other than the woofer flapping in the wind. Mind you, the cabinet is not sealed, but I do have a complete baffle for the front of it, and had the bottom inside covered as well. The back is open, and when placed against a wall the sound is bad, but when placed in the open doorway of the garage I get more bass than before.


The woofer originated from an Astrosonic console, which I don't believe was sealed, most had vent holes in the back and screens on the bottom. Since this speaker was designed to work best in a console like invironment I would think it should work for me in my jukebox... Any sugguestions on what I might be doing wrong here? I'm using a 20 watt RMS solid state amp right now to test it, since this will be close to the wattage my tube power amp is going to be.
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Old 23rd April 2008, 02:16 AM   #7
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Pictures so far

Front:
Front
Front
Back
Back
Front with speaker installed and openings for radio covered up for now
Speaker installed
Admiral Radio
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Old 23rd April 2008, 02:48 AM   #8
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Looks great... but wouldn't it be easier to salvage an old PC power supply to run the CD instead of making a circuit from scratch? That seems easier to me...
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Old 23rd April 2008, 03:03 AM   #9
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Thanks! just wait until its stained...

It wouldn't be easier,as an atx takes up too much space for what you need and also adds a noisy fan.

The power supply you need is just 12.6v CT transformer. You bridge rectify both the 12.6 winding and the 6.3 winding, then you use an LM7805 for the 5v lead, an LM7812 for the 12v lead, and a common ground. Then run a molex into the cd rom

Total circuit parts count is 4 parts if you are using bridges, and it takes up very little space.
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Old 23rd April 2008, 05:58 PM   #10
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Any takers on my LF problem...?
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