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?
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?
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.
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.
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...
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...
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.
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.
Pictures so far
Front:
Front
Front
Back
Back
Front with speaker installed and openings for radio covered up for now
Speaker installed
Admiral Radio
Front:
Front
Front
Back
Back
Front with speaker installed and openings for radio covered up for now
Speaker installed
Admiral Radio
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.
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.
I would expect that speaker to have high enough Q to do what you want. I believe the problem to be cancellation from the rear wave. You need to make the path from the rear of the speaker to the front as long as possible. This may involve closing off part of the rear of the enclosure, not to tune it as in a reflex enclosure, but to lengthen the path. In construction of the amplifier you can limit how much negative feedback you use in a deliberate attempt at not over damping the speaker. If it has a low Fs, say 40 cps or less, this could sound really nice. Bear in mind that open baffle speakers are not generally noted for really powerful bass, but they certainly can have very natural and satisfying bass reproduction.
By the way - very nice construction. What a beautiful project. I'd be very proud to have that in my home.
Best, Wade
By the way - very nice construction. What a beautiful project. I'd be very proud to have that in my home.
Best, Wade
Thanks! I am still trying to decide weather or not I should try my hand at an arched top, or just make it flat so that it looks like an old (BIG!!) radio console. If I do an arched top, I will make archways out of plywood and then laminate oak veneer up to the thickness that I need.
I believe the woofer does have as yuo say a 40-50hz FS. I tried measuring it a while back but I gave up. When you tap the cone its natural frequency is in the 40hz region, so it should have some good bass.
As far as closing the back up goes.. How do I provide ventilation to the tubes? Will just plain 'ol perforated holes work, like the back of old radios? I'm planning on having a hinged oak back door to the cabinet.
I believe the woofer does have as yuo say a 40-50hz FS. I tried measuring it a while back but I gave up. When you tap the cone its natural frequency is in the 40hz region, so it should have some good bass.
As far as closing the back up goes.. How do I provide ventilation to the tubes? Will just plain 'ol perforated holes work, like the back of old radios? I'm planning on having a hinged oak back door to the cabinet.
I'm sure that whatever you decide for the top will look great.
You can use your computer to measure Fs of your speaker. Go to http://www.electronics-lab.com/downloads/pc/006/index.html and download SweepGen. Install it. Connect one of the sound card speaker outputs to the speaker through a 330 ohm resistor. Connect an AC voltmeter across the 330 ohm resistor and set it to the appropriate scale, probably 2 volts. Operate the Sweep Generator whilst watching the voltmeter. When the voltmeter shows the highest reading, read the frequency on the readout of the generator program. This will be Fs. This measurement must be done with the speaker in free air, no box, and with the speaker in its normal vertical position. You can also measure the other T/S parameters of your speaker with the same setup but you will need a closed box with a volume of .1 to .5 of what you would guess appropriate Vas for the speaker to be.
As for closing the back of your juke, I'd say don't close it all the way. Doing so would raise the Q, probably too high, but more importantly will also raise the resonant frequency of the system. The goal is to keep that below 50 cps. The idea is to close part of the back so the rear wave from the driver has to travel a long distance before reaching the front. Close off 2/3 to 3/4 of the back and leave the area open where your amplifier(s) will sit. Here is a chart that shows how large an open baffle has to be to achieve desired frequencies.
You can use your computer to measure Fs of your speaker. Go to http://www.electronics-lab.com/downloads/pc/006/index.html and download SweepGen. Install it. Connect one of the sound card speaker outputs to the speaker through a 330 ohm resistor. Connect an AC voltmeter across the 330 ohm resistor and set it to the appropriate scale, probably 2 volts. Operate the Sweep Generator whilst watching the voltmeter. When the voltmeter shows the highest reading, read the frequency on the readout of the generator program. This will be Fs. This measurement must be done with the speaker in free air, no box, and with the speaker in its normal vertical position. You can also measure the other T/S parameters of your speaker with the same setup but you will need a closed box with a volume of .1 to .5 of what you would guess appropriate Vas for the speaker to be.
As for closing the back of your juke, I'd say don't close it all the way. Doing so would raise the Q, probably too high, but more importantly will also raise the resonant frequency of the system. The goal is to keep that below 50 cps. The idea is to close part of the back so the rear wave from the driver has to travel a long distance before reaching the front. Close off 2/3 to 3/4 of the back and leave the area open where your amplifier(s) will sit. Here is a chart that shows how large an open baffle has to be to achieve desired frequencies.
Attachments
Ok so here are some more pics so far...
Front view Stained
Closeup of 6 peice sides
The two side peices that make up the corners are made of 6 peices of oak each
. I used 1/4 round on each side of the side post, with a 3.5" x 3/4" peice of oak up the middle. On either side of that strip is oak edge moulding. I stained the cabinet cherry, the speaker baffle golden oak , as well as the side peice's middle part. I am leaving the edge moulding bare so they will be the lightest when I polyurethane the cabinet.
TW, I measured the speaker a while back but when it came time to calculating the vas I had problems. Because I didn't have a sealed box at the time, I used the added mass method ... which didn't work out so well. I will probably have to try your method sometime though.
I did however manage to get the FS, which like I said was pretty low. I can't remember exactly but it was something like 45-46 hz. I'll try your method.
Front view Stained
Closeup of 6 peice sides
The two side peices that make up the corners are made of 6 peices of oak each
. I used 1/4 round on each side of the side post, with a 3.5" x 3/4" peice of oak up the middle. On either side of that strip is oak edge moulding. I stained the cabinet cherry, the speaker baffle golden oak , as well as the side peice's middle part. I am leaving the edge moulding bare so they will be the lightest when I polyurethane the cabinet. TW, I measured the speaker a while back but when it came time to calculating the vas I had problems. Because I didn't have a sealed box at the time, I used the added mass method ... which didn't work out so well. I will probably have to try your method sometime though.
I did however manage to get the FS, which like I said was pretty low. I can't remember exactly but it was something like 45-46 hz. I'll try your method.
thanks marsfrogie
TW, were you referring to a soundcard that has speaker outputs, as in an amplified soundcard? ( 1-3 watts or so onboard as a lot of older comp's had)
Because I don't have one of those, I have a creative x-fi so I could have to run it to a seperate amp to generate any kind of voltage.
TW, were you referring to a soundcard that has speaker outputs, as in an amplified soundcard? ( 1-3 watts or so onboard as a lot of older comp's had)
Because I don't have one of those, I have a creative x-fi so I could have to run it to a seperate amp to generate any kind of voltage.
Yes. I use old desktop computers with powered sound cards. You can do exactly the same thing with an outboard amplifier. Maybe better, actually, because a larger power amplifier would be able to generate more swing than the little IC on a sound card can generate. It would be nice to have 10 or 15 volts of swing available.
Bleh, but what about all the EQ'ing betwen the signal and the speaker getting in the way? I have an old 70's receiver... not exactly what I would call having a 'flat' responce. I think flattening out my sound card is no problem because its designed for recording, I just don't have a decent straightforward power amp. My little SE magnavox tube amp is pretty flat from about 45 hz up within its power band, but again its a tube amp so the transformers will affect damping.
Ok so today I made a proper baffle out of 1/2" plywood with a 14" diameter cutout. I put the floor in the cabinet and then the middle shelf for the radio section. This creates a smaller chamber for the speaker. I tried putting some back peices near the unit, and putting it aginst a wall. My bass still is not great
I did notice that if you turn the unit around and put it in the middle of the room, the bass coming out of the back is great, but its almost nonexistant at the front of the cabinet. What is going on here? Its like somehow the waves coming out of the front are either being canceled out or are being somehow re-directed towards the rear.
I did notice that if you turn the unit around and put it in the middle of the room, the bass coming out of the back is great, but its almost nonexistant at the front of the cabinet. What is going on here? Its like somehow the waves coming out of the front are either being canceled out or are being somehow re-directed towards the rear.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.