Don't forget padding (maybe with felt) / damping the speaker basket itself. A lot of sound gets reflected towards the cone off those legs.
I never built an amp... yet. Tho i use a pretty pricy tube amp to power the 12lta, prior to that i was using one of the cutest amps i've ever seen:
Dayton Audio DTA-100a Class-T Digital Amplifier 50 WPC
For $100 i see no reason to build one.
I also like the look of this little tube job. I see it selling for $450.
http://pic6.audiogon.com/i/s/f/1243987118.jpg
The 12lta rocks with very little power. It's more efficient than any driver i've used to date. I can hear my Cary amp hissing and spitting in the background until the music starts.
Dayton Audio DTA-100a Class-T Digital Amplifier 50 WPC
For $100 i see no reason to build one.
I also like the look of this little tube job. I see it selling for $450.
http://pic6.audiogon.com/i/s/f/1243987118.jpg
The 12lta rocks with very little power. It's more efficient than any driver i've used to date. I can hear my Cary amp hissing and spitting in the background until the music starts.
Hiraga 'Le Monstre' is calling me.
I had one of these once when I could afford electricity
jungson ja-88d
Specifications
Type: Integrated stereo amplifier
Output Power: 80 wpc at 8 Ohm
Frequency Response: 20Hz to 20 kHz (-0.2dB)
THD: 0.05% @ 1kHz, 1W
SNR: 98dB
Input Impedance: 100kOhms
Output Impedance: 8 Ohms
Size: 17 x 7.5 x 19 (WxHxD in inches)
Weight: 64 lbs.
Yeah baby 64lbs and it sucked up SOOOO much juice
I had one of these once when I could afford electricity
jungson ja-88d
Specifications
Type: Integrated stereo amplifier
Output Power: 80 wpc at 8 Ohm
Frequency Response: 20Hz to 20 kHz (-0.2dB)
THD: 0.05% @ 1kHz, 1W
SNR: 98dB
Input Impedance: 100kOhms
Output Impedance: 8 Ohms
Size: 17 x 7.5 x 19 (WxHxD in inches)
Weight: 64 lbs.
Yeah baby 64lbs and it sucked up SOOOO much juice
Attachments
Hi,
Sure, these are nice Amp's, but hard to build (you need to match transistors and all).
IF you want to take my advise (you are welcome not to), please thry this:
Use LM3875TF (Plastic Case).
Use Inverting mode, 10K/220...430K for 26dB to 32dB Gain, positive hard to ground. Use Xicon Carbon Composition resistors (Mouser has them) for a warm sound or good metal film for detail, mix the two for something in-between.
Use a 3.3K/3W resistor (or better an LM317 as CCS set to 10mA current) on the output to the negative rail, for a touch of extra Class A.
Use with a 2SK389/LSK389 DC coupled buffer stage (a'la Pass B2) in front, with a really high quality 2.2uF coupling capacitor. If your supply is around 30V or under you can use simple RC filtering from the main supply, something like 3.3K on each rail and a 1,000uF cap will do (I'd use Elna Silmic).
Use a 1M linear law cheap Alps or Alpha Carbon pot (forget any of the cheap stepped attenuators, sound horrible) as volume control if you need an integrated Amp. To get pseudo log response connect a 47K Metal fim presistor from wiper to ground (adjust value in your system so good listening levels are at 12 O'Clock. If you feel spendy, use a Noble Pot.
Use 100uF to 1,000uF local decoupling capacitors on the PSU rails, right next to the chip, I prefer Elna Silmic II 1,000uF/50V. Add something along the lines of Carlos M's snubbers near the Amplifier.
Make the Amplifier on it's own small chassis, materials matter for sound.
For the external power supply use PER CHANNEL a pair of 20V...25V AC torroids of the largest power rating you can find from surplus dealers (I'd probably call it a day with a pair of 230VA units per channel. Stack them on top of each other and experiment with wiring the primary connections such that you get the least leakage current into the system.
Use the largest size/value "computer grade" capacitors (big cans with screw terminals) you can find in 40V or 50V, no less than 33,000uF each please. You need 4pcs per channel. You also need 40A/100V Dual Schottky Diodes. Wire the Diodes as full wave rectifier. Feed one of the Capacitors.
Add a pair of 0.1 Ohm Resistors in + and - lines to the next capacitor, optionally use 0.1...0.33 Ohm DCR Chokes or common mode chokes instead of resistors. Take the feed to the Amp from the second capacitor. Add snubbers and bypass capacitors across each capacitor.
Keep both supplies completely separate all the way up the umbilical cable and to the Amplifier, join only at the Amplifier channels output star ground point.
No, it will not be the best Amp in the world. But the result will be a pretty good Amp and it will do around 25W - 40W, enough for many kinds of speakers.
If you need more power use LM3886 (one pair) in bridge, or more in parallel/bridge IF you must low impedance speakers, rest stays the same, just scale the power supplies up in size proportionatly...
For the bridge amp use the 2SK170 or LSK170 as simple phase-splitter (recent article in Tubecad), with additional 2SK170/LSK170 as buffers.
Ciao T
Sure, these are nice Amp's, but hard to build (you need to match transistors and all).
IF you want to take my advise (you are welcome not to), please thry this:
Use LM3875TF (Plastic Case).
Use Inverting mode, 10K/220...430K for 26dB to 32dB Gain, positive hard to ground. Use Xicon Carbon Composition resistors (Mouser has them) for a warm sound or good metal film for detail, mix the two for something in-between.
Use a 3.3K/3W resistor (or better an LM317 as CCS set to 10mA current) on the output to the negative rail, for a touch of extra Class A.
Use with a 2SK389/LSK389 DC coupled buffer stage (a'la Pass B2) in front, with a really high quality 2.2uF coupling capacitor. If your supply is around 30V or under you can use simple RC filtering from the main supply, something like 3.3K on each rail and a 1,000uF cap will do (I'd use Elna Silmic).
Use a 1M linear law cheap Alps or Alpha Carbon pot (forget any of the cheap stepped attenuators, sound horrible) as volume control if you need an integrated Amp. To get pseudo log response connect a 47K Metal fim presistor from wiper to ground (adjust value in your system so good listening levels are at 12 O'Clock. If you feel spendy, use a Noble Pot.
Use 100uF to 1,000uF local decoupling capacitors on the PSU rails, right next to the chip, I prefer Elna Silmic II 1,000uF/50V. Add something along the lines of Carlos M's snubbers near the Amplifier.
Make the Amplifier on it's own small chassis, materials matter for sound.
For the external power supply use PER CHANNEL a pair of 20V...25V AC torroids of the largest power rating you can find from surplus dealers (I'd probably call it a day with a pair of 230VA units per channel. Stack them on top of each other and experiment with wiring the primary connections such that you get the least leakage current into the system.
Use the largest size/value "computer grade" capacitors (big cans with screw terminals) you can find in 40V or 50V, no less than 33,000uF each please. You need 4pcs per channel. You also need 40A/100V Dual Schottky Diodes. Wire the Diodes as full wave rectifier. Feed one of the Capacitors.
Add a pair of 0.1 Ohm Resistors in + and - lines to the next capacitor, optionally use 0.1...0.33 Ohm DCR Chokes or common mode chokes instead of resistors. Take the feed to the Amp from the second capacitor. Add snubbers and bypass capacitors across each capacitor.
Keep both supplies completely separate all the way up the umbilical cable and to the Amplifier, join only at the Amplifier channels output star ground point.
No, it will not be the best Amp in the world. But the result will be a pretty good Amp and it will do around 25W - 40W, enough for many kinds of speakers.
If you need more power use LM3886 (one pair) in bridge, or more in parallel/bridge IF you must low impedance speakers, rest stays the same, just scale the power supplies up in size proportionatly...
For the bridge amp use the 2SK170 or LSK170 as simple phase-splitter (recent article in Tubecad), with additional 2SK170/LSK170 as buffers.
Ciao T
Waaaaaaa thats a hell of a lot of info......
Way past my current understanding I'm ashamed o say. I was just gonna get a set of boards from www.kk-pcb.com and be done with it. Maybe not now
mmm
Way past my current understanding I'm ashamed o say. I was just gonna get a set of boards from www.kk-pcb.com and be done with it. Maybe not now
mmm
Hi,
Sure, go for it.
What I have described is my own take on a "Gainclone" (this kind of amp has a whole forum here).
If you can get surplus parts it is cheap to make and because it has so very few parts and the actual chip at the heart is fairly hard to blow up it is popular.
BTW, I'm not great fan of PCB's, if they can be avoided...
You can have a look at my own "quick & very dirty" Gainclone (it does not really follow the recipe above, for a range of reasons) here:
http://www.diyaudio.com/forums/chip-amps/79303-chip-amp-photo-gallery-29.html#post2227576
Ciao T
Sure, go for it.
What I have described is my own take on a "Gainclone" (this kind of amp has a whole forum here).
If you can get surplus parts it is cheap to make and because it has so very few parts and the actual chip at the heart is fairly hard to blow up it is popular.
BTW, I'm not great fan of PCB's, if they can be avoided...
You can have a look at my own "quick & very dirty" Gainclone (it does not really follow the recipe above, for a range of reasons) here:
http://www.diyaudio.com/forums/chip-amps/79303-chip-amp-photo-gallery-29.html#post2227576
Ciao T
oops!
Isn't it always the simplest things that make the greatest difference?
I was lazy and had not swapped the head cabinets with the 12lta & tweeters over so that the tweeter was on the outside.
Now I have and OOF!! Imaging is back and really wide.
'zilla, have those pesky phase plugs arrived yet? getting worried they may have been sacrificed to the great machine that is the postal service
Isn't it always the simplest things that make the greatest difference?
I was lazy and had not swapped the head cabinets with the 12lta & tweeters over so that the tweeter was on the outside.
Now I have and OOF!! Imaging is back and really wide.
'zilla, have those pesky phase plugs arrived yet? getting worried they may have been sacrificed to the great machine that is the postal service
>>> zilla, have those pesky phase plugs arrived yet?
They have NOT! I am so disappointed. My Beta 12lta play with gaping mouths waiting to be fed. Perhaps the package can be tracked? If you email me the info i will do the legwork. I feel bad you sent them and i never got them. Maybe they will show up soon? Everyday i cross my fingers but they never arrive. I really appreciate your effort to send JRKO! I know you want me to have them.
Zilla
They have NOT! I am so disappointed. My Beta 12lta play with gaping mouths waiting to be fed. Perhaps the package can be tracked? If you email me the info i will do the legwork. I feel bad you sent them and i never got them. Maybe they will show up soon? Everyday i cross my fingers but they never arrive. I really appreciate your effort to send JRKO! I know you want me to have them.
Zilla
12LTA squished down in a Karlson 12 had 3dB less output than Beta 10cx on a Chinese drum track when driven with an AJ clone. Although similar small signal sensitivity to 80oz slug coax woofer, it seems to take a bigger magnet 12 to get the transients (Eminence with 80oz magnet or P-Audio) last tube amp I built was 40+kg
last amp I built was in 96 (not 1896!)
(watch levels on Al Jolson as I have the audio peaking at 0dB)
YouTube - 40kg single chassis diy 2A3 parallel SET Amplifier
last already made amp I picked up has anode caps - real nice
last amp I built was in 96 (not 1896!)
(watch levels on Al Jolson as I have the audio peaking at 0dB)
YouTube - 40kg single chassis diy 2A3 parallel SET Amplifier
last already made amp I picked up has anode caps - real nice
An externally hosted image should be here but it was not working when we last tested it.
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>>> zilla, have those pesky phase plugs arrived yet?
Thank you so much JRKO! The plugs arrived! They look terrific. I drilled two screws each into them so they stick to the magnet and WOW everything smoothed out so beautifully. Honestly, just removing the dustcap allows for critical listening with the 12lta but the plugs further smooth the sound out a touch and really help present music in a more relaxed fashion. I am so pleased! My system is finally complete and sorted out from a sonic standpoint. Now i just need to sand and stain... then onto the next project!
Today played ping pong with my older son while blasting Bee Gees and Frankie Valley and the Four Seasons. The 12lta plus tweeter plus H-frames goes LOUD without strain. This separates it from more typical (but no less excellent) full rangers. The 12lta is a great driver when tweaked and used properly. Highly recommended!
Zilla
Thank you so much JRKO! The plugs arrived! They look terrific. I drilled two screws each into them so they stick to the magnet and WOW everything smoothed out so beautifully. Honestly, just removing the dustcap allows for critical listening with the 12lta but the plugs further smooth the sound out a touch and really help present music in a more relaxed fashion. I am so pleased! My system is finally complete and sorted out from a sonic standpoint. Now i just need to sand and stain... then onto the next project!
Today played ping pong with my older son while blasting Bee Gees and Frankie Valley and the Four Seasons. The 12lta plus tweeter plus H-frames goes LOUD without strain. This separates it from more typical (but no less excellent) full rangers. The 12lta is a great driver when tweaked and used properly. Highly recommended!
Zilla
Hi Godzilla
Last time I heard the Bee Gees, before my TT needle got mashed, was through a tubed 12" fullrange.
It sounded GREAT, very LOUD.
Do you get your stain & sandpaper from the DIY store John Travolta worked in ?
Nice job dude.
Cheers
Simon
P.S. Is it true that in NYC:- "Girl", rhymes with "Oil" ???...
Glad you found them as effective as I did 'Zilla. And I thoroughly agree that the 12LTA is a superb driver trapped in a PA speakers body!! All it needs is a little help
Hey guys, I just read over all 23 pages of this thread with great interest. I have a question: is 44mm the maximum diameter of a potential phase plug? I've seen mentioned a few times how great it would be to make the Beta 12LTA coaxial, and the nearest solution I could find is this. It's got 96db sensitivity and the cutout diameter is a little under 1 3/4", which means that if you were to saw off the flange then maybe, just maybe, it could fit into a tube in the center. Just how feasible would this be?
That tweeter works quite well with the LTA. One of my many unfinished projects is to mount it as a coax. I tried using it Hammer style but it didnt quite sound right.
I ripped the heat sink off and pressed it into a 1.25" PVC slip coupler. The couplers ID is just slight too small so removing a bit of material is needed. The coupler makes a nice guide so that you can grind or cut the flair off. I used a bandsaw and then a belt sander to clean it up. It does lose some efficiency after removing the "horn". You can check out a review of it on Zaph Audio.
amt
I ripped the heat sink off and pressed it into a 1.25" PVC slip coupler. The couplers ID is just slight too small so removing a bit of material is needed. The coupler makes a nice guide so that you can grind or cut the flair off. I used a bandsaw and then a belt sander to clean it up. It does lose some efficiency after removing the "horn". You can check out a review of it on Zaph Audio.
amt
Attachments
44mm is the figure Dave (Planet10) gave me and I'm not gonna argue with that!
However there is about 48-49mm total but you don't want the voice coil former (tube) rubbing.
The Afterbutner project (google) used a tweeter positioned centrally but held with an arm from the side of the 12LTA. Problems as far as I can see are going to be phase/time alignment. The 15 inch Tannoy Dual Concentric which I owned had a fiendishly complex crossover/time alignment/phase thingamajig so cover these problems.
To be honest though you really dont need a tweeter in the normal sense with the 12LTA. I just use a helper tweeter. My Fostex FT17H just has a Jantzen Silver Oil 1 uF cap to remove the lowest of the low. It comes in around 5-8khz and does the high airy stuff.
The 12LT really is a true 'full range' driver. It needs a little help at the top and a little at the bottom. That's where it's at its not inconsiderable best
However there is about 48-49mm total but you don't want the voice coil former (tube) rubbing.
The Afterbutner project (google) used a tweeter positioned centrally but held with an arm from the side of the 12LTA. Problems as far as I can see are going to be phase/time alignment. The 15 inch Tannoy Dual Concentric which I owned had a fiendishly complex crossover/time alignment/phase thingamajig so cover these problems.
To be honest though you really dont need a tweeter in the normal sense with the 12LTA. I just use a helper tweeter. My Fostex FT17H just has a Jantzen Silver Oil 1 uF cap to remove the lowest of the low. It comes in around 5-8khz and does the high airy stuff.
The 12LT really is a true 'full range' driver. It needs a little help at the top and a little at the bottom. That's where it's at its not inconsiderable best
Figures i gave out were from my (uninstalled) 12LTA phase plugs. A client ordered a custom pair (when we could still do that) and we made 2 pair. Client was very pleased with his. I am just now considering doing up a "miniOnken" style box for the 12LTA, likely not mini at all.
dave
After removing the whizzers, I added these tweeters several months ago. I attached mine by using a steel-based epoxy to glue a T-nut to the back of the heat sink. I then used some threaded rod and an assortment of washers to bolt the tweeter in place. (I also epoxied the heat sink to the tweeter.)
The dark ring on the cone around the tweeter is a shadow from my camera's flash.
The dark ring on the cone around the tweeter is a shadow from my camera's flash.
an Onken would look nice - its still a reflex (a R-J reflex could look cool too and be steampunked) - maybe a properly designed tapered MLTL would be nice and punchy if not tuned too low. 12LTA doesn't have much punch in the little K12 Karlson compared to stronger motor drivers - but its a bargain and fun plus measured smoother than the old B102. 12LTA would have been fun with a 54oz slug and minor changes.
A Karlson coupler would be be another option for 12LTA - it would probably play fine in a stock K15. A coupler built for the purpose might have somewhat better dispersion.
non-optimal tapered pipe + 12LTA -fb probably too low for punch
Way off axis - mic on gound
Dead-on whizzer axis and ~20 degrees off
btw - a fun helper tweeter was to fire an APT80 knockoff upwards into a slotted styrofoam cup as a poor/lazy man's B&O lens
(another Karlson derivative imo) - the "Kup" could be rotated to toe in the HF
B&O
A Karlson coupler would be be another option for 12LTA - it would probably play fine in a stock K15. A coupler built for the purpose might have somewhat better dispersion.
non-optimal tapered pipe + 12LTA -fb probably too low for punch
Way off axis - mic on gound
An externally hosted image should be here but it was not working when we last tested it.
Dead-on whizzer axis and ~20 degrees off
An externally hosted image should be here but it was not working when we last tested it.
btw - a fun helper tweeter was to fire an APT80 knockoff upwards into a slotted styrofoam cup as a poor/lazy man's B&O lens
(another Karlson derivative imo) - the "Kup" could be rotated to toe in the HF
An externally hosted image should be here but it was not working when we last tested it.
B&O
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