I was considering purchasing a kit such as: QKits Electronic Kits: FK656, Power Amplifier Kit OTL 30W (Mono) R1%
To use as the output stage for an amplifier. I just won an ebay auction for a 40VA 24CT transformer. Now obviously the voltage output of the transformer would not be high enough for that kit. So I was thinking about building a voltage doubler circuit. And then after the circuit, I would use a LM317 for regulation.
Would this be a bad idea to regulate the p/s? The max output current of the LM317 is only 1.5Amps, so it would be cutting it pretty close. I wouldnt need the full 30 watt output of the kit, even 20 watts would be fine.
It would be driving a single 8ohm guitar speaker.
To use as the output stage for an amplifier. I just won an ebay auction for a 40VA 24CT transformer. Now obviously the voltage output of the transformer would not be high enough for that kit. So I was thinking about building a voltage doubler circuit. And then after the circuit, I would use a LM317 for regulation.
Would this be a bad idea to regulate the p/s? The max output current of the LM317 is only 1.5Amps, so it would be cutting it pretty close. I wouldnt need the full 30 watt output of the kit, even 20 watts would be fine.
It would be driving a single 8ohm guitar speaker.
It takes a lot of capacitance and probably more transformer
to build a voltage doubler good enough for the power stage
of an amplifier. Normally this technique is reserved for low
current use, as in creating higher rails for front end circuits.
😎
to build a voltage doubler good enough for the power stage
of an amplifier. Normally this technique is reserved for low
current use, as in creating higher rails for front end circuits.
😎
Ah, that makes sense. Even if you used a full wave bridge rectifier in the doubler section, would it be a lot less efficient than a standard power supply?
😉
That's not possible, because that's the essential part how the voltage doubler works.
Have fun, Hannes
That's just normally regarded as a full-wave bridge rectifiier in my books, but I can see why it is called a voltage doubler. Do you need +ve and -ve rails? YES
The simplest solution, is just buy the right transformer. 😀
The simplest solution, is just buy the right transformer. 😀
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Check out Antek toroids - I am sure they make something suitable for your application at a price that will surprise you. (I've been using them for years.)
Antek - Your reliable source of transformers, power supplies, and more. I think a 100VA transformer AN-1232 would be adequate for this application. See page here: http://www.antekinc.com/details.php?p=42
Antek - Your reliable source of transformers, power supplies, and more. I think a 100VA transformer AN-1232 would be adequate for this application. See page here: http://www.antekinc.com/details.php?p=42
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a 2x20v xformer will give aproximatively
20v x 1.4 = 28v DC
20v x 1.4 = 28v DC
2 x 28v DC is ok for a 30 w amp (8 ohm supposed ?)
20v x 1.4 = 28v DC
20v x 1.4 = 28v DC
2 x 28v DC is ok for a 30 w amp (8 ohm supposed ?)
full wave voltage doubler....
😉
It appears the kit requires a +/- supply. You can build a regulated +/- supply with 2) LM317's, but you must have two seperate secondaries, not a CT. Otherwise you would need the - reg, LM337. You will loose a few volts with forward diode voltage and ripple and you would need to have much larger caps. It really would be easier and probably cheaper in the end to find a proper transfo.
Besides, your transfo is undersized by over half that's required.
It's too bad you didn't win two of them.😛
😉
It appears the kit requires a +/- supply. You can build a regulated +/- supply with 2) LM317's, but you must have two seperate secondaries, not a CT. Otherwise you would need the - reg, LM337. You will loose a few volts with forward diode voltage and ripple and you would need to have much larger caps. It really would be easier and probably cheaper in the end to find a proper transfo.
Besides, your transfo is undersized by over half that's required.
It's too bad you didn't win two of them.😛
Sorry for the necrobump, but what about this one:
QKits Electronic Kits: FK658, 35W Mono Power Amplifier Kit
It says supply voltage of 35vdc, it doesnt mention any +/- rails.
24vac * 1.41 = 33.84 vdc, slightly lower than the 35vdc requirements, but would this work with the 12 - 0 - 12 transformer?
QKits Electronic Kits: FK658, 35W Mono Power Amplifier Kit
It says supply voltage of 35vdc, it doesnt mention any +/- rails.
24vac * 1.41 = 33.84 vdc, slightly lower than the 35vdc requirements, but would this work with the 12 - 0 - 12 transformer?
It seems to be half of FK659 kit which requires +35v/ 0/-35v. If so, same problem.
Anyway, a single 35v supply cannot produce 35w/8ohms.
With your transformer you could feed a lm3886 kit for 15watts output.
Anyway, a single 35v supply cannot produce 35w/8ohms.
With your transformer you could feed a lm3886 kit for 15watts output.
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Hmm, the gainclone kit would probably work well, I could just buy the PCB's, and then reduced voltage components since I wont be running it full bore.
Lm 1875 kit also with the possibility to bridge the outputs to obtain more power.
http://www.chipamp.com/
http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=260425122111
http://www.chipamp.com/
http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=260425122111
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how hard would it be to bridge the outputs on that kit for the ebay auction? It will be used for powering a guitar speaker, so I don't need stereo.
Looks like the 2x12v transformer is just barely enough, but it should do!
Looks like the 2x12v transformer is just barely enough, but it should do!
See the datasheet and the following thread.
(This is possible if the speaker is not less than 8 ohms.)
LM1875 - 20-W Audio Power Amplifier
http://www.diyaudio.com/forums/chip-amps/115239-lm1875-bridge-config.html
(This is possible if the speaker is not less than 8 ohms.)
LM1875 - 20-W Audio Power Amplifier
http://www.diyaudio.com/forums/chip-amps/115239-lm1875-bridge-config.html
Well I bought that kit on ebay, thank you for the link. Now hopefully I can figure out how to bridge it! 🙂 Although I probably won't even need the full power output of one channel.
build one channel on a proto board.
Test it with your 12+12Vac supply and then listen to it.
After that decide what comes next, just not now!
Use 50V smoothing and decoupling capacitors. This allows for 28+28Vac transformer later if you want to go that way.
Test it with your 12+12Vac supply and then listen to it.
After that decide what comes next, just not now!
Use 50V smoothing and decoupling capacitors. This allows for 28+28Vac transformer later if you want to go that way.
So what enclosure would you all recommend to use with this kit? I have everything else that I need I think.
I looked at a Hammond Die-cast aluminum enclosure, but it was 35 dollars, more than the cost of the rest of the components!
I was hoping to find something in the 10-15 dollar range.
I looked at a Hammond Die-cast aluminum enclosure, but it was 35 dollars, more than the cost of the rest of the components!
I was hoping to find something in the 10-15 dollar range.
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