*** The DIY Audio Thread ***

Well I didn't get very far before running out of solder. :(

Just ordered some more but it won't be here for a few days! :mad:


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heres how i would do it. Solder all resistors / diodes, then progressively do the bigger components.

If the designer has been clever i bet there is a jumper from PS section to the amp section.

Do not solder anything there yet, thats the last step.

Connect everything up, then check the power rails (from the jumper points if they exist) voltage between ground. I guess +/- 15 v. Also guessing the trimpots set this (vr1).

Show a pic of the whole board.

then connect the jumpers and cross your fingers.

then check the DCoffset (dc with no music, left to ground and right to ground, or take it from the board). If its below about 20mv you should be good to test with some **** headphones.

The issue i can potentially see with this is the lack of matched fets, if they arent matched then DCoffest could prevail. Hopefully this wont be a problem.

EDIT - just seen the previous page with a bigger pic, looks like there are jumpers. do the above.
 
Thanks for the tips Adam, soldering smallest to largest sure does help. I've just finished soldering the PSU, need to buy a 15V AC transformer and some wire terminals now...then I'll test the PSU to see if it outputs the correct voltages.

This is fun!


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How much would you be wanting? I've been looking and there seems to be quite a price range....also is there any downside to having an over-rated transformer like that? I was looking at 7.5 and 10VA transformers but also saw people running 30-50VA in headphone amps...
 
no down side when your running regulated (as this amp is) - as long as it doestn get silly large. Many people will say its a positive.

£13 and its yours.
 
wish i had the time to get do some thing like that i am both impressed and hugley jealous;)

also i thinking on building a gainclone. cant remeber which site i was reading at work during my lunch time google troll but it mentioned theres a chance you could burn your house down if the transformer is not correctly installed.
i am preety much a newbie so would it be risky?
 
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If your worried a few tips:

1 - Suitably rated mains primary fuse in Live lead (essential)
2 - Dual secondary fuses, ideally before bridge rectifiers (optional, but limits damage if there is a fault)
3 - Fuses on amplifier PCB (usually included, again limits damage in fault condition)
4 - Thermal fuse in contact with transformer (optional)
5 - Install in metal case (must be earthed) and have no flammable parts if possible, certainly not near the transformer or mains side
6 - have power supply capacitors rated well above the expected voltage and be certain of polarity

Most manufactured equiptment doesn't have all this protection and is passed as safe. Do number 1, 3 and 5 most importantly :)
 
I am just curious about what voltage regulators folks have used in the past? I am currently drawing up a schematic for a fully integrated gainclone design and need some voltage regulators. I have seen the LT1083 being used, is this a good choice? Looks to have a voltage range of 20V - 32V which seems good, just want to check.
 
I used LM338T as per this design:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=56106&highlight=

for +/-30v to power an amp. This amp only drives the tweeter of a 3 way though, so nominally low current and also it being a planar tweeter perfectly flat impedance. A more variable load like a woofer would likely require more but perhaps not if you can get a good PCB with solid traces :)

Can always parrallel anyhow (providing small value output resistors are used and are acceptable)! Could even parrallel a whole lot of LM317T units, though that's probably more effort/expense than required it would give good heatsinking!
 
Well, connected up the transformer (thanks Adam!) and the PSU section works great, but as soon as I connect the jumpers the amp goes wonky. I get about 10V on the left channel and 2 of the heatsinks get really hot while none of the other ones do.

ARgh! Dunno how to go about troubleshooting this one really...
 
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