Building a Headphone Amp

[hitman47]

So recently I decided to get into DIY electronics and got interested in building my own amp. After a bit of research, I found this baby: http://www.head-fi.org/forums/f6/millett-starving-student-hybrid-amp-319231/

It's a hybrid amp that uses both tubes and transistors and it's apparently quite nice sounding and easy to construct. I've now found all the parts I need online and I'm gonna order them today, can't wait till they arrive :D

[Spart]

OOO starving student! I'm tempted to build one myself.

[hitman47]

I say go for it, they're reasonably cheap (esp. since you live in the US) and they really seem worth it in terms of sound quality.

[Spart]

I haven't decided whether to build one or just buy a little dot.

[hitman47]

Alright, finally all the parts have been ordered and paid for. The main part of it all has already arrived (my mouser order, resistors, caps etc) but I'll prolly have to wait a while for the PCB, the tubes and the PSU which is shipping from Hong Kong.

[Mr. Hasselhoff]

Looks nice, be sure to post picture updates of your project.

[hitman47]

Alright, the PSU just arrived today from Hong Kong, now all I'm waiting for is my package from beezar.com with the tubes, the PCB, the audio jack and the tube sockets..

[hitman47]

Alright, everything has arrived. I'll probably start assembling it tonight or tomorrow, depending on when I see my friend at whose place I'm gonna be doing it next.

[Mr. Hasselhoff]

Sweet, can't wait!

[hitman47]

OK guys, I have now successfully soldered the resistors and the tube sockets to the PCB (although I did mount the tube sockets on the wrong side the first time around and had to go through quite some trouble to get them out again, getting out 7 soldered contact pins is harder than it sounds if you only have 2 soldering irons) but unfortunately, I forgot to put my memory stick into my phone so I couldn't take pics. When I work on it the next time, I'll take some though

[Spart]

What set of cans is this gonna be powering?

[hitman47]

Probably a pair of HD555s, it's the best I can afford. But I haven't bought anything yet, probably gonna be listening to it for the first time through the headphones of my friend's dad

[hitman47]

OK, so I still haven't gotten around to taking pics, but I only need to connect the transistors, the input jacks and the power jack now and jumper a few optional resistors that I didn't order cause I didn't know they were included on the PCB plan. Probably gonna take me like 1 more hour, I'll let you know if it works!

[hitman47]

Alright, so I just finished it, but unfortunately, it's not really working yet... The tubes begin to glow, but there's only a weird, periodic crack coming out of the cans if I connect them... Oh well, I posted on Head-fi, maybe someone there can help me
Edit:
OK, I fixed it, I accidentally fucked up the polarity of the DC input. However, I only get sound on one side now, no clue what might be wrong though... Prolly a blown up cap somewhere in the other channel

[hitman47]

YAY, I did it! It's finally working, I just had to redo some contacts. It's already sounding great, but I still have to let it burn in for a couple more hours and I'm kinda afraid to do it unsupervised because the heatsinks on the MOSFETs get insanely hot so I'd rather be able to turn it off in case anything fucks up

[Spart]

Install some fans in that biotch!

[hitman47]

Yeah I thought of that too, but I haven't done the casework yet. I might install a 120mm fan on it, that should bring the temps down. I've been looking around and I think I've already found my next project though: the AMB y1/y2 DAC. It's a digital-to-analog converter that can do all sorts of awesome stuff, check it out here:
http://www.amb.org/audio/gamma1/
http://www.amb.org/audio/gamma2/

[Mr. Hasselhoff]

No pics? Come on...

[hitman47]

Sorry about the pics, I'll take some when I'm done with the casework. Not much left to do, just 2 big holes for the tubes and some way to fix the MOSFET heatsinks to the case. And I'll have to resolder the audio input and the power plug to their respective wires.

[hitman47]

The amp is pretty much finished now, all that's left to do is fix the PCB to the wooden blocks I installed to hold it, install the copper plate to get some extra ground resources (I'm still getting some noise and scratchy background sound) and fix the lid shut. I kinda fucked up on the holes for the tubes, but I guess that's what you get if you try to make 3/4" holes into a metal box with a 1/4" drill bit... As long as it works, it's cool though

http://i191.photobucket.com/albums/z44/hitmannumber47/DSC01069.jpghttp://i191.photobucket.com/albums/z44/hitmannumber47/DSC01067.jpghttp://i191.photobucket.com/albums/z44/hitmannumber47/DSC01068.jpg
Edit:
BTW, I'm listening to it right now with some Koss phones that belong to my friend, and considering it's from the PC's headphone jack, the quality is pretty good
Edit:
OK, I already managed to screw my amp up again... I finally got the casing more or less done and was running it with my PC as source, so I lifted it onto my desk which has a massive metal frame and there was a huge spark from the casing to the metal frame and now only one tube glows when I turn it on and there's no sound coming out at all.

I wonder what happened there...

[hitman47]

Alright, so I went to the only electronics store anywhere near me that has stuff like this and got some replacement MOSFETs (turns out I actually fried one of those) and got some additional resistors and caps that the original design didn't include, but the PCB has holes for them. BIG MISTAKE. I had jumpered the resistors when building the amp and spent like 2h getting out the jumpers and soldering the 4 resistors in, it was a fucking pain cause the holes were clogged and I nearly lost it. But I'm done with that now and I only have to connect the new MOSFETS and the new bypass coupling caps (I might take those out again depending on how it sounds, I actually wanted to get foil caps but the store only had ceramic ones with a high enough voltage rating, they should be 250V for some reason and now I ended up with some 3000V rated ceramic caps, lol) and then I'm (finally) done. I can't wait to just enjoy the sound

[Spart]

Alright, so I went to the only electronics store anywhere near me that has stuff like this and got some replacement MOSFETs (turns out I actually fried one of those) and got some additional resistors and caps that the original design didn't include, but the PCB has holes for them. BIG MISTAKE. I had jumpered the resistors when building the amp and spent like 2h getting out the jumpers and soldering the 4 resistors in, it was a fucking pain cause the holes were clogged and I nearly lost it. But I'm done with that now and I only have to connect the new MOSFETS and the new bypass coupling caps (I might take those out again depending on how it sounds, I actually wanted to get foil caps but the store only had ceramic ones with a high enough voltage rating, they should be 250V for some reason and now I ended up with some 3000V rated ceramic caps, lol) and then I'm (finally) done. I can't wait to just enjoy the sound


And that sir is why I don't think I could build my own. I don't have the patience!

[hitman47]

Alright, so I went to the only electronics store anywhere near me that has stuff like this and got some replacement MOSFETs (turns out I actually fried one of those) and got some additional resistors and caps that the original design didn't include, but the PCB has holes for them. BIG MISTAKE. I had jumpered the resistors when building the amp and spent like 2h getting out the jumpers and soldering the 4 resistors in, it was a fucking pain cause the holes were clogged and I nearly lost it. But I'm done with that now and I only have to connect the new MOSFETS and the new bypass coupling caps (I might take those out again depending on how it sounds, I actually wanted to get foil caps but the store only had ceramic ones with a high enough voltage rating, they should be 250V for some reason and now I ended up with some 3000V rated ceramic caps, lol) and then I'm (finally) done. I can't wait to just enjoy the sound


And that sir is why I don't think I could build my own. I don't have the patience!

Well, building your own amp isn't really hard if you know what you want to do from the beginning, the problem is that I only found the complete schematic for the PCB version after I ordered everything so I didn't have any bypass caps and input resistors. But the soldering part is really not hard to do if you don't have to replace anything on a PCB. I'd say I was done with the soldering after about 1.5h the first time and I'm a complete noob when it comes to DIY electronics. And the sound quality it delivers (or rather delivered when it worked) was A LOT better than the headphone output of our expensive ass Denon CD player (although that one's from the 80s/90s so the quality won't be entirely up to current high end standards, but still, it cost like 2000 bucks), so I'd say it does pay off. And if you go for the custom Hammond enclosure, you won't even have to do any casework. I say go for it, it really pays off and there's really not a lot of debugging to do with such an easy design (in fact, it worked for me from the start, after I'd soldered the power input jack with the right polarity)