Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › doobooloo's TPA6120-based balanced headphone amp
New Posts  All Forums:Forum Nav:

doobooloo's TPA6120-based balanced headphone amp - Page 9

post #121 of 199
9/3/06 at 1:25am
Thread Starter 
Quote:
Originally Posted by mikemacwillie
I will be trying some high speed opamps as well. the THS look interesting to try out
Yup, I've never tried the THS's myself, they definately do look very interesting.

Quote:
Perhaps when you get back I could purchase some off you?
Sure - I've only got a thousand or so, so hopefully I can meet your demand.
Reply
post #122 of 199
9/3/06 at 5:12pm
Quote:
Originally Posted by doobooloo
Yup, only half rail. Just out of curiosity - Are you going to be using the supplied os-cons or other caps?
One one I'll use the oscons, on the other I'll use Panny FMs. I can't imagine this is going to make any kind of difference but figured I'd do it anyway. Also, the only surface mount opamps that I could find at digikey were the 8620s so that's what I'll be using. The amp is going to be used for Senns so I think that'll work just fine.

Quote:
Whoa. I wish my solder would fly someday.
What can I say, I'm special .
Reply
post #123 of 199
9/4/06 at 1:14am
Ohh yay I like reading updates
Reply
post #124 of 199
9/4/06 at 5:01am
regarding the buf634/opa551 choice:
wouldn't it be better to use the opa551 or any hight current opamp than a buffer like the buf634? the buf634's output impedance is said to be around 10~20ohms, whereas an opamps output impedance in unity gain config should be much lower, right? in this case one could also replace the tle rails splitter with a resistor devider and a cap to ground for noise suppression, because the opamp has a very high input impedance...


and now something completely different: how do you guys solder the TPA6120 chip, especially the thermal pad?
Reply
post #125 of 199
9/4/06 at 5:01am
oh yeah, and yet another thing: could someone post pics of this sexy beast?
Reply
post #126 of 199
9/4/06 at 11:07am
Quote:
Originally Posted by t52
and now something completely different: how do you guys solder the TPA6120 chip, especially the thermal pad?
I'm also interested in hearing about this, I didn't see it mentioned anywhere earlier in the thread. Knowing that Doo had a breadboard prototype going I'm wondering if it's even required?
Reply
post #127 of 199
9/4/06 at 12:27pm
Thread Starter 
Quote:
Originally Posted by n_maher
I'm also interested in hearing about this, I didn't see it mentioned anywhere earlier in the thread. Knowing that Doo had a breadboard prototype going I'm wondering if it's even required?
The solder pads are on the most recent board, but to be honest, during normal operations the chip doesn't get very hot even without the pad soldered. Perhaps around 60 degrees celsius?

To get the PowerPad down on this board, you'll need a pretty powerful iron to keep the solder flowing in that ~ 3mm x 3mm area while the heat is dissipated throughout the groundplane.

And please - those who have completed the boards - post some pics for us! I know Mike posted a nearly completed pic earlier but we need more!
Reply
post #128 of 199
9/4/06 at 2:46pm
Ok, another question mostly as a result of me wanting to be careful since fixing SMD stuff is the devil.

Can anyone tell me why R3 and R6 are different values (49.9ohms vs. 499ohms)? From what I can see on the board they look to be in the same position relative to each channel. My thought is that on each channel one should be R3 and one should be R6, not two R3's on one channel and two R6's on the other. Either that or perhaps they are all supposed to be 499ohms.

Clarification would be stellar.

Nate
Reply
post #129 of 199
9/4/06 at 3:14pm
To oslder the powerpad.. I put lots of flux on the powerpad on the bottom of the chip, and the spot on the pcb before soldering down the TPA chip. Then using a large chisel chip I heated the area on the bottom of the board with all the vias. The vias will conduct the ehat to the top side, and the flux to the chip until you get some solder in there.. Then just slowly add solder to the board and it will flow through the many vias

I clipped all the legs off one TPA chip to see if the power pad was soldered.. and it was.



I will try to get more pictures, but my camera isn't any good! Perhaps natural lighting will help.
Reply
post #130 of 199
9/4/06 at 3:36pm










Reply
post #131 of 199
9/4/06 at 4:23pm


Made good progress today, as much as I can without the digi chip (on order) and without the answer to my above question regarding R3 and R6.
Reply
post #132 of 199
9/4/06 at 4:48pm

Nice clean soldering guys

Wow, that's some nice clean soldering Mike and Nate.

Did you guys do that freehand with a fine tip soldering iron and some fine solder?

It sure takes a steady hand.

I nearly trashed a sound card that I was modifying with a fine tip soldering iron using the thick Cardas solder.
Reply
post #133 of 199
9/4/06 at 7:46pm
Yes, all done freehand with a hakko station. I'm experienced though.. Done lots of SMT rework for a day job.


Looking good so far Nathan! Reguarding your questions about the resistors.. One of the TPA chips is in an inverting circuit, and the other in a non inverting circuit. You need different resistor values to get the same gain.
Reply
post #134 of 199
9/4/06 at 8:20pm
mikemacwillie, are those XLR connectors? They look quite a bit like 1/4th outputs.
Reply
post #135 of 199
9/4/06 at 8:34pm
They are the 1/4" connectors the board was designed for.
Reply
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › doobooloo's TPA6120-based balanced headphone amp