[DaKi][er]

I been following all the headphone amp designs for the past year and a bit and a lot of people have done some nice work, well I decided that I should have a go at my own from scratch

This is done with combinations of other ideas on what works and what doesn’t and putting in what I’ve though has been the most important factors in design. I’m going with the fairly new TPA6102 as they have been said to sound real good from what others have said about it and doesn’t cost much compared to other alternatives. I haven’t decided 100% on what to use in the input opamps spots yet, but it will most likely be either ad8610 or opa637

It’s mostly a smd board, after doing a few projects involving smd (mints, Glassman db, usbdac) I’ve throw away my 'hate' for them and really enjoy working with them now and designing a board with smd is soo much easier than all through hole

So after a few days with eagle, here's what I’ve come up with so far-

Board
Schematic

I'm after suggestions that any of you might have in general about it, anything i should change/add/whatever before I rush into getting a board or 2 made up for it. Also going to put the title to this post in, i dont have a name for my board so i better think of somthing there too

 

[llmobll]

Wow very nice indeed. I'm in the same spot you are, developing a few boards here and there. Your design is probably the nicest I've seen yet from the crowd around here. Good work!

Q: How do you do a ground plain in Eagle?

 

[DaKi][er]

make a polygon and name it the same name as your ground net

this feature is well hidden in there, they could have programed it in better

 

[peranders]

It looks good but I think you should connect all NC pins to groundplane (check my pictures below) so you increase the cooling. I recommend also that you have groundplanes on both sides plus a bit thicker copper if that's possible. The TPA6120 gets pretty hot so good cooling is essential if you are planning to play loud.

I recommend also that you have resistors from the non-inverting input down to ground (check my schematic) becuase the bias currents are pretty high, 12 uA and the offset voltage I've got was 2 and 10 mV _with_ those resistors and only 1 kohms as resistor values.

Reduce also the isolation barriers in the groundplane , keep it only at the pot. You need the cooling.

My amp can be found here.
http://home.swipnet.se/~w-50719/hifi/qrv07
I use AD8610 as buffer and I can really recommend it!

Check my pictures.
http://home5.swipnet.se/~w-50674/hif...r0_topview.jpg
http://home5.swipnet.se/~w-50674/hif...v07pcbsold.jpg
http://home5.swipnet.se/~w-50674/hif...v07pcbcomp.jpg

 

[DaKi][er]

Thanks peranders, some of the ideas for this board came from yours and they are very similar in the schematic

I added in the spot for a resistor from non inverting to ground, top groundplane and cleaned it up a fair bit and I now got this -

I'm thinking of adding in Isolated power rails like the ppa has for the input opamps but i think thats going to add too much to fit on the current layout

 

[peranders]

Looks good! I don't know if it does anything but I have also decoupled the resistor from the non-inverting input. Remember this is a 100 MHz device.


.... but I think you should turn the TPA6120 180 degrees so your output traces don't go under the whole IC. As you can see I have removed the groundplane under the inputs in order to reduce the stray capacitances. I have no idea have bad the stray caps are but it never hurts to do that since this is a highspeed device.

 

[Garbz]

not to mention that it was over emphasised in the datasheet not to run any gnd planes under the input traces. My guess is this device is very suseptable to this interference.

 

[DaKi][er]

cleaned up the ground plane around the input pins and came up with a name for it, DtpaKiller

its starting to looked finished now, I’m going to get boards made up for this in the next week or 2 and someone has pm'd me about wanting a few for himself. I’m getting them made through www.custompcb.com and have a minimum of 2 panels that 3 of these fit on and if anyone wants some of these for themselves I’d be happy to add them in too

 

[DaKi][er]

rotated the voltage regulators to face the edge of the board to fit headsinks to it more easily

 

[skyskraper]

killer if u make this up id defn be in to grab a board and test with u

but perhaps if you intend on wider distribution, then normal resistors would take up not much more space then is already used on the board and give people more options to use their favourites? as well as not intimidating n00bs :

 

[peranders]

skyskraper, have checked out my TPA6120 amp which is alive and working? I tried to create some interest for a group buy but the interest was absolutely zero. Maybe DaKi][er has a more interesting design, who knows?

 

[DaKi][er]

Quote:

Originally Posted by skyskraper killer if u make this up id defn be in to grab a board and test with u but perhaps if you intend on wider distribution, then normal resistors would take up not much more space then is already used on the board and give people more options to use their favourites? as well as not intimidating n00bs :

I wasn’t looking for wide distribution and I’m only doing this for myself and anyone that wants what I’m showing here, feel free to load up eagle and see how easy it is to make this but with all through hole and i can tell you it wont be easy to fit it down to this size. you wouldn’t believe that smd can be a lot easier and quicker to solder on a proper board than through hole is (as well as desoldering) and after a little practice is quite enjoyable as long as you stick to 1206 sizes and no smaller than 0805

I’m getting them made with a minimum of 6 and multiples of 3 after that, i want 4 or so and got people wanting a total of 5 so far. cost is about $8US per board and add postage on top of that for a basic board with no solder mask or silkscreen

If you want any I can put you down, and also the passive smd parts too if you want seeing they aren’t real accessible in aus

 

[guzzler]

Nice layout, very neat. Couple of further suggestions; make all the resistors 1206 package, that way you get rid of the tombstoned resistor (icky, imo) and keeps the whole thing consistent throughout.

The other is about your choice of manufacturer, I've not heard much good about CustomPCB in the past, things like dodgy substrates, traces etc but they are cheap. Personally, I'd recommend you find a better quality manufacturer;

pcb4u.net : nice boards, but got hammered on import tax, likely you will too

www.eurocircuits.com : very cheap, high quality boards, no import tax for me as I'm in the EU, but might be different for you. Personally, I highly recommend these folks.

www.olimex.com (I think), good for designs with wide-ish traces, yours would be fine. The cheapest of the bunch, and I've not heard much against them

good luck, hope it turns out nicely...

g

 

[peranders]

This tombstone effect won't go away with 1206's. This is a matter of designing the pads. If you are concetrated when you are doing the soldering this is not a problem. It's better to choose 0805 because they are more common.

 

[skyskraper]

if its not for wide distribution then i dont have a problem with it. been soldering smd a bit lately and its been much easier then it was previously

if you make a proto run of boards lemme know and ill get one off u