PowerPad and the ultra extreme headphone amp TPA

[peranders]

I haven't tried yet but I think it will go just fine if I just burn thourougly on the "solderside" with the soldering iron. This asumes a pcb with lot's of vias. My pcb will have 18 vias under the metal area.

 

[Upupa Epops]

Per, I mean that it will be not so easy ( I have not experience with it ), 'cos must be used soldering paste for soldering of pad. Device must be " preheated " in this case by hot air and all thrue holes must have correct diameter - soldering of SMD devices is " big science " .

 

[Nicke]

Soldering paste,a good flux and a hot air device is all that is needed,not that difficult..BUT perhaps one should practice some first....

 

[Upupa Epops]

To Nicke : For profi working place is it certaincly no problem, but we are talking about home work .

 

[Nicke]

SMD soldering with hot air

Upupa Epops:I see your point

We use this at work:Hot air soldering mashine

But what I meant was that it is not THAT difficult.
I wouldn´t have any problems using a regular hot air tool(don´t know what it is called in english,"varmluftspistol" in swedish) at home.
What matters is that you should NOT try this without getting used to this and try a it with some junk components first.
And not to heat the components too long...

 

[Upupa Epops]

Yes, no problem with this machine , except price for this .

 

[Nicke]

Yes, no problem with this machine , except price for this .

I´ll agree...

But it wouldn´t be that difficult to use a regular hot air gun like this:
http://www.tumstock.se/itemimages/full/0102434.gif
It isn´t the first thing a beginner in soldering should try...
I would not hesitate,but I´m used to solder things like this

 

[matjans]

oops my mistake... finally read the datasheet.

it's a useful link anyways...

 

[Upupa Epops]

Per, you are strictly using separate PS for each channel - what you will be doing in this case ? This circuit have seemingly separated feeding, but biasing circuity are common. Will you use parallel connection of both channels and two chips ?

 

[peranders]

I have not yet desided if I'm going to use a single or a dual supply. At least I have desided that it wll be an non-inverting buffer with gain and the TPA6120 will go a inverting amp with gain of 1.

I plan to use one AD8620 and one TPA6120.

 

[ericallan]

I like the idea of soldering a copper wire, perhaps mains earth wire, to the pad as a solution. The chip doesnt get very warm at all and I've run it quite loud for extended periods and left it on for hours. I think the important thing is to earth the pad and give at least some conductance of heat. I'm going to build another to go inside an integrated chip amp I've got planned.

I've got some OPA4134 opamps as used in the suggested application on the pdf file - might try to incorporate those as well -any thoughts?

For the power supply, I used a transformer with twin secondaries and fed the outputs into 2 seperate regulators.

 

[carlosfm]

I have not yet desided if I'm going to use a single or a dual supply. At least I have desided that it wll be an non-inverting buffer with gain and the TPA6120 will go a inverting amp with gain of 1.

I plan to use one AD8620 and one TPA6120.

P-A, why don't you use the TPA6120 alone, NI?
That way you will evaluate this chip.
An AD8620 before it?
Why?

 

[peranders]

Good question!

The TPA6120 has rather large bias currents which can cause trouble when the signal source is not known and/or you have AC-coupled input. Therefore to eliminate this I chose to have a buffer and when I have it I chose also to have an inverting configuration of the TPA6120 since I have good drive capability. It's not impossible to modify the pcb into a non-inverting, non-buffered version.

The group buy interest at head-fi.org is zero (to hard to build?) but if anyone here feel this headphone amp could be interesting, send me a message and maybe I will set up a group buy.

It's not ruled out that I can solder the TPA6120 but I won't promise anything.

 

[mandat]

What do you say about OPA1632 opamp (marvellous THD and SR specification) as a buffer for TPPA6120 or THS6012?
Yes, these ICs are very fast and DIYer should take a great care during PCB layout design and power supply decoupling.

 

[peranders]

It may be a good choice but I will concentrate myself on AD8610, just to get at least one "approved" design if you know what I mean.

 

[ericallan]

Peranders - is the OPA4134 opamp a bad choice? TI promise 120db dynamic range using the OPA4134 and TPA6120 together. Have you looked at the Evaluation Model pdf document? I got more ideas from that than the datasheet.

http://www-s.ti.com/sc/psheets/slou169/slou169.pdf

 

[peranders]

Only a single opamp will fit but OPA134/2134/4134 doesn't match the TPA6120 IMHO, you need one the sharpest opamp around for this.

Compare also that AKM and others recommend NE5532 as the best choice for their DAC's!

 

[peranders]

Now... is the layout ready. The pcb will have gorundplanes on both sides. More info will come in a few hours or at least this weekend.

 

[carlosfm]

P-A, if you use a buffer, you can use it before the volume pot.
And the TPA in NI mode.

As for the solder pad...
why not use a big via (around the size of the pad) on the exact place, to fill up with solder?
I can't remember an easyest way to do it.
It should work fine.

 

[peranders]

I have chosen inverting mode just to get ultra extremely low distortion

The PowerPad is made according to recommendations, 18 vias under the PowerPAD. I have also thought about a big hole under the IC.