# TPA6120A2 best headphone amp in the world?



## peranders

http://focus.ti.com/lit/ds/symlink/tpa6120a2.pdf

 Check out this IC! Anybody who has come near this IC?

 0.00014% THD + N
 120 dB S/N


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## Glassman

http://www5.head-fi.org/forums/showthread.php?t=70517

 and yes, it does look great


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## peranders

Oops... still has anybody laid hands on this IC?


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## Glassman

I'm gonna look at it sometime in summer, should be interesting.. the best portable amp & DAC ever?


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## kevin gilmore

Yes i have built a prototype and it sounds mighty good indeed.
 Especially for portable applications, all you need is this ic, 4 resistors,
 a miniature volume knob and a small dc-dc converter. All surface
 mount, and requires attachment to a headsink thru the bottom which
 is certainly a pain. I have a board layout which is not done yet.

 I believe it is actually better sounding than the opamp/buffer solution
 for portable sound.


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## was ist los?

Kevin, do you know of any good dc-dc converters for 9v batteries?


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## doobooloo

Is this the next mighty head-fi DIY project...


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## ITZBITZ

I sure hope so, it sounds like it could rival the MINT in terms of size and parts count.


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## kevin gilmore

With the 12 volt cosel converter, running VERY loud into grado headphones
 the input power is 1.15 watts. A little high for 9 volt batteries.
 But it is very small and it is very high quality.

 In contrast my portable stax box uses about 6 watts of input power.


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## was ist los?

Kevin, so i should get a converter rated at 1.5W. What series would you recommend? I was looking at the ZU series since they are so small. They also seem to have more leeway on input voltage requirements. I may just use 4AAs instead of a 9V.
 Also, what type of heatsink am i looking for?


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## Garbz

excuse my ignorance but what is the DC-DC coverter for, and why would i need it if i start a project with this chip?


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## aos

I also have designed a board and have them coming, hopefully in two weeks I'll build one as well. It does sound like a perfect solution for a portable.


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## doobooloo

If this chip sounds so good, can it be used as a high-end amp solution?

 Or at least somehow made to be a high-end solution? (Sort of like the maxed-out peranders' gainclone solution...)


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## aos

Sure, take two of them (also recommended in TI datasheets) with separate voltage regulators and see how that works out. I am really looking forward to trying them out. My board shipped yesterday and I hate waiting...


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## kevin gilmore

http://gilmore.chem.northwestern.edu/cosel.jpg
 (warning huge)
 Zuw 1R5 1215
 (how you like that antique and rare ruler)

 You don't really need the converter, i like regulated everything so
 i use it. a 8 x AA brick is 12 volts and runs the thing for about 10 hours.
 If you use 10 x powerex Nimh AA you get about 20 hours. 

 board picture
http://gilmore.chem.northwestern.edu/micro.pdf
 Yes that is real size .9 x .9 inch.

 You solder the chip thru the backside of the board then solder
 on a piece of copper that is .3 inch wide and about 1 inch long.

 Why build it. Sounds great and is sjosae tiny. I mean really tiny.

 High end? For high impedance phones, sound is amazing for such
 a little squirt. Low impedance phones, seriously lacking.


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## 00940

Quote:


  Originally Posted by *kevin gilmore* 
_High end? For high impedance phones, sound is amazing for such a little squirt. Low impedance phones, seriously lacking._

 

Great news, I'm wondering how it will power my K340 (400ohm). It'd be perfect with in a small box with an usb dac.


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## was ist los?

Kevin, you mention that the amp is lacking in sound for low impedances, but do you think it's still a better option than an opamp/buffer setup? Also, have you tried it with Ety's?


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## kevin gilmore

Yes it certainly sounds better than the opamp/buffer solution.

 My intended use is with a pair of ety 4s. And is sounds much better
 than my previous unit.

 realy anchient
http://gilmore.chem.northwestern.edu/dynporta.jpg

 a few years old
http://gilmore.chem.northwestern.edu/ety1.jpg


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## Garbz

i still don't see why a DC/DC converter is needed. THe tpa6120 runs from +- 5-15v, two 9v batteries should supply ample power.
 There seems to be a lot of discussion on this forum regarding how bad DC/DC converters sound in the PSU.

 /EDIT: Sorry i missed Kevin's post


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## was ist los?

A DC-DC converter is not required, however, i would rather use 3-4 AA batteries than 2 9V batteries. AAs will have longer runtime too.


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## jasonhanjk

Yes, AA NimH has gone up to 2300mAH here. It does not seems stoping at this point.

 Kevin, which PCB layout did you use for drawing the amp? Cadsoft eagle?


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## doobooloo

Quote:


  Originally Posted by *kevin gilmore* 
_High end? For high impedance phones, sound is amazing for such
 a little squirt. Low impedance phones, seriously lacking._

 

Thanks Dr. Gilmore for your pics and info. It's interesting that the chip drives high impedance well and low impedance not so well - in that case, would it be helpful to add some sort of an output impedance mode for low impedance phones (maybe the 120ohm output adapter)?


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## kevin gilmore

I'm using Proteus Ares at the moment for board layout. I don't really
 like it, but it is way better than what i was using. Expresspcb works
 well, but then you are forced to pay their very overpriced prices.

 Many people will find this little amplifer extremely acceptable for all
 but k1000's. But something that pulls 30ma cannot possibly compete
 with a dynahi that pulls 600ma. However with enough heat sink it
 can actually put out more than 500ma per channel, so with a big
 enough power supply, this sounds REALLY good. With a gain of 10
 the output impedance is about 1.3 ohms. The dynahi impedance
 is one order of magnitude better at .12 ohms. So for 32 ohm cans
 one is a whole lot more tight with a lot more slamm than the other.
 Notice that 9 volt batteries will sag severly under loud conditions
 with low impedance cans.

 A lot of people are going to like this. It is however surface mount
 only, you have to be careful with how you do the heatsinking and
 those with standard soldering irons will not be able to put this together.


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## Garbz

on the point of trying to get this chip on the board, is it absolutly necessary for that pad to be soldiered down?

 I'm thinking along the lines of a large gob of artic silver on the bottom. Also i have plenty of epoxy heatsink resin leftover from my computer work so is it possible to just glue a heatsink to the top?

 If that thermal pad only needs to transfer heat then the actic silver should do it, if not then there's plenty of conductive stuff too.

 /EDIT: Actually i think artic silver is conductive from memory

 /EDIT2: The other thing is would it be possible to put mount the heatsink underneath? Just cut a hole into the board where the thing would sit and mount a bent piece of aluminium in.




 (excuse drawing it's late and i can't finda ruler)


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## jasonhanjk

In the semiconductor firm what they do is solder the chip to a large area PCB copper pad for heatsink. They use in line oven that is capable of heating up to 250 deg C.

 For us poor fella, we need to get solder paste and maybe 100W soldering iron to do the same thing. Actually I like the idea of thermal paste heat sink.


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## kevin gilmore

what i did for my proto was solder the back of the chip to a piece
 of copper foil cut to the right size.


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## Garbz

would it be too much trouble for pictures? That sounds like it's worth seeing!


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## was ist los?

I plan on trying what Kevin did on his proto.


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## kevin gilmore

I'll post some photo's when it is done, hopefully next week.
 Still trying to finish other stuff, plus i'm busy at work.


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## 10SNE1

From p. 24 of http://focus.ti.com/lit/an/slma002/slma002.pdf

 An alternative to attaching the thermal pad of the package to the
 thermal land of the PCB with solder is to use thermally conductive
 epoxy for the attachment. This epoxy can either be dispensed from
 the liquid form with a material that will cure during the reflow cycle,
 or a “B” staged preform that will receive the final cure during the
 reflow cycle. These materials can be the same as normally used
 with externally applied heat sinks. When epoxy is used as the
 attachment mechanism, then the effective attachment area is 100%
 of the die pad area, and there is some added benefit as thermal
 transfer to the PCB can occur, even with no copper thermal land at
 the surface of the PCB.


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## eric343

Hmmm......... I may have to build this


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## dip16amp

Here are pics of it on a 16 pin DIP socket and a penny heat sink soldered to it. It sounds quite good with a dual voltage +14v and -14v supply. Drives my Grado headphones with very good bass. The penny does get very warm so a binder clip keeps it cool.


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## was ist los?

dip, how does it compare to other amps you've built?


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## dip16amp

I'm amazed it how much power it can put out and how simple it was to put together. The 700 mA output current spec is what caught my eye and it certainly has more bass than my double buffered BUF634 X12 amp. Only my X16 (gilmore) amp has more bass.


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## kevin gilmore

3 penny opera anyone


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## 00940

with audio quality going up with impedance and such a good current capacity, what about using it as a preamp ?


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## Garbz

i thought ur Gilmore V2 amp in DIP sockets was amazing but now you bring smd parts into the equasion, and with a penny as a heatsink! Now that is awesome


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## JohnFerrier

To try to find weaknesses of this part, beyond the noise spec that may not be the best it could be, I notice that the performance at low frequencies is not as good as at mid and high frequencies...


 JF


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## GainHead

Mr. Gilmore, would you mind sharing the resistor values you used with your build? I think I am going to try a dead bug arrangement with this sucker and sure as hell do not feel like swapping resistors out. Thanks!


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## was ist los?

I believe he merely copied the schematic on the datasheet.


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## null

could someone build this for me?


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## eric343

Quote:


  Originally Posted by *kevin gilmore* 
_board picture
http://gilmore.chem.northwestern.edu/micro.pdf
 Yes that is real size .9 x .9 inch.

 You solder the chip thru the backside of the board then solder
 on a piece of copper that is .3 inch wide and about 1 inch long._

 

I think that PDF's scaling is a bit off. I printed it out and there's no way you could solder the chip on that -- the pad spacing is off by a few mils, and the board is for a chip package .193in wide vs. the TPA's .292in...


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## chillysalsa

Looks really interesting.. 
 Dip16amp (or anyone else) - how would one rank the sound of this with your X16 Gilmore amp or RA-1 with a pair of Grados? If bass is so good, everything else fall into place as well?


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## kevin gilmore

Correct, wrong package. Working on fixing that now. Glad i did
 not have boards made yet. This whole heatsinking thing is a pain.
 Nice thing however is that the chip is symetrical. So with a little
 work you can solder it in upside down. Then you can attach a real
 heatsink.

 fixed file with same name uploaded. This is the top copper and silk only.

 On my printer the vertical size is exact and the horizontal is ever
 so slightly small.


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## DCameronMauch

Quote:


  Originally Posted by *kevin gilmore* 
_Nice thing however is that the chip is symetrical. So with a little work you can solder it in upside down. Then you can attach a real
 heatsink._

 

That's exactly what I was thinking. Going to pick up some random cheapo soic chips localally to practice bending the leads with some tiny needle nose pliers. I am somewhat worried about the mechanical strain this places on them. Mostly the output pin. Besides making it weaker, doesn't it also add a little resistance at the bend? With regular through hole stuff, when I need to bend it, I always use the shaft of a small screw driver to get a nice rounded bend, thus minimizing the strain. I am kinda suprise this chip is not available in any other type of package.

 Started working on a PCB design myself. But I think I want to use two of these chips for balanced output. One chip per channel. One side inverting, the other non-inverting. Should do the trick nicely. Though this doesn't apply to my intended implementation, the voltage rails could be a lot lower this way too. Downside is you now have two protection output resistors in series with the load, thus slightly lower damping factor. I use HD650s, so with their 300 ohms, it shouldn't be a big deal adding 2x 10 ohms.


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## kevin gilmore

How's this for nutty. Buy a bunch of the zero ohm surface mount
 ultra tiny resistors. Then solder them to the board. Then solder
 the chip to them. No bending of pins.


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## DCameronMauch

Wow. That is pretty nutty. But I would expect nothing less from you. 
	

	
	
		
		

		
			





 My PCB is coming along nicely. Hope to have it posted by end of day.


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## Earwax

1) On a scale of CMOY -> Meta42 -> PiMeta -> PPA where would this thing rate? 

 2) Would the chip fit on one of these BrownDog adapters? 
http://cimarrontechnology.com/index....WPROD&ProdID=6
 Assuming there's a way to deal with the heatsink issue...


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## dip16amp

Quote:


  Originally Posted by *chillysalsa* 
_Looks really interesting.. 
 Dip16amp (or anyone else) - how would one rank the sound of this with your X16 Gilmore amp or RA-1 with a pair of Grados? If bass is so good, everything else fall into place as well?_

 

I like my X1 amp (ra-1) for portable battery power use and X16 amp (gilmore) for home use. The TPA6120 bass is the most noticable thing over my X1, X3, X12 and everything else also sounds good so far. My X12 amp (ppa circuit) is using opa627 and double buf634 on each channel, so I can't compare it to a standard PPA. My concern of the TPA6120 is on battery power as it won't run as long as the X1 without a bigger battery pack. Runs good on my dual voltage power supply but not as good as my X16 amp.
 The TPA6120 draws 21.7 mA on my +14 volt supply and 21.6 mA on my -14 volt supply.
 The X1 draws 8.2 mA on each 9 volt battery.
 The X16 draws 106 mA on each 14 volt supply.


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## DCameronMauch

Okay. Think I finished my PCB layer for this sucker. Using two TPA6120A2s for balanced output. Three AD8620s. One per channel and one for buffering ground for the non-inverting configuration feedback loop of each TPA. I like keeping absolutely all current off my ground planes. The circuit includes the Meier crossfeed circuit too. All opamps have their power JFET isolated. Here is the PCB layout in PDF format. I don't have a schematic drawn. For me, the PCB layout is the schematic. If anyone is interested, I can provide the Cadsoft Eagle format layout file. Also I guess I could draw up a schematic. The layout includes six large vias per TPA for the power pad. Should be empty space left inside to get solder through from the back side. Also didn't fill the ground plane under the critical areas of the TPA as the data sheet recommended. Whole board is 3" by 2.5". The the power, there are 3x 18mm caps and 10x 8mm caps. I planned on using Nichicon KZ series. The two big squares are Panasonic 470nF ECWF metalized polypropylene caps for the xfeed. I had to place a few resistors under them to keep the board small and get everything routed nicely. All resistors are SMD1206 variety. Attached is a tiny low resolution gif image of the board. The PDF is much high quality.


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## aos

It's hard to follow the circuit without schematics, but I don't understand what you did there - there's ground driver for one side of the balanced configuration but not for the other (it's grounded directly to ground plane it seems)? Also, unless you own $300 Cardas balanced cable, what good does it do - I mean, from practical perspective (the benefits of completely separate channels are obvious but without headphones that are wired in such fashion, and inability to get the connectors to make your own cables, it's useless)?


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## DCameronMauch

Attached is the schematic. That should make it a little more clear what I am doing with the grounds. Only the high impedance + terminal of any given amp chip is connected to ground. No current there. The feedback loops of the TPAs definitely have current flow. Thus the ground buffering. Amps 1-3 are AD8620s. Amps 4-5 are the TPAs.

 I purchased the Cardas regular headphone cables. Both those and the stock HD600 cables were four conductor all the way to the plug. So I just chopped off the plug and put on a four conductor XLR. Easy.


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## aos

Why don't you drive the other TA with the same ground driver instead of through ground plane then? You're losing the symmetry. Your other opamp is driving the same combination anyway (non inverting plus inverting). Neat idea otherwise.


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## DCameronMauch

Both TDAs have their own seperate ground buffer for the non-inverting feedback loop. Those two ground buffers are done with an AD8620 dual channel opamp. Take a close look at the schematic. It is completely symmetrical.


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## aos

No, your non-inverting input is tied to ground, not buffered ground. That makes it non-symmetrical. Since the other opamp already drives inverting and non-inverting inputs anyway (signal driver) I don't see why can't the ground driver do the same and drive ground for both inverting and non-inverting.


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## DCameronMauch

I'm not following. I don't see any difference between the way the two TDAs are being driven. Do you mean the two opamps inside the TDA? The inverting one has 50 ohm to ground on the + pin. I didn't buffer that ground because there is no current flow there. The non-inverting has the AD8620 going through a 50 ohm to the + pin. And the feedback loop is going into the ground buffer. Could you download the image, circle what you mean, and post it back up?

 Edit: Did you notice the opamp input pins are + on top on some and - on top for others? I did that to make the schematic visually symmetrical.


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## aos

Your 3's are driving the inverting pins of upper 4 and lower 5, but not the non-inverting pins of lower 4 and upper 5. There might not be (much) current there but it would still be symmetrical to connect them to 3's outputs. At the very least it will add to the offset, though in all probability it won't make much difference - but then you're already adding opamps to drive the ground which in itself probably won't make much difference.


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## DCameronMauch

Oh, okay. Now I'm following you. Sorry about that. I was thinking in terms of opamp with an inverting or non-inverting configuration. Not the input pins themselves. I had not considered the DC offset of the AD8620. This might be a case to pick the better grade. I checked to see if there was any easy way to route the other ground connection to the buffered ground. Unfortunately, there isn't. Looking at the data sheet for the TPA, it says the input impedance is 300k. Is that the + terminal? I would imagine for a current feedback design, the - terminal should be a great deal lower than that. Anyways, I was expecting something greater than a few meg. So there may be a tiny bit of current flow, but still quite minimal. Shouldn't disturb the ground plane too much. I'm not sure though if the DC offsets would cancel eachother out or double up at the headphones. In the second case, it might be better to only have one side subjected to the offset.


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## null

Sooooo.... anyone gonna take on building it for me? I'll pay them.


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## Kenny12

hm... how large a heatsink do you need? 

 also anyone have a simple layout for this thing?


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## TrevorNetwork

I still want to hear this one AOS 
	

	
	
		
		

		
			





 If its as good as people say it is, it should beat a PPA no?


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## ppl

This chip is a relabeled DSL Driver and there are plenty of DSL driver chips that will do the same thing and my fav is the LT-1210 1.8 Amps out put current and easy to deal with TO-220 http://www.linear.com/prod/datasheet.html?datasheet=217
 slightly less output current 450 mA is available from elantec 
http://www.intersil.com/data/fn/fn7039.pdf

 My favorite configuation for any CFB op amp is what is called a composit op amp made by using a Multi-Loop technique to meld a conventionial VFB opamp and a CFB output stage. This is described in this TI/BB app note and will work with the Headphone driver discribed and any other CFB type of op amp. I like AD-8610 and LT1210 for a compoisit op amp that you can directly hang a Volume pot on the input. You will be limited to low resistence pots if using this in a cmoy type circuit as the input Bias current will result in a changing DC offset with different Volume comtrol posistions. see this link for more info
http://focus.ti.com/lit/an/sboa002/sboa002.pdf


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## morsel

Trevor: No.


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## TrevorNetwork

Morsel,

 I was being facitious. There is a large amount of hype surrounding this chip. I think many of us would be happy the results were indeed good.






 Trevor


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## Garbz

ur setting goals a bit high. Beating ppa is pretty difficult. It will beat Cmoy and A74 and similar amps possibly.


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## intlplby

ok so i was planning on building a PPA but i dont have the money to do that right now.....

 i am thinking of building gilmoures 16dip with this amp.....

 they would be for use with RS-1s

 any recommendations as far as using it with rs-1s?

 what type of pot should i use?

 how is the LED resistence going to effect the circuit?

 what voltage should i run it at?

 i think i can devise quite a decent heatsink for that amp that should dissipate quite well

 i'll show it when i am done


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## DCameronMauch

If anyone is interested, here in post #3 is a schematic combining the new OPA1632 single ended to differential converter with the TPA6120A2. Designed for balanced output with HD580/600/650s.


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## phugger

If I were to build a very simple amp from the chip, would I just have to build the circuit to the right of OUT A through D on spec sheet pdf?


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## blackreplica

Hi there everyone,

 I am quite a newbie to this forum(my only other posts over in headfi was with regards to an AudioTechnica earphone review i wrote in the phones forum) but am quite keen to give the DIY headphone amp thing a try.

 I've already ordered the parts i will need to make a CMoy and that will probably be my first project. 

 The specs of this new chip though, just cant be ignored. I'm now also considering giving this chip a try in a second project if the first one goes well.

 With regards to the attached schematics(which i got from the TPA6120A datasheet), does anyone here think that it would NOT be a good idea to give these a try? I hope to use 2 in-series 9V batteries for a +9V / -9V power supply. I'm also wondering which one i should try to build first. I'll probably go with the first one since it has higher gain. The third one is if i want to incorporate balanced inputs with the amp right? I'm not sure if differential = balanced but i am assuming it to be so.

 Lastly, can anyone also suggest a pot value to substitute for the input resistor? Will i still need a resistor on the inputs after the pot, and if so, could someone suggest a value as well? I need variable input sensitivity because i plan to hook the amp up to my PC soundcard outputs.

 Thanks everyone for your patience, and for taking the time out to answer so many of my questions.


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## intlplby

yeah i am going to make this as well but also want to know what to use for the input pot

 David Gilmore i think used this schematic but it might be dip16amp 

http://f2.pg.photos.yahoo.com/ph/dip...&.dnm=39fd.jpg

 and in it he used the same setup as the spec sheet for the TPA6120a but for Rs instead of the 50 he used 100


 i was looking at the panasonic evj pot or an alps rk27 pot

 should i use a 10k or 50k pot? will the Rs value change for either of these?

 what is the DC offset of the dip16amp setup used? is an input cap necessary? if the dc offset is too high could it be solved by changing the gain instead in order to avoid bass roll off and phase distortion?

 as far as parts i figure vishays/dales from mouser
 pot from digikey
 neutrik 1/4" gold plated vertical jacks (anyone recommend a source or a different type of 1/4" jack?)
 goldplated dip16 from mouser

 i am looking for metallized polypropelyne or regular polypropelyne. whats a good brand and source for these?


 i plan on using these with grado rs1s so i figure i need a lower gain and higher current

 -------------

 on a side note has anyone tried mounting an amp in a tube type setup?

 e.g. 

 _____________ __________
 input [ [ ] | ] output
 ------------>>>> [ **** <<<<--------------
 input [_________[__]__|________] output

 amp^

 please pardon the horrible diagram.....

 but basically i am suggesting mounting the amp and battery cells in the base of the tube and nead the end mount the pot on the same axis as the tube

 have the amp be made of two tubes - base side with amp and input and and end cap with the output but since the pot is mounted on the same axis as the amp the end cap would serve as the volume knob

 some sort of coupling would have to be devised to prevent the two caps from pulling apart 

 bottom cap

 _______ 
 | /
 |---/

 end cap

 ___________
 //

 together
 _______ ___________
 | // /
 |---/

 in addition there would be problems internally with twist for the 3 connectors going from the amp to the output jack on the end cap....

 the connections could be incorporated into the outside of the coupling joint as outline above by having 3 rings (L,R,G) on the bottom and end caps and a tight fit plus a conductive grease....... it would work kind of like the bottom cap was a jack and the end cap was the plug or vice versa.....

 perhaps you could even use a 1/4" jack at the end of the pot shaft so that when you push in a 1/4" plug it terminates at tip of the pot shaft then you just "key" the tip of a 1/4" plug so it fits into the pot shaft tip and turns it when you turn the end cap

 i know that sounds convoluted but i will try to make a diagram for you all in illustrator


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## dip16amp

I connected the input directly to my soundcard and connected the output directly to my headphones. I use the soundcard volume control to adjust the level. The 100 ohm resistor happened to be what I had on hand and I haven't tryed a 50 ohm yet. The DC offset is less than 2 mV as long as the input is connected. Otherwise, it will go to the rails. See the user manual for it's eval board for more about that.


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## intlplby

if you were to use a pot would you use a 10k or 50k or some other value?


 and since the dc offset is low i guess there is no need for an input capacitor


 what would you set the gain to for grados?


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## dip16amp

I'd probably try the 50K pot. I'm using the gain in the data sheet figure 24 of 2 V/V with the 1K ohm resistors in the circuit for my Grados. My sound card volume control level is currently set at -40 dB for normal listening.


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## Garbz

just a question on what type of surface mount resistors would be best for this project, i've never used any before.

 from Rs-Components i have access to...
 0603 1%
 0805 1%
 and 1206 1% I believe is the other option. 

 There are 5% resistors availuble but i don't think it's wise to get them. The resistors above are marked as thick film resistors and have RS part numbers around 422-0315. Any recomendations?


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## blackreplica

Hi everyone

 Thanks for the help so far. I will probably put a 10K pot on the inputs(have one spare). Will this be ok if i just use this with the 50 ohm input resistor? Does anyone see anything wrong with trying this out?

 I have a problem though....i cant get my hands on the TPA6120A chip in Australia. Are there any aussies here who know where to get one or does anyone know a website where i can order the chip online? I googled, but nothing came up. Called all the burr brown distributors in sydney as well but none bring in the TPA6120 
	

	
	
		
		

		
		
	


	




 With a chip that specs this well, you'd think the distributors would be all over it lol.

 Any help appreciated!


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## dip16amp

Maybe you can buy the evaluation module from ti online. For only $49, you get their board and a lot of good parts already put together. Just have to add a power supply.


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## blackreplica

Thats an interesting idea! Do you have the link to the evaluation module? I tried searching TI but couldnt find it.

 Is it anywhere on the TPA6120A page?

http://focus.ti.com/docs/prod/folder...tpa6120a2.html

 EDit: oh wait, i think i found it, am checking up on it now


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## blackreplica

Hmm...i definitely like the look of it....might definitely give it a try(although nothing beats making it yourself eh?). I'm quite new to chipamps, is it normal for TI to offer evaluation boards for their chips like this one? I'm pretty surprised no one has tried it yet! Also, the schematic for their evaluation board looks very much more complicated compared to the application diagram found on the chip's data sheet(that schematic was the one i was initially planning on following). I suppose its a stupid question to ask, but which one is better?


 BTW i have attached the schematic for the evaluation board here.

 ROFL...the pics too small now that it fits in the attachment limit,

 the link to the evaluation board pdf and schematic is here:
http://focus.ti.com/general/docs/lit...9&fileType=pdf


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## dip16amp

The schematic is basically the same since R13, R14, R15, and R16 are not installed. R11 and R12 are just jumper wires. They did add the 4.02K ohm resistors R9 and R10 to keep the DC output offset down. They also added capacitors to make sure the power was good. These changes do make it better.


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## intlplby

how about their part selection... is there room for improvement in selecting the quality of parts?

 they got panasonic caps from digikey
 tdk ferrite beads from digikey
 vishay and thin film technology resistors from vishay and thin film technology
 rca jacks from switchcraft
 usm eyelets banana jacks from bisco
 aluminum shandoffs from digikey
 switchcraft kheadphone jack from digikey

 are there components there that you would replace?


 i didn't list it all the part numbers but they are found in table 4.1 of the EVM pdf file

 and as far as the pot.... panasonic evj or alps blue? which is better?


 what other changes would you make?


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## blackreplica

is there a pot in the evaluation board? i didnt notice it...which part is it from the table?

 dip16amp> Thanks a lot. The more i think about it, the more i like the idea of giving the board a try. Some of the components in there look pretty good. I'm not very familar with electronic components and branding but i've heard some good things about the panasonic caps and the vishay resistors at least.

 maybe i could just mount the evaluation board in a case and extend the inputs/ outputs to the case and that would be it. Oh yes, not forgetting the power supply too


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## dip16amp

If you need a volume control, then you would need to add a pot. Alps blue would be better than a Panasonic EVJ but either would work fine. A stepped attenuator would be best.

 For portable use, two 9 volt batteries would work but a +15V and -15V power supply would sound better for home use.


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## intlplby

just to confirm before i place my order.

 which would be better to drive grados... this tpa6120a evm or an A47?


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## dip16amp

The TPA6120 has much more power than the A47 and works best with a dual voltage power supply. It may not run as long on batteries as the A47 though.


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## intlplby

will that much more power make much of a difference for hp-1000s?

 what would you suggest for a DIY portable dual power suppply if i choose the tpa6120a


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## DCameronMauch

The bass will probably sound pretty weak with the TPA and Grados. My reasoning being the required 10 ohms output resistance for stability. Given the Grados are only 32 ohms to begin with, this will mess up the damping factor pretty bad. I believe Kevin Gilmore also said he tried it, and the bass was in fact pretty weak.

 On a second thought, please take a look at the attached schematic. Got a technical question. Pretty sure, but want to be certain. If this TPA configuration is driven with a true balanced input, the ground connection shown shouldn't be necessary. It should float at ground. Am I correct? The voltage at the inverting inputs on either side should be equal in magnitude but opposite in polarity with respect to ground. So given the two 1k resistors are matched extremely well, that point should be virtual ground. Does this reasoning stand up?


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## dip16amp

I find the bass to be stronger than the BUF634 buffer. Could try a couple of 12V battery packs. If you want a good portable amp for Grados, then I would go with the RA-1 circuit.

 I think the ground is needed on the 1K ohm resistor to set the gain and to keep the DC output offset from going to the rails. Figure 26 on the data sheet would be a true differential circuit for the TPA6120.


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## intlplby

i really would ideally like to build a PPA, but

 1) i can't afford to build it now. if i am going to build it i am going to go all out and that is going to be like $250USD

 2) I have some experience building circuits, but never audio circuits so I am going to start with something simpler.


 so it's between an RA-1 and an A-47 i guess

 i was looking at Sijosae's amps on headwize and they are beautiful....

 how do other DIY amps like the porta corda, basic szekeres and mini SDS do with grados?


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## 00940

Quote:


  Originally Posted by *intlplby* 
_basic szekeres and mini SDS do with grados?_

 

The szekeres is very good. You could also have a look at the Zen headamp.


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## DCameronMauch

Quote:


  Originally Posted by *dip16amp* 
_I think the ground is needed on the 1K ohm resistor to set the gain and to keep the DC output offset from going to the rails. Figure 26 on the data sheet would be a true differential circuit for the TPA6120._

 

But I'm not going balanced to single ended. I'm staying balanced. So I'm using the TPA as dual buffers. Exactly like figure 24.


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## intlplby

i can't seem to find a thread about the MINT with grados (or the pimeta)


 it seems that whenever i use the search function it always finds a bunch of irrelevant threads because the keywords happen to be part of people's signatures


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## chrisallan

I managed to build a test model with a regulated +/- 12v power supply and have the chip on a small piece of pcb with the pad soldered to a wide copper track which in turn is clamped to a small heatsink. It is working but had some noise at turn on - then the chip gets fairly hot. Anyone managed to make a simple pcb for this chip - and could lengths of leads to the legs cause the noise? 
 Sorry - no pics at the moment.


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## peranders

I have ordered samples and will definitely make a pcb. This will be an autum project.


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## dip16amp

Quote:


  Originally Posted by *chrisallan* 
_I managed to build a test model with a regulated +/- 12v power supply and have the chip on a small piece of pcb with the pad soldered to a wide copper track which in turn is clamped to a small heatsink. It is working but had some noise at turn on - then the chip gets fairly hot. Anyone managed to make a simple pcb for this chip - and could lengths of leads to the legs cause the noise? 
 Sorry - no pics at the moment._

 

Should be ok if the .1 uF caps are within a quarter inch of the chip. Otherwize, it may be oscillating and causing it to get hot. It should only get warm under normal use.
 Did you include the 4.02K resistors that are shown in the evaluation board manual. That will keep the DC offset down when there is no source connected. It will go to the rail and draw mad current without it.


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## chrisallan

I've had another shot at this project. Better heatsinking, better wiring and added .1 uF caps 4.02K resistors as per the EVM. I've managed to get noise almost down to nothing but am getting a channel imbalance problem. It's suspiciously like the problem a gainclone had when one of the input signals was inverted : although the stereo image sounds fairly even, vocals are pulled to one side. Also if I pull one of the inputs, the result is a mono, centered signal. This only happens one one channel. I've checked the wiring several times to no avail. Anyone had this. I suspect the vocals show the effect most as it effects the signals most that are identical in each channel.
 Weird!


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## dip16amp

Seems like maybe a ground problem. Make sure all the grounds are connected together. Shound be grounds for power, input signal, output signal, and the negative input resistor for unbalanced use. Should also have the 10 ohm resistors in series with the outputs and 50 ohm resistors in series with the inputs.


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## chrisallan

It was a very basic problem - incorrect wiring of the heaphone socket - doh!
 Now its really a runner, incredibly clean and fast sound - no muddling of complex pieces, plenty of volume and plenty of space around the sound.
 I'd like a bit more bass, but apart from that, Im very pleased with it.


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## DCameronMauch

A suitable opamp could be used with the TPA as a buffer inside it's feedback loop. That would address the 10 ohms output impedance / damping factor problem with low impedance headphones.


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## HiGHFLYiN9

Quote:


  Originally Posted by *intlplby* 
_i can't seem to find a thread about the MINT with grados (or the pimeta) it seems that whenever i use the search function it always finds a bunch of irrelevant threads because the keywords happen to be part of people's signatures_

 

The mint sounds very nice with my SR225s and my D-EJ2000


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## was ist los?

Just built this amp a few days ago, sounds very good. It's the only amp next to the Gilmore Dynamic and A47 i have not been disappointed by after hype.
 I still have quite high dc offset even with 4.32k resistors from the input to ground, around 20-30mV.


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## was ist los?

Well did a bit of tweaking and got dc offset in half by adding .01uf caps.


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## DCameronMauch

I sent some email to TI asking about the possibility of getting a spice model. Here is what they said:

  Quote:


 Thank you for your inquiry regarding the TPA6120A2. Unfortunately, the product group has chosen not to offer any simulation models on these devices. Please let us know if there are specific questions you would like answered which will assist in your application and/or design. We apologize for any inconvenience this may cause and if there is anything else that we can help you with, please let us know. 
 

Bumber. Not sure why they chose not to make a model. I guess they figure the expense of making the model is not worth any additional interest in the product and thus additional revenue.


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## Question

Hi,

 Anyone have any new experience with this chip lately?


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## peranders

This is my most successful amp design so far despite the fact that it's made of SMD parts.


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## mendiola

Dear All:

To achieve a gain of 5 Can I use a Rf=5000 ohm and Ri=1000 ohm or Do I have to use Rf=1000 Ohm and Ri=250 Ohm ?

I will use the R9 resistor = 1.6K to reduce the DC offset voltage.

Schematic: (Evaluation Board)
http://www.ti.com/lit/ug/slou169/slou169.pdf


Regards.
Alfredo Mendiola Loyola
Lima, Peru


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## mendiola

Dear All:

To achieve a gain of 5 Can I use a Rf=5000 ohm and Ri=1000 ohm or Do I have to use Rf=1000 Ohm and Ri=250 Ohm.?

I will use the R9 resistor = 1.6K to reduce the DC offset voltage.

Schematic: (TPA6120A2 Evaluation Board)

Gain = ( 1 + (Rf/ri))

Regards.
Alfredo Mendiola Loyola
Lima, Peru


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## jcx

for CFA op amps compensation, "speed" depends on the value of the feedback R
  
 using 5k Rf will slow the chip, make it a little more stable, but applies less feedback possibly giving a little more distortion
  
 the +,- inputs of CFA op amps are not the same, balancing Z seen at +,- inputs doesn't help offset as much as it does with VFA bipolar input op amps
  
 lowering the + input R to gnd value does reduce Voffset - but is a heavier load for your source
  
 raising the feedback R increases Vos from the - input bias current
  
 the THS6012 data sheet is invaluable too - more DC specs - they are the same chip
  
  
 for headphones that the TPA6120 is a good choice to drive the Vos shouldn't be a problem but it isn't the chip's best performance spec - a DC servo, output blocking cap or a better DC spec input op amp in multiloop around the TPA as output stage all would be better on Vos


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## jasonhanjk

mendiola
 
 No.
  
 You should gain up using opamp at the front stage.


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## peranders

When you increase the feedback resistor you will get more instability. Check also the datasheet.


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## jcx

simply wrong there - for CFA the feedback R directly enters the GBW product equation - the larger  the R the slower and more nearly single pole the open loop gain - increasing feedback R overcompensates CFA op amps
  
 the effect you may see and misinterpret is that CFA are very sensitive to parasitic C on the -input, particularly any output to -input parasitic C
  

http://www.ti.com/lit/ml/sloa080/sloa080.pdf


> The manufacturer determines the optimum value of RF during the characterization of the
> IC. Referring to Figure 8–6, it is seen that when RF exceeds the optimum value recommended
> by the IC manufacturer, stability increases. The increased stability has a price
> called decreased bandwidth.


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