[TrevorNetwork]

I still want to hear this one AOS

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

 

[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

 

[morsel]

Trevor: No.

 

[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

 

[Garbz]

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

 

[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

 

[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.

 

[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?

 

[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.

 

[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

 

[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.

 

[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?

 

[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.

 

[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?

 

[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!