Hello,
I got a new MP3 player and its mighty quiet. Too quiet. I need to build a portable headphone amplifier for it and my Grado SR 80s (and occasionally my Senn MX-500 earbuds which are even quieter).
I'd really like to design and build an amplifier, but I need recommendations for chips to base it off of. I did some Op Amp work a while ago in school, I still have my old texts, but I need some silicon to start from. If there's pressing need to go away from simple to do Op Amp systems, please elaborate. I'm listening.
Efficiency is a concern. Size would be nice.
Sound quality is semi-nice, but I dont plan on taking extrodinary measures in this project, given that my mp3 player itself doesnt produce the best sound. I'm hoping that it provides good sound at lower volumes, produces less clipping, and that a good pocket amplifier will give me better volume with better sound.
I'm assuming I'll need a very efficient dc-dc converter as well. my mp3 player uses a single aaa battery. i'm probably going to rip it out of its shell and use an aa battery, maybe go dual aa if the amp warrants it.
I've been checking HeadWize, but most of that seems to be non-portable systems. My searching here has resulted with a similar lack of starting place, although I have found a number of interesting in depth discussions. I believe with a starting place I'll be able to do far better research. Thank you for your assistance.
What silicon to use?
thanks
myren
I got a new MP3 player and its mighty quiet. Too quiet. I need to build a portable headphone amplifier for it and my Grado SR 80s (and occasionally my Senn MX-500 earbuds which are even quieter).
I'd really like to design and build an amplifier, but I need recommendations for chips to base it off of. I did some Op Amp work a while ago in school, I still have my old texts, but I need some silicon to start from. If there's pressing need to go away from simple to do Op Amp systems, please elaborate. I'm listening.
Efficiency is a concern. Size would be nice.
Sound quality is semi-nice, but I dont plan on taking extrodinary measures in this project, given that my mp3 player itself doesnt produce the best sound. I'm hoping that it provides good sound at lower volumes, produces less clipping, and that a good pocket amplifier will give me better volume with better sound.
I'm assuming I'll need a very efficient dc-dc converter as well. my mp3 player uses a single aaa battery. i'm probably going to rip it out of its shell and use an aa battery, maybe go dual aa if the amp warrants it.
I've been checking HeadWize, but most of that seems to be non-portable systems. My searching here has resulted with a similar lack of starting place, although I have found a number of interesting in depth discussions. I believe with a starting place I'll be able to do far better research. Thank you for your assistance.
What silicon to use?
thanks
myren
the Chu Moy Pocket Amp is a portable design and goes into a lot of detail about the design.
Another good portable amp sit is
http://tangentsoft.net/audio/
and a links page that is more or less headphone amp specific :
http://www4.head-fi.org/forums/showthread.php?t=21563
Check www.headwize.com, projects section:
http://headwize.com/projects/index.htm
The best reference for headphone amps on the net.
Bye...
http://headwize.com/projects/index.htm
The best reference for headphone amps on the net.
Bye...
Start out doing a simple Cmoy amp based on OPA2132/2134. If you like, you can then experiment with different opamps to see what your prefer (commonly used types for headphone amps are OPA(2)227/(2)228, OPA(2)604, OPA627/637, AD8610/8620, AD823, AD843, AD845 and a few others). If you then want something better, then check out one of the designs from the tangentsoft-page linked above or start digging in the headwize archives for something you think looks interesting. Happy building 
/U.
PS: The chip jackinnj is referring to is called TPA6120.
/U.
PS: The chip jackinnj is referring to is called TPA6120.
Don't you think it'll get too complex with a dc-dc converter? It would increase circuit size, also this could introduce switching noise...
For my tiny portable mic preamp, I'm planning to use those hearing aid batteries (Zinc-Air) which exist in several sizes and the strongest are 11.6mm diameter, 5.4mm thick, 1.4V with over 500mAh!! That's a lot of capacity! And the OPA228 works fine with +- 4.2V, which means two times 3 cells, so 11.6 x 32,4mm.
Of course, you'd better estimate how much current the circuit will consume before choosing the batteries.
Regarding the choice of OP-amps, there are a lot, but do you want to build surface-mount or conventional style? Some of the newer OP-amps only exist for surface mounting.
Cheers
Dominique
Edit: I'm not sure if I understand you right:
You want to build the amp in a tiny extra box, do you?
For my tiny portable mic preamp, I'm planning to use those hearing aid batteries (Zinc-Air) which exist in several sizes and the strongest are 11.6mm diameter, 5.4mm thick, 1.4V with over 500mAh!! That's a lot of capacity! And the OPA228 works fine with +- 4.2V, which means two times 3 cells, so 11.6 x 32,4mm.
Of course, you'd better estimate how much current the circuit will consume before choosing the batteries.
Regarding the choice of OP-amps, there are a lot, but do you want to build surface-mount or conventional style? Some of the newer OP-amps only exist for surface mounting.
Cheers
Dominique
Edit: I'm not sure if I understand you right:
You want to build the amp in a tiny extra box, do you?
Myren said:
I have been using a TPS61020DRCR STEPUP with a effiency of 96% for a handheld design (Cannot tell you about it... Brandnew hardware for another industry).. And it works like a charm...
It puts out 5VDC from a single AAA cell. and it has a battery low detector.
By the way... Size is 42mm*10mm*5mm on a 1.6mm FR4 PCB.
And it is very simpel to use.
The go for opamp's like AD8027/8028 which can run from singlesupply. Deliver 50mA into a load.
And you can control the crossover region of the input stage...
from the SMPS??
i use 6.2uH inductors from panasonic which is shielded.
Also i use an LC output filter. so i have like 10mVpp at 700KHz.
it is placed in close proximity to a LF trasnponder reader, and this runs with no problem, with no reduction in reading distance.
And they are sensitive to radiated noise.
i use 6.2uH inductors from panasonic which is shielded.
Also i use an LC output filter. so i have like 10mVpp at 700KHz.
it is placed in close proximity to a LF trasnponder reader, and this runs with no problem, with no reduction in reading distance.
And they are sensitive to radiated noise.
thanks
thanks all!
yes, to confirm, i'm looking to build a small single unit portable head phone amplifier. size is an object, and i'm coincidentally quite eager to start some surface mount work.
one or two aa batteries are my ideal power source: i have a bunch of 2200 mah double a rechargables I payed a mint for, but work excellently. i presume most amplifieres will require a +/- voltage. dc-dc convertors will get me this voltage split, i presume. what other techniques are there? i suppose dual battery is another option.
out of a morbid sense of curiosity, how different are the parameters to turn a headphone post-amp into a mic pre-amp? it occurs to me i have a microphone in need as well.
I'm with you guys through everything else, I have absolutely no idea what any of this means:
thanks
Myren
thanks all!
yes, to confirm, i'm looking to build a small single unit portable head phone amplifier. size is an object, and i'm coincidentally quite eager to start some surface mount work.
one or two aa batteries are my ideal power source: i have a bunch of 2200 mah double a rechargables I payed a mint for, but work excellently. i presume most amplifieres will require a +/- voltage. dc-dc convertors will get me this voltage split, i presume. what other techniques are there? i suppose dual battery is another option.
out of a morbid sense of curiosity, how different are the parameters to turn a headphone post-amp into a mic pre-amp? it occurs to me i have a microphone in need as well.
I'm with you guys through everything else, I have absolutely no idea what any of this means:
thanks
Myren
Re: thanks
Yes, that's what I meant. Using 3 of those tiny batteries for + and another 3 for -
Of course a rechargeable AA & dc-dc booster is more economical.
I just opted for those small batteries because of the size and because my project had to be simple and my mic preamp only needs very few current anyway, so the batteries live for a long time, about 100hours.
Well, it should be no big deal - at least with the easy circuit I use for my mic preamp - You could for example use a different feedback resistor. I don't know if there are switches which could do the job fine, I used those jumpers you find in a computer for a similar case to select the resistor I want.
But not every op-amp works stable at that big range of gains.
Cheers
Dominique
Myren said:
Yes, that's what I meant. Using 3 of those tiny batteries for + and another 3 for -
Of course a rechargeable AA & dc-dc booster is more economical.
I just opted for those small batteries because of the size and because my project had to be simple and my mic preamp only needs very few current anyway, so the batteries live for a long time, about 100hours.
Myren said:
Well, it should be no big deal - at least with the easy circuit I use for my mic preamp - You could for example use a different feedback resistor. I don't know if there are switches which could do the job fine, I used those jumpers you find in a computer for a similar case to select the resistor I want.
But not every op-amp works stable at that big range of gains.
Cheers
Dominique
I built a slightly modified CMOY using the Burr Brown OPA2132PA opamp. I used a TI TLE2426 virtual railsplitter instead of the resistors to create a split supply from a single 9V NiMH reghargeable battery. Battery life is still unknown - I've been running part-time on one charge for a few weeks now.
All including volume control fits into a case the size of the iPod (if I could find one). I ended up using a Serpac case that's just slightly longer than the iPod, vut still quite ergonomic. Velcro on the back of the iPod and top of the headphone amp keeps them firmly attached to each other.
Sounds great with my Gen4 iPod and 75 Ohm Sony phones. The volume control is overkill - it's easier to adjust the volume via the iPod. I'd just build the CMOY to a gain of about 8-10 and use the volume control of the iPod. I think if I did it again, I'd forget about the volume pot and case with the replaceable battery compartment, and just build in a charge jack and 9V rechargeable.
Bryan
<edited>
All including volume control fits into a case the size of the iPod (if I could find one). I ended up using a Serpac case that's just slightly longer than the iPod, vut still quite ergonomic. Velcro on the back of the iPod and top of the headphone amp keeps them firmly attached to each other.
Sounds great with my Gen4 iPod and 75 Ohm Sony phones. The volume control is overkill - it's easier to adjust the volume via the iPod. I'd just build the CMOY to a gain of about 8-10 and use the volume control of the iPod. I think if I did it again, I'd forget about the volume pot and case with the replaceable battery compartment, and just build in a charge jack and 9V rechargeable.
Bryan
<edited>
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