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Power supply for rechargeable portable DAC/headphone amp
Power supply for rechargeable portable DAC/headphone amp
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Old 15th December 2017, 01:39 PM   #1
Nikolai Petrenko is offline Nikolai Petrenko  Viet Nam
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Default Power supply for rechargeable portable DAC/headphone amp

I am planning to build a portable DAC/headphone amp with balanced output (not just a part of portable player, but also as an "output soundcard" for my music processing)

I want to use an 18650 battery since their shape allow easy replacing, pretty enough capacity and most important: rechargeable. Also because primary cells occupied a lot of space. But DAC chip and opamps need higher, even isolated or symmetrical power supplies.

But I am considering about choose voltage booster. TPS65135 or other transformerless method vs inverter style (convert DC to AC/pulse before supply to multi-output transformer). Any comparison of small, high efficiency, low EMI, easy-to-suppress ripple? Two later features are more important.

Thanks!
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Old 15th December 2017, 01:53 PM   #2
abraxalito is offline abraxalito  United Kingdom
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Depending on what impedance headphones you're driving (and hence the voltage swings likely to be needed) you may only need a voltage doubler IC. I'm using LM2662 for this purpose in my DACs and headphone amp - it has no shortage of output current (200mA) is low cost and lowest EMI (by virtue of being a charge-pump rather than a boost converter needing an inductor). If you need a negative voltage too you can use another LM2662 to deliver that - the boost mode needs an external diode to prevent latch-up.
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Old 15th December 2017, 03:00 PM   #3
Nikolai Petrenko is offline Nikolai Petrenko  Viet Nam
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Originally Posted by abraxalito View Post
Depending on what impedance headphones you're driving (and hence the voltage swings likely to be needed) you may only need a voltage doubler IC. I'm using LM2662 for this purpose in my DACs and headphone amp - it has no shortage of output current (200mA) is low cost and lowest EMI (by virtue of being a charge-pump rather than a boost converter needing an inductor). If you need a negative voltage too you can use another LM2662 to deliver that - the boost mode needs an external diode to prevent latch-up.
I use an 16 Ohms orthodynamic headphone. Any suggestion? Many information seem about 32 Ohms dynamic headphones, not ortho.
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Old 16th December 2017, 09:54 AM   #4
abraxalito is offline abraxalito  United Kingdom
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With 16ohm load impedance you might not need any step-up converter at all. I have an SE classA amp powering my 56ohm Superluxes which does fine, no shortage of volume running on a single 18650 with no step-up. What's the sensitivity (dB/mW) of your 'phones?
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Old 16th December 2017, 01:24 PM   #5
Nikolai Petrenko is offline Nikolai Petrenko  Viet Nam
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Originally Posted by abraxalito View Post
With 16ohm load impedance you might not need any step-up converter at all. I have an SE classA amp powering my 56ohm Superluxes which does fine, no shortage of volume running on a single 18650 with no step-up. What's the sensitivity (dB/mW) of your 'phones?
Mine is 94 dB/mW SPL, seem medium.
Can you also give my suggest about volume control method. I have terrible experience with small stereo potentio. Accuracy enough pot seem only too large. I have no experience with digital volume control.
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Old 16th December 2017, 02:11 PM   #6
JPS64 is offline JPS64  Germany
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Power supply for rechargeable portable DAC/headphone amp
@Nikolai

TKD 2CP601 potentiometer not soooo large but not cheap.

My 2 cents.

JP
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Old 16th December 2017, 02:44 PM   #7
Nikolai Petrenko is offline Nikolai Petrenko  Viet Nam
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Originally Posted by JPS64 View Post
@Nikolai

TKD 2CP601 potentiometer not soooo large but not cheap.

My 2 cents.

JP
I think they are not cheap immediately after see the image
Channel matching seem good enough
But I wish I could make smd stepped attenuator I like the feel of mess up with crazy small stuff

Last edited by Nikolai Petrenko; 16th December 2017 at 02:48 PM.
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Old 16th December 2017, 03:41 PM   #8
JPS64 is offline JPS64  Germany
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Power supply for rechargeable portable DAC/headphone amp
... a few mA more from battery!

JP
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Old 17th December 2017, 03:38 AM   #9
Nikolai Petrenko is offline Nikolai Petrenko  Viet Nam
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Originally Posted by JPS64 View Post
... a few mA more from battery!

JP
What about TPS6513x series? I just began feel scare of discrete or low integration method.
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Old 17th December 2017, 04:38 AM   #10
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by Nikolai Petrenko View Post
Mine is 94 dB/mW SPL, seem medium.
By my calculations you'll only need 1.8V peak to reach 120dB so no need for step-up.

Quote:
Can you also give my suggest about volume control method. I have terrible experience with small stereo potentio. Accuracy enough pot seem only too large.
My suggestion would be to build an integrated DAC-amp using TDA1387 as your DAC. Its volume can be adjusted by a DC voltage control on its 'ref' pin so no need for any pot. Or alternatively use digital volume.
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