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Old 25th November 2012, 07:57 AM   #11
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Take a look of this one http://www.hi-wave.com/downloads/dat...IAM-USB213.pdf
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Old 25th November 2012, 10:54 AM   #12
AndrewT is offline AndrewT  Scotland
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looks like
Quote:
DyadUSB is based on the AS2002, highly power efficient, switching, stereo audio power amplifier from Audium Semiconductor,
is using the 5V from the USB to create a +-9Vdc supply to drive a bridged amplifier (4 channels for stereo). That would expalin the preference for 16ohms to 8ohms speaker recommendation.

But
Quote:
2x 13W peak power output (8ohms)
may really be 6.5W into 8ohms.
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Old 25th November 2012, 11:17 AM   #13
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The chip (AS2002) has a boost converter for maximum ~21 V high-rail voltage. It can therefore deliver higher peak power. This is similar to a boosted Class D.
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Old 25th November 2012, 11:24 AM   #14
qusp is offline qusp  Australia
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Quote:
Originally Posted by AndrewT View Post
looks like is using the 5V from the USB to create a +-9Vdc supply to drive a bridged amplifier (4 channels for stereo). That would expalin the preference for 16ohms to 8ohms speaker recommendation.

But may really be 6.5W into 8ohms.
i'm sorry, but how on earth does a convertor make 6.5W out of a 2.5W supply? they should patent that quickly!! surely you can only increase the voltage at the loss of current, overall power should remain the same minus losses from the convertor
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Old 25th November 2012, 11:41 AM   #15
AndrewT is offline AndrewT  Scotland
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The pdf states that average music power is many times lower than maximum output power.
I happen agree with this statement.
If they designed for an average to peak ratio of 20dB (130mWpeak from a 13Wpeak) amplifier and used a very efficient DC to DC converter to create the supply rails and used a very efficient switching amplifier then it is very possible that the 500mApeak supply @ 5V could maintain the average levels required and capacitor storage can then supply the peak power for the high current transients.

The pdf does state
Quote:
DyadUSB is a USB powered stereo audio amplifier module; designed to be embedded in to USB speaker systems.
and that implies they are designing to suit the limitations imposed by the USB power.
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Old 25th November 2012, 11:56 AM   #16
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The chip is designed for high crest factor signal, music, instead of sine wave. It can deliver high short-term power, but low average power. It uses "big" reservoir caps at boosted high rails.

The board is available at RS http://hongkong01.rs-online.com/web/...ivers/7616037/.

Last edited by panson_hk; 25th November 2012 at 12:04 PM.
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Old 25th November 2012, 12:25 PM   #17
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Quote:
I cannot find anymore that accept the analog signal from the headphone jack which is what I need because the Xbox does not produce a digital audio signal through usb.
LM386, TDA7052, etc. run on 5V @ <500mA and are designed to drive small speakers and headphones. They use simple-to-build circuits that accept an analog input.
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