kamieldehond
New Head-Fier
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- Jan 5, 2015
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Did some research on the internal architecture of the Mixamp. It seems that bypassing the internal amp is not only doable but not that difficult. Let's take a look.
Images are blurry but the AKM logo is clearly visible. Moreover, by applying CSI-level image enhancement techniques (commonly known as crop and squint) we can conclude that the final digits of the product number are 86 followed by letters VT. There is only one AKM chip with those letters in that order and that chip is AK4386VT DAC.
http://www.akm.com/akm/en/file/datasheet/AK4386VT.pdf
Pins 10 and 11 are right and left channel analog output respectively. These are 2V so pretty much line-level output. I don't know whethere these can be directly soldered to a jack for a true line-out but This is interesting enough to investigate. If anybody here has any experience with DAC-building, SMD components and such please weigh in. True line-out for the Mixamp (not the noisy Stream Out port) would be helpful.
Does not look like the chip is intended to be used directly as a line out. There is no mention about short circuit protection and esd protection.
They mention 25pF max load capacitance. This is very low because 1 foot audio cable will probably exceed this maximum. Not to mention all the other parasitic capacitance.
If you want to try it you need to add a large capacitance in serie with the output signals to block the dc output voltage. Otherwise if the amplifier you will use does not have a dc block you can damage your headphones.
If you want to modify the mixamp to have a line out I would look at the following possibility: use the digital I2S signals that go to the AK4386VT and connect them to a spdif transmitter. This way you create a mixamp with a digital output that you can connect to any optical dac. Something like this might work http://m.ebay.com/itm/112049871117
It is just an idea. I have not looked into this idea.