Hi,
I have a pair of 0.5+0.5:1 line transformers. I have an idea about that if I can connect each primary winding of transformer to each output of AK4399 chip in mono mode separately.
Since the each balanced output of AK chip will carry the same signal, primaries should act like connected in parallel. Maybe it is not a good idea but simulation confirms such implementation with benefits of very low distortion and 2x gain. Another thing is very simplistic method of getting unbalanced signal from two balanced sources. My concern is what kind of troubles I'm going to to deal with in real world conditions.
I appreciate for any opinion on this idea.
Thanks.
Edit: "from two *balanced* sources"
I have a pair of 0.5+0.5:1 line transformers. I have an idea about that if I can connect each primary winding of transformer to each output of AK4399 chip in mono mode separately.
Since the each balanced output of AK chip will carry the same signal, primaries should act like connected in parallel. Maybe it is not a good idea but simulation confirms such implementation with benefits of very low distortion and 2x gain. Another thing is very simplistic method of getting unbalanced signal from two balanced sources. My concern is what kind of troubles I'm going to to deal with in real world conditions.
I appreciate for any opinion on this idea.
Thanks.
Edit: "from two *balanced* sources"
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It should work fine, I did something similar a few years ago with PCM1794A and Sowter transformers.
Pay attention to decoupling the opamps inside the AKM DAC chip - the low frequency loading might be quite significant depending on the primary (shunt) inductance of the particular trafo you choose. It might be better to do the trick I've seen on poweramps - run the two outputs out of phase (digital inversion of one channel) and swap the polarity to one trafo winding to compensate. But then again if 'mono mode' is implemented internal to the DAC this won't be a possibility.
What is the difference between being "out of phase" and "reverse polarity" which in case with swapping legs of one channel ?
They're the same. Inverting the polarity can be 'undone' (made true phase once again) by inverting the polarity again, or 'wiring out of phase'.
In fact since you have two mono'd outputs, you could get the same effect by inverting one output. Then your DAC becomes analogous to a BTL (bridged tied load) amplifier and you could use a 1:1 trafo between the (bridged) outputs to get the 6dB of gain.
<edit> Oops, sorry I see your DAC already has balanced outs so ignore my machinations here! I hadn't read carefully enough that your sources were already balanced.
In fact since you have two mono'd outputs, you could get the same effect by inverting one output. Then your DAC becomes analogous to a BTL (bridged tied load) amplifier and you could use a 1:1 trafo between the (bridged) outputs to get the 6dB of gain.
<edit> Oops, sorry I see your DAC already has balanced outs so ignore my machinations here! I hadn't read carefully enough that your sources were already balanced.
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Yep, there are also some good things about modern Vout type dacs. But this doesn't mean my plans about TDA1387 will be shelved. I'm also not sure about that all Vout type dacs contain an I/V stage with bare opamps. Maybe they are doing some more sophisticated things or maybe they are not containing any internal I/V stage.
You're right, sometimes the internal opamps aren't doing I/V. My understanding is that some DACs are 'voltage mode' (rather than current mode like the older-style TDA DACs) so they've no need for I/V. They natively produce a voltage. This might be because the internal elements are capacitors rather than resistors.
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