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When I have started to play with DAC my idea was to explore the entire world of the DAC chips to find the best.
After the Crystal and Burr-Brown the last chips to test were the Analog Device products like the very good AD1860.
In this case I don't have found an evaluation board or a kit so I have searched a low price product to modify.
I have found the D18 model produced by Monarchy Audio, this is a very interesting company that produce also many class A amplifier without feedback.
The D18 model give a very clear and an incredible near analog signal with the normal output stage but some confusion.
The DAC chips AD1860 are used with the new Piggy Back technology doubles up the D/A converter chips for even more analog sound and higher output drive.
Also with this DAC I have used the LL1638 Lundahl with a turn ratio 1:20 because two AD1860 in the Piggy Back configuration give the same output current of one PCM63 (see fig. 5, 6 and 7).
The signal to connect to the output transformers will be get directly from the DAC chips pins (see image) ad the little inductance shoudl be disconnet.
I have tested this DAC and currently I listen at music with it (see
photo below) together with the LL1636
1:20 Lundahl transformers and the DACT
CT2 100K+100K stepper attenuator.
I consider the sound of this DAC modified very well but the little bit lower than the DAC 2.0 with Burr-Brown, this probably is due to the lower bit resolution of the DAC chip that are 18 for the AD1860 and 20 for thePCM63.
At this point I have decided to test the upper model of Monarchy Audio the 22B using the PCM63K Burr-Brown that are a selected version of the PCM63.
zoom of the DAC section
and here follows the schematics of the modification proposed