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The TACT 2.2x is a stereo digital preamplifier with
dynamic room correction, it can manage Hi-resolution PCM signal until 96KHz
A my friend ask me some upgrade to increase the sonic performances, he use this preamplifier to driver the 845 amplifier with only two stages.
The common DAC and CD/SACD players have a rather low performance because the common usage of high NFB operational amplifiers "destroy" the sound given compression effects and poor soundstage stability.
In the TACT 2.2x the DAC section use the Wolfson WM8740 followed by 2 stage op-amp.
The WM8740 is a very high performance stereo DAC designed for audio applications such as CD, DVD, home theatre systems, set top boxes and digital TV. The WM8740 have 2 channels fully differential voltage outputs with 2Vrms so the I/V conversion is integrated.
The best method to convert a differential signal to an unbalanced signal is to use an audio transformer.
Here I have use the same solution used in many my DAC like the DAC 1.0, DAC Final, HI-Res. with EMU 0404.
The Main Output DAC board has been clear from op-amp and relays using an infrared solder station and 2 x LL1527 Lundahl has been inserted in the same position.
After this modification you will ear a little bump on loudspeakers on switch on and switch off because the relay has been removed but there is not enough space to keep these and add the transformers.
The analog section of the DAC chip is powered by a normal
78M05CDT linear regulator so I suggest to replace it with a better type.
There are many good regulator in the market like the LT1086 but if you search the best performance you can try the Belleson Super Regulator SP78 (+5v).
This new regulator increase the performances given a more natural sound.