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12 Sep 2018

Philips CD751 + dedicated tube output


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Marantz CD751 has several twin brothers in different dresses:
Marantz CD48, CD5000, Philips CD740 , CD921 and many other CD Player with the same chip!
TDA1549  D/A converter is a very nice chip . It has a quite high , refinite and musical output that makes every tweaking simplier than usual.
If you like a low output it's possible to use a simple buffer on signal path.....if it's a tube -buffer you can design a simple cathode follower  throwing opamp in the trash can.

If you like a thicker and higher output signal without resistive attenuator filter on the path,  you have to invent a gain stage with very low gain and usefull to lower the impedance enough to please the mosts of amplifier input.
Me and my friend "mister X" ( he don't want to be mentioned ;) )
invented  the AMNT system  (Amplifica Ma Non Troppo)
......I don't think many people around here are using this system  :D 
...what is it???? actually I won't tell you......
In this way I respect the best minimalistic project I can.

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The final result of this Philips 751 with a TDA1549 D/A converter  tweaked with a dedicated tube audio stage












The russian 6N14P is a very good solution for a LPF out project in a CD Player adopting a "V.out internal DAC" with an  high output level like TDA1549 , 'cause we need to obtain a relative low gain , but always GAIN and chip highest frequencies cut.
This is the right tube , but not only for this player! 




...Power supply caps was swapped for better ones (Nichicon muse gold etc.)


...the new power switch works on 220V main , before was on secondary. Now it controls both original and added tube part






...original...




...work in progress...





...swapped all caps around DAC with Sanyo Oscon or other better ones



...completely disassembled.....



...the mess befor became tidy...





...




...OpAmp was removed and every muting transistors too



...6N14P is quite linear and clean sounding tube , most says a substitute of the rare ECC84 (be carefull to PIN out)








...another Sanyo Oscon , Elna RJH,and PP capacitors close up!




...very nice frequencies response of this cable bought by to my favourite retailer , but terrible to weld.









...mmmh well done power supply



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...Listening impressions was very good since the very first note: a lot of air, a quite large and deep soundstage with enought precision allaround ....really very musical and enjoiable player now!
A pleasure for the ears!!!!!!

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