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17 Nov 2018

Carmenta Tube Preamplifier tweaking



Carmenta (funny name for a serious preamp), an english assembled preamp with an heavy superserious box with heavy full iron handgrips.........but inside..............nothing more than a chinese layout!

This is a serious reason to put the hand on it...the final resul could be only better than original!












Original layout with series capacitors.

.....coupling cap are average quality but only 0,1uF!!How can we feel and hear the lowest harmonics??!!!





....disassembling









....testing solutions......






.... polypropilene bypass





....the final soulution with the best result!

before it sounds narrow and flat compares now! 
Now it has its weight and its space...a pleasure to listen!

12 Sep 2018

Marantz CD36 lampized with a couple of subminiature 6J1B pentode...a kind of masterpiecece



Marantz CD36 lampized with a couple of 6J1b pentode is one of the most refinite and beautiful sounding player I've ever listening at!!!!!
I swapped the main capacitors for a Pana 4700uF and the other one 3300uF and the two caps  closest to DAC with Sanyo 1000uF 25V (green ones) ; the first on the 5V supply the second one on Vref pin wich is the one connected at the I/V resistors.
For I/V resistors conversion I used two paralel  1K resistors each channel , one of them was SFR by Philips wishay wich gives great details and accurate image.
I think you can go for Caddok, Dale,Kiwami,Holco or other brand  resistors........to please your taste with the best quality!
The 6J1B pentode gives a great quality and they don't ask too much in terms of current or high anodic voltage.
The result is a real analogic masterpiece!!!
CD36 is one of the most analogic player i've ever modified!!!!!!....a pleasure for the ears!!!!!




















We have to work with a very low signal in output, equal to 1/4 of his brother TDA1541 , we're talking of 1mA out to be treated without the use of any op-amp!!!
It's funny when I read of some peoples using a simple universal  buffer after a TDA1545 without any opamp :D  , but more sad looking at people believing them........alas!... what we can do.....this is the world of MARKETING !

This player with 6J1B penthodes, gaves really one of the best result I've ever obtained in a CD Player and gives a tad of satisfaction to the tweaker  just 'cause it need an accurate job to sounds such good!!!

Philips CD751 + dedicated tube output


***
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.

*******







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



***
...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!!!!!!

*********