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71
Other DACs / Re: Marantz 94 mark 2
« Last post by zenelectro on November 27, 2017, 10:53:19 AM »
Ian,

Nice work. Quick question - Are you running digital filter or 0 x OS?

T
72
Other DACs / Re: Marantz 94 mark 2
« Last post by brenden on November 27, 2017, 03:45:38 AM »
Here are the  tda1541 chips  with  the Panasonic pps copper foil capacitors
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Other DACs / Re: Marantz 94 mark 2
« Last post by brenden on November 27, 2017, 02:23:46 AM »
Here is a photo of the  big cap beside the clock  module held in place by a resin capacitor  clamp on ths base of the 94 .
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Other DACs / Re: Marantz 94 mark 2
« Last post by brenden on November 27, 2017, 01:54:58 AM »
This is the clock with integrated  power  supply   all caps replaced  one by one and assessed . Mostly Silmic 2 super golds  but Silmic 2 standards very good too.  Bypassed with Jupiter copper foils  and  pps copper foil caps  This lowered the  subjective noise floor immensely . I also added a couple  of film caps very close to the active  devices underneath .

  The Silmics are much better than the supplied panasonics and philips caps
   Not shown is a larger cap in parallel with the  power supply  . I think from memory 4700 uf  elna for audio . The two 1000uf caps are just not enough for the clock .Much better  sound with the bigger
   capacitance .   The clock power supply needs to be as noise free as possible and very reactive  .so dont skimp on .01 bypasses .  Dont  use mylar here .

  What seems to be most important here is to get the power supply to the clock as noise free as possible   .noise means jitter .  Jitter means loss of fidelity .
    Would love to try a Zen clock here one day Terry . ☺



Here is also a photo of the  new Valab clock  with original capacitors   .
75
Other DACs / Re: Marantz 94 mark 2
« Last post by zenelectro on November 26, 2017, 10:18:58 PM »
Great question Steve ,and one i have wrestled wit a lot . I owned both at the same time and compared them side by side . Firstly the mk2 had a bit more weight  . It probably  had  more drive due to the  doubling up of dacs and amplification  stages  in dual differential .
    The mk1 was a bit sweeter  and  and  maybe a bit less grungy . This was almost certainly due to the better film caps around the tda1541 a   even though they werent great caps ( mylar ,   inductive)
     Certainly not optimum .   As you could hear   ( comparatively ) grungy plodding in the mk2  can be  totally fixed .

    I am not 100 pc sure the weight of the  mk1 can be  made to equal the mk2   but certainly could be improved  .
     I think the dual differential architecture is superior  as far as noise and distortion  are concerned  but  the extra room in the mk1 opens up lots of  possible  choices for  even better   exotic decoupling  caps around  the tda1541  and for top line caps the cost will be  halved  needing 14 instead of  28 .
      The caps in the CD12 and CD 7  around the dac were  top quality  non inductive  polypropylene foil types   i believe .   These would be impossible  to  fit on the tiny mk2 board  .I was lucky enough to get a few of those green  pps copper foils for mine ,  but they are no more The only ones I have ever seen are the ones i got .
   The mounting arrangement for the dac board in the mk 2 is also not optimum either  , using steel prongs . This will be the last thing I will do .My last one was hard  wired with Discovery signature  wire .really nice wire and made a clear difference.
     

WRT 94 MKII:

They run dual differential but still do L and R ch in same DAC. So one TDA does L+ R+, other does L- R-.
Would have been better to use 1 x TDA L channel +and- /  other R channel +and- but as they say, it is what it is. :)


They also used 5 opamps / channel in the dual dif configuration which was fairly complex.
Maybe this was to allow for FET switched de-emphasis circuit. I'd be pulling that out.

A simple 3 opamp config with class A opamps is the way to go.

I never tried the AD827 / AD847, however I got great results with OPA627 biased into class A
I recommend biasing them into class A - I have never found an opamp that didn't sound better with class A bias.

But as you say it's all a balancing act. The opamp PS bypass makes a difference too. Some people use double
caps, ie; electro with film cap but I think this gives slight artificial sound. With the 827 / 847 you have to be a
little careful as they are very fast and can oscillate. But it will usually not sound right if this is happening. 

I used to enjoy doing this sort of simple modding to SS gear, it can be a bit maddening at times - this opamp,
that cap, etc etc

Oh and it's also worth trying running the analog OP stage straight off batteries with no regulation.
This can sound really good - if you don't mind being a battery slave..... charge etc  :-X :)

T



76
Other DACs / Re: Marantz 94 mark 2
« Last post by brenden on November 26, 2017, 08:26:38 PM »
Great question Steve ,and one i have wrestled wit a lot . I owned both at the same time and compared them side by side . Firstly the mk2 had a bit more weight  . It probably  had  more drive due to the  doubling up of dacs and amplification  stages  in dual differential .
    The mk1 was a bit sweeter  and  and  maybe a bit less grungy . This was almost certainly due to the better film caps around the tda1541 a   even though they werent great caps ( mylar ,   inductive)
     Certainly not optimum .   As you could hear   ( comparatively ) grungy plodding in the mk2  can be  totally fixed .

    I am not 100 pc sure the weight of the  mk1 can be  made to equal the mk2   but certainly could be improved  .
     I think the dual differential architecture is superior  as far as noise and distortion  are concerned  but  the extra room in the mk1 opens up lots of  possible  choices for  even better   exotic decoupling  caps around  the tda1541  and for top line caps the cost will be  halved  needing 14 instead of  28 .
      The caps in the CD12 and CD 7  around the dac were  top quality  non inductive  polypropylene foil types   i believe .   These would be impossible  to  fit on the tiny mk2 board  .I was lucky enough to get a few of those green  pps copper foils for mine ,  but they are no more The only ones I have ever seen are the ones i got .
   The mounting arrangement for the dac board in the mk 2 is also not optimum either  , using steel prongs . This will be the last thing I will do .My last one was hard  wired with Discovery signature  wire .really nice wire and made a clear difference.
       
     
 
       
77
Other DACs / Re: Marantz 94 mark 2
« Last post by stevenvalve on November 26, 2017, 07:19:47 PM »
Time to buy a Marantz 94. Some say the Marantz 94 with a single chip was a better idea than the mark 2, with 2 Chips. They feel going to the two chips compromised the performance in some ways. I have no idea, any thoughts. Question is buy a mark 1 or 2.
78
Other DACs / Re: Marantz 94 mark 2
« Last post by vitavoxdude on November 26, 2017, 03:56:55 PM »
Well, I for one will look forward to your audio travels IRT the Marantz silver spinner.  Of course having two of them I have an obvious interest on finding the things that worked  ;D
79
Other DACs / Re: Marantz 94 mark 2
« Last post by brenden on November 26, 2017, 03:26:36 PM »
  Its difficult to know  where to  start.  I could seriously  write a book  about  my  experiences .
       i bought   myself  a brand new  Marantz cd 94 mk2  around 1990  , but i was never satisfied with my sound  and , after being on the merry go round  for a number of years  buying and borrowing high end equipment it seemed that every substitution  always had tradeoffs  when it came to  musical satisfaction.
     My gear was mostly excellent  design and  build  quality  such as the Stax mono blocs Classe DR6  so  I came to the conclusion  that  it would be worth modifying  my  gear to  add refinement   to the reasonably  dynamic sound i had .
  During the late 90s i had performed literally thousands of mods  and built up a memory bank of  practical  experience  in what  worked and what didnt  . Not knowing  aĺl that much in theory  I wasnt constrained  by preconceived  ideas   so I tried  lots of radical  stuff back then . I was even running  battery clocks  a decade before  i realised there were other  nutters out there 😊 . Eventually  i   achieved  excellent sound  quality   through perseverance   and trying to understand  why things changed . For example this led me to studying capacitor construction  quite intently .
     Not algebraic  theory mind you   ,    rather , what different construction  and materials   bought to the  table  in a practical  sense .

    Anyway ,   kids came along  and  the system was totally  dismantled  sold or stored .
 
 A few years ago i decided  to  rebuild  a  sound  system   based around  the 94   and was confident  i could improve on my original.
 
   The  Marantz cd  94  machines  had all the ingredients  for greatness . Arguably  the best  drive  ever made in the CDM 1   and possibly  the  best  chip  ever made  in the tda1541a  ,excellent  multiple regulated power supplies   with  generally  good parts quality   for a commercial  product.

   So what do we do  to improve it if its so good ?     Well the devil is in the details.

      Firstly , to achieve  greatness   ,a component is only as good as its weakest link.  There is no single  place to start  really .Its a matter of  identifying and working through every single weak link till they are all eliminated or  improved  .
           
        In the  90s  I did a shootout  with probably  20 different op amps   .The bottom line without boring everyone  about the differences  was that the  AD 827    and  AD 847  were the clear favourites being excellent in all areas  including dynamics  which seemed to be a problem for many op amps being too smooth or bland  . The originals  in the 94 also had good dynamics  but are coarse   or ragged  in comparison.
 
   These are the op amps in my machine today .  Not cheap   but  very capable.   Op amps upgrade probably gave a few percent of the  improvement  in sound quality  so dont expect miracles  from  any  single mod or you will be sadly  disappointed   as with any of the other mods  in isolation  .As I said  it is a wholistic approach   with each  mod being rather small incremental  improvements
       I will detail some more of  the 94  changes in a number of posts as  there is a fair bit to get through  ,so i will end this one  for now .. Cheers Ian .
80
Other DACs / Re: Marantz 94 mark 2
« Last post by brenden on November 25, 2017, 01:18:58 PM »
Hi guys . I am travelling back home to Newcastle  at the moment. Rest assured  I will    post a detailed account  of  my  experiences  with  the Marantz cd 94 mk 2 as well as  other equipment  upgrades.
    One thing I will say now is that it is a holistic approach rather than using a super  TDA1541  double crown chip for example .  You need to reduce noise in every circuit  because its all connected .
  In digital ,  added noise means jitter . Capacitor quality  both in Electrolytic  and   film bypasses are critical to take things to the next level . Attention to clock power supply is critical as well as  the decoupling caps around the TDA1541  ( super sensitive )  .
     Thanks again to Steve  and Jen for being so welcoming   .It was an absolute  pleasure  to spend  quality  audio time   at their home . 
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