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MDAC First Listen (part 00100011)

Discussion in 'audio' started by highfi, Nov 3, 2014.

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  1. highfi

    highfi pfm Member

    John, I'm very excited with the prospect of an inbuilt phono stage if you manage to get around the limitations. One less pair of interconnects, too.
  2. ChrisPa

    ChrisPa pfm Member

    Not quite. The version I've got is battery powered
    (hope I haven't left the battery in! :()

    I still have my AC1 and AP3 - both in need of TLC

    Owned from new, bought at the same time as the Jeremiah Braithwaite esq, and, as I came to realise a couple of years ago when I read through the Lecsonaudio site and Stan's site, bought from Stan himself.

    I'd lusted after the Lecson amps since I first saw them (as a schoolboy/teenager in the London Design Museum IIRC). Some time in the early 80's I saw a small ad in the local Cambridge paper advertising Lecson amps(!). So I bought an end of line AC1 and AP3 (and a JB esq) at a bargain price from this man I met - who with hindsight probably had to be Stan, as he was the one with all the leftover stock who sold it on.

    As implemented, dismantling and reassembly of the power amp was/is a complete pain. An act of Origami.

    The problem you've got with a cylinder - when you use both halves - is that you need to effectively allow for wiring harnesses to allow it to be interconnected before assembly. It's all much easier if you simply have to remove a top panel to access everything.

    (Many many years ago) One channel blew. A friend repaired it and fitted some uprated capacitors at the same time. We also installed some beefy coax connected directly to the input of the power boards allowing the DIN connector to be bypassed. The amp ran very successfully for some considerable time in dissected form (the 2 halves laid side by side). Until I decided to reassemble it. At which point I blew up one channel again, and it's sat in a corner ever since, on the list of 'things to fix'

    As an aside I've sketched a few cylindrical design iterations for my ncores :D
    (another activity on my list of things to do)

    This was driven more by a 'form meets function' based on the fact that the ncore is round (and has LEDs on top) than an homage to Lecson. But the cylindrical amps do look gorgeous.

    I'll try to have a look for it.

  3. JohnW

    JohnW Trade: Lakewest

    Trust me, I'd love to have the next trench of funds - but I must complete the Analogue PCB first (sans ADC section for now) :) I'm just working on the ESS DAC sections at the bottom corners of the PCB - been working with the simulator to design the DAC's local PSU - I've cracked the digital supply rails - now just to confirm the supply for the DAC's analogue section, its looking good :)

    I'm really looking forward to testing the PCB as so much of the design is new - in fact I'd go so far to say EVERY circuit block is a unique design, I just hope I've not push my limits too far... Thankfully the first two PCB have given me more confidence and experience with the computer simulations... Without the simulator, I'd never dare to take such huge design steps !
  4. JohnW

    JohnW Trade: Lakewest

    Already thought of a simple solution which is to mill the sliding rail sections that join the 2 halves together so they only have an inch or 2 at each end, then you only need to slide the halves an inch or so to lock / unlock the sides together - then you have no problem with cable harness etc.

    Maybe you will have time to visit us here in Czech sometime next year and I can happily repair the amp for you (also convert it to balanced inputs - the Pre-Amplifier is the weakest link and sadly really only good as a show piece...

    It be good to have a play with the MC preamp if its I/V based - even if the battery's have leaked.... :)
  5. ChrisPa

    ChrisPa pfm Member

    They're really interesting (at that price!)

    But it then got me wondering whether there was a similar low cost balanced input device which might allow cheap experimentation. At first glance the Behringer Ultramatch Pro SRC2496 looks interesting.

    I'm starting a new thread for any other low cost suggestions
  6. ChrisPa

    ChrisPa pfm Member

    That's effectively how the Lecson power amps are. You still need an allowance in the harness for that movement and to hinge the two halves apart.

    I would love to visit - I look forward to it when the MDAC2s start appearing.

    I may even bring the AP3 ;) - a wonderful offer, thank you.

    It's real physical constraint is all the connectors hidden/recessed/concealed on the bottom panel. A wonderful piece of industrial design because they're concealed, but there's very limited space (hence the 8-way right angle DIN plug) and the press button speaker terminals leave a little to be desired - hence the reason for the umbilical phono leads that were fitted. The 8way DIN also contains the headphone feed back to the preamp.

    My suspicion is that the output devices have gone. Darlingtons IIRC.

    I'll do a proper search and see where I've put it
  7. JohnW

    JohnW Trade: Lakewest

    On my AP1 you have to slide apart the halves the whole length of the extrusion to open the unit - my solution would be to mill the interlocking "Rails" so that you only have lets say a couple if inch rail sections (like segregated teeth sections) so you only have to slide the extrusions up or down by a couple of inchs to split open the halves - not the whole length of the extrusion as with my AP1.

    No problem, sometime its fun to work on old units like this :)

    It might even be worth designing a new AMP PCB - even considering using the VFETs (I have to dream while working on the mundane PCB design).

    I was toying with the idea to mill the base and have a recessed flat sections on the rear and sides of the base for the power and audio Connectors

    Thank you (and good luck in your search) - it be nice to play with a real I/V unit - and to confirm simulated results....
  8. jiminsd

    jiminsd Active Member

    I appreciate how exciting it is to design the ultimate pcb for the ultimate DAC but for me I just want the ultimate DAC. Any extra features (ADC, room EQ, Headphones, AV bypass, phono,etc) will go unused for me. I have a great vinyl rig already and I'm looking for my digital rig to get closer than the current MDAC. I'm looking for a straight up DAC that'll beat out an Auralic Vega (my current top pick for a new DAC.)
  9. JohnW

    JohnW Trade: Lakewest


    The Features you mentioned will not distract from the designs ultimate performance as the best DAC I can squeeze into the MDACs original chassis. I've added a "Full out" Vishay resistors option on the PCB - I have no idea of the final cost of the full Vishay resistor package - this will be the highest performance version of the MDAC2.

    Once I've the PCB on the lab bench I'll buildup a version with the "Full" Vishay Bulk Foil resistors to see if it brings a meaningful improvement - thats 60 Vishay resistors! Ouch - Mega Fusion!
  10. fred sonnen

    fred sonnen pfm Member

    Did 60 V res. make sence if the TDAC is "just ahead" the MDAC2?
  11. fusion5

    fusion5 on the dark side of hifi...

    Mega Fusion :)
  12. JohanH

    JohanH pfm Member

    Times say €20,- makes up for a hefty markup...
  13. JTC

    JTC PFM Villager...

    I think MDAC v1 L2 Toy is probably in the same ball-park so I'd expect MDAC2 to achieve your goals...
  14. JohnW

    JohnW Trade: Lakewest

    Does anyone here trust my time-scales???? :p

    I think the TDAC will be a much more expensive design - the new chassis alone will eat a far chunk of funds...

    I'm not promoting the Mega Fusion - I cannot even say if its going to make a significant difference - just during the design of the PCB I used a dual "Footprint" part (so I can build the PCBs with either the standard Surface mount parts or the Vishay Bulk Foils).

    I'm constantly requested for the very best DAC performance - and indeed the Vishay Bulk foils do reap a difference (as has been expedience by those who who attended Steve Toys recent DAC bake-off) - if they are worth the cost is another issue!

    I hoping for better prices by buying direct and in much larger Qtys...
  15. JohnW

    JohnW Trade: Lakewest

    That would be crazy indeed - I hoping for much better direct pricing.

    Mega Fusion is only a crazy idea (where every "Dual footprint" position on the PCB was fitted with Vishay Bulk foils)- I've designed the PCB with the option to use Bulk foils in critical position, listening test will determine the final "Fusion" resistor options.

    Mega Fusion is not a serious proposition at this stage!
  16. JohnW

    JohnW Trade: Lakewest

    Good news :)

    It seems like the PCB mounted 5W Mini XLR Male connectors are available - I'm still in discussion on pricing and shipping etc. so I should be able to confirm the Balanced headphone output connections soon.
  17. EIffel

    EIffel Cereal Killer

    Would it make sense to ship every MDAC2 with a matching 5W mini female connector? This may increase costs slightly, but may allow to negotiate a better deal and could save some of us some 'hunting time' later on. Just a thought...
  18. JohnW

    JohnW Trade: Lakewest

    Yes, maybe - still waiting upon the quote, but hopefully it will be in the region of a "Couple of dollars" :)

    Same goes for the ADC inputs....
  19. Steven Toy

    Steven Toy L3 Toy

    The additional fripperies may also be delaying the completion of the project.
  20. JohnW

    JohnW Trade: Lakewest


    Your MDAC PCB arrive safely today - I'll take a look at it in the next few days as soon as I've completed the layout of the ESS DAC section on the PCB :)
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