Obi1
Swedish HiFi enthusiast
Hot, i'll give you hot....
98lbs of Class A room heater.
Yamaha NS1000?
Thoose are lovely.
MDAC First Listen (part XXV)
- Thread starter ChrisPa
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Yamaha NS1000?
Thoose are lovely.
travelfotografe
pfm Member
OK - so finally managing to get acceptableperformance out of "troublesome" units - so there will now be a L4 Toy - there are no "bad sounding" L3's (as we retained any units that did not meet the performance requirements) - just that the L4 build should insure greater constancy among units.
Now just to see if I an fine tune the L4 for even greater performance
John, hope that L4 does the trick! The earlier the current units complete their upgrades, the earlier the MDAC2 gets started!
1. Is my silver MDAC a troublesome unit?
2. Have there been any more butchered MDACs in the units you are upgrading?
3. Is L4 to be applied to all remaining units?
4. With L4, is it still recommended to unplug the PSU from the wall, or can we just power off using the switch on the MDAC?
(patiently) waiting
Leon
travelfotografe
pfm Member
Hmm, so the high frequencies that John mentioned might cause a problem for certain amps is also creating havoc inside the MDAC too?
Leon
No, we're all guessing - 2 + 2 + 2 = 47
I could guess at various other uses of the caps within the overall circuit design - it would be just that, a guess. I'm not dismissing SQ's guess, but I'm treating it with the level of qualitative and quantitative information it contains
And certainly I've no idea where the word 'havoc' came from. I don't think there has ever been any 'havoc' in any part of the MDAC or any component that's ever been connected to it
Never jump to a conclusion based on guessing. Let's wait for accurate information. We may never know; no other designer would give us detail of what was being changed, unless it was to describe foo. And when we are told, it would seem that information is open to misinterpretation - 'havoc' for example
travelfotografe
pfm Member
I personally treat "havoc" as not a strong word. A quick check on word defination suggest something horrible and serious. My apologies if my poor choice of words offended anyone or resulted in misinformation.
Leon
Leon
Okay Leon - understood. Yes, havoc means the worst kind of chaos and disturbance possible
Steven Toy
Accuphase newbie
Look what's just turned up! A purchase inspired by the new MDAC
Richard Kimber
pfm Member
sq225917
Bit of this, bit of that
Well i haven't seen where he is putting them in the Mdac, but given the numbers i ordered for him I know how many he's using per dac and given their size and the numbers per dac i can figure the usage. Frankly there's not a lot you can do with 22pf and 33pf caps. I'm sure john will answer but my guess in on stopping an RC filter from ringing.
Look what's just turned up! A purchase inspired by the new MDAC
Oooh just had a listen and I like what I hear
FYI, check out these girls if you like that sort of thing:
http://www.youtube.com/watch?v=khhb_ey3Lmk
Saw them supporting Feist last year, superb!
JohnW
pfm member
I've not got to listen to your unit - but due to the great difficulty achieving the "reference" sound quality with these upgrades I've had to take the following steps:-
1. Completely strip down the analogue stages and replace most of the passive components (Capacitors and resistors).
2. Extensive modifications to the analogue circuit - this involves "Micro" hand modifications to circuit connections etc. Following experiences with Jiri's & PlutoX's units (which sounded especially "HARD") the circuits have been extensively changed - without these modifications I cannot accept the unit to unit variations...
The units built to to these new and LAST spec. are labelled as "MDAC Premium L1" for the basic version and "MDAC Premium L2" for the units fitted with "Fusion" resistors.
Due to the amount of work I put into these units I'd hate to see these "Scrapped" for MDAC2 units - better to sell these on (or keep as a second DAC) and buy a new condition "Salvaged unit" for GBP350 to GBP400...
I'm very disappointed with the variance I've heard between "Original" MDAC's... something that will not accepted with MDAC2 units - I'll personally listen to each MDAC2 PCB before shipping out to insure constancy - I'll sign off each unit. This is not to sound "Big Headed" in anyway, but I've been so distressed at some units SQ...
No only the 2 units so far
Well as stated above, "MDAC Premium L1" for the basic version and "MDAC Premium L2" for the units fitted with "Fusion" resistors.
No, I've added extra protection to all units I've upgraded to prevent any similar instances of capacitor failure. (L2, L3 & Premium).
JohnW
pfm member
Chris,
Without going into too much detail (to prevent helping Audiolab with an SE or Mk2 version), I replace most of the passive components in the analogue stage + hand built "Circuit redesign" to correct deficiencys with my original circuit that would suffer with "Hot" Gain transistors - I've found "rogue" transistors with hfe's of 860 as opposed to a manufactures quoted max of 400... this has added an extra layer of variability ontop of the passive component deficiencys...
Significant to say, that MDAC2 will be designed from the onset to cope with these super Beta transistors and will have very different circuit topology to do away with the Miller compensation capacitor which combined with a very widely spread unit to unit OL gain inconstancys effects the sound in varying degrees finding transistors with such a hot gain really upset the apple cart its all been very depressing indeed
JohnW
pfm member
The capacitors are a unique part of the latest "MDAC Premium" circuit redesign... I just to need to clear out these units and finally get to work on the MDAC2 PCB even if its such an extended rebuild
but the results should suffice until the MDAC2 I was seriously considering selling my to-be-L2 unit to a friend when MDAC2 was announced. That is - selling at the time MDAC2 is released & scraped MDAC skeletons available. I guess that's a distant future at this point.
Can't wait to get my hands on my upgraded unit.
Hi John,
as you well know I have one of the 2 L3 Fusion units; for now where does that put me? I'm confused by L4, L2 Premium etc.
So far I seem to be happy camper but seeing as you don't want my unit "butchered" for MDAC2 I'm looking for directions....
Cheers,
Johan
Planning to post more impressions on my unit later this week
as you well know I have one of the 2 L3 Fusion units; for now where does that put me? I'm confused by L4, L2 Premium etc.
So far I seem to be happy camper but seeing as you don't want my unit "butchered" for MDAC2 I'm looking for directions....
Cheers,
Johan
Planning to post more impressions on my unit later this week
JohnW
pfm member
Johan,
Well Fusion'ed units are a different matter due to the cost of the Bulk foil resistors
I can understand the reluctance to buy a second set of resistor + "a salvaged unit"! I was referring to the "MDAC Premium" units... your hardly going to get a DAC for the "Salvaged unit cost" of GBP400 anywhere its quality so its a shame to "Scrap" them....Looking forward to your feedback
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