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MDAC first listen (part XXII)

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Asphaltradler said:
Really top recording of a Pop group with gifted instrumentalists around singer/songwriter Lori Lieberman:
http://www.cdbaby.com/cd/lorilieberman4
The session was recorded live by Mark Levinson with the same pair of omni mics Denon used for its recordings, AFAIK (Brüel&Kjaer). Valve mic preamp built be Levinson directly onto a 2-track Nagra recorder without any mixing. Nice album also ;) Lot of ambiance around the musicians, piano and percussion mostly a bit farther away as one is used to, guitar, acoustic bass and vocalists right before you in your listening room. In "Women like me" Lieberman is backed by 2 more female vocalists, 1 of them Amanda McBroom, and the three are separated in space wonderful. (Only to be beaten by the "Rosenkavalier"-Finale with its 3 soprano heaven :))
I've heard no better recording in "popular" genres.

I am really anxious to hear this with the L2 MDac some time, but I fear I'm far off on the list. Maybe still 40 entries before me?
Click to expand...

Maybe 30 or so...
 
JohnW said:
Sometime back, over 20K MDAC's had been manufactured - over a lifetime of a product its inevitable there will be some slight variance - an odd resistor here - an odd component there. As the designer I was able to give "Critical" components a "Q" prefix on the bill of materials (BOM) which meant they could not be substituted - however as I'm now learning even the humble resistor seems to impact the sound quality in a far bigger way then I'd could have imagined...

Its all rather frustrating...
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It would seem the dark-side is more prevalent than you had hoped it to be.

I cant help but think the information you are gathering here will benefit the future products to a great degree.

Keep up the great work and stay strong! good all ways prevails right? :D
 
JohnW said:
Basically yours and JohanH MDAC's (which incidentally are both black MDAC's) don't sound as good as the unit I modified for Jem (a Silver unit).

There is some obvious component variation between the builds of the Black and Silver units (I'm guessing that silver MDAC's where built together a a batch).

I can only conclude that its these differences in components that is effecting the SQ - otherwise I'm lost. Its just a very slow and tedious process to go through each component trying to narrow down the cause - Hopefully the Bulk film resistors arrive tomorrow and I can upgrade these component position of Fusions MDAC to see the effect on SQ.. this would give me clues as to how critical the component location is...

The biggest headache is that no 2 MDAC's are 100% the same - some units have there own issues - while there are component variations between units. I was not expect such a variance...

Once I get a better handle of what's going on by working on a section of units I'll be able to develop a better picture what needs to be changed asides from the main upgrade components.

For example, will I have to upgrade the blue resistors in units that have them fitted? I just feel the pressure of everyone's units that we have sitting here - but without be able to work on a wide selection of units I'd not be able to gain the experience of what else needs to be upgraded besides the main "upgrade package" for a particular MDAC "build variant".

Sometime back, over 20K MDAC's had been manufactured - over a lifetime of a product its inevitable there will be some slight variance - an odd resistor here - an odd component there. As the designer I was able to give "Critical" components a "Q" prefix on the bill of materials (BOM) which meant they could not be substituted - however as I'm now learning even the humble resistor seems to impact the sound quality in a far bigger way then I'd could have imagined...

Its all rather frustrating...
Click to expand...

Although I miss my MDAC I'd rather have it good than fast.
Depending on your findings and if possible in a reasonable time frame I would consider the 4 pcs bulk foil upgrade.

Please keep us posted on the progress.
Hope you find the answers soon.

Cheers
Johan
 
JohanH said:
Although I miss my MDAC I'd rather have it good than fast.
Depending on your findings and if possible in a reasonable time frame I would consider the 4 pcs bulk foil upgrade.
Click to expand...

Good thinking Johan, I recognise a good bandwagon when I see one...

Same for me please John :)

Will
 
John have you checked to see if any of those resistors are magnetic? With similarly specced and matched parts surely that's about all that can make a difference...

The named Vishsays are 100% none magnetic.
 
Right, I'll get my arse to the post office and send them via Parcelfarce on a next day to CZ. It'll cost me 40 quid but if it keeps you lot happy... ;)

I could pay a bit less and get a courier to collect but that's an extra day and I don't have a printer for the labels.
 
Fusion:-

This tiny package has just arrived !!! yep have the bulk film resistors in hand - but not your MDAC yet...

Obviously, I'd only consider "officially" offering the Toy / Fusion versions if the Vishey Bulf Foil resistors make any difference to the SQ...
 
sq225917 said:
John have you checked to see if any of those resistors are magnetic? With similarly specced and matched parts surely that's about all that can make a difference...

The named Vishsays are 100% none magnetic.
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I need to find a Magnet to try!

SMD resistors might tend to sound better then there equivalent Through hole variants as they have less Metal to Metal transition boundary's.

A SMD resistor is just the Film / Ceramic substrate which is then directly soldered to the PCB.

Trough hole parts have a Metal "End Cap" attached to the ceramic substrate with lead wires wielded too these end caps... resulting in extra Metal to Metal contact boundary's.. not to mention extra metal materials in the signal path.

I've hardly EVER used though hole resistors (all my designs are SMD) - it could be why I'd not noticed the resistors effect on SQ.

Edit:- just noticed that my speakers use magnetics to hold-on there speaker grills... standard SMD Resistors are non-magnetic (but not the MELF type I use in the Analogue signal path) - the trough-hole parts are strongly magnetic.

The really horrid sound Mulitcomp resistor is heavily magnetic...
 
Steven Toy said:
Right, I'll get my arse to the post office and send them via Parcelfarce on a next day to CZ. It'll cost me 40 quid but if it keeps you lot happy... ;)

I could pay a bit less and get a courier to collect but that's an extra day and I don't have a printer for the labels.
Click to expand...

Maybe you don't need to rush them over as John now has some Vishay resistors in hand to start experimenting?
 
JohnW said:
I need to find a Magnet to try!

SMD resistors might tend to sound better then there equivalent Through hole variants as they have less Metal to Metal transition boundary's.

A SMD resistor is just the Film / Ceramic substrate which is then directly soldered to the PCB.

Trough hole parts have a Metal "End Cap" attached to the ceramic substrate with lead wires wielded too these end caps... resulting in extra Metal to Metal contact boundary's.. not to mention extra metal materials in the signal path.

I've hardly EVER used though hole resistors (all my designs are SMD) - it could be why I'd not noticed the resistors effect on SQ.

Edit:- just noticed that my speakers use magnetics to hold-on there speaker grills... standard SMD Resistors are non-magnetic (but not the MELF type I use in the Analogue signal path) - the trough-hole parts are strongly magnetic.

The really horrid sound Mulitcomp resistor is heavily magnetic...
Click to expand...

What's the theory here? If they are ferromagnetic then the resistor could become polarised? If the resistors are ferromagnetic or not they could be susceptible to EM fields. IIRC aluminium was selected for linear motors but is not ferromagnetic. :confused: The effect should be the same in every MDAC as long as the orientation of resistors, shielding and EM fields should be the same as the layout is the same? But this seems like a big can of worms if it's causing a problem?
Edit: Isn't it the frequency response of the resistors that's suspect here and if it turns out the bad ones are magnetic that's a quick test to reject alternative makes?
 
jamjar784 said:
What's the theory here? If they are ferromagnetic then the resistor could become polarised? If the resistors are ferromagnetic or not they could be susceptible to EM fields. IIRC aluminium was selected for linear motors but is not ferromagnetic. :confused: The effect should be the same in every MDAC as long as the orientation of resistors, shielding and EM fields should be the same as the layout is the same? But this seems like a big can of worms if it's causing a problem?
Edit: Isn't it the frequency response of the resistors that's suspect here and if it turns out the bad ones are magnetic that's a quick test to reject alternative makes?
Click to expand...

Well any "Magnetic material" has properties such as hysteresis and non linear "magnetic reactions" to electrical fields - if you start thinking along the lines of converting electrical current into magnetic fields and back to electrical current its easy to start imagining how even an apparently simple passive part such as a resistor could effect sound quality in the way it appears to...

As you say - its a huge can of worms... scary if true as the "system" starts become massively complex. I warned about the freaky Dark side of HiFi - I'm going to be glad to get back to relative sanctuary by using non-magnetic components just to be sure... Standard SMD resistors without magnetic end caps to help reduce unknown factors (Goodbye MELF resistors) - Maybe sometimes its good to heed respect too the unknown!

I'd just like to be able to shipped upgraded MDACs without the variability in SQ we are experiencing - and I'd rather retain my sanity in the process... thats all :(
 
jamjar784 said:
What's the theory here? If they are ferromagnetic then the resistor could become polarised?
Click to expand...

Gosh - I'm not trying to claim any theory here - just trying to come up with a "logical" explenation as to why a simple passive component appears to have such an effect on sound quality - while retaining what little sanity and respect I still have...
 
You gain more respect from me for not dismissing what your ears are telling you and investigating further..
 
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