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MDAC First Listen (part 00011110)

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JohnW said:
With display dimming, the OLED display panel will outlive the capacitors in the MDAC.... At the low panel brightness used in the "Dim" setting, the panel lifetime has dropped off the "lifetime curves" provided by the panel manufacturer...
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What is the expected lifetime of capacitors in the MDAC?
 
JohnW said:
Crappy Europe directives - they just pile more and more legislation onto manufactures - I cannot blink an eye without breaking some rule...

I'm not sure what advantage (legal or otherwise) that "Auto off" would bring...

The ClassA and shunt PSU design of the MDAC2 does not lend itself to a "low Power mode" without a good deal of extra complexity. If I reduce the ClassA standing current - then the Shunt Regulators would then just end-up dissipating the extra current - I would also have to reduce the Current sources to the shunt Regs = 4 output stages + 4 Shunt supply rails that would need to be switched... that's a lot of extra circuitry to switch all of these circuit blocks, while insuring no detriment to SQ...
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Yes! Please no more changes to MDAC2, unless it will improve sound. This will just delay production and defeat the purpose of this project.

sound, sound, sound. Please no Gimmicks!
 
JohnW said:
John,

I wish I could say I'd shipped your board - but I've been engrossed in the MDAC2 design.

I'd performed some quick design simulations and I can reduce the gain by 20dB BUT:-

1. The headphone output will also be reduced by 20dB

2. The Dynamic range will also be reduced by upto 20dB (I'd need to confirm exact number by measurement).

3. Cannot say how it will sound without first making the modifications...

Your call - I can modify but at your risk.... let me know as your units on the bench ATM (I'm going to get a few hours sleep now)....
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Hmmmmm.... interesting one. I think a lot hinges on whether using the MDAC in preamp mode in conjunction with another preamp is a bad idea or not. I reckon setting the MDAC to (say) -10dB in preamp mode would give more range on the actual preamp's volume pot. However, am I likely to experience any performance drop by activating the preamp on the MDAC and running at -10dB (say) as opposed to non-preamp mode? It could be a balancing act with the main preamp, as of course there could be trade-offs with its volume pot at the lowest range....

Difficult one :) What would you recommend?
 
Your unlikely to experience much sound degradation with only -10dB digital attenuation.

If your using an external preamplifier then I cannot see the need to modify the MDAC.

While I earlier listed the negatives there are a couple of positives - there will now be an extra 20dB feedback gain with will lower the MDAC's output impedance still further & improve its Power supply rejection ratio (MAYBE less sensitive to warm up).... how this will impact the sound is only "Theory"...

You still have a "standard Gain" MDAC board... really hard to say - its your call.... ;)

I'm going to have a quick wash - so you have time to think about it :)
 
Chertilo777 said:
What is the expected lifetime of capacitors in the MDAC?
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The rated "half life" of the capacitors is 5000 hours - the MDAC has multiple paralleled parts so even at half there rated value there's plenty of energy storage available - so hard to say, accept that the caps are getting older :p

Most designs use parts rate at 1000 or 2500 hours (and normally without multiple paralleled parts) - to give you a comparative idea...
 
When ive used inline Rothwell attenuators I found it best to fit them on the power amp not the CD player or dac.

I run my M-dac through a AS Passion passive preamp and the m-dac set to +3 on its volume as that sounds better to my ears than M-dac direct and having to run the M-dac down in the 60 to 50 db range as I don't play loud and have lots of gain in the system.

If my system had less gain and I played louder then there will come a point when M-dac direct would sound best but as I have 2 analogue front ends I need the passive anyway.
 
JTC said:
However, am I likely to experience any performance drop by activating the preamp on the MDAC and running at -10dB (say) as opposed to non-preamp mode?
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AFAIK the "dac mode" just locks the volume on 0dB. To be honest, I'm not sure why anyone bothered with adding it - perhaps to prevent kids from playing with the remote?
It's more than a year ago, but I believe I measured voltage across the RCA terminals with a 1KHz sine wave when running 0dB normally and via the "dac mode" and it was exactly the same. It makes sense - (as far as I know) the DAC in the MDAC is just a single chip, the rest, the analogue stage, is basically an amplifying section. And some supporting circuitry (digital/analog).

Feel free to correct me if I'm wrong. :)
As far as I know, MDAC2 could be a bit different in this regard - at least with later firmwares.
 
OK, John, let's leave the MDAC board as-is, and I'll revert to using it in preamp mode to give a little more range on the main preamp's dial. It may be that when MDAC2 comes along I prefer the MDAC2 in preamp mode to that of the MDAC2-into-valve-pre. Which won't be a big deal, I'll just sell on the valve pre if that happens*.

* as I'm slowly coming around to the idea that I can live with Turntable->PhonoStage->ADC->MDAC...
 
Been a long while since I have been on here !, Australian summer kiteboarding most days :).

I have had my L2 Fusion on v.90 since it came back but decided to change it today to my original firmare when I got the unit .96 and feel the stage is much better on my system.

Where do I START !!! the number of thread pages has gone to some crazy number !
 
As a convenience (not a necessity) I'd quite like the ability to lock the output level at any level not just 0dB.

Some playing that I've been doing recently makes me think it's possible that the high output level from a DAC can, if not overload, then push a preamp's input further into distortion and dependent on the overall system and other components, lowering the output level from the DAC and winding up the volume on the preamp can improve the overall sound quality.

jirij said:
AFAIK the "dac mode" just locks the volume on 0dB.
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Yes
jirij said:
To be honest, I'm not sure why anyone bothered with adding it - perhaps to prevent kids from playing with the remote?
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Kids? Anyone really. I keep seeing the volume level being changed on my mdac, most usually by accidental presses. Someone's intended to change the input and instead they've tweaked the volume. If you're using the MDAC to control the volume then of course this isn't a problem, but knocks things out of adjustment if you're trying to preset the output level of the DAC.
 
elteesang said:
Will be picking up my new MDAC tomorrow, really excited about it as well as getting the future MDAC2 upgrade!
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Guess today's the day! :)

A couple of points to get the best out of your new MDAC:-

1. From new, the MDAC needs about week to "run in" to sound its best

2. Try various software updates.

V0.90 - In my system the best sounding, with Basic features and a few bugs.

A08 - Fully featured + a "fuller sound" but less delicacy

A10 - I've not spent the time to listen to it - but was developed as a Bug fix of the original V0.90.

Your MDAC will be shipped with V0.99 which IMO is the worst sounding version.

MDAC2 a much more advance design - I've spent almost 3 years on its design (developing its new circuit topologies) - with separated digital and analogue sections, it will be upgradable with Tube analogue stage at a later date - in fact I've just bought 100 tubes to test there variability and start "Life time tests".
 
Vaughan said:
Been a long while since I have been on here !, Australian summer kiteboarding most days :).

I have had my L2 Fusion on v.90 since it came back but decided to change it today to my original firmare when I got the unit .96 and feel the stage is much better on my system.

Where do I START !!! the number of thread pages has gone to some crazy number !
Click to expand...

Welcome back :) - not seen a Boeing 777 down your neck of the woods have you? I wonder if they are going to find it of your west coast?

On the software, if you like V0.96 then its also worth trying A08 or A10 :)

V0.90 - In my system the best sounding, with Basic features and a few bugs.

A08 - Fully featured + a "fuller sound" but less delicacy

A10 - I've not spent the time to listen to it - but was developed as a "Bug fix" of the original V0.90.
 
JohnW said:
MDAC2 a much more advance design - I've spent almost 3 years on its design (developing its new circuit topologies) - with separated digital and analogue sections, it will be upgradable with Tube analogue stage at a later date - in fact I've just bought 100 tubes to test there variability and start "Life time tests".
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John, I know nothing about electronics, I'm an IT guy.
So, forgive me on this one. :)

IMHO tubes are not ok, they're old technology. They're more fragile, harder to get and replace, more expensive, less efficient, and I'm not sure about their reliability in terms of consistency between units and consistency during their life span.

If tubes do provide some advantages, why not simulate tubes behaviour with modern components?


Michael
 
JohnW said:
Guess today's the day! :)

A couple of points to get the best out of your new MDAC:-

1. From new, the MDAC needs about week to "run in" to sound its best

2. Try various software updates.

V0.90 - In my system the best sounding, with Basic features and a few bugs.

A08 - Fully featured + a "fuller sound" but less delicacy

A10 - I've not spent the time to listen to it - but was developed as a Bug fix of the original V0.90.

Your MDAC will be shipped with V0.99 which IMO is the worst sounding version.

MDAC2 a much more advance design - I've spent almost 3 years on its design (developing its new circuit topologies) - with separated digital and analogue sections, it will be upgradable with Tube analogue stage at a later date - in fact I've just bought 100 tubes to test there variability and start "Life time tests".
Click to expand...

I like the nice bite-size upgrade path based on future development effectively future-proofing existing product. :)
 
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