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MDAC First Listen (part 00100000)

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I got the croft 7 power today. Had a good 6 hour listen. I must say I am amazed at how much difference this amp has made. So much more musical. The soundstage is huge in comparison to the creek and the mids are much sweeter. It sings,it's like it has a funk mode compressor on it.
The creek power stage must be vastly inferior.
I am very very happy :)
 
JohnW said:
Your unit in "original" MDAC L2 form:-

https://dl.dropboxusercontent.com/u/86116171/Origianl Mod.JPG

The analogue stage completely stripped and PCB cleaned - ready for rebuild:-

https://dl.dropboxusercontent.com/u/86116171/Stripped.JPG

And finally rebuilt to the latest Fusion Sec:-

https://dl.dropboxusercontent.com/u/86116171/Fusioned.JPG

You units now on final test and will be shipped tomorrow - Renata will Email you shortly.
Click to expand...
...

Looks good John, Thanks. And look forward to auditioning of the sonic improvements.

Regards

Graham
 
Graham,

Been in rather a flap today - I listened to your DAC first thing this morning and it just did not sound right - I've spent the day trying to understand what was wrong - I believe I've found the issue (a problem with the performance of the Clock regulator).

I'll listen to it first thing in the Morning - I'm fairly confident I've resolved the issue ... I really need my Lab with its listening room so I can listen during the night without disturbing anyone... :(

I'm very sorry for the slight delay...

In an effort to understand what was wrong with the sound quality I lost more then a few hours chasing a problem that did not exist. Your unit was loaded with V0.90 software so I didn't reflash with V0.90 as I normally do for my listening session... However the MDAC indicated 24bit data when it should have been 16 bit wavefile... So I blamed my computer and spent a couple of hours trying to understand what was wrong - only to realise that you had LSB restoration set to "leave unmodified"!!!! once I'd corrected this it was closer to my expectations but still not right...

I've been using a CDQ since I sent my MDAC's PCB to JTC many months ago... the CDQ is really a distant second best...
 
Hayche said:
I got the croft 7 power today. Had a good 6 hour listen. I must say I am amazed at how much difference this amp has made. So much more musical. The soundstage is huge in comparison to the creek and the mids are much sweeter. It sings,it's like it has a funk mode compressor on it.
The creek power stage must be vastly inferior.
I am very very happy :)
Click to expand...

Hayche,

I'm very happy as I know you purchased the amp "blind" in my recommendation...

The Creek is a Middle of the road, honest design - but nothing that's going to set the world alight, its conventional in design with Op-amp signal and Transistor output stage.

The Croft is VERY nice, Tube front end with Mosfet output stage - a sure recipe for massive holographic sound stage, a lively mid-band & sweet top end...
 
rtrt said:
I'd be unlikely to need masses of volume, but would like to be comfortable i'd not damage the MDAC with directly driving speakers with 5 watts.

It seems to me that MDAC delivering 5 Watts of Class A directly into high quality smallish speakers could be an interesting match.
Click to expand...

The output stage of the MDAC is design to drive a 1.5Ohm load to full 2.2RMS Balanced.... so its OK with 4 or 8ohms loads (When driven "bridged / balanced" the load will appear as half the load impedance to the output devices, so 4ohms becomes 2ohms and likewise 8ohms appears as 4 ohms.

To insure linearity and speed x4 Mosfet output devices are used per output phase - so making a total of x16 Mosfet devices in an MDAC2!

Each set of these output devices "per phase" are mounted on a heatbar, so there are x4 heatbars in the MDAC2 to help dissipate the output stages ClassA heat.

You can see the heatbar with the x4 osfet output device mounted on the first MDAC2 prototype PCB (they are "Crudely" mounted on the underside of this test PCB to allow me clearance on the topside to work with the SMD components which would otherwise be obscured by the heatsinks).

https://dl.dropboxusercontent.com/u/86116171/MDAC2 OPS heatsink.JPG

While the output stage is design to drive 1.5 ohms - unfortunately the MDAC2 PSU is not rated to deliver the required current on an indefinite basis - (Being a DAC, not a Power amplifier) - but I suspect it will do a pretty amazing job driving small efficient speakers directly ("only" to 5W but hey ho...)
 
iansr said:
What you need is a pair of very high efficiency speakers like horns. 5w is more than enough to deafen you with some circa 100db sensitivity speakers.
Click to expand...

I'd love to try that oneday - but its not gonig to be with my Martin Logan CLS's :p
 
adamdea said:
as a matter of interest John, is it possible for the M-dac reading of actual sample rate to have resolution below 1Hz? Just wondering, since the 170.3 reads 44,100 whether clock locked or not.
Click to expand...

Adam,

Sorry, been working on the MDAC upgrades which I've just completed so I can work on the MDAC2 PCB :) - I do owe you a reply but its now 4.50am.. so I'll catchup with some sleep first :)
 
JohnW said:
Hayche,

I'm very happy as I know you purchased the amp "blind" in my recommendation...

The Creek is a Middle of the road, honest design - but nothing that's going to set the world alight, its conventional in design with Op-amp signal and Transistor output stage.

The Croft is VERY nice, Tube front end with Mosfet output stage - a sure recipe for massive holographic sound stage, a lively mid-band & sweet top end...
Click to expand...
What Creek was that?
I own the Destiny 2 integrated and it's all mosfet as far as I know . Thought that was typical for Creek.
 
I understand it was the Creek 50a (Dominik and myself work on the project with the front panel / OLED display :) , Backlit Buttons etc.) It probably Creeks best "budget" design.

The Croft Series 7 is twice the price of the Creek (power amplifier only) - but its a different class of product - It will measure quite poorly, but will be hard to beat sonically...
 
mattgbell said:
John, what power amp do you use with your MLs? I ask as an ML owner.

(Apologies for going off topic.)

Matt
Click to expand...

"Sample 104" it was a small power amplifier prototype I designed for Cambridge Audio many years ago - Limited power but can supply high peak currents - although its easily over-driven especially with Female vocals which can cause it to "Break Up" if played too loud.
 
JohnW said:
I'll listen to it first thing in the Morning - I'm fairly confident I've resolved the issue ... I really need my Lab with its listening room so I can listen during the night without disturbing anyone... :(
Click to expand...

Graham,

Good news - your MDAC Fusion is now ready to go :)

The sound had a forward character to female vocals - the problem was traced to a "Hump" in the Clocks PSU noise floor, the hump was very broad reaching its peak at about 30KHz at -132dB.

https://dl.dropboxusercontent.com/u/86116171/Graham1.jpg

The Clock PSU noise floor once corrected:-

https://dl.dropboxusercontent.com/u/86116171/Graham2.jpg

Note a different Frequency span - but its clear to see the noise floor is flat at around -162dB which is the analysers noise floor.

It never ceases to amaze me how sensitive human hearing is!

You unit is ready to ship :), again I'm very sorry for the delay.
 
JohnW said:
Graham,

Good news - your MDAC Fusion is now ready to go :)

The sound had a forward character to female vocals - the problem was traced to a "Hump" in the Clocks PSU noise floor, the hump was very broad reaching its peak at about 30KHz at -132dB.

https://dl.dropboxusercontent.com/u/86116171/Graham1.jpg

The Clock PSU noise floor once corrected:-

https://dl.dropboxusercontent.com/u/86116171/Graham2.jpg

Note a different Frequency span - but its clear to see the noise floor is flat at around -162dB which is the analysers noise floor.

It never ceases to amaze me how sensitive human hearing is!

You unit is ready to ship :), again I'm very sorry for the delay.
Click to expand...

Hi John,

So this doesn't happen with all original MDAC's ?
Will you measure and adjust all MDAC2 individually or design such you can rely on the optimized circuit design ?
 
No, the orginal MDAC design does not have this peak - there is a small peak but its below 100Hz.

I made a component error while rebuilding Graham's unit to the latest Fusion Spec. - obviously it does not show up in standard Audio tests - only during final listening.

The MDAC2 will be correct 'by design' - and apart from full measurements, I'll listen to each PCB before shipping to double insure constancy... its the advantage of small "bespoke" production.
 
JohnW said:
Hayche,



I'm very happy as I know you purchased the amp "blind" in my recommendation...



The Creek is a Middle of the road, honest design - but nothing that's going to set the world alight, its conventional in design with Op-amp signal and Transistor output stage.



The Croft is VERY nice, Tube front end with Mosfet output stage - a sure recipe for massive holographic sound stage, a lively mid-band & sweet top end...
Click to expand...


Hats off to you for the recommendation john.
I am guessing it makes more sense to use a mosfet amp with a mosfet dac now.
I can't stop listening with not a tad of ear ache in sight for all the people who say the mdac is harsh!
Mids are supreme!!

Creek 50a was bipolar btw. Worked well with the intergrated pre but sounded a little mechanical to me.
 
Hayche said:
Hats off to you for the recommendation john.
I am guessing it makes more sense to use a mosfet amp with a mosfet dac now.
I can't stop listening with not a tad of ear ache in sight for all the people who say the mdac is harsh! Mids are supreme!!
Click to expand...

That's why we plan to release our own matching power amplifier - There are so very few decent power-amps in the MDAC's price range... as you say like the Creek they tend to be "average" and unemotional...
 
John, how much do you reckon the power amp will cost (mono or stereo)? Also are you planning on making a new box or taking an old widely available one and modding the innards? I really should stop asking you questions shouldn't i?
 
adamdea said:
John, how much do you reckon the power amp will cost (mono or stereo)? Also are you planning on making a new box or taking an old widely available one and modding the innards? I really should stop asking you questions shouldn't i?
Click to expand...

Adam, you're right to ask. There's lots of interest in this. A power amp to complement the MDAC2 would be most excellent. Even better if it could drive Martin Logans ... :cool:
 
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