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MDAC First Listen (part XXVIII)

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JohnW said:
I've not seen a physical isolator in the flesh - but it appears the olimex inserts between cables - so you will need second USB cable.
Click to expand...

Been using mine for 2 years or so with no problems , the gimp like pcb (shrink wrapped in rubber) looks a bit diy, but works a treat.
Any USB 2.0 spec cable works fine don't spend more than £5.
Yes you need 2. And they recommend not to go over 1.8m for each one.
 
Interestingly this whole debate "What Does A Computer Sound Like?" is in full swing again. Why spend 7K on a Weiss or fraction of that on a NetTop and an Async USB Dac ?

I'd just like to ask the question here and understand what steps MDAC owners have taken in order to ensure the best sound.

In regards to Olimex, can you totally isolate the DAC using one of these isolators ? What else can get through the USB cable that can upset the final analogue signal to the DACS output?

Do I recall John stating that their were no significant differences by modding the power supply to the current Toy/Fusion versions?

I read that someone was selling their MCRU power supply after the T/F L3 upgrade, as they were unable to detect a difference.

Who has taken steps in filtering or isolating their usb cables and/or power inlets to the DAC?

Has anyone gone to the extremes of shielding their computer source or implemented internal SATA filters , special wiring looms etc..?

Has anyone gone further up stream to the DAC ?

If the isolator is not 100% effective would it not make sense to spend a little extra on a well constructed shielded USB cable ?
*** please this is not in respect as to whether the digital signal reaches in bit perfect condition to the DAC, but purely in relation to RFI/EMI isolation. ( I don't want to hear "my printer still works if I use a cheapo USB cable compare to a £100 audioquest blah blah" ).


I've taken what I think are common sense precautions such as;


  • ** edit Olimex USB isolator

    Separating power and signal cable runs with the myriad of AV cables running from my hifi cabinet.

    Using Tacima Mains conditioner and RFI filter mains extension blocks.

    Spikey Surge protectors inserted on first socket of spur.

    Provided sturdy granite platforms for DAC and amps with DIY rubber feet.
 
Shielding would only help if the noise doesn't come from the computer via the usb socket- which it does.
 
ManMan said:
Is this one or anything better?

https://www.olimex.com/Products/Modules/Interface/USB-ISO/

do I need 2 USB cables now to connect PC-isolator-MDAC or the isolator can be connected directly onto either MDAC or PC itself?
Click to expand...


This one can connect straight to the USB port on your PC

http://electronicsshop.dk/?id=1038

I have one, however I cannot detect any difference with or without it between my Samsung RV510 Laptop and MDAC. I guess Samsung Laptops don't cause a problem! It always sounds good. YMMV of course.

Clive
 
I also have the Danish isolator, which works fine (bit perfect and all) with computers as well as my SBT.

I haven't detected any significant impact on sound, and use it more as a precaution.

I should also say that there is no audible noise/hiss coming from the MDAC or amps, even when cranking up the volume beyond reason.
 
JohnW said:
Jim,

Yes, the USB isolator should solve your issue :)
Click to expand...

Thank you all. I will place an order today for the isolator. Is there any reason that this should pop up with no changes to the system after 2 years or is this just random?

Thanks again,

Jim

By the way...The Mojo Audio Mac Mini has a bunch of mods to it below that are either voodoo or help with filtering, but it has worked beautifully up to a few weeks ago.

Internal Filter Module features:
LCLCLCCCCC spread spectrum filtering for expanded bandwidth
Removes EMI, RFI, digital, and clocking noise above 100MHz
High-performance hardwired or convenient removable DC power cable
Fully shielded inductors on both the positive and ground
Anti-resonant thermally transparent internal mounting system
No unnecessary dielectric covering to add noise and hold heat (shrink tubing)
Comparable to our competitor’s "Level 3" Internal Power Filter
We use only the highest-quality parts:
Organic polymer capacitors with ERS as low as 7mOhms
Metallized film or foil and film bypass capacitors
IXYS ultrafast soft recovery Hexfred diode bridge
Vishay 5ppm 1% resistors and 15ppm film trim pots
Furutech rhodium-plated IEC AC power inlet
Neutrik silver-plated XLR DC power outlet
Heavy gauge all-aluminum chassis
All non-magnetic stainless steel hardware
Durable high-temp powder coated inside and out
Your choice of black or clear anodized face plate
Triad precision wound 160VA toroidal transformer
EAR antiresonant feet
 
jiminsd said:
The computer source is a Mojo Audio Mac Mini with an outboard linear power supply and optimized for music - no fan, no extraneous programs, SSD internal and thunderbolt external HD, etc,

The noise goes away completely if I unplug the USB cable or power down the Mac Mini so it's clearly coming from the Mac Mini.

I've read here about some Olimex USB isolators that are available from the EU. Is this what I need?

Jim
Click to expand...

I had a similar noise suddenly. It was due to a USB hard drive power supply that developed a fault, and it was fixed with a new power supply. You can identify the culprit by disconnecting everything from the Mac mini and then connecting it one by one. Of course it could also be the mac mini's power supply. Can you use the original Apple one? Identify the fault rather than using an isolator.
 
All USB specification compliant cables are already braid and foil shielded, no need for anything more, add an isolator if you need one to help with noise on the 5v or gnd wires.
 
This might be interesting for the ones going for M-DAC2 which will support HS USB 2 and use an isolator.
http://www.diyaudio.com/forums/digi...g-regarding-use-usb2iso-usb-2-0-isolator.html

Seams like there are no (cheap) USB-isolators that works with high speed USB 2.0.
There is even a risk for fire or burnt equipment.

I dont want to scare anyone, but sure dont want anyone to burn down their house or toast their equipment.

It might be a good idea to have the isolation done in the M-DAC2 from the start, what do you think about that John?
http://www.analog.com/library/analogdialogue/archives/43-06/USB_isolator.html
 
Obi1 said:
This might be interesting for the ones going for M-DAC2 which will support HS USB 2 and use an isolator.
http://www.diyaudio.com/forums/digi...g-regarding-use-usb2iso-usb-2-0-isolator.html

Seams like there are no (cheap) USB-isolators that works with high speed USB 2.0.
There is even a risk for fire or burnt equipment.

I dont want to scare anyone, but sure dont want anyone to burn down their house or toast their equipment.

It might be a good idea to have the isolation done in the M-DAC2 from the start, what do you think about that John?
http://www.analog.com/library/analogdialogue/archives/43-06/USB_isolator.html
Click to expand...
The use of an isolator with USB 2.0 has been already discussed in one of the MDAC First Listen threads. The conclusion being that there aren't much usable USB 2.0 (High Speed) isolation implementation - the only one being that GBP400 optical extender thing. There are however some promising unfinished products for USB3, which might show up later, like http://www.corning.com/CableSystems/OpticalCablesbyCorning/products/USB-3.Optical.aspx and as long as USB 2.0 compatibility is implemented, they should get the job done, hopefully a lot cheaper.

AFAIK John didn't want to implement an isolator within the MDAC due to RFI leakage. Although I'd even pay extra to have that functionality within MDAC2, even if it means a separate shielded mini PCB mounted on/above the main PCB. Doing the isolation outside is simply not viable, there's hardly going to be anything below GBP200 for USB 2.0 ...
 
I have not tried using an isolator, I dont have any reason to since there is no need for one in my current system.
But if it could be done in a way that dont affect sq in a negative way, I would also be prepared to pay extra for it. You never know if you might need isolation if you change something in the future.
 
Ian M said:
Looks like I'm still weeks away then John, it's been a long time. 😢
Click to expand...

Ian,

I hear you! I'll work on your unit over the weekend as well - I'm extremely sorry for he extended delay - I'll make it up to you with the MDAC2.
 
John,

A few words on the Fusion upgrade, old news to many I know.

Wow what a transformation, all the positive comments made by the other guys are spot on. This is a very significant upgrade and all the better after burning in for a few days. I’m finding the bass is much improved and whilst not cavernous, is much more defined, clear & fullsome. The mid-range is truly remarkable with a real life-like feel.

I’m finding the projection very well balanced, with the different strands of the music all at the right level, nothing is shouting too loud. The detail is there, but it’s greater detail with a more life-like sound.

If the MDAC 2 is better than this we’re in for a major treat, this MDAC is b****y brilliant now. :D

Top job John
 
MattN, btw, let me know which filter you end up with after the upgrade. I used to prefer XD filter, but after the upgrade, i am now deciding between Minimum Phase and the first Optimal Transient filter (a bit more clarity vs a bit more drive).
 
Hi John,

I'm listening to my long time missed fusioned MDAC atm and can only state, that the waitening has been more than worth it!!! The first few days after letting it run in for 2 days, I've been a little disappointed as for the bass performance - it seemed very restrained. And although the mids and highs were already great, the overall representation was no real revelation for me...

But now... I can not reveal, how delighted I am :) :) :) Everything opened up and the representation is so unbelievable magnificent. I did not expect that my current setup (which includes a simple 400€ PA amp as interim solution until the Mimps will be available) is able to reproduce that corporeal, holographical, unchained! Thanks a ton for this great work!!!
 
I've collected the adopters today. Nothing fancy but solid quality. I think they will suffice.

Everything should be en route tomorrow.
 
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