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MDAC First Listen (part 00101110)

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Fred,

Sorry for the delay. your HDCD IC is genuine - tested in an IsoMagic I recently purchased from Ebay (one of my designs from 1999) - its scary how time flys!

That's good news, I also got one from the same vendor.
PMD100.jpg

the link @ DIYaudio
 
That's good news, I also got one from the same vendor.

Do you think it is worth testing?
PMD100.jpg

Probably OTT, but just wondering if a fake one could potentially cause any damage ?

No, it will not damage the FDAC... I could always insert your IC for you....

Do you want to order a PMD200? Jarek and I have decided to add an internal Daughter board "socket" that will allow us to design small PCB's to cater for such options as different hardware filters in the future - you can never tell whats coming around the corner in a few years - we want to keep the FDAC as flexible as possible. I have no desire to need to update the design in a few years - after 4 years working on the FDAC I never want to see a DAC design :)
 
I recently bought one from Ebay as Its one of my favorite designs - while I've not yet had a chance to compare against the MDAC (as its only Single ended output and I only have balanced cables also no preamplifier) I suspect its better then the MDAC in certain areas.

Its certainly my favorite design by far for Cambridge Audio - very underrated....

Heres one on my lab Bench ATM with Fred's HDCD chip under test:-

https://dl.dropboxusercontent.com/u/86116171/Isomagic cropped.jpg

You can use with just a BNC / optical SPDIF, make sure the little silver toggle switch on the rear is flipped in the up position if your not clock-locking it to a suitable CD transport.

Excellent John, thank you.

PS The MDAC you sorted for me is superb, totally superb. Wish it wasn't so good as I'd order an FDAC. :D
 
For Mid Range and Highs yes, but they have Zero practical bass - it would drive you nuts...!

The CLS are a odd speaker, in some rooms they work REALLY well - and nothing comes close, but sadly in others they sound like a telephone handset...

The Aeons that a I use as a more "normal" amplifier load seem to work in almost any room.

https://dl.dropboxusercontent.com/u/86116171/CLS and Aeons.JPG

That's the challenge isn't it .. To get it to work in your room. I guess the CLS needs more space to work because of its physical size. The cancelling effect of the rear waves could destroy soundstage also as well as reflection points ...but that does sound extreme to sound like a telephone headset :eek:

Having separate subs gives you the flexibility to move them around the room to avoid certain issues and to have their own eq applied.

Have a lot on at the moment with the listening room being extended, so not sure about the risk . And the summits just work :D
 
Excellent John, thank you.

PS The MDAC you sorted for me is superb, totally superb. Wish it wasn't so good as I'd order an FDAC. :D

That's why I didn't hesitate ordering the FDAC after John had modified my MDAC to a fusion spec
 
Do you want to order a PMD200? Jarek and I have decided to add an internal Daughter board "socket" that will allow us to design small PCB's to cater for such options as different hardware filters in the future

Hmm... I'm tempted by this if someone else was interested (it's for 2 pc)

http://www.aliexpress.com/item/PMD-200-HDCD-QFP100/32290824938.html

but worried it might not be genuine, especially as it states "9998 lots available" !
Is there any way to test it?
 
That's the challenge isn't it .. To get it to work in your room. I guess the CLS needs more space to work because of its physical size. The cancelling effect of the rear waves could destroy soundstage also as well as reflection points .

The Quad ESL panels have a fine fabric applied to the rear stator presumably to dampen the rear wave,and prevent the cancellation effect.
So far as I am aware ML do not have such. Maybe try a diffusion panel behind the speakers.

Some insight here.

http://www.stereophile.com/content/sound-lab-1-electrostatic-loudspeaker-page-3#lktWqH3tR1dTr9wX.97

My next project is to make new frames with mass damping as opposed to the flimsy/floppy factory version.
 
That's why I didn't hesitate ordering the FDAC after John had modified my MDAC to a fusion spec

In all honesty I'd have ordered one Phil, but as the massive specs. grew I fear it'd be wasted on me. I'm USB from laptop and phono's to pre amp only. I'd use none of the other features sadly.
 
In all honesty I'd have ordered one Phil, but as the massive specs. grew I fear it'd be wasted on me. I'm USB from laptop and phono's to pre amp only. I'd use none of the other features sadly.


Lets wait for the FDAC little :)
 
Hmm... I'm tempted by this if someone else was interested (it's for 2 pc)

http://www.aliexpress.com/item/PMD-200-HDCD-QFP100/32290824938.html

but worried it might not be genuine, especially as it states "9998 lots available" !
Is there any way to test it?

Hi TimR, I'd be willing to join you in getting this PMD200 chip....please PM me on how to proceed....( I could send you 50% by paypal)

I wonder if you could ship these straight to JohnW for testing and maybe for later installation into our units?
 
but that does sound extreme to sound like a telephone headset :eek:

With the Aeons installed there was still alittle "Shoutyness" yet congested midrange so I made up a new pair of Balanced interconnects and they for sure reduced the problem - I also think I'm pushing the Power amps too far with the CLS's - I really need the VFETs now.

I've jut installed a far more powerful computer in the Lab, as the laptop that was here before is unable to handle the Computer simulations I need to confirm some new ideas for the VFETs - I plan to spend 2 hours a day on the VFET design - I'd like to see these in "production" late summer or as soon as FDAC is complete.

Having separate subs gives you the flexibility to move them around the room to avoid certain issues and to have their own eq applied.

Well I just bought a S/H Rel Sub Woofer, but I suspect that the CLS's don't go deep enough in practice to integrate well, but lets see. At the very least the sub should be good with the Aeons.
 
Nothing I have here has lids on!

John, most of your boxes don't have to live with the house decor! Also, they are competently wired up......Misterdog, thanks for the rescue operation. Of course there isn't much information in the picture, though with careful inspection you should be able to pick out the screen of my MDAC. I agree that the Calex runs a bit warm, though in the lash-up version I only tried the finger test; the vertical panel above the terminal block was the hottest. Today I ran more careful tests with an IR thermometer, first with the lid on , so it's the case temperature. It started at 19C, reached 30C after 2hr., and 31C 90 minutes later. At the same times the MDAC front panel was at 27C and 32C, so given time the MDAC actually gets hotter. Taking the lid off, I measured maxima of 31C and 32C on the top surfaces of the two Calex units, and 47C and 46C on that panel above the terminals.
 
The Quad ESL panels have a fine fabric applied to the rear stator presumably to dampen the rear wave,and prevent the cancellation effect.
So far as I am aware ML do not have such. Maybe try a diffusion panel behind the speakers.

Some insight here.

http://www.stereophile.com/content/sound-lab-1-electrostatic-loudspeaker-page-3#lktWqH3tR1dTr9wX.97

My next project is to make new frames with mass damping as opposed to the flimsy/floppy factory version.

Cancellation due to reflection off the rear wall only occurs at lower frequencies. A fine fabric cover on the back of the panel will do nothing to absorb LF sound.

In other words, cancellation due to rear reflections applies equally to Quad and ML designs.

The best way to prevent cancellation is to nullify the reflections altogether, with a wodge of absorbent stuff on the rear wall. For an ML X-Stat panel (which goes down to about 350Hz) you would need a thickness of absorbent material of around 50cm (i.e. around half the wavelength of a 350Hz signal).

EDIT This assumes of course that you haven't got the luxury of an enormous room, with the speakers pushed way out from the rear wall, in which case none of the above applies.
 
Cancellation due to reflection off the rear wall only occurs at lower frequencies. A fine fabric cover on the back of the panel will do nothing to absorb LF sound.

In other words, cancellation due to rear reflections applies equally to Quad and ML designs.

The best way to prevent cancellation is to nullify the reflections altogether, with a wodge of absorbent stuff on the rear wall. For an ML X-Stat panel (which goes down to about 350Hz) you would need a thickness of absorbent material of around 50cm (i.e. around half the wavelength of a 350Hz signal).

EDIT This assumes of course that you haven't got the luxury of an enormous room, with the speakers pushed way out from the rear wall, in which case none of the above applies.

Actually you need to absorb a quarter wavelength , and foam isn't particularly good in high pressure low velocity areas, you would really need membrane traps ,helmhotz resonators .
Keith.
 
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