Da-capo issue (John W?)

[sq225917]

Holy ****

[loris.p]

Originally Posted by JohnW

MDAC

It will be a nice toy to play with

[anthonyf]

i suppose it's out of the question for christmas?

hey it already is christmas.....

[SY]

sq, I had to manually edit your post because of your attempt to get around the obscenity filter. That makes work for me. When I have to work, I get very, very grumpy.

Don't make me work again.

[sq225917]

Sorry Boss. :-(

[muz640]

yeah i suppose the spec is ok... Lol!

Thats pretty much exactly everything i need or want in a DAC preamp!
People have been waiting a long time for this to come out, im sure it will sound great and it will be a big success, if it comes in at under £500 i'll be very shocked, whatever the price is, i cant wait to hear it.

The other thing is, looking back through the thread it obvious to me that John W is not only a talented designer etc, but is a true enthusiast helpful and generous with his time and knowledge, an all round good egg!

Looking forward to the amps too (even if they take some time )

best, John

[JohnW]

I thought SQ was kind of clever with that all important "5".... maybe I'm behind the times... I can't even manage to send an SMS...

Anthony.

The MDAC is just going into Pre-production now – so unfortunately unlikely to reach the Sunny Shores of UK before Christmas - there’s little margin to Air Freight them...

John,

Well occasionally life can surprise - price has yet to be confirmed, however we are pushing for 5 Pence under GBP400.... if you get my drift... I'm just a little over BOM cost target… and asking for forgiveness (without having to reducing the products Specs).

Betto,

The amplifier will be released end of first quarter 2010 – however I expect demand will outstrip supply for a very long time – it’s not going to let the side down…

I didn’t mention the CD players with DAC / Pre-Amplifiers did I?

John

[Betto]

Thank you John, I am a happy man now
I am expecting the amp to be on par with the DAC...
Current dumping class A ... what a clever idea... finally done right!!
Now to put the cherry on the cake you really should work on a loudspeaker project...some grounbreaking design ... a full range panel speaker based on BMR concept for example. Why not?
All the best from rainy Brescia, northern Italy
Betto

[Studley]

John
its surely not controversial to say that the (forseeable) future of recorded music for playback is the computer hard disk. Given that, I'd be very interested to hear your views on how the sonic performance of the new DAC differs when comparing spdif input from a CD transport to the USB input from hard drive - ?

Regards
Ian

[JohnW]

Betto,

I'm an ESL Man - nothing comes close.... I'm working on a pair of speakers for Peachtree Audio (based upon Ribbon Drivers), but that will be for later next year.

Ian,

Indeed - Computer playback / IPod / IPhone is the future... Erh... soon to be reviewed in a magazine in Dec or Jan issue of..... (I'm not sure how much I can say - so sorry for being so cryptic).

If the Data Stream is Bit Accurate - then ideally the sound quality should be the same whatever the replay device - if it where not for:-

1. JITTER of the Data source
2a. RF noise injection from source to DAC (Directly via RF Emissions, Mains and Signal cabling).
2b. Noise injected into DAC via Earth leakage currents and Ground loops.

Clock locking and Asynchronies USB go a long way to solving issue 1 (MDAC has both options), however the effects of issues 2a & 2b will also effect the Phase Noise of the DAC’s internal Master Clock (worsen the Clock Jitter levels via external noise injection onto the DAC’s Ground plane / PSU etc).

MDAC has a novel circuit block I’ve called a “Cascaded Asynchronies Time Domain Attenuator” to help reduce the detrimental effects of non synchronies clock sources (i.e. when using the MDAC without clock-lock or Asynchronies USB) – Still nothing beats a correctly synchronised Data Source.

The subject of Jitter, RF and Ground noise is endless….

Betto,

Yes the weather’s also been really lousy here in CZ, has not stopped raining – car’s covered in Mud as it’s churned up our once grass drive…

10 years ago or so, I spent 2 years developing and understanding “Analogue amplifiers”. After 2 years of development – and achieving results better than I could measure – I realised that really Analogue amplifiers where not the way to go – and then started R&D on switching amplifiers. However at the time, I fell in love with the elegance of Current Dumping – and could not understand why it had not been developed further. Current Dumping to this day is still very miss-understood – 10 years back I achieved breathtaking performance with the topology.

When Peter Walker (and the other Co-designer (sorry I currently forget his name)) developed the original Current-dumping circuit, transistors where a major part of a units cost, so the design was inherently compromised. Today, the cost of transistors constitutes very little to the total BOM cost of a design, allowing far greater design flexibility – a luxury that Peter Walker and Co. did not have.

However, one area which is still common today manufacturing in China (if not more so), and manufacturing 30 years ago in England is insuring stable and consistent performance over the products entire production life – unit to unit. Adjusting OPS bias Current is strictly a no – no. This is an area where current dumping really scores…

The limitations of Current dumping are not in its topology – but its cost constrained 30 year old implementation.

One of Class A/B’s greatest issue is accurately setting the bias current – which amazises me, as during my "R&D" 10 years back I developed a VERY simple circuit to perform the task that would added less then 10 cents to a standard design’s cost – in fact cheaper then the cost of the Bias POT… Its really poor refection that Class A/B designs still rely on Bias settings… I hope one day to release a commercial design with the simple “Bias circuit”… just Pls. don’t ask me when…

If you where about to ask, one of the best sounding amplifiers I’ve ever built was Class D, however there’s just to much public negative pre-judgment towards Hi-Fi Class D, the reason I chose to use a 10 year old development of Current Dumping for the coming amplifier.

John