MDAC First Listen (part 00100001)

[JohnW]

Some people really must have nothing to do in India to bother messing about with our Wiki page....

What total losers... They really need to get a life!

 

[fusion5]

What total losers... They really need to get a life!

Or a good (M)DAC

 

[rmgalley]

18.3V, Yep that's going to be the UK on the "high side"... Good for MDAC2

Hi John,

Now you have two units have you compared the SQ between them?

Actually no, not yet. The second unit was installed in the bedroom for temporary headphone duties but there it has remained. I haven't got around to updating the firmware (still v0.99/v0.97).

I'm still loving my Toy unit but, with the weather being so favourable for outside construction work, I have been obliged to get stuck in to repairing a collapsed sewer!

I'm still looking forward to the comparison and will update you in due course.

Roger.

 

[fusion5]

I still have all the firmware updaters for windows in my dropbox including some rare (and perhaps faulty) versions: https://dl.dropboxusercontent.com/u/75485064/mdac.html

Some of the wiki links should also link to my dropbox.

 

[JohnW]

I have been obliged to get stuck in to repairing a collapsed sewer!

Funny, today I was wondering how you where doing as I worked on the Lab for the first time in months - progressing on the roof (it had a temporary covering before).

I guess I'd rather be working on the roof (even though I get very nervous when peering over the sides) then working in the sewer .

We have been flooded here twice last week, so I really need to get the test equipment out of the basement where its been in storage since we returned from China - hence the motivation to work on the roof... I've just no time... but it will change my life and make things so much easier when I have my lab back up in operation - the equipment is just so heavy and bulky I'm dissuade to lug it about - when I could really benefit from using it during the development of the MDAC2... Case in point is the phase noise test set-up...

 

[rmgalley]

I worked on the Lab for the first time in months - progressing on the roof

I know what you mean about roofs. It seems a lot further looking down to the ground compared to looking from that same place upwards. How long will it be before you can start bringing your precious test/measurement kit in there?

With my hole-in-the-ground activities I have only yesterday caught up with the VFET power amp project. I was intending waiting for 4 x MIMPs or 2 x MAMPs but I've been giving the VFET amp consideration and have decided it is not only preferable to a pair of MAMPs but, cost-wise, is just 'do-able' for me.

If it is possible for me to be added to the project list, what is the procedure for the upfront payment?

Here's hoping ....

Roger.

 

[JohnW]

Roger,

Well I dragged the most expensive items into the loft (up 6 flights of stairs, with each item weighing anywhere between 20kg to 50kg it took me 2 days I could ill afford)... however I'm seriously concerned about the loading on the "ceiling", however the water had entered the basement so I had no choice (luckily the equipment was on pallets which kept them clear of the water, but it was a close thing...).

Can you please PM me your Email address as Renata says she has 3 on record for you? - Renata will then send you a PayPal invoice Thank you and welcome to the VFET amp project - luckily I just order 30 more pairs of VFETs

The VFET amps will be my own "Reference" units so they will be a stepup to the MAMPs / MIMPs, I'm also not limited by chassis size etc. Not to mention that due to there limited hand built "production" run, I can use exotic components in the design such as the VFETS and Tubes Very nice indeed This is when its really fun

 

[JohnW]

Or a good (M)DAC

Yes, but I wonder what the mains voltage will be over there?

 

[spiderlane]

Some people really must have nothing to do in India to bother messing about with our Wiki page....

What total losers... They really need to get a life!

Regarding the Wiki page, I noticed that it had been defaced the other day and the August 2nd revision is the one that I restored from (what appeared to be) the last known good copy. The "Very Nice Site" stuff was there before and has come back steadily over the last few days, you can see the history here -> http://mdac.referata.com/w/index.php?title=Main_Page&action=history

Edits have been made from Ukraine, India, Spain, US, Indonesia, Thailand etc suggesting to me that it's an automated spam bot using compromised PC's in various locations around the world rather than a human so you can't block access by source IP addresses. It's fairly smart in that it vandalises the pages in stages over a period of time, slowly removing the real content and adding "Very nice site" presumably so that it doesn't get blocked for making massive edits in a single hit.

It also adds comments like "At this time it seems like Movable Type is the best blogging platform available right now. from what I've read Is that what you are using on your blog? dfebdkcdaegadfck" which are supposed to look like human generated content, but if you Google that comment you'll find lots of matches of that string in other forums around the web, presumably compromised in the same way.

The original content is always restorable (as fusion5 and myself have done) but I fully believe that this will start to happen again over the next few days as it's an automated process. Perhaps the wiki should be configured so that only authorised and/or registered users can edit the content? It's a shame that this has to be done, but on the wild west of the internet stuff like this will always happen on open access sites

If I can help in any way with I'd be more than happy to do so, since I hate seeing a useful, community generated resource continually defaced.

Cheers
Mark

 

[TimR]

The VFET amps will be my own "Reference" units so they will be a stepup to the MAMPs / MIMPs, I'm also not limited by chassis size etc. Not to mention that due to there limited hand built "production" run, I can use exotic components in the design such as the VFETS and Tubes Very nice indeed This is when its really fun

Hi John, Thanks very much for the PM a couple of days back, much appreciated. Sorry for the delay, I'm still pondering my decision on this...

One quick question (I hope):
If I recall correctly, there was some excitement about your MIMP design (or was it the MAMP?) incorporating some clever circuitry where it could some how detect and compensate (for want of a better word) for an electrical imbalance in the attached components? Hopefully you'll understand what I'm rambling on about I wish I could remember more about it but as you know, I'm not very technical!

So basically I was wondering if all the same magic you were planning for the MIMP/MAMP was going to be included (or even required) in your VFET amps?

 

[anjora]

There seams to be a lot of interest for new MDAC2 units, i want a silver unit but i have missed the opportunities for buying a salvaged one. I posted about mdac2 on a swedish forun and there where a lot of interest there aswell. would it be possible to build new cases+psu:s instead of taking it from broken MDACs, time is not really an issue for me, maybe this could be a future project?

I think a lot of people would be interested in the mdac2 l3 unit(there is no 768kS/s ADC on the market and all interesting ADC:s are overpriced).

 

[Rosewind]

John.

Please, reserve one set of V-Fet mono blocks for me. I've sent you a PM.

Does anyone know of an article that touches upon the special qualities and sound properties of V-Fet amps? So far I have read a lot of accounts of how exposed the V-Fets themselves are due to failure in other components that they rely on, and very little about what they do to the sound compared to valves and mos-fets etc.
Best wishes,
Peter

 

[iansr]

Peter
You might find some comments on diyaudio.com where people have made their own amps with them. Also perhaps relevant are the SIT amps made by Nelson Pass under his First Watt brand. They utilize modern day versions of the VFETS as I understand it. There are reviews on 6moons amongst other places. The most interesting thing for me is that they behave like triodes. Have you ever heard a good SET amp driving efficient speakers? Something special. Now, if you could get that SQ but with lots of power . . . . And no nasty output transformers in the signal path. Got to stop, getting too excited )
Ian
PS. I should add that John's amps will be very different to the first watt amps in design, and a lot more powerful.

 

[Rosewind]

Peter
You might find some comments on diyaudio.com where people have made their own amps with them. Also perhaps relevant are the SIT amps made by Nelson Pass under his First Watt brand. They utilize modern day versions of the VFETS as I understand it. There are reviews on 6moons amongst other places. The most interesting thing for me is that they behave like triodes. Have you ever heard a good SET amp driving efficient speakers? Something special. Now, if you could get that SQ but with lots of power . . . . And no nasty output transformers in the signal path. Got to stop, getting too excited )
Ian
PS. I should add that John's amps will be very different to the first watt amps in design, and a lot more powerful.

Thanks Ian.

I stumbled upon the Nelson Pass thread but was put off by the need to read everything to get to the info I am after - sort of like having to read through the MDAC2 threads. But I will make the effort. After I have sold off the Nap 200s + Tunebox, I will still have a Nac 252 sitting here. It was bought when we added 50square meters to the house, so it's not a unit that I can sell without my wife's consent. I will have to see what the Nac does to the sound in comparison to just running the V-Fets from the MDAC2 L3-4 and then convince her. We run all sound through it - TV (two channels are enough), Dac/music player, DVD-recorder etc.

Peter

 

[JohnW]

If I can help in any way with I'd be more than happy to do so, since I hate seeing a useful, community generated resource continually defaced.

Cheers
Mark

Mark,

Thank you for your support - Yes editing by a Botnet sounds more plausible as I cannot understand who would bother with our own little Wiki page....

Maybe we are just innocent victims of an extortion attempt on the owners of the Website.

 

[JohnW]

John.

Please, reserve one set of V-Fet mono blocks for me. I've sent you a PM.

Does anyone know of an article that touches upon the special qualities and sound properties of V-Fet amps? So far I have read a lot of accounts of how exposed the V-Fets themselves are due to failure in other components that they rely on, and very little about what they do to the sound compared to valves and mos-fets etc.
Best wishes,
Peter

Peter,

OK noted - hopefully I'll have confirmation of my latest order of 30 pairs of VFETs today.

 

[JohnW]

Hi John, Thanks very much for the PM a couple of days back, much appreciated. Sorry for the delay, I'm still pondering my decision on this...

One quick question (I hope):
If I recall correctly, there was some excitement about your MIMP design (or was it the MAMP?) incorporating some clever circuitry where it could some how detect and compensate (for want of a better word) for an electrical imbalance in the attached components? Hopefully you'll understand what I'm rambling on about I wish I could remember more about it but as you know, I'm not very technical!

So basically I was wondering if all the same magic you were planning for the MIMP/MAMP was going to be included (or even required) in your VFET amps?

Tim,

The VFET Amp will include the "Current dumping Bridge circuit" - this is a feedforward error compensation system. This relies on the "balancing" of an electrical bridge circuit to correct for any errors without relying on negative feedback for low distortion.

The aim of the design is to have the simplest circuit topology (well by my standards at least), a low feedback design while achieving the highest linearity.

The unique circuit requirements of VFETs make them very desirable for Amplifier output stages (they have a 'hyperbolic-like' operation, so you gain the benefits of classA operation with substantially reduced heat generation) - these will be stunning power amps, I only wish we could "mass" manufacture amplifiers with VFET's.

 

[JohnW]

There seams to be a lot of interest for new MDAC2 units, i want a silver unit but i have missed the opportunities for buying a salvaged one. I posted about mdac2 on a swedish forun and there where a lot of interest there aswell. would it be possible to build new cases+psu:s instead of taking it from broken MDACs, time is not really an issue for me, maybe this could be a future project?

I think a lot of people would be interested in the mdac2 l3 unit(there is no 768kS/s ADC on the market and all interesting ADC:s are overpriced).

anjora,

I'm just about to order a couple of salvaged MDAC's (and the new donor MB's) next week, if your interested in a salvaged unit (GBP370) then PM me (or Email Renata) and we will make the arrangements. In your PM / Email please state if you require silver or Black unit

 

[Morph3R]

Googleing around I run onto this: http://www.psaudio.com/perfectwave-p3-power-plant/

Does this have any sense for us with poor quality AC ?

Can this "PowerPlant" be used to drive all electronic equipment (Audio/Video/PC) in house?

Does this "power conditioning" equipment have any impact on SQ?

Branislav

 

[JohnW]

Branislav,

I'd be cautious, it might be beneficial if implemented correctly - however I'd rather build you a PSU with the correct voltages and remove any uncertainty.