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MDAC First Listen (part 00100100)

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Well, let me clarify, they will be able to operate at such high power levels until the heartsinks reach their maximum operating temperature and then shut down to prevent over temp - so lets say 15 to 20 minutes, but with real Music this will never be an issue - so you have the 500W+ on hand into 8 ohms and silly power levels into lower impedance, the x24 output devices insuring plenty of peak current, and evenly distributed thermal dissipation.

To be honest, I've not looking into total output power as its more then will ever be need, its not an important design matrix for the VFET amp where my primary goal is sound quality.

Totally with that John. Nice to know they will have that kind of umph when needed though 😀
 
Rune.
That sounds like overkill ... Methinks. But how would they sound in an active system, I wonder? I know what I think. Don't forget our plan for a trip to pick up the VFETs.
Cheers,
Peter
That is still the plan and I am looking forward to it.
 
jarip,

I'm not sure why a speaker would not be recommend to be driven by a Differential amplifier OPS (Bridged output stage) the only situation these would case a problem is where one input terminal is Grounded to Mains Earth which would be an unnecessary and bad practice...

I don't see any problems with driving your ML Hybrids, in fact I'll be testing the amps on my own pairs of Acustat and ML hybrids speakers.

Driving a speaker "differentially" is in my mind the correct way to drive a load as feedback is sensed correctly from both arms of the load while full use is made of the PSU (in a SE amp, only half the PSU is ever being utilised into the load at one instance).
 
I'm not sure why a speaker would not be recommend to be driven by a Differential amplifier OPS (Bridged output stage) the only situation these would case a problem is where one input terminal is Grounded to Mains Earth which would be an unnecessary and bad practice...
Well, I just noticed this statement from Zu Audio regarding their Definition speaker: "Amplification Considerations: Definition Mk.IV is designed around conventional or parallel mode amps, bridged amplifiers are not recommended (black speaker negative leg [sp–] of bridged amps will see the virtual ground node of the internal bass amp)". Is this the case of bad practice you mentioned above?

I don't see any problems with driving your ML Hybrids, in fact I'll be testing the amps on my own pairs of Acustat and ML hybrids speakers.
Ok. I don't have ML hybrids yet but have considered getting Montis together with the VFET amps.

Thanks.
 
Definition Mk.IV is designed around conventional or parallel mode amps, bridged amplifiers are not recommended (black speaker negative leg [sp–] of bridged amps will see the virtual ground node of the internal bass amp)". Is this the case of bad practice you mentioned above?

Its hard for me to understand what they are saying without seeing a schematic, but IF they have grounded the Negative Terminal of there speaker (rather then using a differential feed to their Sub amplifier) then this is inexcusable and truly amateurish.

If true (its the only reason I can see why they could have a problem with a BTL amp), then this makes me angry as this industry seems to attract a larger share of poor engineering!

Upon reflection, I cannot see Zu Audio making such a fundamental error, so I'm at a loss as to what they have an issue with...

Martin Logan will have designed their input circuits to the internal Sub-Amplifier correctly.
 
Some ( semi ) active speakers have problems when combining stereo signals ( they use shared ground for both sides )

My REL sub have similar issue, but the trick is to just fish the ground somewhere else ( the chassis of the pre or similar ) They have problems with real balanced amps as well ( like mu pascal class-D amp )

Im sure this will give me a fun houer or two when installing the VFET's monos at home :D.
 
The VFET amplifier is a "real balanced amp" rather then two amplifiers bridged - can you input a line level input to your REL?

Or as you say, just connect one phase of the Amplifiers output to the Signal input on the REL, and connect the Subs Negative to the Amplifiers Ground post - I can add this extra post to the rear of your Amplifier :)

Its VERY bad design practice for active speakers not to have a differential input - It upsets me to be associated with an industry where the level of engineering skill is so poor.
 
Dear John

First, yes pleas make an extra post for that ;). Wonderful solution...

Rel's argument is that taking the signal from the power amp you get the phase / time domain correct compared to the main speakers and that's why there is 3 inputs ( HOT, signal and extra signal for home theatre signal ). They advocate quite a lot for that ;)...

But yes, it's a 1300£ sub so it's not OK, mabee one should have bought a svs instead.....
 
I've never heard anything bad about REL subwoofers - so I dont think you can go too wrong.

Its a reoccurring theme when speaker company's design electronics its beyond there hemisphere of competence and you commonly encounter such "basic" errors.
 
I've been following this thread for a while and it's easy to get lost in its 400+ posts. I've also read these:

http://mdac2.referata.com/wiki/Main_Page
http://mdac2.lakewestaudio.com/

Do these reflect the current feature set of the MDAC2? Or can someone point me to an up to date feature list? I remember various talk over the ADC aspect and a number of other features but it's hard to keep track of where things went.....

No, I must update the website as soon as I've issued the PCB files I'll spend a day or two updating the site with the latest additions and project statues etc.

My priority is to issue the prototype Analogue PCB files - for me this is THE major milestone! :)

Please give me a few more weeks.
 
What, no banter? Has this thread been moved? :-D

Question, will we get some LAKEWEST badges or labels to mask/cover up the AUDIOLAB insignias on the MDAC chassis per chance?

Thanks
 
Think Johns got his head down. Either that or has taken a trip to China to talk to his contacts in regards new chassis.

For previous modifications to the MDAC the logo changes to Lakewest on the OSD and a little label with a serial number on the back. As this is a PCB replacement I can't really see any other possibility :D

The VFETS on the other hand :)
 
Sorry,

I've been crazy busy with time split between designing the MDAC2 PCB and the carpenters completing the Lab require more time then I'd envisaged - I have to install wiring / electrical fittings so they can complete their work - I worked until 7am this morning on the wiring!

The Lab needs to be completed so I can build the units, but I'd ATM I'd rather be spending my time completing the PCB....
 
Question, will we get some LAKEWEST badges or labels to mask/cover up the AUDIOLAB insignias on the MDAC chassis per chance?

I'm not considered a front panel label, obviously the new rear panels will be Silk screened with LakeWest / MDAC2. I'm not ashamed of "Audiolab" :D

We have plans to offer a full width retrofit "Lakewest" Chassis - with HQ internal PSU, this will be offered "At Cost" for the original MDAC2 development sponsors :)
 
I'm not considered a front panel label, obviously the new rear panels will be Silk screened with LakeWest / MDAC2. I'm not ashamed of "Audiolab" :D

The issue is not being ashamed of anything. It is the fact that the MDAC2 is not an Audiolab product. It just lives in an Audiolab case.
 
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