MDAC First Listen (part 00100001)
- Thread starter stellablues
- Start date
- Status
JohnW
pfm member
JohnW
pfm member
Great news
I probably need to go back and re-read some of this thread, but just quickly, re the amps, is there going to be any kind of trigger link from the MDAC2 to take them in/out of standby, or will it be necessary to power them off when not in use? I'm just thinking of the component life.
There will be both options 12V trigger (for systems without MDAC) & a more advanced MDAC's Comm's link.
I could also add a "Music detect / Auto standby" feature, but worry about any potential impact on SQ - maybe I can design it to be switched out of the circuit of not used...
Spoke with IAG today, and MB's will be shipped next week.
JohnW
pfm member
It's nice to be able to play something from the iPhone or iPad in an instant.
Not so much for a long listening session, but just to show some music or album to someone that is not in Hifi in the same way most of us are (here in pfm).
And please, please, don't strip out the Optical SPDIF inputs.
Michael
Dont worry
:-https://dl.dropboxusercontent.com/u/86116171/MDAC2 rear panel conector arrangement.jpg
On the left of the USB -B conector you can see the x4 optical connectors, Two optical inputs + Optical output & Optical ClockLock output
Oh, if you're using a comms link to do this then that's fine by me
I'd classify "music detect" as nice to have, but not essential.
JohnW
pfm member
Phil,
No problem
- it s a completely new design (The signal detect circuit is mounted on the original PCB) - I'll just be reusing the Chassis, connectors, heatsink & transformer etc.
uwe061
pfm Member
Ok, I understand. Thanks, John!
Uwe,
Spectral's "VMOS-FET" Refers to the Vertical MOSFET structure output devices , not to Sonys VFET.
I'll use Vertical MOSFET's for the current dumping stage - but the ClassA stage is VFET
I always switch every thing off at the wall so auto stand by is not important to me especially if it has a negative effect on SQ.
But 12v trigger and MDAC comm's link would be nice.
misterdog
Not the canine kind
misterdog,
Just to confirm 23rd's your birthday?
Indeed, must be why it is a bank holiday ??
Morph3R
pfm Member
Yes - this output can be also used as a second 'Selectable' balanced audio output (for what ever odd reason)
I can easily imagine a pair of powered/active desktop speakers and main "living room" speakers with power amp(s).
What about subwoofer out (with user selectable cut frequency)
Branislav
JohnW
pfm member
Well a nice little package arrived today
https://dl.dropboxusercontent.com/u/86116171/VFET x15 Pairs.JPG
With x30 more pairs on there way over
I performed a quick test on a Semiconductor analyser and indeed they appear as power JFET's its really exciting to work with such a unique devices.
I've been offered 60 pairs of lower power devices - I can see a future TDAC with VFET output stage if these work as well as claimed in the Power Amps
https://dl.dropboxusercontent.com/u/86116171/VFET x15 Pairs.JPG
With x30 more pairs on there way over
I performed a quick test on a Semiconductor analyser and indeed they appear as power JFET's
its really exciting to work with such a unique devices.I've been offered 60 pairs of lower power devices - I can see a future TDAC with VFET output stage if these work as well as claimed in the Power Amps
JohnW
pfm member
What about subwoofer out (e.g. filtered to 400Hz)
Branislav
With the DSP versions we can add LPF subwoofer output via the digital output.
JohnW
pfm member
davidjt
pfm Member
Well a nice little package arrived today
https://dl.dropboxusercontent.com/u/86116171/VFET x15 Pairs.JPG
With x30 more pairs on there way over
I performed a quick test on a Semiconductor analyser and indeed they appear as power JFET's
I've been offered 60 pairs of lower power devices - I can see a future TDAC with VFET output stage if these work as well as claimed in the Power Amps
Daft I know, but for some reason I expected them to look exotic.
(If word of their rarity/value gets around, there'll be a production line soon in China with tons of obsolete power transistors, gallons of carbon tetrachloride and carefully faked Sony stencils........
)
sam_cat
C'est Crounchifique!
And a HPF on the other outputs so we can tweak the crossover to our hearts content?
Dont want my mains trying to play the lovely low stuff that the sub has taken over...
This would save me some work over having to build a analog lowpass filter but i think i will have the bass in stereo.
BTW: i do not really see anything wrong in using analog active XO, if you are worried about SQ degradation you can always buy the vishey Z-foil resistors and since there already is 33 resistors used in the mdac2(if i remember correctly) adding 2...4 per channel should not make any difference.
JohnW
pfm member
Daft I know, but for some reason I expected them to look exotic.
(If word of their rarity/value gets around, there'll be a production line soon in China with tons of obsolete power transistors, gallons of carbon tetrachloride and carefully faked Sony stencils........
Luckily, there is nothing that measures similar to them - so no re-badging of "cheaper" devices.
I was curious as to how they would measure - my "intelligent" curve tracer identified the Nch parts as JFET's, but had a problem with the Pch parts which it could not "identify"... I guess they had no considered VFET parts when they designed the "semiconductor analyser".
I manually measured the Pch parts and they are OK
Here's the internal's of the lower power single die version, that I'm considering using in a SE version of the TDAC:-
https://dl.dropboxusercontent.com/u/86116171/sony-vfet-642x336.jpg
And the higher power devices I'll be using on the Power Amps (note the dual die):-
https://dl.dropboxusercontent.com/u/86116171/2sk82opensm.jpg
The TO3 Metal package is pretty "exotic" for me, rarely seen these days of plastic body power devices.
JohnW
pfm member
Yes - easy for the DSP version...
- Status