MCD-255 amp

Very nice sound;)

[IMGDEAD]http://www.grotel.nl/photo/MCD255front.JPG[/IMGDEAD]

[IMGDEAD]http://www.grotel.nl/photo/MCD255top.JPG[/IMGDEAD]

mods
LM4562 as input IC now
shortcut on coupling cap. offset now 30mv on both channels, was 5.
output relais on MCD pcb shortcut, using a speaker protection pcb now. Is more sensitive and looks at more variations on the speaker lines, either neg. or pos.
 
good job Bgt

you find an special way to install the modules :)
you attention that the place of the mosfet.
but the heat sink of mcd-255 is just 3mm ,
we Proposal that the best way is install to the bottom board as heat sink (if using the Aluminum bottom board )

but if your job will ok for home using , :)

about the opamp, we used the dip transposon, so is very easy to replace the bb2134 with any OPs.

LM4562 is a very good op, 0.00003%:hot:


hi TheShaman
we also have high power version.

rg
fumac
 

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jkeny said:
Hi Fumac,
Looks like some excellent work on this "next generation" of class D amplifier!
Can amplifier modules be purchased?

hello jkeny, not to talk about saling here, just mail to me
thanks
fumac


Bgt said:
Fumac, the amp stays really cool. Should not be a problem.
BTW the "mosfet side" is closest to the amp. side pieces.
Sound is very..................very nice :D
Positioning of the modules is done for symmetry.
Crosstalk at 20khz is>100Db at full power/8Ohms/>80W/ch.


hi Bgt,
i'm so happy that you really like the sound from MCD-255
I do care about any modules out to the world,
all this modules is my babies.
i like them running at a good state, Healthy, and long life .
this time is winter, so the temperature is not hot.
but at summer , the temperature will rase up,
a high temperature of house will cause the more higher temperature of mosfet,
because the RDS(on) will higher when the temperature is higher,
and the RSD higher will cause more power loss into the mosfet....
this is a bad loop
so take care

about Crosstalk
if you use one transformer to one modules, Crosstalk will be best

rg
fumac
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
Bgt said:
jkeny,
Be patient. My tweaked UCD's are really nice so finding differences is a bit difficult. Need some time still.

Comparing amps. directly through an A/B switch is quite different from comparing amps. where you first listen to 1 amp. and than change all the wires to the other amp. and listen. You just cannot fool your ears this way.
Sounds like the other amps on your list are your less preferred ones?
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
jkeny said:
Hi Bert,
You seem to have a collection of the most highly rated class-damps available, from your sig, and I, for one, would be interested in your ratings for all in your possession!
This was really what I was wondering as well. I do understand there are personal preferences involved. But just wanted to get some feeling. Just judging from listening impresson instead of comparison is fine.
 
soongsc said:

This was really what I was wondering as well. I do understand there are personal preferences involved. But just wanted to get some feeling. Just judging from listening impresson instead of comparison is fine.


Soongsc,

What I found is that the input opamp of any amp. has the biggest impact on the sound. Also DC coupling and way of doing the main PSU has an influence as do the bypass caps. on the input opamps. Having made this equal for all of the amps shows minimal differences so to be honest it all comes down to the price of these modules and practical implementation considering PSU size and cabinet size. Probably with super expensive(if quality is super too) speaker/dac/preamps/other stuff? you're able to separate the differences. Have been busy for days on end to listen to the different systems, at normal levels, and it is hard to hear differences. I do this with A/B switching so the state of mind/ears is/are not relevant for judging. I'll continue in trying to find "listening" differences so will keep you informed.

PS "normal level" for me is a level that's comfortable for the ear so you don't hear back round noise and it is also necessary nobody is talking in the room and also no TV on or whatever disturbing factor. In Db level that should be more than 45Db.
 
Bert,
Recently I've gotton some small speakers to the performance I think is okay. I also listen quite often at very low levels, most of my focus during listening is how much recorded room reflections I can hear, the attack and timbre of cymbals, brush drums, tenors, violins attack and continuous notes during these kinds of listening sessions. Sometimes if I hear somthing funny, I change the absolute polarity to make sure I'm getting the music correctly. All this is leading me to wonder how critical amplifiers are, and how much it will improve reproduction. I have listened to the NCD1, it's good, comes very close to the old HAFLER XL120 I've been using, but not quite there by a very little, mainly the difference was in the details I mentioned. I am wondering whether the MCD has overcome this aspect with the higher switching frequency.