thinking about the UCD modules.

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#181
#182
maxlorenz said:
Dear cowanrg:
There's plenty of info here about DC blocking. There's one particular thread that is very informative, but I can't find it now!
It is called something like "how to stop TX hum" or "DC blocking for humming Tx". Sorry I'm sleepy :xeye:

Try this also:
http://www.diyparadise.com/dablok.html

http://www.diyaudio.com/forums/showthread.php?threadid=2080&perpage=10&highlight=&pagenumber=1

Enjoy 🙂
Click to expand...

cool, thanks. ill have to try it. i just answered my question. i was going to ask why use only 16v rated caps. i guess its the DC rating, not the AC rating that matters... and since i only have like 0.5vdc on the line, 16 is overkill... ill give that a try and see if it stops the hum. thanks guys.
 
#183
cowanrg said:


cool, thanks. ill have to try it. i just answered my question. i was going to ask why use only 16v rated caps. i guess its the DC rating, not the AC rating that matters... and since i only have like 0.5vdc on the line, 16 is overkill... ill give that a try and see if it stops the hum. thanks guys.
Click to expand...


The cap needs to be rated a healthy margin above the voltage it see's. The line is only AC coupling +- a few diode drops at the zero crossing, beyond which the diodes or TVS's take over conduction.

A real slick solution also includes some PI line filtering along with that 🙂

I said half a volt is alot because these circuits normally only a diode going either way, that diode drop is the extent to which DC gets blocked. If you never have more than a diode drop's worth of DC it's OK, two might be better.

Better use some serious power diodes, TVS' seem like a real smart way to do it. You can get them in any voltage you want and they can flow some serious current.

A properly rated MOV might be neat too.

Since it is mains power flowing through here a nice PCB could be a good safety feature.
 
#186
maxlorenz said:
Dear cowanrg:
There's plenty of info here about DC blocking. There's one particular thread that is very informative, but I can't find it now!
It is called something like "how to stop TX hum" or "DC blocking for humming Tx". Sorry I'm sleepy :xeye:

Try this also:
http://www.diyparadise.com/dablok.html

http://www.diyaudio.com/forums/showthread.php?threadid=2080&perpage=10&highlight=&pagenumber=1

Enjoy 🙂
Click to expand...


I checked the diyparadise link. I may have a really stupid question/remark.

I would guess that the caps should be connected the other way around. As they are now connected, the diodes will prevent any postive voltage large than 0.7V occuring on the + terminal of the caps while a large positive voltage could occur on the - terminal of the cap as the diode over the cap would be non-conducting un der that bias condition. This may not be good for the caps, I would guess the direction of each diode needs to be reversed. Can somebody educate me on this?

Furthermore, as the diodes are mounted back-to-back, it will block any DC, not just up to 0.7V as stated on that web site, so adding more diodes seems useless to me.

Am I wrong here?

Best regards

Gertjan
 
#188
Gertjan:

will prevent any postive voltage large than 0.7V occuring on the + terminal of the caps while a large positive voltage could occur on the - terminal of the cap as the diode over the cap would be non-conducting un der that bias condition. This may not be good for the caps,
Click to expand...

Indeed. It won't pass DC nor AC after a while, perhaps.
I didn't had the time to check and dear Yeo said it works (?). Sorry.
I would not try it because the circuit Chris posted is wiser IMHO
...and it can be added to my humble mains filter :angel:

http://www.diyaudio.com/forums/showthread/t-67413.html

Thanks for the diagram 🙂

Mauricio
 
#190
alright, here is the post many of you have been waiting for...

a showdown between goold old class AB versus new school class D. and by this i mean a comparison between passively bi-amped rotel b-1070's and a pair of mono UCD400's. the rotels are roughly 185 watts into 4 ohms per channel. i passively biamped with them, so i was getting around 370 theoretical watts per speaker with them. so, the wattage was very close between these two. i used the same cables and everything. the only variance was the amplifier. look back a couple pages in this thread to see the entire system.

im not going to bore you with which tracks i used, etc. if you really want to know, you can email me. but, its nothing special. in my opinion, you can use anything, as long as you are familiar with it and have critically listened to it before. i ran both amps full range and turned off my subs for this test. my subs do way too much to have them left on. plus, the levels of these amps were slightly different, so i would have had to recalibrate the subs each time i switched. so i just ran each amp full range and didnt use a crossover point in my processor.

now, it took me so long to get results to all of you because the amplifiers sounded very similar. i dont think i could do a blind test and tell which one was which. i could hear differences for sure, but im not sure if i could do it blindly, but maybe. the main differences between the two were soundstaging, bass, detail and overall "listenability".

the UCD's pretty much won on all these categories. there was a couple things i liked better on the rotel, ill go into that later. my speakers are soundstage monsters to begin with, so this was actually a hard one. ususally, i get a massive soundstage no matter what i do. i could use a home theater in a box receiver from wal-mart and get a great soundstage. but, the soundstage was taller and wider with the UCD's. it was a little more laid back, but not by much. its not that it was necessarily "bigger", but it seemed more filled in. the UCD's gave more of an impression of a wall of sound. however it sounded like this with the rotels, just not as much.

the bass was almost identical. but, the UCD's had a little bit more of it. the rotel wasnt leaner, but it was a bit sloppier and was lacking mid-bass punch. you really had to turn it up a bit louder to get what you wanted out of the speakers in terms of bass. however, neither one was really fantastic. my speakers are very difficult to coax bass frequencies out of. but, on some tracks, i was overall pretty happy with the results full range. but, in NO case would i have not used my subs if i had the choice. but in general, if i had a speaker that WAS full range capable, i would probably use the UCD, it just seemed to have more to it, and a better quality.

one of the first things i noticed with these amps was there was a bit more pronounced detail that i hadnt noticed before. now, its not like i heard things id never heard before. my system has always been absurdly detailed (almost a bad thing). but the UCD's seemed to make things seem more natural without being flaws as much. when you could hear toe-tapping or coughing in the background before, it seemed more like it was meant to be there, rather than a flaw that they tried to cover up. i did notice things that i hadnt noticed before. but when i went back and used the rotel amp, i heard it there too, just not quite as apparent.

now here is the most vague of all the differences. the UCD's overall just sounded better to listen to. the rotels have a slight edge to them. this is partly due to the fact that the magnepan tweeter is a 20+ year old design on my speakers and naturally has a slight edge to it. on poor recordings, it comes out and is VERY apparent. the UCD's didnt necessarily alter the quality of the music, they just smoothed off the edge. i still had a shimmer on symbols that was realistic, it didnt compress anything, but it took off the edge. this was a nice and welcome improvement. i have a lot of bad cds (dont we all!) that are still great to listen to because its good music. but, i cant turn them up that much without hearing serious flaws. overall, the UCD's were just easier to listen to. plus, as i mentioned before with the soundstaging, there just seemed to be more of the sound filled in. the rotels sounded slightly leaner.

so, thats basically what i heard. however, i would take either amp without question. if i were in a store and they were the same price, i would simply choose based on appearances of the amp. i just wouldnt have a chance to A/B them like i did. i think in a store environment it would be impossible to hear any differences. maybe on a switcher it would be easier though.

overall, im not BLOWN AWAY by the UCD modules, but they dont sound any worse than my rotels, and on almost all fronts, they sound slightly better. i might try some better caps and a bit more complex power supply on the final versions to get every last bit of performance from them. but, all in all im pleased. in the past week or so that ive had these running, everything has just generally sounded good and i have been happy with my system. ive not heard my speakers sound better, and there weren't any tradeoffs with these amps either. i didnt have to give anything up. so, im in. they will get a case built for them and become my main amps.

so thats the review. its not as absolute as i would have liked it to be. but, im not disappointed at all. i didnt expect much from these (i just didnt know what to expect). in any event, for DIY, they are robust, relatively cheap, easy to put together, and small. plus, the heat issue is completely gone. i ran them on pathetic heatsinks and they got warm, sometimes hot, but never dangerously so. but, like i said, they are pathetically small.
 
#191
DC couple it and that bit of a wall will be gone, or yeah, better caps. A "filled in wall" is not a desirable characteristic and hints at a loss of micro dynamics, it lessens the soundstage.

Experimenting with power supply and wiring could fix that too, so since you plan on doing that already keep us posted on the improvements, I'd expect it to really outshine the rotel in the end.

I wouldnt' guess you are blown away considering what you're used to already, but just curious, total cost of previous system to that of UCD based is, also how do the quality of the parts used to implement it compare?

Regards,
Chris
 
#192
classd4sure said:
DC couple it and that bit of a wall will be gone, or yeah, better caps. A "filled in wall" is not a desirable characteristic and hints at a loss of micro dynamics, it lessens the soundstage.

Experimenting with power supply and wiring could fix that too, so since you plan on doing that already keep us posted on the improvements, I'd expect it to really outshine the rotel in the end.

I wouldnt' guess you are blown away considering what you're used to already, but just curious, total cost of previous system to that of UCD based is, also how do the quality of the parts used to implement it compare?

Regards,
Chris
Click to expand...

well, maybe i wasnt 100% clear about what i meant. its not really filled in. its more like there is more air and detail around the instruments and sounds. so instead of hearing a voice just floating in the soundstage, you hear more cues as to if its in a studio, a hall, a stage, etc. you hear more of the echo, reverb and stuff that defines the sound more. its definately better, not just more cluttered and mushed together.

i really dont think there is a way to improve on the wiring itself, unless i use better wire, which i plan on doing. but all critical signal wire is shielded, and the wires are kept pretty separate. there is NO noise at all when the amp is on.

i have heard a lot of talk about upgrading various points in the amp. im not a huge fan of experimenting. it takes me long enough to complete my projects as it is. i would rather find a few things that are pretty unanimously regarded as improvements and go through with them. for instance, its pretty clear that everyone thinks adding small caps across the rectifiers is benefitial. i have also heard of using higher quality bridge rectifiers or discrete fast recovery or hexfred bridges. since that is a relatively cheap solution, i might look into that.

also, im using lower than suggested capacitance. ive got only 6,600uf per rail, 13,200 total. and these are just caps i found in my parts bin, nothing special. i plan on doing 3 3,900uf nichicons per rail. that will give me just over the suggested amount for a 4ohm load. the better quality of the caps and the extra capacitance should help out.

the only thing left to upgrade would be the internal wiring. i use either audioquest or synergistic research internal hookup wire on most of my stuff because i get it for practically free. its decent stuff. at the very least, its what most of my interconnects are made of, so its consistant. but, ill be honest, im not expecting any noticable improvement. it looks nice and is easy to terminate, and its not any more than any other hookup wire.

those are the areas of improvement i have more or less decided on. i dont need more bass punch, thats what my subs are for. so, from what ive read, there is really nothing more i can do to substantially change the sound of the amp.

from my experiences though, my speakers dont seem to be very picky about the quality of amplification, they just like power and control. if the amp has that, all amps more or less sound the same. some speakers really bring out the good and bad qualities of amps with any piece of music, mine arent like that.

so, if anyone else has any other tweaks that i can do for these modules to squeeze just a bit more out of them, im open. but im not looking to dump a whole lot of cash.
 
#193
the rotels have a slight edge to them. this is partly due to the fact that the magnepan tweeter is a 20+ year old design on my speakers and naturally has a slight edge to it. on poor recordings, it comes out and is VERY apparent. the UCD's didnt necessarily alter the quality of the music, they just smoothed off the edge
Click to expand...

This particular bit seems to come back with a lot of reviews, sometimes in other wordings.

As magnepans are obviously revealing, couldn't it be that the "edge" you hear in the high frequencies is your typical class AB distortion? UCD have linear harmonic distortion vs frequency, with classic amps, the distortion is higher as the frequency goes up (due to the feedback IIRC) resulting in your "edge". UCD distorts a lot less in your tweeter range, resulting in the smooth sound.

Same for the nautilus I use - the alu tweeter is known for being "ear-piercing" if the amps are not ridiculously high quality (or high price) yet I have zero problems listening to them for a longer time, in my room that is far from optimized (ceramic stone floor!) - nothing ear-bleeding going on.

I gues somewhere along the line everyone got used to the "class AB" sound, with higher distortion at higher frequencies. I even read things like "UCD is rolled off at the top end" - it is slightly if you check the frequency plots but not so much that it could be audible - it's highs sounding "calmer"...
 
#197
cowanrg said:
a showdown between goold old class AB versus new school class D. and by this i mean a comparison between passively bi-amped rotel b-1070's and a pair of mono UCD400's. the rotels are roughly 185 watts into 4 ohms per channel. i passively biamped with them, so i was getting around 370 theoretical watts per speaker with them. so, the wattage was very close between these two. i used the same cables and everything. the only variance was the amplifier. look back a couple pages in this thread to see the entire system.
Click to expand...

can you clarify this setup some more? Were you running the Rotels with an active crossover (removing the Magnepan passive XO), while running the UCD400s with the stock XO full range?

Or were you essentially running each Rotel full range but just driving half the speaker using the bi-wire inputs on the passive XO to split the signal?

Peter
 
#198
Ignore my last post - duh - I guess i can see that you're running them full range "passive"

Interesting results, since I am looking at switching from one 300W amp per channel to at least two UCD 400s on my maggies going active.

the UCD700s are tempting, but expensive, and based on your results, I don't think I have to go for the extra output with a biamp solution, which will simplify my quest for parts and

Peter
 
#199
pburke said:
Ignore my last post - duh - I guess i can see that you're running them full range "passive"

Interesting results, since I am looking at switching from one 300W amp per channel to at least two UCD 400s on my maggies going active.

the UCD700s are tempting, but expensive, and based on your results, I don't think I have to go for the extra output with a biamp solution, which will simplify my quest for parts and

Peter
Click to expand...

i was thinking about the ucd700's as well, but its much more expensive all around. the modules are pricier, the transformers would need to be bigger, caps would need to be rated at 100v, etc... there is just a lot more cost involved.

i am just going to do stereo UCD400's per speaker. i might end up putting an active xover inside the case too if i have room. its a BIG case. then, i would have an actively bi-amped system. but in any event, im going to do two stereo UCD400 amps.
 
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