Is the schematic of the UcD 400 available somewhere?
I understand that most of the components used to built it are very standard off-the-shelf parts.
Input coupling caps are cheap elkos.
I understand there is just a pair of standard mosfets in the output stage (do not know the model though).
I wonder what this technology could reach with the best parts available on the market (like Sanken output devices for instance. I understand they are by far the best output deivces).
I am quite astonished after my first listening session.
In the next future I will test it on my recalcitrant Dynaudios.
By now I am extremely impressed by what I have listened.
Thank you very much to anyone.
Kind regards,
beppe
I understand that most of the components used to built it are very standard off-the-shelf parts.
Input coupling caps are cheap elkos.
I understand there is just a pair of standard mosfets in the output stage (do not know the model though).
I wonder what this technology could reach with the best parts available on the market (like Sanken output devices for instance. I understand they are by far the best output deivces).
I am quite astonished after my first listening session.
In the next future I will test it on my recalcitrant Dynaudios.
By now I am extremely impressed by what I have listened.
Thank you very much to anyone.
Kind regards,
beppe
Greetings Sir Beppe,
Do they make decent mosfets for power switching? Requirements are probably a little different than what's best for linear amplification.
The modules have some decent mosfets for switching already. I wouldn't bother swapping them around at all.
You can play around with things like caps though.
There is no schematic available.
Good stuff though, huh? It only gets better.
Best,
Chris
classd4sure said:
The modules have some decent mosfets for switching already.
Thank you Mr Chris for the kind advice.
As usual I am quite superficial.
You can play around with things like caps though.
I have seen the pcbs. Actually the tiny input caps look poor enough to swap them for something better performing.
I would try to place some PP caps there.
As I understand the input impedance is 100 Kohm, a 0,47-1uF film caps should be fine. Am I wrong?
I feel a little uncomfortable about direct coupling, even if this is the best solution by far.
I think this technology is a tremendous achievement.
Very very remarkable.
I read some listening impressions and power amps based on UcD embarassed well known high-end amps.
High-end for the masses ?
thank you very much again.
Kind regards,
beppe
classd4sure said:
Yes Mr Chris. My Bryston has a 4,7uF output cap.
So the caps are after the input op-amp.
I think I would not touch anything, at first.
The amp I listened had modules 400 in stock form and performed just wonderfully.
Expecially considering where I come from (Adcom GFA 545).
Thanks a lot and regards,
beppe
Forgive me for posting here....but I need some advice on my UcD 400. The amp was built for me (since I know nothing about electronics) but it kept on blowing fuses (4 A) after a few starts when the power was turned on. There must be hundreds of reasons but what would be the most likely one? Is it normal because of power surge and what can I do to solve it?
Most grateful for any answer, and once again sorry to interrupt.
Most grateful for any answer, and once again sorry to interrupt.
OK, bad advice then. Since it includes a soft start and is blowing the fuse I'd be a hell of alot more paranoid.
If you don't know electronics at all, is there a possibility you can bring it back to whoever built it and have them look it over?
Otherwise it might be time to invest in a multimeter and get familiar with it, check for shorts to the case.
If you don't know electronics at all, is there a possibility you can bring it back to whoever built it and have them look it over?
Otherwise it might be time to invest in a multimeter and get familiar with it, check for shorts to the case.
I followed your advice and called the tech. He suggested that I try an 8A fuse first and that it might be the caps (Jensen's) are still new and suck up too much current. He definitely will check the unit if it blew up again. Does it make sense?
I am going to follow your other advice and take up some electronics primer soon. I have not touch a soldering iron for over 20 years
.
Thanks again.
I am going to follow your other advice and take up some electronics primer soon. I have not touch a soldering iron for over 20 years
.Thanks again.
lucpes said:
I wonder if this behaviour could be related in someway to what is called "break-in" of brand new equipment.
This is a real effect, IMHO of course.
I experienced a vast change in sound after some hours of continuous use. And for the better of course.
Nevertheless I would like to know your point of view on the so-called break-in.
Thanks and regards,
beppe
Sorry to switch back to the much-debated issue of the input caps, but I really need some sort of comfort before I start tampering with my modules.
By putting together the various pieces of wisdom I've been able to gather across several threads, it looks like [limited to the input caps issue!!!]:
A) There's seems to be wide consensus about the absolute sonic best being attained without any caps on the input signal, i.e. shorting or - even better - completely removing the stock electrolytic caps. Drawback: DC vulnerability of the setup.
B) If unsure about the presence of DC at the input, the second choice in sonic terms would be to remove the stock caps and to put 6 uF (approx.) high-quality caps (Auricap, Mundorf, etc.) between the input XLR/RCA and the input of the module.
C) The last option, in sonic terms, would be to replace the stock caps with higher quality ones, like Black Gates.
Did I get it right? Suggestions?
Now the tough questions:
I am thinking about setting up a temporary rig whereby I could switch in real time between option A) and B).
This could be implemented via a four-way switch (for balanced operation), that would alternatively place a cap or a jumper in the signal path.
The possibility of real time comparing two different setups really attracts me.
Do you think this is a worthwhile effort? How much sonic degradation do you reckon the switch will introduce?
Last questions: does anybody know whether the Pass Labs X-1 has an output cap? I wouldn't like the pre to fry my speakers when I DC couple the UCD...
By putting together the various pieces of wisdom I've been able to gather across several threads, it looks like [limited to the input caps issue!!!]:
A) There's seems to be wide consensus about the absolute sonic best being attained without any caps on the input signal, i.e. shorting or - even better - completely removing the stock electrolytic caps. Drawback: DC vulnerability of the setup.
B) If unsure about the presence of DC at the input, the second choice in sonic terms would be to remove the stock caps and to put 6 uF (approx.) high-quality caps (Auricap, Mundorf, etc.) between the input XLR/RCA and the input of the module.
C) The last option, in sonic terms, would be to replace the stock caps with higher quality ones, like Black Gates.
Did I get it right? Suggestions?
Now the tough questions:
I am thinking about setting up a temporary rig whereby I could switch in real time between option A) and B).
This could be implemented via a four-way switch (for balanced operation), that would alternatively place a cap or a jumper in the signal path.
The possibility of real time comparing two different setups really attracts me.
Do you think this is a worthwhile effort? How much sonic degradation do you reckon the switch will introduce?
Last questions: does anybody know whether the Pass Labs X-1 has an output cap? I wouldn't like the pre to fry my speakers when I DC couple the UCD...
deafandumb said:I followed your advice and called the tech. He suggested that I try an 8A fuse first and that it might be the caps (Jensen's) are still new and suck up too much current. He definitely will check the unit if it blew up again. Does it make sense?
I am going to follow your other advice and take up some electronics primer soon. I have not touch a soldering iron for over 20 years
Thanks again.
Yeah leakage is higher in new caps, but quite frankly, I think that's a load of ****. The little bit of extra leakage is just not going to fry a fuse.
Are you _sure_ there's a soft start circuit, and if so, what does it consist of? Thanks to these nice little modules there's far too many people who think they can build amps but hardly have a clue what they're doing. It sounds like what you got wasn't even plugged in for a first test..... scary **** man.
If you ask me a 4A mains fuse is just way too small anyway, and I would go for something closer to 8 or even 10. But I'd make damn sure nothing is wrong with it first... if it does have a soft start that actually works, there's no reason in the world for the fuse to blow when powering it up!
Buyer beware eh?
m.parigi said:
You can go with a boutique film type cap if you want but... probably any will do and be an improvement over the electrolytics. It's up you.
Also up to you is wanting to play around with some sort of A/B test setup, personally I don't need it. If the caps are close enough that you need an A/B test of anything more than swapping balance from right/left, you can probably consider it a safe bet that they're the same.
Personally I just change one module at a time and keep the other as a baseline, makes it nice and fast to tell what sort of difference there is. Of course, now the argument about the need for blind testing and all that will start, but that's all I have to say on the matter.
m.parigi said:
You can get away with as little as 1.6 uf for a highpass corner frequency of 1Hz on the input caps at the module. 6uf would be 0.3Hz and I don't see the point of going that low... (the series capacitor and the 100K input resistor to ground form a highpass filter)
I have 1uf coupling caps at the preamp end and it works just fine...- Status
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