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classd4sure 6th October 2004 10:19 PM

Ucd400 Q & A

I thought it an appropriate time to start this thread.

I've read before there were two versions of the UCD400 being develloped at the same time.

Which is currently available, will there still be another version comming out soon, if so what can we expect on it should we wait that we won't find on the currently available version?

Exactly what kind of protection does it feature? Overcurrent? DC? etc.

I've a question about the order form as well but I'll ask that privately in email.

I'd like to comment on the picture used on the webpage, it's very dark, especially the one that pops up when you pass your cursor over it :)

Do the drivers for it feature adaptive dead time?
Are there any other ways in which it differs from the UCD180, filter, input..?

What op amps does it use in the input stage?

That's it for now, thanks alot.


DSP_Geek 7th October 2004 12:10 AM

Another question: how is overvoltage protection implemented? Does the whole unit shut down or does the current limit kick in at lower threshold?

Thanks in advance,

hansen 7th October 2004 07:44 AM

And another one:

What is the input impedance of UcD400?

I'm thinking about building monoblocks, place them close to the speakers and driving them directly with my CD player with volumecontrol. But the input impedance probably has to be fairly high for that to work.

classd4sure 7th October 2004 08:50 AM


Just had a thought regarding (yes..aaaagain) the colo(u)r of the heatsink.

Would black not be the optimal choice since it is best at radiating heat? I think it would be important to go for the optimal choice here since no one wants to go with forced air, and the cooler it runs the better.

Have you ever tested to see what the actual difference between black or the dark blue it currently is?

I'm also curious as to why you want to go with a UCD700 now, originally you were deciding ~700/900. 700 doesn't seem like a worthwhile jump from 400, but 900/1000 is.

Thanks alot

UrSv 7th October 2004 09:00 AM

Well actually that is not the heatsink. It is the bracket that is used to attach the module to the actual heatsink to be used for dissipating the heat. The difference between the blue and black colour here is probably insignificant.

classd4sure 7th October 2004 09:15 AM

Sure you bolt it to the case for "extra" cooling, likely a necessity with this version, but let's not go so far as to say it's not the heatsink.

If it turns out to be 1% or 5% better being black in color, your mosfets won't find that insignificant, will they?

Jan-Peter 7th October 2004 10:05 AM

Hi Guys,

All answers in one time, I hope :D

There is at the moment only one version available, you can see the actual version on the website, we will make the picture more lighter.
Picture was edited on a laptop.......

The version is with JST connectors, this connector can handle 10Arms. We supply with every shipment a JST cableset.

The protections are;
When there is a overcurrent/overvoltage it shuts down the amp for 1-2 sec.

There is an adjustment for the Idle current, we will adjust this for the best performance.
We use now an OPA2134 opamp and the inputimpedance is 100K, and no coupling caps anymore. (sorry for the mods guys)

The T-shape aluminium is blue and need to be connected to an alumnium frontplate/mountingplate or whatsover. To change the colour to
black has no advantage at all. You can't use the T-shape to cool the amp in free air, it must be connected to a frontplate/mountingplate.
Besides this the blue colour is pretty dark :D

There will be some heat generated by the internal regulators and outputchoke so you must have some free air cooling around the pcb.
Please put some holes for free airventlation in your housing, a fan is ofcourse unnecessary.



classd4sure 7th October 2004 10:15 AM

Thanks for the reply.

Adjustment for idle current? I guess that explains the pot I see on it. How does that affect the rest of the circuit (feedback loop/ripple etc) or is this just for the protection circuit?

Would it ever need to be tweaked or could I drop some epoxy on it?

Glad to hear you're including all the connectors for it and those mods to the input sound good to me too :)

Cheers to you, Jan-Peter.

Jan-Peter 7th October 2004 11:17 AM


The Idle current adjustment is an adjustment for the Dead Time. The lower the DT the higher the Idle current.
Hereby an acutal measurement with different Idle current settings.
You can easy which version you like the most :D



ghemink 7th October 2004 02:26 PM


Originally posted by Jan-Peter

The Idle current adjustment is an adjustment for the Dead Time. The lower the DT the higher the Idle current.
Hereby an acutal measurement with different Idle current settings.
You can easy which version you like the most :D



Hi Jan-Peter,

So that variable resistor is for the dead-time, very interesting, I`m afraid a lot of tweakers will play with that setting and maybe some tweakers will blow up the output stage when they change this Class D amp to a Class A setting :-) I assume the lowest distortion graph is for the highest idle currrent setting. Very impressive, down to 0.003%. Very good that the coupling caps are gone, saves me a few bucks and don`t have to worry anymore about them. However, there maybe some other caps that can still be tweaked for people that really want to use their stock of BG caps.

Anyway, looking forward to these modules, I`ll order a couple of them later, just burning in my UcD180`s and these are really very good. I use them now in my active system and I have the best sound I have ever heard in my living room. They stay clean even at high levels, last night my wife complained afterwards that my music was too loud (she tried to sleep:-)), louder than normal. This is just because everything stays so clean, you turn up the volume further than you used to do, and it is so easy if you have a remote control volume pot.

Best regards and lots of succes with these modules


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