UCD180 questions

[Jan-Peter]

IVX,

Thanks for the tip, but in the past I have decided to STAY FAR AWAY from caraudio business.......

Prices are very low, and I don't see ANY reason for high power (>100w) in a car. There is normaly so much noise in a car that MP3 is (for me!) sufficient.

Let this world be for the competitors..........

Regards,

Jan-Peter

www.hypex.nl

[IVX]

Ok.. $200 for single channel 100W Xtant1.1i not so much cheap yet..

[Mr Teal]

Xtant isn't exactly a low end brand either. Car audio generally has very low margins, there's a few premium brands that are able to make a decent profit per unit, but they're a very small market segment.

Car audio is a segment where you need alot of power though. For one, just to get above the noise floor requires alot more power. As well, car audio subs tend to be designed with large motors, big VCs, and stiff suspensions, with makes them great for providing loads of output in very small boxes. Getting 120+dB from a one cube box is great, but it takes alot of juice.

[classd4sure]

Hi,

Juice is what class D is for. I tend to agree with Jan-Peter here though, car audio is all about power, so much power you can't even sit in it. Hi-Fi has no place in SPL competitions which is really all they seem to care about, UCD would be wasted in it.

Jan-Peter I found your new PDF file for the UCD180, perhaps you'd consider adding more information in it. For instance, most of the questions which always get repeated, what kind of supply, what size transformer, how much capacitance and what kind of caps... Raw DC or regulated.. that kind of stuff. Might save you having to answer it over and over again.

Regards,
Chris

[rosbacke]

I'm curious how the Ucd180 react to different supply voltage levels with regard to sonic quality at moderate listening levels.
If I am using, say 10W of average power into an 8ohm speaker, will the sound quality be affected if I'm using 25V instead of 50V? Is there any reason to prefer a higher voltage even if a lower will suffice for the requested power level.

I have an unfounded belief that a class D amplifier could use a higher voltage to decrease switching time and therfore have better control. Is this totally bogus? Or is it something of the opposite, the shorter switching time increases overshot and general noise levels?

--- Mikael R

[matjans]

Originally posted by IVX
PS: BTW, J.P. could blow up this wild market segment by the UcD based subamp for starting.

I don't exactly get what you're trying to say but i know hypex has a few class d sub (plate) amps, although not advertised on their site.

EDIT:

oeps, they do. the ds 1.2. overlooked that one.

[jam]

Maybe Jan-Peter could post the users manual on their site. I have a few questions as well.

[Bruno Putzeys]

Originally posted by matjans
So, lets quit bugging psaudio (or open another thread for that) and get back to the ucd180.

Yay!

Originally posted by matjans
How big are your transformers, va-rating, voltage etc. How does this influence sound?
What's the psrr of the ucd module? couldn't find that anywhere...
Do I need a state-of-the-art extremely low output impedance psu with a LOT of capacitance etc?
Has anyone tried building a nicely regulated supply for these babies? Or maybe even a (ie OPA549) 'buffered' supply?
Has anyone tried replacing the opamps used?

The modules have about 65dB PSRR (frequency independent). I tend not to use overrated supplies because I found the sonic benefit to be rather small. The quality of the power supply caps does more than the quantity.
My own reference amp has a 160VA transformer and 2x4700uF - for a stereo amp (2x90W).
(The new "esoteric" design, 1.2kW/2ohms, on the other hand, uses 2x20000uF all black gate caps and a 1kVA transformer. Yeah it sounds a bit better :-).

[Bruno Putzeys]

Originally posted by rosbacke
I'm curious how the Ucd180 react to different supply voltage levels with regard to sonic quality at moderate listening levels.
If I am using, say 10W of average power into an 8ohm speaker, will the sound quality be affected if I'm using 25V instead of 50V? Is there any reason to prefer a higher voltage even if a lower will suffice for the requested power level.

I have an unfounded belief that a class D amplifier could use a higher voltage to decrease switching time and therfore have better control. Is this totally bogus? Or is it something of the opposite, the shorter switching time increases overshot and general noise levels?

Yes/no. In general MOSFET switching times increase with increasing voltage (more gate charge to throw about). It means that the relative portion taken up by dead time gets longer at lower voltages. If an amp was designed to operate at 50V, reducing supplies to 25V, THD is likely to go up. The UcD180 module is best used as designed.
The UCD400 circuit has drivers that prevent this mechanism (the reason for this design change was different though). It will produce the pretty much the same THD at any power supply voltage. Of course, who would buy a UCD400 module to run it at 25V...
Now, if you only need 10W at any time, you're better off building a power stage with lower voltage FETs (same Ron), because it'll easily provide faster switching times than a similar power stage made with higher voltage FETs.

[anomalous]

for those in australia, i found a local transformer manufacturer that will custom wind toroids to your spec.

they are making me up a 300VA 33+33V, which i will use to drive a pair of UcD180's (which i hope will arrive any day soon now!)

they are called TorTech, www.tortech.com.au.

the transformer i ordered cost $99 australian ($70US) - which is not too far above what an off the shelf 300VA toroid would cost here.

cheers,

ben