UCD180 questions

[classd4sure]

Hi,

I'm going to try reeeeeaaaaaaaaal hard not to copy that

Nice to see how it's done though, thanks. Additionally, may I be so bold as to ask, why capacitive coupling?

Chris

[Jan-Peter]

Charles,

If you take a look to the original Philips IP datasheet about the UcD there is written the inputimpedance of the modulator.
Inverting input 1.8K and none inverting 10K. Because of the extra Opamp, you now have a true balanced input.

Ok Chris, we make the deal, don't copy it!

No to be serious, if you like it feel free to use it. It's not protected by the NDA what I have signed with Philips.

Regards,

Jan-Peter

www.hypex.nl

[Jan-Peter]

Charles,

Did you like the blue color of the UcD180?

Wait till you have power it up!

Regards,

Jan-Peter

www.hypex.nl

[classd4sure]

Hi,

I'm starting to drool over the idea of that 400!

I admire your generosity. I will certainly try it, but only to compare with what I've done, satisfy my own curiousity, as the Ref design I've been playing with wasn't intended to be a UCD clone from the beginning, I'd hate to see it go even further in that direction.

The protection circuitry on the other hand is of special interest. I was sure you wouldn't have posted it had you minded anyone using it.

I hadn't read it anywhere that I can recall, I was wondering if your 400 comes bridged already, and what sort of load that power level is rated for, as I'm interested in powering a 4ohm load with it.

Thanks,
Chris

[ghemink]

Originally posted by Jan-Peter
Charles,

Please take a look on the attachment. The inputimpedance of the UcD modulator is 1.8K.

Regards,

Jan-Peter

www.hypex.nl

Hi Jan-Peter, Charles,

Jan-Peter, thanks for the schematic input.gif.

If you check the file input.gif, you can see that the input resistors at the input of the opamps are 100k. However, when I check my modules, that are actually 10k (1002 written on them). I also measured them and they are 10k. All the other resistors around that opamp have the same value as given in the schematic input.gif. So it seems that the input impedance is 10k.

Also thanks for the tips on tweaking. I`ll first try the modules unmodded of course. Sometime after that I`ll make a trip to Akihabara to pick up some black gates and other caps, opamps to try those out.

Has anybody fired up the modules yet? I need to build up a test setup first. Will use the predator power supply that I bought previously for the ZAPpulse modules. So I would also be able to compare ZAPpulse and UCD with the same power supplies.

Best regards

Gertjan

[Jan-Peter]

Oeps,

Gert-Jan you are completly right!

I send this yesterdaynight from mine Home PC, the schematic at home is having two difference. Guess which one?

The input impedance is 10K, probably we are going to change this to 2 x 100K. In this case you can use a tube preamp.

Regards,

Jan-Peter


www.hypex.nl

[ghemink]

Originally posted by Jan-Peter
Oeps,

Gert-Jan you are completly right!

I send this yesterdaynight from mine Home PC, the schematic at home is having two difference. Guess which one?

The input impedance is 10K, probably we are going to change this to 2 x 100K. In this case you can use a tube preamp.

Regards,

Jan-Peter


www.hypex.nl

Hi Jan-Peter,

Thanks for the confirmation. I`m OK with the 10k inputs:-)

About the risk of powersupply pumping when the caps are removed (will not do that for now). When does this occur, only when a too high DC input voltage is applied to the inputs? Or can it also occur due to some other reason? I understand that dangerously high voltages may occur at the output of the amp when powersupply pumping occurs (higher than the powersupply voltage itself, this is correct isn`t it) so I will likely not remove those caps. However, it maybe interesting to move the coupling caps to the input of the opamps so that a smaller value can be used. Another disadvantage that I can think of when removing the coupling caps between the opamps and the UCD module itself is that a higher DC offset voltage may appear at the output since the UCD module will amplify the output offset voltages of the opamps.

Best regards

Gertjan

[Jan-Peter]

Gertjan,

By an Half-Bridge Class-D amplifier you always have the problem with powerupply pumping effect. On the website of www.irf.com is a good explanation, please search there for the Class-D tutorial.

A good powersupply with enough capacitors will work in the most cases (2 x 10.000uF). If you will drive a servomotor or very low frequencies you will get problems. If you like I can post a overvoltage protection.

Regards,

Jan-Peter

www.hypex.nl

[ghemink]

Hi Jan-Peter,

Thanks for the link. I downloaded the file, now printing.

Yes, please post an overvoltage protection. The power supply I plan to use at the moment for testing purposes has 2x10000uF, I may add more uF`s in the final version.

I will read the tutorial to find out the details on power-supply pumping.

Thanks

Gertjan

[ghemink]

Originally posted by Jan-Peter
Charles,

Did you like the blue color of the UcD180?

Wait till you have power it up!

Regards,

Jan-Peter

www.hypex.nl

Hi Jan-Peter and others,

I have powered them up. I thought I could keep the ON input open since there is an internal pull-up. However, it seems you have to connect that ON input to GND to get the modules in a working state.

I first powered them up on some old speaker lying around. First impression. With the ON input grounded, so module always on when power supply is on, the switching on and off behavior is very clean (switching the power supply on and off). One can here only a small click, not much. This clean on and off switching behavior is very important for me since I want to connect a tweeter directly to the output of the amp. Second very important observation is that the amps are extremely silent. The noise level is very, very low. This was a very welcome surprise. My other Class D amps (a ZAPpulse and a Tripath based Marantz) are for more noisy. The gain of the Tripath and the ZAPpulse is a bit higher, gain of about 33dB while the gain of the UCD180 is 26dB, however, the difference in noise level is far more than that 6-7dB difference in gain. The Tripath and the ZAPpulse have too high noise for my taste when they are directly connected to a tweeter, I can hear the noise of those amps during silent periods in the music. I have not yet hooked up tweeters directly to the UCD 180, However, on my B&W CDM9NT passive speakers, they were extremely silent, even with my ear pressed against the tweeter it was very difficult to hear the noise of the amp (with shorted input of the amp). With the Tripath, there is really far more noise.

Then I listened to music. First problem was that I`m normally listening to my active 3-way that is still under development. This 3-way sounds quite a bit better than the CDM9NT, so I had to get adjusted to the CDM9NT again. Comparing the power amp stage of the Accuphase E407, the UCD180 sounds cleaner, more dynamic, seems also to have faster better controlled bass. However, judging the UCD180 on the CDM9NT seems not to be the best test, I need to check it in the 3-way system that has higher resolution than the CDM9NT. I plan to use the UCD180 first for tweeter and midrange where it will replace the Marantz which is a 4-channel amp. I can do then a comparison between UCD and Tripath, I know already that the UCD is a clear winner on the noise front. I will probably use the ZAPpulse modules that I have for the woofers.

So for now, my first experiments with the UCD180 are very positive. I`ll use them later for my active 3-way. After that, I will probably start some tweaking. First point would be the caps between the opamps and the UCD module. I think replacing those with something more high-end would not be a bad idea. For the tweeter amp, I can use much smaller and higher quality caps. Even for the midrange amp, the caps can be significantly reduced in size. This will also give me some extra protection for the drivers. Second point would be the opamps.

Anyway, need to get those 3-ways in a working state again (they are now lying apart for construction) before I can have more fun.

Best regards

Gertjan