UcD400 Q & A

[classd4sure]

Hi,

Francois, I do appreciate such a mistake corrected, I make them often enough, nice to know someone is paying attention

lne937s, I'm sure you're correct about the silicone but what a mess, I also understand it's rather expensive.

If it were a class A amp sure. I wonder if the silicon would dampen better than air, being a liquid it must have the potential to transmit pressure rather effectively? I dont' think you'd end up with a "water hammer" inside but all the same, with a few humming transformers in the soup your electrolytics may disagree.
Are you really considering doing this or was it just some out of the box thinking (which is very cool)?

Ewildgoose,
Have you tried contacting Farnell and asking for a set of transformers in exchange that weren't built on a monday? Maybe they'll surprise you, surely they must stand behind their products?

It's little wonder you looked everywhere else first, low mechanical hum is supposed to be one of the reasons we use them in the first place, all the same I've learnt from your experience here.

I sure hope I dont' have the same kind of luck with my Plitron, they're just too expensive to start trying one after the other, but, if that's what you have to do....

I hit google with "toroid site:.uk" for you and the first link was..

http://www.toroid.co.uk/ (cool huh?) I dont' recall what VA you're using but they've got them up to 600VA with potted cores, 4% load regulation, same as Plitron rates them from 500VA and up.

Here's the direct link to their "non-enclosed" units:

http://www.toroid.se/docs/prod1.pdf

Here's your second choice:

http://www.ecmelectronics.co.uk/

Ooooooooh I found my prize choice there!
http://www.ecmelectronics.co.uk/pdf/...mers_nexus.PDF That's in my next amp I swear!

Actually, they just may be a source for "Hypex" like transformers, check it out:

http://www.ecmelectronics.co.uk/pdf/...ormers_SRT.pdf

I'm sure you'll find more with the same google search too.

Happy hunting and better luck with the next ones.

Cheers,
Chris

[maxlorenz]

>>I sure hope I dont' have the same kind of luck with my Plitron,<<

I have a 300VA Plitron feeding 4 UCD180 and its completelly silent and cool

However, if I had mecanical humm I would try dampening with a big wood base (I do in fact) or submerging in some natural resin if epoxi is too expensive.

[Yves Smolders]

A question...

The UcD400 quality bit me in the a.. so hard that I'm thinking to combine the best of both worlds, stereo and surround.

I will be using my stereo UcD400 amp as L & R for my main channels, fed via unbalanced from my receiver.

Now, I'd like to add a "switch" so that I can either:

A) Take inputs "A" via cinch straight to the UcD modules (using input caps) - this would be for connecting the receiver.

B) Take inputs "B" via cinch to a passive volume control inside the amp's case, then to the UcD modules *bypassing* the input caps (as I'll be feeding it from a modified source) - connecting my CD player direct.

I realise that the caps on the UcD400 can be removed and make shorts on the PCB.

But as for switching the signal - How can I do this with good quality? What kind of switch should I look for? Should I use the signal through the switch or use relays?

Finally, how are the input caps connected? In series with the signal?

Any idea for a good volume control is welcome as well. I was thinking Dact DC1 or DC2?

Thanks for your tips,
Yves

[classd4sure]

Hi Yves, have a look at a sound card like the 1820M from EMU.

[Yves Smolders]

It's an option, but an expensive one

I'd like a volume control and use my Pioneer 868 direct to the UcD's.

Somewhere on this forum is a nice mod for the 868, 3 ad8620's and 5 caps to improve on the sound.

Now if I had soldering skills... smc soldering skills...

[sx881663]

Yves,
I use and recommend the DACT CT2 10k-2 control if you are using a solid state front end. 50k or 100k would be more appropriate with tube stuff driving it.
The Elma switch is the same basic design as DACT uses. I use a 4 pole 3 pos. 30deg sw. This is a non shorting type and if you switch the grounds as well you may have to connect them all together with something like 470 ohm resistors to eliminate switching pops. All inputs should be tied to ground with 100k res for the same reason.
Roger

http://www.elma.com/us/products/rota...y%20Switches/6
http://www.dact.com/html/attenuator_datasheet.html

[Yves Smolders]

Thanks for the suggestions, Roger.

So 470 ohms between the grounds and the inputs to their ground with 100k... ok

I'll have a look at the elma!

[Bgt]

what's the best Schottky rectifier to use for a PSU for an UCD400?
I know it must be somewhere on this site but the threads are just way too long. I want to use a halogen electronic PSU for this but a normal recifier will blow if you load it. Now these power units give a 50Hz sinewave out of a 40Kc carrier and this is the destructive part for a normal rectifier. Modified some 250VA units to do the job if possible. Anyone?

[Yves Smolders]

Roger,

What are quality resistors to use in the audio pathway (for the switch?)

Is it not harmful for the signal to put resistors between live signal and ground?

Sorry for the beginner questions, but I don't really know much about electronics' effects on audio. But I've learned a lot since I'm here...

[sx881663]

Yves,
I have used a large variety of resistors over the years and found that standard Dale 1% metal film, nonmagnetic are hard to beat for neutrality. They also don’t take weeks to break-in as some of the other far more expensive types do. When people tell you they like the sound of a part this generally means the part does have a sound and is not neutral. I really work at avoiding these kinds of parts and feel my designs have benefited greatly because of it.
The resistors I suggested you use are not harmful and will keep you from having problems with switching noise.
http://www.mouser.com/catalog/623/458.pdf
Roger