UcD400 Q & A

[Yves Smolders]

A question about designing amps around the UcD400 modules.

I'd love to have RCA and XLR inputs. Is there an easy way to connect these both together, without some sort of switch?

I know I need to connect - and gnd together for RCA, but then I can't use XLR like I should.

Can't quite figure it out.

[Bruno Putzeys]

Originally posted by Yves Smolders
I'd love to have RCA and XLR inputs. Is there an easy way to connect these both together, without some sort of switch?

I know I need to connect - and gnd together for RCA, but then I can't use XLR like I should.

Mount the RCA electrically floating wrt. chassis. Tie RCA shell to XLR pin 3 and RCA signal to XLR pin 2. Then, if you want to use the RCA input, make a dummy XLR plug to connect pin 3 to pin 1 through a low resistance (you can try a resistance, a resistance in parallel with a capacitance or a dead short).

[Yves Smolders]

Excellent idea, thanks a lot Bruno.

[Bgt]

Besides, resistors are cheaper to dissipating power into than silicon.

So, can I just increase the resistor value to 1.8k/2k2 so the transistor doesn't dissipate that much heat. Does it have any influence on the sound?

[BOB LEWIS]

Jan-Peter

Re: separate supply for driving regulator section ;what voltage would you suggest as ideal?

Curious,
Bob Lewis

[Bruno Putzeys]

Originally posted by BOB LEWIS
Re: separate supply for driving regulator section ;what voltage would you suggest as ideal?

It only powers the op amps and some CMOS logic. I'd say +/-12 (for the AD8620) or +/-15 (most other op amps).

[wytco0]

I cant believe this problem has not been tackled before but I have seached this thread and elsewhere and I cant find the answer.

I am after a 42-0-42 230v Torodial Transformer about 500VA to power my 2 new UCD400's via the Hypex High Grade power supply.

I thouhgt it would be easy to find such a beast but I cant find them anywhere. I have checked Maplin RS Rapid and some other trafo sites.

Does anyone in the UK know where I can get one ??

Or have i just made a big mistake and sized the transformer wrongly?

[ewildgoose]

In the uk we tend to have 250v mains so a 40v tranny might be better.

Farnell have ones for around £25

[Ouroboros]

Farnell have a couple of 40V-0-40V 500VA parts listed with a 230V primary. (They are end of line stock, as the website says these will no longer be stocked, but they have some left).

One is a normal open toroid, the other is in a metal screening can as far as I can see from the pictures.

[RickOray]

Hello all,
I'm following (well, I try) this thread since a moment, and learned a lot.
I plan to build a 5 mono UCD400 amp, I will surely apply some basic tweaks on modules (capacitors replacement), but I actually have doubts about power supply.
Some said there are improvements choosing high quality components rather than other ones (fast rectifier, slit foil capacitors...), but I wonder if building a regulated PSU won't be more advantageous.
Many years ago, in a french diy magazine, a Hexfet based amp was using a regulated PSU, the autor believed in its superiority. But if it really is an improvement, why regulated PSU aren't used in diy project?

So I attached the schematics of this regulated PSU, I would be pleased that gurus tell me (us) what they think of it, and if it could be a good solution for UCD modules.
(note: this schematic was designed for a stereo amp, I suppose that one darligton per rail would be enough for one ucd400...)

Thierry