UCD400 Build-Need Help Selecting Components

[14U2NV]

First tings first...This is my first time posting here so I wanted to thank all of you for all of the wonderful information I've gathered here. This is truly an amazing resource!

Although I have a basic understanding of electronics, this will be my first time building an amplifier, so I'm sure some of my questions will seem elementary and even silly to some of the experts out there, but I'm one of those people that likes to sort out as many of the details as I can first, just to limit problems later.

The Project...

I've decided to build a 3-channel UCD400 based amp and have questions about transformers and the Hypex UCD power supplies among other things. I've read and searched and still have some questions.


Would it be worthwhile to run one Hypex UCD Supply HG to each UCD400 if using one central transformer? If not, I know you can use it for two UCD400 modules, but could you use it for three modules? I don't know if I want to use one HG power supply to power two UCD400s and another to power one UCD400, I'm sure that would have to give some unbalanced result.

I want to get the most I can out of the UCD400s, so I don't want to make much of a sacrifice in sound quality, etc here and have no problem running three HG power supplies if it's worth it.


Power supplies...
At this point I'm trying to get the three channels in one enclosure and am planning on using one large transformer but I'm a little unclear on the specs for the transformer voltage for the UCD400. Hypex's specs for the UCD400 say 45 to 65v, but the transformer they recommend (not the one I'd be using) has 42v sec, which is below their recommended minimum which leaves me confused and wondering if I'm comparing the correct specs.

I'd like to run the sec voltage as high as possible, but don't want to trigger the overvoltage protection. I've measured the AC voltage at my home and it fluxuates between 116.8-126.1v with an average of 122.1v over time.

At this point I'm considering this transformer to power three UCD400s:
Avel Lindberg Y236904 800VA 55V+55V TOROIDAL TRANSFORMER
http://www.partsexpress.com/pe/showd...number=122-715

I'd be willing to do a triple monoblock (if it's worth it), but would like to keep it all in one enclosure and I don't think I could get three transformers in one case, but I'd be willing to buy whatever would give me the best results out of my UCD400s within reason.

I will be using a standard 19" rack enclosure, but havent decided which one yet. Probably one with external heatsink like this one...
http://www.hifi2000.it/default.asp?id=104&mnu=104




Thanks again,

John

[classd4sure]

Hi John,

Most of those choices are left up to you entirely based on what you want to spend and what you expect out of it. Start small, see how it is and build up later, or just go all out right off, it's up to you.

You need to realize that transformer secondaries are always rated in AC volts, while the module of course needs DC.

Example:
The transformer you say they recommend has 42Vac secondaries, convert to rectified DC would be 42*sqrt(2) or 42*1.414, minus ~1.4volts drop across the rectifiers. Should give you something like 55Vdc.

From there you need to account for an extra ~5% (depending on the size of transformer) for an unloaded/idle condition and another 10% to account for worst case mains overvoltage condition. That's for worst case real world conditions, and thus should not exceed the trip point of the overvoltage protection circuit.

If you have more questions on this I strongly encourage you to read the threads first because it's all been said already.

Regards,
Chris

[Portlandmike]

Originally posted by 14U2NV


The Project...

I've decided to build a 3-channel UCD400 based amp and have questions about transformers and the Hypex UCD power supplies among other things. I've read and searched and still have some questions.


Would it be worthwhile to run one Hypex UCD Supply HG to each UCD400 if using one central transformer? If not, I know you can use it for two UCD400 modules, but could you use it for three modules? I don't know if I want to use one HG power supply to power two UCD400s and another to power one UCD400, I'm sure that would have to give some unbalanced result.

I want to get the most I can out of the UCD400s, so I don't want to make much of a sacrifice in sound quality, etc here and have no problem running three HG power supplies if it's worth it.


Power supplies...
At this point I'm trying to get the three channels in one enclosure and am planning on using one large transformer but I'm a little unclear on the specs for the transformer voltage for the UCD400. Hypex's specs for the UCD400 say 45 to 65v, but the transformer they recommend (not the one I'd be using) has 42v sec, which is below their recommended minimum which leaves me confused and wondering if I'm comparing the correct specs.

I'd like to run the sec voltage as high as possible, but don't want to trigger the overvoltage protection. I've measured the AC voltage at my home and it fluxuates between 116.8-126.1v with an average of 122.1v over time.

At this point I'm considering this transformer to power three UCD400s:
Avel Lindberg Y236904 800VA 55V+55V TOROIDAL TRANSFORMER
http://www.partsexpress.com/pe/showd...number=122-715

I'd be willing to do a triple monoblock (if it's worth it), but would like to keep it all in one enclosure and I don't think I could get three transformers in one case, but I'd be willing to buy whatever would give me the best results out of my UCD400s within reason.

I will be using a standard 19" rack enclosure, but havent decided which one yet. Probably one with external heatsink like this one...
http://www.hifi2000.it/default.asp?id=104&mnu=104




Thanks again,

John

Hi John,

I'd do the 40VAC Avel 800VA transformer.

It will be lower voltage, but stiffer. I suspect you'll get about 55V rails unloaded, and the big toroids have decent regulation.

I think people get to crazy over rail voltages. 5 more volts at 55V will not be percievable in volume. The higher, say 45VAC version will not be as stiff.

I think running three seperate transformers would for sure be better. smaller transformers are faster. I've heard that two smaller transformers are better than one of twice the VA. I believe it has to do with primary inductance. The bass is better with two I've heard said. I haven't tried it though.

That's my opinion anyways, but hey, I don't even need 50 Watts to get loud, so maybe I'm biased.

Regards,

Mike

[ray bronk]

Hi John,

Ok, so here's the other extreme. Go over to Kevin Haskins DIYCable and get the UCD400 1KVA (That's 1000) for $125. It's design is to handle at least 4 UCD modules in one box. Just a thought.

Ray