UCD180 with chipamp PS?

[MtBiker]

Has anyone built a UCD180 with a snubberized power supply from chipamp.com, or is that just dumb? It looks like diycable.com sells transformers with dual 30V secondaries for the UCD180 along with 50V caps, and the chipamp power supplies also use 10kuf 50V caps.

I need some help, so tell me where my logic is failing me. My AC at home regularly ranges as high as 124-126V, so for a transformer rated at 115V, you are looking at a 126/115=~10% increase. That means 33V at the secondary instead of 30V. So rectified, we would have almost 45V after diode losses, right? That gives just over a 10% margin below the 50V rating on the cap. Close enough, right?

The chipamp power supplies don't have fuses and don't address the UCD turn-on thump, but should I care? The UCD power supplies are just so expensive, especially when wanting to build 6 monoblocks.

TIA

[cowanrg]

Originally posted by MtBiker
Has anyone built a UCD180 with a snubberized power supply from chipamp.com, or is that just dumb? It looks like diycable.com sells transformers with dual 30V secondaries for the UCD180 along with 50V caps, and the chipamp power supplies also use 10kuf 50V caps.

I need some help, so tell me where my logic is failing me. My AC at home regularly ranges as high as 124-126V, so for a transformer rated at 115V, you are looking at a 126/115=~10% increase. That means 33V at the secondary instead of 30V. So rectified, we would have almost 45V after diode losses, right? That gives just over a 10% margin below the 50V rating on the cap. Close enough, right?

The chipamp power supplies don't have fuses and don't address the UCD turn-on thump, but should I care? The UCD power supplies are just so expensive, especially when wanting to build 6 monoblocks.

TIA

fuses are easy enough to add. also, there i no turn-on or turn-off thump from the UCD's.

i guess if you used a big enough transformer for the UCD180's, it would be a sufficient power supply for cheap!

[cowanrg]

of course, one supply could do a pair of UCD180's, dont try running all 6 from one! just get three of them.

and your calculations are correct. you would be looking at around 45v rails. the 50v caps are CLOSE. however, you could just get other caps instead of the ones it comes with. panasonic tu-p series from digikey is like $10 per, for 12,000uf 63v.

[Z33]

I'm playing with a pair of UCD180ADs right now, each powered from a BrianGT chipamp supply using standard 50V caps, and with a pair of Antec 500VA, 31VAC toroids giving +/- ~44VDC. My mains are typically 120VAC, and are connected through a Delta switched, fused and EMI-filtered IEC entry module and Volex 17604 14AWG shielded power cord. The entry module uses a 5x20mm ceramic fuse, 6A slow.

Wired thusly as monoblocks, the UCDs sound very, very good. I intend to try them on a proper Hypex HG supply soon, just to see, but I consider the chipamp supply entirely adquate for a single UCD180. Although the line filter, and line cord, are perhaps in questionable taste, they appear to have no discernable impact on sound quality, and it may be that the generous 500VA toroids are a predominating factor. The entire supply, from line cord to DC output, cost < $100.

When I had both Hypex amps on a common chipamp supply, they sounded simply awful, and I can't recommend doing this. A pair of Greg's GB150Ds OTOH sounded great on the shared supply, no doubt due to their design insensitivity to PS defects. It's possible that using another pair of chipamp PS boards, without diodes and purely as additional 10k uF filtering downstream of the main PS would improve things, but I haven't tried this.

[MtBiker]

Thanks guys. That sounds encouraging. Here is what I think I am going to try:

- 6 channels of UCD180 split into 2x 3-channel amps
- Each 3 channel amp shares a single 630VA toroid
- 1 chipamp.com board with 2x10kuf 63V caps per UCD module