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Hello, I've placed my order for one Placid HD and one Placid HD BP to power my third party DAC. My requirements are: +15VDC for the digital sections (~250mA) +15VDC for the analogue (~400mA) -15VDC for the analogue sections (~200mA) If my calculations are correct (based on voltage, current, and regulation/sagging), the Avel trafo that Brian and Russ sell would do the job (15V, 30VA). I would get two, one for analogue +/- 15V and the other for digital +15V. I think I could get by with a smaller trafo for the digital, however, I would have to buy from Avel. I'm not sure they sell direct... I checked their website and didn't see anything to this effect. For my enclosure, http://www.lansing-enclosures.com seems interesting. Here's a rough layout with AC on-off button at the front (left side) and DC chord gland on the back as well as fuse holder and AC inlet (lower right side) based on their 7.3x9in CW enclosure. Edited by user Sunday, January 20, 2013 3:52:37 PM(UTC)
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I've used Lansing enclosures for other projects and they have a good product. My concern would be ventilation for the warm running Placid shunting power supplies. I don't recall seeing vented encloures in their catalog; a couple years ago when I last looked anyway. Edited by user Thursday, December 27, 2012 11:32:04 PM(UTC)
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Ah, yes, thanks for pointing this out. I could probably drill cleanly enough some holes in the top and bottom of the enclosure.
Speaking of thermal issues, once concern I have is that if I inadvertently power off my DAC, then all the current normally taken by the load will be shunted and the Placid will overheat. I guess there is no safeguard against that? Can I at least assume that something will fail open at some point before the condition becoming a real hazard (fire or otherwise)?
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You should wire you switch at the connection between the main and your primaries (with a ~ 1-2A slow blow fuse in series). :) Then you need not worry. Just be very careful wiring mains as always. Be safe. Edited by user Friday, December 28, 2012 12:05:24 AM(UTC)
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If the case is aluminum, you can also just use it as the heatsink for the Placids, by mounting them to the floor below the PCB, with pins bent 90deg up.
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You can call Avel to order directly, they are very nice. I think the one-off price (with shipping) for a smaller transformer will be close to what we charge for the larger unit (I buy them in large lots).
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Brian, thank you for both replies. The case is aluminum, so floor mounting is definitely an option.
Although the spec in my first post indicates +/-15VDC, I hope that I can go using the Placid and the 15V 30VAC Avels as high as 16VDC as I'm told that SQ may benefit from slightly higher voltage. I'm also told that the current could be as low as 250mA on the +15VDC rails and 150mA on the -15VDC rail. The DAC is an Audiolab M-DAC by the way (in case anyone was interested to know).
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Hello everyone, I would be interested in getting opinions on the proximity of the floor mounted transistors in the layout I attached below. My application does not require floor mounting per se as the current draw is in the range of 300mA on each of the 3 15VDC rails, however, the load has its own power on switch and I would like dissipate the full power in the shunts of the Placids without any safety hazard in the event that I disconnect my load and forget to turn off the Placids. Another option I'm considering for thermal protection is a thermostat such as http://ca.mouser.com/Sea...000virtualkey802-STO-170 . But perhaps this is really unnecessary. Cheers, Martin Edited by user Saturday, January 12, 2013 5:13:54 PM(UTC)
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Well, my Placid HD BP and Placid HD Single are now singing via my Audiolab M-DAC. Early listening sessions seem to confirm an improvement in the SQ. Time and more listening will tell. The Placid kits and Avel transformers arrived well packed a few days after the order was placed. As usual, everything was very well labeled and kitted. Assembly went well except for a couple of low current transistors which I noticed I mounted backwards just after I soldered them, duh. The adjustment of the Placids was straightfoward. My voltages and CCS minus shunt currents are as follows: Analog +15.87VDC: 235ma Analog -15.91VDC: 155ma Digital +15.94VDC: 390ma Shunt current is set at roughly 50 to 70mA per rail. The digital rail is the most dynamic with the DAC (shunt drops by 30mA ave while the DAC is busy making music) so I set the shunt current on this one at around 70mA. Heat sinks of the digital rail are hotter than the other ones, but I can still keep my finger on them (for a few seconds at least). My DC DIN-connectorized cable going from the Placids to the DAC has roughly a 0.35R resistance on the analog rail wires so I need to do some custom work to beef it up by substituting for lower AWG wires over most of the 2-foot run. Here's a link with a few pics of the PSU and DAC. Next step is to put everything into an enclosure. I will be using a Lansing Type C 7x9 inch case. https://plus.google.com/...?authkey=CKCaovSqv5WslQECheers, Martin Edited by user Sunday, January 20, 2013 4:26:06 PM(UTC)
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