Mixing Console Power Supply - Page 1
Forum section: electronics / projects

author: H713
author_rank: Regular Contributor
timestamp: March 31, 2019, 06:14:43 am
content: So my latest project is looking like a power supply for a mixing console. The desk requires +/- 18V @ 5A, +48V (phantom power for the mic preamps) and +5V at about 5 amps.In addition to not getting the snakes with it (which would have saved me about 50 hours of soldering and panel design), I also did not get the power supply.Reliability here is pretty, as failure could potentially kill 25 channel strips (lots of time to rebuild)I have not had much luck finding any used console power supplies for less than $500, and very few have the required specs.So I'm looking to build something. Let's forget about the +5 and the +48 volt phantom power rails- I've got modules for that in stock. For the 18V rails, I've had two ideas, one considerably more attractive than the other.1) I've got transformers, rectifiers and caps in stock, then use a 7818/7918 with a pass transistor. Protection circuitry could be designed without too much difficulty. How stupid of an idea is it to place trust in a circuit like this?2) Do what everyone building new power supplies for Trident and SSL consoles does, which is to stick some Power-One modules in a box. I like this better, because it saves a lot of testing and design. The problem I'm finding is a lack of 18V modules. This brings me to the main question of this post. The IHD15-6 and F24-12A modules are pretty common- I see them all over eBay. I know there's some adjustability, but does anyone here know if I could realistically get an additional 3 volts out of one of the 15V modules?I'd really like to avoid a switching power supply for this. For some applications it could be fine, but there is a lot of gain in parts of this console, especially the mic preamps, and given that the board was designed with a linear supply in mind, I'd like to stick with that.

author: LapTop006
author_rank: Unknown
timestamp: March 31, 2019, 11:45:31 am
content: I've not built replacement console supplies before, but I will add one thing to check to avoid an expensive mistake.Some of them had the rails related to each other in weird ways (ex Audio GND is tied to 5v digital high), triple check that in the schematics if possible.

author: Cliff Matthews
author_rank: Unknown
timestamp: March 31, 2019, 12:51:19 pm
content: Getting the +20% may be possible with a few mods, including the Vref on the PCB. Apparently they have an adjust POT for up or down 5% and specs indicate a 55% typical efficiency, so this may indicate there's lots of Vcc headroom* to work with (for 3 x 2n3055's to deliver just 6 amps). What voltage is present on the main filter cap?*If not, you still have the 100vac primary tap you could run at 108vac with the help of a 12v/5a halogen light transformer on the AC input (as an auto-transformer reducing the 120vac down to 108vac).

author: H713
author_rank: Regular Contributor
timestamp: March 31, 2019, 08:32:22 pm
content: Quote from: LapTop006 on March 31, 2019, 11:45:31 amI don't have any reason to believe this console (Sony MXP-2900) does anything like that, though it does have both a 5V and a 5V Reference line. That said, it is a broadcast console, and it is made by Sony, so there is no shortage of bizzare features and "Sony-isms" that make ridiculously complicated for what it is. It's also rather poorly engineered, having 10 foot ribbon cables wrapping around the frame under the trim because someone at Sony realized that oh S***, we need forgot our desk needs to interface with the Sony Editors!So far I haven't been able to find a schematic for either the original console power supply or the IHD15-6 modules I was thinking of using.

author: The Soulman
author_rank: Super Contributor
timestamp: March 31, 2019, 09:03:30 pm
content: Instead of searching for a used power supply, search for a complete console they usually come with the psu.Something like a crest x-series: x-four, x-eight, x-vca, (not the small rack mount consoles) come with adual 18V (5A) psu that also has a 12v and 48v rails.Schematics are available for that, also some soundcraft, yamaha, midas etc psu's may work or at least offer a solidstarting point for modifications.Used analog consoles are cheap as chips here especially with issues as scratchy faders or pots etc.