power supply – io 0.0.1 beta++

rack: loaded and powered up

Han-earl Park — Tue, 21 Oct 2008 10:51:34 +0000

Here’s the test of the power supply and the power inlet of the patch panel.

rack, loaded and ready for power on test

rack, loaded and powered on

enclosure and power supply (intermediate version)

Han-earl Park — Sat, 18 Oct 2008 11:54:28 +0000

Here’s photos of the intermediate version of the power supply in its enclosure.

power supply loaded into enclosure

power supply loaded into enclosure (alternate view)

The front of the unit is at the top of the image, and the back is at the bottom. You’re also looking up at the the unit in these photos. Power switch and LED indicators are at the top left of the image, all external connectors are on the panel at the bottom (see the panel arrangement). The 12V supply is above the 9V in these images. The pre-amplifier is missing in this version (there’s a pass-thru as a place holder).

You might notice the slightly odd choice of securing the components to the top of the enclosure instead of the bottom (I hope this will not prove to be a problem in terms of heat dissipation). I’ve done this because it’ll be easier to access the internals of the device due of the arrangement in the rack case. We’ll see how well this works…

power supply (early version)

Han-earl Park — Sun, 12 Oct 2008 15:11:06 +0000

The power supply has to provide, at a minimum, 0.7A @ +12V for the VL70m (power consumption measured at 0.6A @ 13.1V), and 1.3A @ +9V for the pitch-to-MIDI converters (GI-10: 0.26A @ 10.2V; GI-20: 0.8A @ 11.3V). Eventually, it will also provide bipolar power for the pre-amplifier (±12V or ±15V likely created using a charge pump converter).

Mains electricity is dropped down to 15V by a switched mode power supply (thus, I won’t have to work with 230V directly). The 15V supply is then regulated to 12V and 9V.

Quasar Electronics 3060 schematic (image copyright Quasar Electronics)

I use two 3060 kits from Quasar Electronics to provide 12V and 9V with the following changes:

use the L78Sxx regulators (L78S12CV for the 12V supply, and L78S09CV for the 9V)
use superbright LEDs (5.1kΩ current limiting resistor for the 12V supply, and 3.6kΩ for the 9V)

Additionally, I’ve modified the 9V supply as follows:

replace WO2M bridge rectifier with a 2W01G to account for the greater current
two heatsinks to help dissipate power (we’re dropping almost 3V @ 1.3A)

enclosures: pre-amp and power supply panels (physical artifacts)

Han-earl Park — Thu, 18 Sep 2008 16:48:35 +0000

As an update to the previous post, here’re photos of the machined and loaded panels.

Front panel

The front panel holds, from left to right, the power switch, 4 LED indicators (+15V, +12V, -12V and +9V), two filter bypass switches and two output level pots.

Rear panel

The rear panel holds, from left to right, stereo audio inputs (unbalanced), stereo audio outputs (balanced), power output connectors (two for the +9V supply and one for the +12V), power input connector (+15V DC).

enclosures: pre-amp and power supply panels

Han-earl Park — Tue, 16 Sep 2008 17:01:04 +0000

One handy box that forms a crucial (if unglamorous) part of io 0.0.1 beta++ contains the audio preamp (basically, a couple of filters, signal amplifiers and a balanced line driver) and power supply/distribution components (9V, ±12V). I don’t have a name for this box yet, but here are the layouts for the front and rear panels.

Front panel (click to see SVG image)

Rear panel (click to see SVG image)

The enclosure I am using is the Hammond RMCS9018 half-width, 1U rackmount enclosure [see PDF drawing].