Soundtracs Topaz PSU

Topaz PSU TRX topaz psu

On the left is the real Soundtracs Topaz PSU & on the right is my Transformer replacement.

I consider my Soundtracs Topaz recording console the center piece in my home studio, maintaining & keeping it functioning has had it's challenges. Using a schematic available from The Soundtracs Guy . Seen here on this page are pictures of the two replacement transformers I made for my Soundtracs Topaz console.

The prototype

I built my first Topaz psu replacement into a open rack mount case. I choose to hollow out a Behringer UltraFX because it had XLR sockets (perfect for the Neutrix connections) already drilled out on it's rear faceplate. For some of my wiring, like wiring the power socket to the terminal block, I use a common three wire computer power extension cable. I just cut the ends off and use the cable. I have brought this up, because you will notice that in my prototype I used the green wire (ground) to connect the neutral run from my power socket to the terminal block. I correct this in the second enclosure build, and used the inductry standard white wire for the run in the final project (see pic below). Sorry if this confuses anyone. This first build was somewhat of a rush job after my original transformer blew. Argh! I built this replacement as fast as the parts arrived in the mail. I have a hard time without my Topaz working. This prototype had no ON / OFF switch, the circuit was plugged into a power strip which had the power switch.
Please safely secure an open rack transformer like this. This can be a real electrical hazard. DO NOT TOUCH or HANDLE a powered transformer.

topaz rack psu 02

Power Strips & Surge Protectors can serve as both power switch and fuse box. A quick and easy solution when prototyping a power related device.

topaz rack psu 01

The SoundTracs Topaz PSU Replacement

Parts List

Avel Y236651 250va 18v+18v Toroidal Transformer

Neutril XLR Connectors

Part Description Mouser Part Number Qty 
250v 15a chasis power socket 562-703W-00/02 4
rocker power switch "Illuminated" DigiKey # EG4769-ND 2
Neutrik XLR Connectors 4P male 568-NC4MXX 8
Neutrik XLR Connectors 4P female 568-NC4FXX 8
Neutrik XLR Connectors 4P female outlet socket 568-NC4FD-LX 4
Molex Barrier Terminal Blocks 8 position 538-38770-0305 or
DigiKey # WM5766-ND
Binding Post for ground wiring 1
Bud Industries Enclosures 563-WA-1542 1
Heat Shrink Tubing 1/8" or .125 diameter 602-221018-4BK
HeilSound Heilwire 10' 4 conductor 18 awg  2

Notes on this parts list ...
I over purchased because I made two versions of the Soundtracs Topaz PSU;
                        a rackmount and a portable unit.

                        Suggest purchasing the 1/8" heat shrink tube insulation for the internal power connections.

wiring the power socket to the terminal block, I used a spare common
                        three wire computer power extension cable.

Building the XLR cable

Building the XLR cable is a straight job. Each of the Neutrik XLR 4 pins is labeled on the connectors. Labeled by the solder buckets on the inside of the Neutrik connectors, you will read 1, 2, 3, 4. You will need a soldering iron to join these two Neutrik connectors by 10 feet / 3 meters of 4 conductor 18 awg wire. Solder to each end of the four wires in your 4 wire cable, 1 Neutrik XLR Male Connector to one end & 1 Neutrik XLR Female Connector to the other end. The Heilsound wire that I used is color coded. So I identified each of the four individual colors within the Heilsound 10 foot / 3 meter cable to the Neutrik pins found on the connectors. The maximum length for the cable is 10 feet / 3 meters. In both of the transformer replacement example I have presented on my webpage, I cut the cable length to 9 feet. I used 1 foot of my Heilsound cable for connecting the Neutrik female socket of the PSU to the terminal block, seen in the pics below.

You will not be able to exceed 10 feet / 3 meters on your connecting cable's length. Cables exceeding 10 feet / 3 meters will experience a voltage drop and the console will not power up. I have made two of these cables in my efforts, a 5' and a 9.5'. From the Heilsound 10' cable that you purchase you can use 1 foot - 1/2 foot of the cable for the PSU's internal connections. This will also visually help you line up the circuit correctly through the wire's identification colors.

Building the PSU

The following pictures were made during the building of this PSU unit. I used crimp connectors on all the wires connecting to the terminal block.

tpsu 01

The AVEL Y236651 Datasheet
Use the datasheet to understand the wire color schem and function.

blue & violet wires of the transformer need to be connected to BLACK (HOT) wire to your power outlet.
gray & brown wires of the transformer need to be connected to the WHITE(Neutral) wire to your power outlet.
Orange, Yellow, Black & Red wires of the transformer need to be connected to their cooresponding wires of the XLR cable run that will eventuall connect your replacement transformer to your Topaz' XLR power connection on the rear of the mixer.

(seen in the picture above)

I used crimp connectors on all the wires of the Toroidal transformer & screw mount attach them to the terminal block. Then I crimp connected one end of the 1 foot I cut from the HeilSound & soldered the other end of my HeilSound cable to the Neutrik female socket. pictured below. The toroidal's primaries (115v); blue & violet, gray & brown(see picture above) as well as the power mains to the power socket (Black & white in picture above) are crimp connected and screw mounted to the terminal block. Using a terminal block is great in this application, making an easy job if I ever have to replace the transformer.

tpsu 02

From the rear of my PSU enclosure: Female Neutrik socket "LEFT", power socket "RIGHT". Probably over kill was the binding post I used to wire the ground "GREEN", of the power socket to. Please note the picture above was taken before the rear panel faceplate was installed. In order to complete this project these components, the XLR socket & power socket must be mounted to the rear faceplate and then wired correctly back to the terminal block, and the ground of the power socket needs to then be wired to the binding post. Leave yourself some slack in the connection wires. 

tpsu rear

This next picture shows the wiring up of the switch. I used an illuminated ON / OFF switch I bought from Digikey. I drilled the hole into the front panel of the enclosure using a stepper drill bit on my drill press. This project was made in part by me having a drill press. Without it, mounting the switch would have been a problem and drilling without a stepper drill bit in this application will no doubt drill a jagged hole in your panel and possible ruin your enclosure. Also seen here in this picture is the metal plate that the transformer is mounted on. The riser in my enclosure is made of steel and without a drill press would be a real nightmare to drill. See how I elevated this deck plate that the transformer is mounted on for wiring purposes and keeping the central spoke of the toroidal centered, locked in and not touching anything. For these enclosures sold through DigiKey there is a central elevated riser piece that you can purchase. But in my design the Bud Industry riser put the transformer to high & created problems when considering the back of the XLR socket. So I went with making my own riser for this enclosure project. With enough nuts & bolts I can adjust the riser to any height. I also used my drill press for the needed holes through the bottom of the enclosure that connects the riser to the bottom of the enclosure.

topaz rear plate

Here is a view of the back of the PSU with the faceplate I designed usng the Front Panel Express application. Here is the Front Panel Design I made for this project.

Fuse Protection

As far as choosing the right fuse to work with this DIY transformer, mine is mounted internally, between the power socket & switch. If your transformer will be just powering a Topaz 24-32 channel mixer without the meterbridge, use a 2-2.5Amp Fast Blow. If your Topaz has the meterbridge connected use a 3.15Amp Fast Blow.

The last part to my project was adding the internal fuse box, & not out of consideration to the original schematic. I plug all of DIY circuits and builds directly into an isobar which has a circuit breaker fuse. That is connected to a UPS which has a fuse breaker. With any and all DIY home built transformers or self powered devices I highly recommend that you DO NOT EVER plug directly into the wall. Unless you feel very secure about the surge protection, current flow & outlet's breaker you are plugging into. So put a fuse on it or always plug into a surge protector.

Part Description Mouser Part Number Qty 
Cooper Bussmann 3.15 Amps 125 Volts 504-GMA-3.15 10

psu illuminated switch soundtracs topaz power

Last, at different stages while building this transformer circuit. You certainly will want to test. Please again, plug into a power strip / surge protector. Always have a surge protector on the wall outlet. If your power strip has a built in surge protector, even better. If you have incorrectly wired something in your transformer circuit or improperly grounded the transformer, it will trip the circuit. Easily fixed at the breaker, but if you are testing your transformer project in a room with other electronics and you blow the rooms circuit, everything will power off. Given what was on in your room / studio, this might be upsetting. So be safe & happy; when testing, using and enjoying your replacement transformer, always plu into a power strip / surge protected AC wall outlet. 

The end result is a small well vented portable Toroidal transformer for the Soundtracs Topaz.
Works Great!

There are numerous mixers that have been manufactured over the years,
that employ the use of an external transformer. They have their advantages.

Not a Soundtracs owner, but need to replace your external PSU.
With a few changes you might find that this transformer design could work for you.

Different connectors, transformers & fuses maybe...
but still the same design.

more Soundtracs Topaz pages...

Soundtracs Topaz Information

Soundtracs Topaz Electronics

Soundtracs Topaz meterbridge VU meters & lamps

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Saint Augustine, Florida