PC amplifier project

Below is a sketch to detail how I wired up a home made cable from the AM30 to a PC's sound card.

The PC Serial data port to 13 pin DIN plug connection in my case was via an FTDI USB to 5volt TTL cable, there are other types that will also work. Make sure that they are 5 volt TTL output type. You will probably have to install a driver for windows to use the cable as a COM port.

I had to use  an optical TOSLINK to coax converter, from eBay, as my PC sound card had a TOSLINK optical digital output and the BOSE AM-30 only uses a DIGITAL coax S/PIDIF connection. This converter needed a +5v power supply, I used a spare PC USB socket as the supply for this converter. You could also use an old 5v charger to do this.

I used a 13 DIN plug from eBay to connect to the AM-30 as I wanted to be able to switch between either of two AM-30's that I had bought from eBay. The AM-30's cost me about £30 ($40) each. You could wire directly to the AM-25/30 digital PCB or make up a different type of connector and solder it to the AM-30 digital PCB rather than use the DIN socket, depending on your own PC connectors.

Note:-

The analogue stereo input common (ground) MUST only be wired to pin 5 of the DIN plug as the AM-25/30 line input amplifiers are differential to cancel noise from the sound source (PC sound card, mains hum etc.) so do not use the other ground pins (2,6 or 10) for analogue input.

 

For more detailed technical details on the BOSE AM-25/30 bass modules download the service manuals and schematics (in PDF format) on the download page.

 

The sketch below shows the 11 wiring connections to the 13 pin DIN plug for this project, followed by the PC program screens:

PARTS LIST

Below are the connection details between the PC audio and the Bose AM-25/30 Bass box.

The cable length will depend on the distance between your computer and the Bass box.

You can make up connectors and twin screened audio cable or cut up existing cables to solder to the 13 pin DIN plug.

So you will need to find or buy:-

MINIMUM PARTS REQUIRED TO USE THE AM-25/30 (analogue stereo sound feed only):-

PARTS to make the cable:

1 x audio cable with a 3.5 mm plug on each end, allowing you to cut one plug off (your sound card may need RCA plugs).

1 x FTDI (or similar make) USB serial to 5 volt TTL cable.

1 x PP3 battery (or 9v wall wart DC PSU) very low power as a battery lasts 18-24 months of daily use.

1 x PP3 battery connector

1 x small DC switch to turn power to the AM-25/30 on/off (you could leave battery on 100% of time and switch mains).

OPTIONAL PARTS (required to use a digital connection to the BOSE):

1 x TOSLINK digital audio to COAX S/PDIF converter box (usually has optical cable & USB power cable supplied).

1 x RCA to RCA single screened cable, cut one end off and wire it to the 13 pin DIN plug.

Note: if your sound card has a coax output RCA cable connector you won't need the TOSLINK converter.

 

PARTS to connect the AM-25/30 speaker output sockets to your stereo/surround speakers:

5 x RCA to twin screw terminals off of eBay to wire to speaker cable.

1 x roll of speaker wire (size depends on your room layout).

 

Surround sound speaker output connections

Image of Base of the BOSE accoustimass AM-25/30 showing the group of five RCA sockets which are OUTPUTS to the five 20 watt rms satellite speakers. This is the only equipment I have found that have used RCA's in this way, they are usually used as low power connections.

Below shows the Pinout of the 13 pin DIN socket on the base of the AM-25/30

Use the above 13 pin socket details when wiring up the 13 pin DIN plug to the wires that lead to the PC sound card and serial port.

 

Below are details of the Windows PC program that acts as a remote control for the BOSE AM-30.

 

Screen shot of the windows PC program to send control commands to the BOSE Accoustimass 25 or 30 bass module. This program needs a PC with a USB to TTL (5 volt version) serial port adapter cable. These are available on ebay, amazon etc.

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