ACTEM -  Audio development

2 x 95W 4 Ohm wireless amplifier on a 4 mm aluminium plate and below the transmitter module
2 x 95W 4 Ohm wireless amplifier on a 4 mm aluminium plate and below the transmitter module

24 bit wireless amplifier and transmitter modules.

The DSPA70 wireless amplifier module is based on the IP of Texas Instruments Pure Path Wireless. It has been proven itself very robust in 3 years of testing in rooms with many other WiFi transmitters.

The wireless interface transmit up to 48kHz / 24 bits and it reaches up to 100m in free air.
It uses the 2.4GHz band. This performs better than 5GHz, when the signal has to go though walls or if any obstacles are placed between the transmitter and the receiver.
The TI Purepath automatically set up a second frequency, and it switches without problems to the second frequency, if the first frequency is disturbed.

The DSPA70 also contains an analogue input.

The audio signal is routed to an Analog Devices ADAU1701 Sigma DSP. Analog Devices offer some really easy graphical software, where no programming knowledge is required, except building with blocks.

The standard version is capable of :
  • Tracking Filters
  • DC Blocking
  • De-Emphasis
  • Various sources
  • Time delay up to 41mS (Appr. 14m at 48kHz) Other versions offer longer delay.
  • FIR Filters
  • Biquad filters
  • Soft/hard clip and more

The DSP is routed to the the TI Class-D amplifier section (digital input)
This 2 channel amplifier has build in protection for:
  • Short circuit
  • Over current
  • Over temperature

Power output for each of the two channels:
Using a single DC Voltage of 28 V DC, the typcial power is
50 W in 8 Ohm
70 W in 6 Ohm
95 W in 4 Ohm

Only a single DC voltage is needed. A voltage above 34V DC might cause damage to the amplifier.
A single minimum 18V DC is needed for proper sound quality.
2 pcs 12V car batteries in series will work well as back-up power.

PCBs are available fitted on 4 mm Aluminium mounting plates. They also act as heatsinks.
Maximum height is 52mm due to PSU capacitors. This includes the 4 mm Aluminium plate.
A version with a maximum height of 36mm is available. Using 25 mm tall capacitors.

The pairing button is mounted on the downside of the PCB. There is also a LED that indicates turned on. The Aluminium plate has a hole for the pairing button, airsealed by a screw. The Aluminium plate
contains a mains power inlet with the power on/off switch, and a fuseholder.
The PCB does have a rectifier, so it can also be powered by AC from a normal mains transformer.
Suitable 115/230V to 18V AC transfomers are available. Absolute maximum AC input is 24V AC.

Higher voltage and power versions are available. Maximum 300W in 4 Ohm and 400W in 2 Ohm.
A wireless DSP PCB frontend for the Pascal S-PRO 2 2x500W in 4 Ohm is in development.
Several transmitter HUB PCBs are available, with many types of inputs.

The unmounted header row in the front has the analogue input and access to some GPIO pins on the DSP.

Programming is done from a PC using the 10 pin multipin connector near the programming button.
The other 10 pin connector and 14 pin connector is not for customers. They are used for other programming of the PCB board during production.

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