Ross™ Compressor

This is a replica of the RossTM Compressor referred to as DNR in these documents (MXR™ Dynacomp™ can also be built on this PCB). This compressor is one of the all time “classic” compressors and has a great sound. Use the project documents provided, starting with the General Build Instructions. The original unit used the now obsolete 2SC1849 transistors. The current production 2N5089 transistors are quieter and sound excellent in this circuit. If you want to source some 2SC1849 transistors, you will need to twist the pins around to fit in the CBE format that this PCB uses. The sound difference between tantalum capacitors and aluminum electrolytic capacitors is very subtle, if even at all detectable to the ear. You would most likely not hear any difference. It's also debatable which type of capacitor would sound better (if you could hear the difference). We have found that either Tantalum or Aluminum Electrolytic both sound good. The original units had ceramic capacitors that we have upgraded to film. Outside of distortion circuits, there is usually no debate that film will sound better than ceramic (if you can hear the difference).

Here's an inside view of the unit we built to give you some general ideas if needed.

Comments and questions are welcome and can be sent to [email protected] Here is a chart of voltages taken at the transistor and IC pins. This information can be used to help find and fix problems if your OSQ doesn't work when you test it.

Component

Location

9 volt power supply Q1

Voltage

9.3v

Collector

7.5v

Base

2.4v

Emitter

2.0v