19" 2RU Rack Enclosure for Dual 1176 Clone

A 2RU rack enclosure from Altronics which is sturdy and well-built, with plenty of room inside. It's called a "System PF-19" enclosure (PF-19 2U D2) and I imagine it's available from many suppliers. The case itself is steel and the front and rear panels are aluminium (front panel is about 3.5mm thick). It is finished in a dark charcoal powdercoat which is also quite durable.

The front panel was made by Front Panel Express and designed using their designer software.

Box Plan Drawing (pdf) Module Connection Drawing (pdf)

 

In order to make maximum use of the front panel space the rack handles were left off. There are some socket-head screws provided to attach the front panel to the chassis when doing this.

 

1176 internal view 1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The rear panel was marked and cut to house the sockets and IEC connector. I included both XLR and 1/4" connectors for the input and outputs. The rear panel has two steel bars attached to it for mounting to the sides and top/bottom of the enclosure.

A gear plate was made using two of the steel bars supplied with the enclosure and an aluminium plate. This allowed all the modules to be mounted without having to make holes in the bottom of the case. The two steel bars are mounted to the case using screws through the side of the enclosure. The gear plate is shown below with the two 1176 modules, the PSU-8 power supply module and the gain reduction disable module.

The toroidal mains transformer neatly fits against the side with the mains switch and mains inlet, allowing easy wiring of the AC and separation from the rest of the interior.

 

1176 module mounting plate

 

 

 

 

 

 

 

 

Finally the unit was wired and calibrated. If you can get a multi-turn trimpot for the Q-bias, I'd recommend it. The FET curves are quite steep and getting that 1dB drop does not take much movement in a single turn trimmer.

 

1176 internal view 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Once calibrated, the unit was put through several tests with different source material. It's very quiet and really performs well.

The actual ratios can be measured using the procedure detailed in one of the accompanying articles.

A troubleshooting guide has also been compiled for those who have problems with their units.

 

Front of Flashstar meter unit