Building My First DIY Audio Compressor

On August 29, 2013

I’ve finally made the leap into the addictive world of DIY audio. After buying lots of kit for the college and myself over the past decade, I’ve decided to invest my money in expanding my knowledge of electronics while also getting some great kit for a small amount of money.

My first adventure will be a DIY audio compressor – the Gyraf  Audio G1176 Voight/Kampf edition. As a first build, I thought it best to avoid the dangers of tubes and stick to a FET design. It’s also a project that has been done by many people online and some of my own friends – so I’m not short on support if/when it all goes wrong.

Gyraf 1176 DIY Audio Compressor Front Panel

The Gyraf G1176 is based on the classic 1176 first built by Bill Putnam (Universal Audio) in 1966. The UA 1176′s are a workhorse in many studios around the world and are still available from UA in their latest revision - The 1176LN. Although still a great unit, many folks prefer the older models and some even prefer to build there own.

I started the process by locating the majority of the parts on PCB Grinder - a site dedicated to selling DIY kits, especially those by Gyraf audio. Their 1176 V/K kit supplied the PCB Set, FETs, power switch, OMEG pots, audio switches,  op-amps, all Poly-caps, all metal film resistors (1%), all Ceramic caps, elcos and tants, Diodes, regulators, rectificers, Wire, Sockets for op-amps and PCB Stands. Not only was it quite cheap (on sale for €135), it was a timesaver.

While I wait for that kit to arrive, I contacted Frank Röllen at NRG CNC engraving, otherwise known as frontpanels.de. Frank does a pre-made set for the G1176, but also does custom jobs. For €10, Frank did a personal engraving on the front – just to give it that custom feel. The entire case with shipping and XLR/IEC components came to €140.

Next was the hunt for the toroidal transformer. With a lot of different information on what to use, I settled on a 30va 2x25v transformer from Farnell. I also picked up some knobs for £15. This should provide me with enough power for the board and the Sifam VU meter.

jFunk DIY Audio Compressor

The last parts I needed were the Sifam VU meter and the Lundahl output transformer. I turned to Andy “jFunk” Jackson who built the 1176 clone in my studio (above). Instead of him sending me hyperlinks, the legend of a guy found spares of both the meter and the Lundahl in his house and sent them to Oxford! What-a-guy!!

All parts are now on route. In total, thanks to favours and discounts, I’ve managed to grab everything for about £280. The only other investment left is personal time and maybe some solder burns.

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