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I haven't DIY'ed for a long time, so to kickstart this hobby again, I decided I'm going to build an 1176 Compressor.

The 1176 is one of the classic compressors in used by almost every recording studio out there. (The other classic compressor is the LA-2A). Bill Putnam designed the 1176, based on the 1108 preamp. Back in 1966, the Field Effect Transistor (FET) was just developed and he's experimenting with the properties of this new device. Basically, think of an FET as a "voltage controlled variable resistor."  The FET has three terminals. Drain, Source, and Gate. The resistance between the Drain and Source can  be varied/controlled by the Gate voltage. So what Mr. Putnam was doing with the FET is using it as a variable resistor to contorl the gain reduction in the circuit.

The output stage of the 1176 is a Class A line level amp, feeding a load of 600 ohms. It's got an output transformer which converts the output from unbalanced to balanced, and also do impedance matching. 

If you don't know or don't want to DIY, you can buy an 1176LN (for Low Noise) compressor for about $1800. Or, you can purchae "virtual" 1176 plugins from $130 to $225 price range. Click here for software plugin versions of the 1176.



But hey, if you want real knobs you can tweak, with the warmth of output transformers in your signal path, but can't afford $1800, then DO-IT-YOURSELF is the best way.

I'll update this site as I build my 1176 compressor. You can find plans for the 1176 by Googling "G1176." Thanks to Jakob Erland from the Gyraf website for sharing the plans for the DIY 1776.

Electronic parts were purchased from Mouser.com, Digikey.com. For the Lundahl transformers, KandKAudio.com for the input and output transformers. Aluminum/Steel 2u rack chassis were purchased from Par-Metal.com.

I have a few of the components already in my parts box, so I didn't buy them. The PCB I got from the "Swedish Chef." If you're interested to know where I bought the PCB, email me. On of the most expensive item here is the VU meter. I got lucky since I bought this VU meter from some ham radio operator guy cleaning out his basement for a few dollars. But if you have to buy this new, it may cost you $100+. So shop around... but be careful and don't get fooled.



P.S: Do not buy those cheap small tape recorder VU meters. They are not real VU meters and you can't just hook them up to our 1176 project. They need supporting circuitry to make them work like VU meters.




These are the list of parts I purchased from Mouser.com... you can also use this as your parts list guide. (Note: Sometimes, there is a minimum quantity that you need to purchase so you'll see a lot of 10pcs for resistors. On the other stuff, I figure I'll be needing them in the future for some other projects, so might as well purchase a few extra. From experience, nothing is more frustrating than ruining a component during soldering (or losing it) and finding out  you don't have a spare. So I almost always purchase a few extra.)

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Digikey Parts List:


Mouser Parts List:


The Lundahl transformer prices are as follows:

1 x LL5402            $54
1 x LL1540            $60
Shipping                 $7
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Total                    $121

Schematic, plans for the G1176 are at www.gyraf.dk.

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