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.)
Click here for continuation of article...
Digikey Parts List:
Mouser Parts List:
The Lundahl transformer prices are as follows:
1 x LL5402 $54
1 x LL1540 $60
Shipping $7
---------------------------
Total $121
Schematic, plans for the G1176 are at
www.gyraf.dk.
Click here for Continuation...