Flatline Compressor

Flatline Compressor

Project description

A nice and transparent compressor based on this schematic by John Hollis.

The weird LED/green wire combination represents an optocoupler. I've used the VTL5C2 in 2 of my builds. Here's a nice read about them optocoulers and LED/LDR combo's: http://home.orange.nl/fvrijswijk/guitar_electronics_diy/flatline_compres...

The flatline is really suitable for use on bass and can even give a nice boost to drive a tube amp into fat crunch!

Bill of materials

R1: 10K
R2: 10K
R3: 10M
R4: 10M
R5: 10K
R6: 47K
R7: 10K
R8: 220K
R9: 330R
R10: 100K Log (A)
R11: 100K Log (A)
C3: 1nF
C5: 1μF
C1: 10μF
C2: 10μF
C4: 100μF
IC1: TL072
D1: 1N34A
D2: 1N34A
D3: 1N34A
D4: 1N34A
D5: 5mm
6 jumper wires
10 trace cuts


Click here to see the bill-of-materials as a list or download it as a comma separated values file (.csv).


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RE: R10 lug 3....

Sorry, lug 1.


Lug 1

D, Lug 1 is attached to lug 2 ... I agree, brown on brown is a bit hard to see, let me fix that ;)

On a side note: it doesn't change the workings of the potentiometer, which is wired as variable resistor in this case.

RE: Lug 1 (2)

Many Thanx for that !

So i'm connecting a wire from lug 1 to lug 2. Is that right ?

I am really sorry if i'm coming across like I need to be walked through this but I am really new to this and don't want to get it wrong.

Thanx again


Lug 1 and 2

Sorry for wasting time....spotted it. D'oh !


R10 - lug 3...

Sorry again for the ridiculous questions :-) but is lug 3 on R10 not used. What I mean is, is it not used for the ground ?



The weird LED/green wire combination

Firstly, i'm extremely new to circuit building and stomp boxes so please bear with me if this sounds obvious....

Do I need to put in the LED and the wires ? If so, is it just a normal LED conected across the two tracks with the green wires passing over the cuts ?

Thanx in advance :-)

D E Holt

P.S. Great great site by-the-way :-)



Is D5 de Led/ldr combinatie of de VTL5C2? En dan aan de kant waar de led staat de led en aan de andere kand de weerstand?



Je mag zelf kiezen maar ik

Je mag zelf kiezen maar ik vind de VTL5C2 wel het beste werken in deze compressor. Het LED-gedeelte zit waar de LED op het bordje is getekend en de LDR dus aan de rechterkant.

Quick translation: the LED-part of the optocoupler is where the LED is drawn on the board, the LDR part is at the right side lf the LED.

RE: D5...

Many thanx for that. I think i've got it.

Great stuff

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