Hi all, this is a simplistic noisegate that was published in the 80's in the dutch electronics magazine 'Elex', which was a subsidiary/small brother to Elektuur (which was the dutch version of Elektor magazine). Their projects were simple and aimed at beginners. All volumes have been released on CD and you can probably find it online somewhere.
I built this noisegate on a piece of perfboard in the early 90s and it performed 'ok', for what I recall.
Just today, I've put the schematic in Eagle and made a layout for it, but I haven't tested nor verified this layout yet (!!!). The original called for a symmetric power supply (+/-9 ~ +/-15V), I made it with a Vref so only +9V is needed. It's a quicky so there's quite a bit of improvement possible, and not only layout-wise: as-is it has an unbuffered audio-path so the obvious first improvement would be to add this.
A few more notes:
* the 'off' pad (PAD1 in the schematic) can be switched to GND to turn the unit off (if no true-bypass is used)
* R7 determines the speed, substitute with a pot or a pot in series with 10k or so for a variable setting
* D2 was originally a germanium (AA119)
* I didn't have a BF256 footprint on hand so I used a 2n5457. Check the pinout before soldering! Actually, the original article mentioned that there are different pinouts of the BF256 around, depending on manufacturer...
Attached are the schematic (inline) and the eagle project, the zip includes images for the pcb and the parts placement.
Elex Noisegate
- Pruttelherrie
- Solder Soldier
- Pruttelherrie
- Solder Soldier
Ouch, I just realized: this isn't going to work right, with regards to the referencing of the signal (as alluded to above).
The signal is actually not referenced at all, we need at least two caps and two resistors to make it work ok.
The signal is actually not referenced at all, we need at least two caps and two resistors to make it work ok.