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Enclosure not stated · 2 knobs

Effects Layouts (blog)

Baja Optical LimiterVerified

Based on the BAJA Optical Limiter· 2 other boards clone it

Category
Compressor
Controls
Limit · Level
Layout
Verified · Effects Layouts (blog) marks it as built and working
Tags
Baja, Limiter

From the post

Here's one of Bajaman's non-amp emulating circuits, the Optical Limiter. It's based on the Demeter Compulator, but is not a compressor but a limiter. What's the difference?

The ratio is the main difference between a compressor and a limiter. A compressor has a low ratio that turns down SOME of the volume when it goes above the threshold. A limiter has a huge ratio that turns down ALL of the volume that goes above the threshold. (from Musician on a Mission)

Here's the schematic for reference. It's designed as a buffered bypass pedal, with the input jack going to the In pad on the board, and a third of a a 3PDT footswitch selecting between the buffered out and effect out. The off board LED pulses with the signal but probably isn't going to be great as an on/off indicator. Just use another third of the 3PDT to make/break the connection between the LED- pad and the cathode of the LED. And then use the final third of the footswitch to wire an on/off indicator LED as you normally would. (At least I think that's what Bajaman had in mind...) Also, the LDR should have 5k light resistance, 500k dark resistance (a GL5516 should work). Oh, and I added an extra pad so GSD pinout JFETs (J201, 2N5457, etc.) can be used in place of the 2SK117.

Schematic

This is a board layout, a drawing of where each part goes, and the post may link the schematic it was drawn from. Open the layout at Effects Layouts (blog). No KiCad fragment has been drawn for this circuit yet.

Parts list 25 rows

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RefValueNormalizedTypeNotes
Resistors 11
×21K1kread from the layout by eye
×21.5K1.5kread from the layout by eye
×2100K100kread from the layout by eye
×410K10kread from the layout by eye
×12.7K2.7kread from the layout by eye
×268K68kread from the layout by eye
×5560Ω560read from the layout by eye
×24.7K4.7kread from the layout by eye
×1100Ω100read from the layout by eye
×247K47kread from the layout by eye
×11M1Mread from the layout by eye
Capacitors 5
×1220uF220uelectrolytic; read from the layout by eye
×210uF10uelectrolytic; read from the layout by eye
×21uF1ubox film; read from the layout by eye
×1100nF100nread from the layout by eye
×110nF10nread from the layout by eye
Diodes 2
×11N40011N4001read from the layout by eye
×21N41481N4148read from the layout by eye
Transistors 1
Q12SK1172SK117JFET; read from the layout by eye
ICs 1
×2LF353NLF353Nread from the layout by eye
Opto 1
×1LDRLDRtype not given; read from the layout by eye
Potentiometers 2
LimitB10KB10kPotentiometerread from the layout by eye
LevelB10KB10kPotentiometerread from the layout by eye
LEDs 2
×15mm yellow5MM YELLOWon board, faces the LDR; read from the layout by eye
×15mm yellow5MM YELLOWoff-board, LED+/LED- pads; legend 'LEDs: 5mm yellow'; read from the layout by eye

Other boards based on the BAJA Optical Limiter