thread: Behringer 2600
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Old 24th April 2021
Gear Head
I got mine also the other day. Mine was badly calibrated. The Sine on VCO2 sounded awful. Once I got it on my scope I could see why - it was over 20v p-p double what it should be. Symmetry, purity and gain all needed adjustment

VCO Calibration works just the same as the OG, and now the sine on VCO2 and VCO3 sound identical.

I also upped the gain a bit on the ADSR exp control on the VCA to make it more like the OG and allow for some overdrive. The trim pot for that is the right most one in the group of three in the VCA section. The pot was set to its default middle detent. I turned it clockwise about 30degrees

And I have had it apart and have figured out what resistors I need to change to allow to me to switch to orange LEDS for everything and maintain even illumination
This is because different colour LEDs need a different current for the same light output.

The LEDS are divided into 12 groups. Each group has its own constant current source circuit. Each colour group has a different bias resistor, the rest of the circuit otherwise being the same.

Four groups already have suitable resistors for red/amber/orange and don't need to be changed.
8 resistors covering the blue, white and green groups need to be changed out

Currently the resistors - which are all 0603 size are

green - 2.4k - 3 resistors, one per group - 2.2v per led, 0.19mA from constant current source

white - 680 ohm - 3 resistors, one per group - 2.55v per LED, 0.5mA from constant current source

blue - 500 ohm - 2 resistors, one per group - 2.52v per LED, 0.67mA from constant current source

red/amber 10 ohm - 4 resistors, one per group, 1.84v red, 1.9v amber, 3mA from constant current source

So 8 resistors need to be swapped to 10 ohm. I have the parts on order and will test out next week and report back.

So provisionally:

green = 2.4K = R480, R482, R592

white = 680ohm = R483, R486, R581

blue = 500ohm = R479, R481

red,amber = 10ohm = R484, R485, R591, R628(this is for the amber group - located by S&H level fader)

The LEDs are standard 2mm x 3mm rectangular parts and just pull out. For replacements, you just need to trim the legs to the correct length. Loads of different types on ebay for example but you may need to experiment with resistors to get the brightness correct

You can safely swap to red or orange leds without opening the unit up, but they will be extremely dim in the locations previously occupied by the green, blue and white leds. Conversely, if you put blue or white leds in the red or amber slots, they will be far too bright compared to the rest.