Remote Gain Control for (almost) every preamp!
Digital snake systems like our ADAT Multicore Extender have many advantages. But with these systems, the mic preamps are usually located on stage, and you cannot adjust the gain locally from FOH - this can be an issue if you just wanted to "give some dB less" during the show. Remote controllable preamps are the solution, but they are hard to find and even more expensive - not the right thing when building a low-budget system. That's why we developed a modkit which works with most preamps and allows you to add remote gain control via MIDI. Simple to do, even simpler to use.
Principle of operation
In remote mode, gain adjustment is entirely done over the optocouplers. They are controlled by an external box (the Remote Gain Controller) which is in turn controlled via MIDI from the mix console at FOH position (the MIDI channel of the ADAT-Multicore-Extender ADX-32B and ADX-64B-PRO can be used for this purpose). When remote control is active, the original gain pots must be in leftmost (min) position. If local control is desired, the Remote Gain Controller can be switched off by either pressing the "MODE" key, by issuing a MIDI message, or by simply removing the control cable from the preamp.
- The Remote Gain Controller RGC-24A-M is capable of controlling up to three preamps (24 channels)
- Up to four RGC-24A-M (96 channels) can be controlled over a single MIDI port (via daisy-chaining)
- Works with most preamp models. The adaption to different preamp models can individually done by the DIP switch (even mixed models). Please send us a mail if you like to use it with a particular preamp (we need only the gain/resistance curve of the original potentiometer).
- The unique, individual sound of each preamp is kept (no changes in the signal path)
- Very low THD+N thanks to special high-class audio couplers
- No hum and noise due to fully isolated design
- Modded preamps retain their original function
- Outputs can be configured as digital switch for reed relays (e.g. to switch pad or phantom power)
- Does not need any power from within the preamp
- Last setpoints are kept after loss of power
- Robust aluminum case 148x94x35mm with mounting flanges, does not eat up rack space
- Quality product „Made in Switzerland“
- 1 pc. Remote Gain Controller RGC-24A-M
- 24 pc. analog optocouplers (for modding 24 channels)
- 3 pc. 9-pin D-SUB male jack
- 3 pc. ribbon cable
- 3 St. 9-pin D-SUB cable, 1:1
- Wall mount power supply 90-240VAC
- LED for "dry-runs" (connect instead of optocouplers, to check control is working)
- Printed manual with detailed instructions
- ART TubeOpto 8
- Behringer ADA8000
- Focusrite OctoPre mkII
- Focusrite OctoPre mkII Dynamics
- Mackie Onyx 800R
- Presonus Digimax D8
- RME Octamic
- all other preamps where the gain pot is between 5k and 50k
(log taper) and is used in 2-pin (rheostat) configuration.
Special pots with dual or triple wiper are supported on request.
- Focusrite OctoPre Platinum
- Presonus Digimax FS
- SM Pro Audio PRE 8 E
Which Functions can be Remoted?
All functions which are controlled by either pots or switches are remoteable. To remote switches, reed relays (not contained in the kit) instead of optocouplers are required.
The mod takes about one hour and requires no special tools (only screwdriver, cutter and soldering iron). The original gain potentiometers remain in place, but become paralleled with analog optocouplers. The whole thing is controlled over a 9pin D-SUB connection which could be mounted on the rear.
There are several possibilities to control the RGC-24A-M module via MIDI:
- VST Plugin The most convenient way, enables seamless integration in Windows audio software like Cubase or SAC.
- Windows Standalone Program
- BCR2000 Template for Remote Gain Controller Templates are available for Behringer's BCR2000 rotary knob controller.
- Yamaha DM 2000 console
- Yamaha 01v96 console
- Manual setup: Gain is adjusted via
standard "Control Change" messages. The default scheme is:
MIDI Channel = Preamp, CC = Input, Value = Gain. E.g.
MIDI Channel 2 = Preamp 1, CC 24-31 = Input 1-8, Gain = Value 0-127
MIDI Channel 3 = Preamp 2, CC 24-31 = Input 1-8, Gain = Value 0-127
MIDI Channel 4 = Preamp 3, CC 24-31 = Input 1-8, Gain = Value 0-127
Above mapping can be further adjusted via SysEx commands, please refer to the manual.
The most easiest way to remote control your preamps with the RGC-24A-M is via computer. Our control software is available as standalone version (Windows), and also as VST plugin for a wide variety of DAW software, e.g. SAC (Software Audio Console).
The plugin allows remote gain control of up to 48 channels (two RGC-24A-M's), directly from your favorite DAW software. It supports full "Scene Recall" (all settings can be saved to different "Scenes" and later be recalled) as well as "Channel Linking" (links the gain knobs of two channels together, e.g. to control stereo signals). After gain adjustment is done, the window can be minimized to save screen space, and it can be instantly restore when it's needed.
VST-Plugin running in SAC
The standalone variant of the control software runs directly under windows (no host program required). All settings can be saved to files and recalled later.
|229 kB||Free Download|
(all 48 channels)
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Windows Installer EXE
If you have any questions regarding installation or usage of the
software, please contact the author directly:
Achim Kaiser <>.
|Buy now >>|
My preamp model is not listed. Can it still be modded?
Chances are very good! If it actually can be done, depends only on the type and connection of the original gain pot:
- It must be between 5k and 50k log taper
- It must be in 2-pin (rheostat) config. Stereo wipers in 2-pin config (but not in 3-pin config) are also possible with a special tweak (please contact me if this is the case).
You can try out before, its simple:
1.) Get yourself a 10k (or 20k, 50k) log taper pot
2.) Connect it in parallel with the original pot:
3) Turn the original pot to "minimum"
4) You should now be able to adjust the gain using your test pot.
If the above works, the Remote Gain Controller works as well.
Can PAD and PHANTOM switches also be remoted?
Yes, if you connect relays instead of the couplers. Each bank of the RGC can be switced to "digital output" mode. Due to output circuit limitations you will need to use low-power relais, e.g. MEDER Type DIP05-1A72-12L. Please contact us if you have different requirements.
How does the RGC behave if my MIDI controller crashes, or if power is lost?
The RGC remembers the last setpoints and state in its internal EEPROM.
Once set, it keeps its settings, even after power loss
(it comes back to the last state when power comes up again).
I don't want to mount an D-SUB jack on my preamp. What can I do?
You can solder the supplied cable directly to the couplers. Cut-off the female plug, drill a hole anywhere on the back of your mic and run the cable through it.
How stable is the gain when controlled through the couplers?
In short words: Very stable. We took a couple of measures to keep it as good as possible:
- The couplers operate in a logarithmic scale and allow about 55dB of dynamics (about the same as an usual gain pot allows). Luckily, most of the coupler's drifts are "linear" and very small compared to the total dynamic range.
- The couplers are, due to their nature, not "precision parts" in terms of part-to-part tolerance. The resistance varition of standard (non-selected) couplers can exceed factor 2 when supplied with the same reference current. That's why we ship only sorted couplers which are matched to a resistance tolerance of ±5%, resulting in a channel-to-channel matching of about ±0.2 dB. This is a better value than most stock gain pots allow!
- The couplers are driven by a precision current source which provides very stable LED lighting intensity. The biggest influence is the temperature drift of the LDR substrate which is about 0.7% / K. This means that 10K increase in temperature results in about 0.3dB level change, which is perfectly acceptable for most applications. (You have to consider that nearly everything else in your signal chain has also a temperture drift - sometimes positive, sometimes negative).
- There is also no clicking or "zipper noise" when changing gains: The D/A converters used to control the LEDs are of ultra-low glitch type, and an inherent dampening is done by the couplers which are rather "slow" devices (they have a response in the order of several milliseconds).
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