IMPORTANT ORDERING NOTE:

500 Series modules utilize a card edge connector. When ordering, choose "YES" on the Edge Connector option and select Immersion Gold(ENIG) as your surface finish. This ensures long-term durability of the edge connector.

Additionally, this project includes four distinct PCBs in a panelized configuration. When ordering, select "Panel by Customer" and set the number of "Different design[s] in panel" to 4.

Project Overview:

The REDDISH-500 is an inductor-based passive equalizer based on Ian Thompson Bell's REDD eq, adapted for the 500 series format. Great care has been taken to provide the highest quality project possible. More than 100 units were built in the limited release on GroupDIY, and the project's popularity has led me to make it available here so that future builders can have access to this wonderful studio tool.

User Controls:

• RS-127 Brilliance Control: The REDDISH-500 boasts this famous circuit with two added frequency points to create an even more useful version of this popular control. Have you ever used the Softube plugin version of the RS-127? Well now you can build the real thing!
• Bass Control: Provides +/-10dB at 100Hz in 2dB increments.
• "Hi +": This pushbutton switch allows users to engage a fixed-gain boost at 10kHz. The amount of gain is selectable by the builder, and this process is laid out in simple terms in the build guide.
• In/Bypass: The REDDISH-500 utilizes a relay-based true bypass, meaning you can A/B the unit with the push of a button.

Other highlights:

• The EQ curves of the REDDISH-500 are wide and very smooth, making this the perfect EQ for shaping everything from individual instruments all the way up to mix bus and two-track applications (build a matched pair in this case).
• A high quality make-up gain amplifier based around a Burr-Brown OPA2134 is used to set unity gain.
• Transformers: A Carnhill or UTM 10k:10k transformer is used on the input, while the make-up amplifier drives a 600:600 Cinemag or UTM output transformer
• PCBs have been designed to accommodate a wide range of component footprints, meaning builders have tremendous flexibility when selecting components (see build documents for more information)
• Community support is available on the REDDISH-500 GroupDIY Project Thread

Front Panel and L Bracket available here. (Please note: the current version of the PCB uses a different, off-the-shelf part from Keystone for the "small 90˚ bracket," which you will find listed in the BOM. When ordering metalwork from frontpanels.de, order the Front Panel and L Bracket only, but do not include the "small 90˚ bracket.")

The Build Guide can be accessed on the GroupDIY Project Thread linked above, or by clicking "Other files for Assembly" on this page. Happy building!