>>>UPDATE 4/11/24: orders for pcbs are now closed.<<<
>>>UPDATE 4/30/24: BOM, Schematic, and some initial build notes attached to this post<<<
Hi Everyone,
I'd like to share one of my latest projects with you all. I present the "Redd-ish 500" EQ, a 500 series equalizer based on @ruffrecords amazing work. After building a standalone "RS127 Brilliance Control" box awhile back, I wanted to build a more robust version of the eq in a compact format. This version of the passive equalizer features the Bass and Brilliance sections of Ian's own Redd EQ with an added frequency point in the Brilliance section at 7.2k, and a pushbutton option to engage a treble boost based on the treble control section of the original circuit (the amount of boost is selectable between 2 and 4 dB via a shunt on the circuit board). The makeup amplifier that follows the eq also comes from Ian, and is based around a Burr Brown OPA2134 driving a 600:600 output transformer. I also included a relay-controlled true bypass.
I've used a UTM 2571 on the input, along with their multi-tap inductors in the EQ circuit, and a Cinemag CMOB-3S output transformer. PCBs and mechanical layout are my own, and the front panel was designed by me and produced by the ever-outstanding Frank at frontpanels.de.
Lots of lessons learned along the way here, including "you can't always guarantee that a manufacturer's mechanical drawing and dimensions are 100% precise" and "holy cow, don't ever get yourself into a position where you need to remove an already-soldered Grayhill switch from a PCB."
I can't thank Ian enough for his patience and generosity in answering my questions and giving suggestions. He is a true gem of this forum.
Please enjoy the photos! Just know that in the photos with the front panel, the panel is only loosely affixed (I was still futzing around with things), so you might notice that the metal parts look slightly askew.
>>>UPDATE 4/30/24: BOM, Schematic, and some initial build notes attached to this post<<<
Hi Everyone,
I'd like to share one of my latest projects with you all. I present the "Redd-ish 500" EQ, a 500 series equalizer based on @ruffrecords amazing work. After building a standalone "RS127 Brilliance Control" box awhile back, I wanted to build a more robust version of the eq in a compact format. This version of the passive equalizer features the Bass and Brilliance sections of Ian's own Redd EQ with an added frequency point in the Brilliance section at 7.2k, and a pushbutton option to engage a treble boost based on the treble control section of the original circuit (the amount of boost is selectable between 2 and 4 dB via a shunt on the circuit board). The makeup amplifier that follows the eq also comes from Ian, and is based around a Burr Brown OPA2134 driving a 600:600 output transformer. I also included a relay-controlled true bypass.
I've used a UTM 2571 on the input, along with their multi-tap inductors in the EQ circuit, and a Cinemag CMOB-3S output transformer. PCBs and mechanical layout are my own, and the front panel was designed by me and produced by the ever-outstanding Frank at frontpanels.de.
Lots of lessons learned along the way here, including "you can't always guarantee that a manufacturer's mechanical drawing and dimensions are 100% precise" and "holy cow, don't ever get yourself into a position where you need to remove an already-soldered Grayhill switch from a PCB."
I can't thank Ian enough for his patience and generosity in answering my questions and giving suggestions. He is a true gem of this forum.
Please enjoy the photos! Just know that in the photos with the front panel, the panel is only loosely affixed (I was still futzing around with things), so you might notice that the metal parts look slightly askew.
Attachments
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Reddish 500 2.jpeg3.1 MB · Views: 12
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Reddish 500 3.jpeg1.3 MB · Views: 7
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Reddish 500 4.jpeg3 MB · Views: 11
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Reddish 500 5.jpeg1.1 MB · Views: 24
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Reddish 500 6.jpeg4.6 MB · Views: 20
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Reddish 500 1.jpeg3.2 MB · Views: 23
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Reddish 500 EQ Schematic.pdf187.7 KB · Views: 1
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Reddish 500 EQ Build Notes.pdf44.8 KB · Views: 1
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Reddish 500 BOM.pdf154.7 KB · Views: 0
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