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jwb 20th July 2003 06:37 PM

FS: relay volume control attenuator boards
2 Attachment(s)
For Sale: 5 each printed circuit boards for balanced stereo 64-step attenuator. $95 each shipped in the USA, additional for shipping internationally. Compare 24-step rotary switches, without resistors, costing $170 or more!

This is the board discussed in "Yet another relay attenuator". The board is professionally manufactured on two layers, with solder mask on both sides and silkscreen nomenclature on the top side. The dimensions are 3.9" x 5.4" (99mm x 137mm) with a mounting hole pattern of 3.5" x 5" (89mm x 127mm). I am offering the board only, not a kit and not a fully assembled product. If you want kits or assemblies, mail me. You will also receive the bill of materials, including Digi-Key's part numbers, and cross-referenced with the board nomenclature for easy assembly. Furthermore I will include the schematic for your reference, and the software required for the microcontroller.

The design provides 64 steps of attenuation from 0dB to -80dB on four channels. Inputs are provided for left and right balanced signals, and the channels are completely separated on the board. Of course, it can also be used in a single-ended system if you prefer.

The control logic operates from an on-board AVR microcontroller, or the builder could choose to install a header in the microcontroller's place and interface with external logic. Provision is made for an on-board power regulator, allowing inputs from 6.5 to 24VDC, or it can be bypassed and 5V applied directly.

This is a very flexible design made with the tweaker in mind. Besides the options of control logic and power supply, all connectors use a standard .100" pitch, so the builder can choose to use the Molex connectors I chose, or the connector they prefer. Furthermore the attenuation can be changed to provide a larger range, finer steps, or a non-linear curve. Options abound.

The cost of parts for this board are approximate US$175 for balanced, or $90 for single-ended.

Please use the mail button below to contact me, or send directly to


PS here is a poor picture of part of the board, to give you some idea of the quality of construction.

jleaman 20th July 2003 07:45 PM

you should post a picture of the Full board so we can see it...

jwb 20th July 2003 07:56 PM

Will do, but right now I have only a bad webcam to get photos into my PC. I'll get a better picture on Monday.


jwb 21st July 2003 07:58 PM

2 Attachment(s)
This is the top side of the board without parts installed.

jwb 21st July 2003 08:02 PM

For the stuffed version of the boards, see

Jos v E 30th December 2003 05:24 PM

Relay attenuator circuits & analysis tool
I have just created a web-page on the design
of relay-resistor attentuator networks.
It contains an embedded Java program
to compute attenuator and impedance characteristics
for <I>your own</I> design.



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