i2c controlled monitor attenuator board

[Majestic12]

I just wanted to share something with you that I have designed for an upcoming monitor / control room controller project. It's a relay based, passive attenuator with 6 bit resolution to attenuate the signal down to -63dB. Also included are dim and mute functions. The board is controlled over i2c, so it can also easily used with an Arduino board for example. You just send one byte over the bus that equals the amount of gain you need and the relais will switch the corresponding resistors in the audio path.

Unfortunately, my layout software had the power pins of the PCF8574 port expander reversed, so some wire fixing was neccessary in this prototype...

 

[henk]

Sorry to say......... but this looks 20 years ago......
Many design were made in those days , just like then with 8051/8052........... did do a lot in assembler for that 8051.....
Phillips did gave you the software for that and how to use it the i2c..... that was in DOS times.... and windows 95.....

 

[Rochey]

Henk,

thats a little harsh!

As a building block, within a larger system, I think it's good...

 

[Majestic12]

It it cheap, easy do and works perfectly. So why not ?

 

[spiri]

A long signal way and many relays contacts in the signal path is not a good audio solution for me. 
The Muses72320 is the best volume control what I know and ever heard.
The SPI instead of the I2C interface is also easy to control.

http://www.njr.com/semicon/PDF/MUSES72320_E.pdf
http://www.akouo.at/select-volume.html

 

[Andy Peters]

A long signal way and many relays contacts in the signal path is not a good audio solution for me. 
The Muses72320 is the best volume control what I know and ever heard.

Wow, $25 each qty 1 from Mouser!

-a

 

[spiri]

It's not expensive, when you can get the best.
I use it in preamps and monitor control and as input attenuation in my ADC's.
One per channel to get fully symmetrical signal path.

 

[bobkatz]

A long signal way and many relays contacts in the signal path is not a good audio solution for me. 
The Muses72320 is the best volume control what I know and ever heard.

Wow, $25 each qty 1 from Mouser!

-a

Hello, guys, I thought I'd report on this Muses Chip:
I'd like to report that I recently built an AMB M3 headphone amp and as an experiment I included a Muses 72320 chip on a DIY board with software provided by Academy Audio. To truly evaluate this chip it goes into a 4pdt switch that allows me to switch between the Muses and a TKD 1 dB/step resistive attenuator. The entire circuit is DC coupled, the Muses is configured strictly as an attenuator and the output of the 4pdt switch goes into an OPA 627 opamp. So it's a very high quality circuit for evaluation. I've spent days comparing and switching and I am happy to report that for me the Muses chip is audibly transparent. I cannot distinguish it from the TKD attenuator. I was quite surprised, I thought I would hear at least a small sonic difference, a loss in transparency, depth or other attribute with the Muse but I was not. This is very promising. It's not a cheap chip, but in many cases and especially for remote control purposes it's more practical than other volume control topologies.

My next installment in Katz's Corner at Innerfidelity will discuss the project in detail.