My Preamp Project: Arduino, I2C, relay selector+attenuator, tube stage

[TheShaman]

Originally Posted by maxw

What I have done is set up a BlinkM that changes colour with the volume level. This is behind the volume knob, inside the case. It is an I2C controlled RGB LED. So it goes from Blue>White>Red as the volume gets higher. It's a really nice effect and I think works well.

Nice!
I was looking at a similar led/gadget at Sparkfun and, no matter how hard I tried, I couldn't come up with anything useful for it...
I guess some people are more imaginative than others..

Btw, I think it could be even cooler if it changed color every time you changed source (like Blue illumination = Input 1, Red = Input 2, Green = Input 3 etc.) and have the brightness of the specific LED color "simulate"/follow the volume setting.

[maxw]

Originally Posted by TheShaman

Btw, I think it could be even cooler if it changed color every time you changed source (like Blue illumination = Input 1, Red = Input 2, Green = Input 3 etc.) and have the brightness of the specific LED color "simulate"/follow the volume setting.

Ha could do! It would be easy to implement. That's what I like about working with the Arduino, its so quick and easy to work with or add new features

[washburn_it]

Hi, very nice job !
I'm working around a similar project, my "digitally controlled" preamp is controlled by a board equipped with an ATMega32 that I've developed time ago.
The input selection is made through a touchscreen LCD (320x240 256 colors) where it is also shown the volume level (controlled by an optic rotary encoder and a PGA2310) in dB and through a graphical scale.
Max and min volume levels are set through software (in a "settings page") and the PGA basically replaces the analog potentiometer of the analogic preamp "P97" by Rod Elliot.
The input selection, mute and power on/off of the analogic section is done using some relays through a 74HC595 (8 bit serial-to-parallel converter shift-register) and a ULN2803 driven by the ATMega32.
The firmware is not complete yet but the basic functions are already working.

Regards,

Roberto

[maxw]

Originally Posted by washburn_it

Hi, very nice job !
I'm working around a similar project, my "digitally controlled" preamp is controlled by a board equipped with an ATMega32 that I've developed time ago.
The input selection is made through a touchscreen LCD (320x240 256 colors) where it is also shown the volume level (controlled by an optic rotary encoder and a PGA2310) in dB and through a graphical scale.
Max and min volume levels are set through software (in a "settings page") and the PGA basically replaces the analog potentiometer of the analogic preamp "P97" by Rod Elliot.
The input selection, mute and power on/off of the analogic section is done using some relays through a 74HC595 (8 bit serial-to-parallel converter shift-register) and a ULN2803 driven by the ATMega32.
The firmware is not complete yet but the basic functions are already working.

Regards,

Roberto

Sounds good! Post some pictures.

[maxdd_nj]

Agree that the LCD displays are tacky.

You ever consider using a Sure 8x32 LED matrix?
in action: HT1632-AVR + Arduino + DE-DP104 on Vimeo

Could look similar to the display on the SimAudio Moon Evolution preamps: http://www.simaudio.com/images/xlg_moon600i.jpg

[glt]

LCDs are cheap but can look real good:
More HIFIDUINO…in SERBIA H i F i D U I N O

[TheShaman]

Yeah, that's one of the many impressive builds at your blog, glt.
Proves that with enough creativity (and running around to get things done), DIY can match commercial gear.

Max,
What are the impedance specs of your attenuator?
I'm considering using it along with a Salas DCB1 buffer (which is optimally paired with a 10-20k pot).

[maxdd_nj]

Wow that looks good glt!

[maxw]

Originally Posted by maxdd_nj

Agree that the LCD displays are tacky.

You ever consider using a Sure 8x32 LED matrix?
in action: HT1632-AVR + Arduino + DE-DP104 on Vimeo

Could look similar to the display on the SimAudio Moon Evolution preamps: http://www.simaudio.com/images/xlg_moon600i.jpg

That LED matrix is massive!

[maxw]

Originally Posted by glt

LCDs are cheap but can look real good:
More HIFIDUINO…in SERBIA H i F i D U I N O

That is the example I was going to post as it neatly shows the problem with LCD screens - Yes they can look really nice BUT the front panel must be machined to fit the LCD perfectly. Having access to machining tools is a luxury I don't have. I think you need to know someone otherwise the tooling and set up costs are crazy! Cutting a nice circle using a hole saw with my drill press is about the extent of my tools

This is the kind of implementation that makes me dislike LCD screens:

DIY: AMB/linuxworks labs alpha10 audio preamp | Flickr - Photo Sharing!