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

[OlegSh]

Here is the link to your post in my thread offering the code. And the code is from this thread post #16. Your code is just what I need at the moment. I hope you still don't mind if I use it. Just let me know if I should not.

Oleg

 

[OlegSh]

I have finally got what the function does. I even figured out why it is necessary after looking again at the schematic and ICs pins arrangement. I would probably solve this problem with the look-up table... Anyways, your knowledge helped me a lot!

Oleg

 

[maxw]

I have finally got what the function does. I even figured out why it is necessary after looking again at the schematic and ICs pins arrangement. I would probably solve this problem with the look-up table... Anyways, your knowledge helped me a lot!

Oleg

Cool, glad you worked it out. A look up table would work too, less elegant in my opinion though

 

[OlegSh]

I am not so good with binary operations, so look-up table would me my choice
Thanks for sharing your work!

 

[Tailgunner]

I have seen some of these attenuator schematics with relays and resistors but I never have seen one with a snubber diode parallel on the coli of the relay to short inductive spikes. Why aren't these necessary in these circuits?

 

[maxw]

I have seen some of these attenuator schematics with relays and resistors but I never have seen one with a snubber diode parallel on the coli of the relay to short inductive spikes. Why aren't these necessary in these circuits?

My design uses a ULN2803ADW to drive the relays and this IC includes the diodes inside, so they are not required.

 

[JWCoffman]

Hi there. I'm very much a beginner in this area but looking at a similar project involving a tube linestage with a relay based input and attenuator run through Arduino. My question is around power supplies. The linestage (the VTA SP14) has it's own regulated power supply circuits for B+ and H+. That leaves a separate 12v supply needed for the Arduino and relay circuits. My thought is to just get a cheap modular SMPS supply coming off the IEC inlet, but worried if line noise would become an issue for the B+ supply. Is there a better solution for a relative beginner?