My new preamp design: Arduino, 6 input selector, MDAC attenuator, IR etc

I've made a new design where the MDAC attenuator, input selector and RCA board all sandwich together into a nice compact unit:

Scphbd3.jpg


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My last preamp project had only 3 inputs which was a little annoying so I designed a new one with 6 inputs and mute:

iXo877S.jpg


I've written the initial Arduino code for two rotary encoders, one for volume and one for input selection, infrared and start up mute. The code is here:
https://github.com/FutureSharks/preamp-two

For now I'm using an Arduino Pro Micro 5V but I think I'll switch to something more modern like a NodeMCU or something that uses an ESP32.

PCB layout files are here:
https://github.com/FutureSharks/preamp-two/tree/master/PCBs

The power supplies I'm using are these two:
http://www.diyaudio.com/forums/power-supplies/252133-simple-lt1763-based-5v-psu.html
http://www.diyaudio.com/forums/powe...diy-friendly-dual-tps7a3301-power-supply.html
 
Here it is in a temporary "enclosure" made from Makerbeam
 

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A couple questions:
1. Can anyone recommend a company for machining small quantity aluminium parts in Europe? I would like to get a front panel made from 20mm thick aluminium.
2. Has anyone used a bluetooth 4.0 / BLE remote with an Arduino?
 
Hi Maxw,
it's also seemed great project! What type of the display for this amplifier?
Still neopixel?? I hope the LCD or FND!! 😀
also more cheaper encoder is profer🙄ed.

Thanks. For display I don't know yet. I think LCDs look cheap so not so keen on that idea.

You can definitely use cheap encoders! I don't know what problem you had in the other thread but I've used many cheap encoders before without issues. Sometimes they need some hardware of software debouncing but it's definitely possible 🙂
 
Thanks. For display I don't know yet. I think LCDs look cheap so not so keen on that idea.

You can definitely use cheap encoders! I don't know what problem you had in the other thread but I've used many cheap encoders before without issues. Sometimes they need some hardware of software debouncing but it's definitely possible 🙂

Okay. I'll try again and let you know.
Thanks!!
 
Very interesting, thanks for posting and for putting this on Github. I'm especially interested in an ESP32-based version, and if a group buy for PCBs / kits ever happens. With my level of experience, making my own BOM for this would be a little above my head (I could do it, but it would require a lot of research on package sizes etc that I just don't know yet). I've never had a PCB printed. I have a decent amount of experience with ESP8266, Arduino, rPi, RFM69HW, etc and software development in general (my day job). I might try to take this on after the holidays, since I have some LXMinis and 6 channels of amplification to build first.
 
Originally Posted by maxw View Post
A couple questions:
1. Can anyone recommend a company for machining small quantity aluminium parts in Europe? I would like to get a front panel made from 20mm thick aluminium.
https://www.schaeffer-ag.de/produkte/frontplatten/

Schaeffer only does up to 10mm.

I had case parts for a headphone amplifier made at a local shop (front is 25mm)... maybe do some shopping around in your neighbourhood.
Sometimes smaller companies do small runs of parts that are not too expensive.
 
I'm especially interested in an ESP32-based version

Me too but I think we need to wait a bit longer before the ESP32 gets more popular with DIY. Support, code and libraries still need to catch up a bit I think. There is already a NodeMCU-32S module released, you can get it on Aliexpress:
https://www.aliexpress.com/item//32758824128.html
And another model I've seen:
https://www.aliexpress.com/item//32758824128.html

I might get one soon.


making my own BOM for this would be a little above my head

I'll add an example BoM soon.


Schaeffer only does up to 10mm.

I had case parts for a headphone amplifier made at a local shop (front is 25mm)... maybe do some shopping around in your neighbourhood.
Sometimes smaller companies do small runs of parts that are not too expensive.
Ah I see. I definitely want something more than 10mm. Is this the piece you are talking about?

An externally hosted image should be here but it was not working when we last tested it.


How much did that front panel cost to get made?
 
Didn't see you reply Maxw...

No, that's not the one, front and back panel were made from Ureol on this one.
The future case of the F5 HA will have the thick alu front.

Unfortunatly I can't tell you a quote since I got the parts practically for free (good connections, I was lucky 😉 ).
I think it all depends on the hours the shop has to take into account... when you supply 3D data and the shop just
has to put it on the milling machine it should not be too expensive. Say sub 100 GBP??

When it is just a rectangular slab of 20mm it should be even less. I just googled a shop in Germany where I ordered before...
a plate of 400x150x20 for instance is almost 40€ just for the material. You do the drilling and tapping. 😉

EDIT: Definitely worth it with your attention to detail!
 
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Max,

Please pm me with details of what you want for the front - I know a few case makers / metal workers - I can have a chat with them.

And when you need 3D data... maybe I can help.

Thanks very much guys. I need to decide on what I want first and create a design. I've used Autocad before for some other projects so I am able to create the required files but finding the time is another story 🙂