Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Passive Preamp: Arduino based, remote control, Relay R2R, input selection
Passive Preamp: Arduino based, remote control, Relay R2R, input selection
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th June 2015, 02:31 PM   #1
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
Default Passive Preamp: Arduino based, remote control, Relay R2R, input selection

Here is my new Preamp project. After my last preamp project, I wanted to make something a bit more simple and completely passive

My goals are:
- Passive
- Remove controlled
- Uses a mobile phone charger for power
- Low power consumption
- Looks nice
- Simple
  Reply With Quote
Old 7th June 2015, 02:47 PM   #2
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
Default The R2R attenuator

I made a new 256 step R2R relayed based attenuator. There's nothing special about it, the design has been done hundreds of times on here and elsewhere.

Other examples include:
TP Joshua Tree
Jos van Eijndhoven
RelaiXed -- Balanced pre-amplifier
AMB Delta 1
Some old versions I made
http://www.diyaudio.com/forums/analo...elections.html
Pop/click free HW-based relay attenuator
And probably more...

I made mine with small latching relays and surface mount components.

Features:
- 256 steps with latching relays
- Small
- SPI controlled (uses a MCP23S17)
- Metal film 1206 sized resistors

PCB is from OSHPark.

Eagle PCB files, BoM and sample Arduino code (for use with encoder) is attached
Attached Images
File Type: jpg IMG_0032-2.jpg (808.0 KB, 2366 views)
File Type: jpg IMG_0031-2.jpg (811.9 KB, 2289 views)
File Type: jpg IMG_0033-2.jpg (688.1 KB, 2219 views)
File Type: jpg attenuator-schematic.jpg (189.8 KB, 2239 views)
Attached Files
File Type: txt att_256_v2_with_encoder.txt (3.7 KB, 267 views)
File Type: zip Relay-attenuator-eagle-pcb-files.zip (85.5 KB, 180 views)
File Type: zip Attenuator-BOM.zip (6.1 KB, 181 views)

Last edited by maxw; 7th June 2015 at 02:54 PM.
  Reply With Quote
Old 7th June 2015, 02:56 PM   #3
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
Default Input Selector

The input selector is the same one I used in my past preamp project but I didn't use the mute section.

Features:
- 3x inputs
- Mute
- 1x spare I/O (could be used for a power relay or something later)
- SPI controlled (MCP23S08 IC)
- Compact
- Costs about 19 to build

Full details, schematic, BoM etc is here:
Building a complete Preamp with an Arduino, remote, volume and input control
Attached Images
File Type: jpg IMG_20150607_115800-2.jpg (960.2 KB, 2202 views)
  Reply With Quote
Old 7th June 2015, 03:00 PM   #4
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
Default IR module

I also made a small IR module PCB. Mainly just to make the mounting of an IR sensor behind the front panel easier.

Here is the BoM:
IR1, IR2, IR3: Farnel part: 4913190, Part: VISHAY TSOP4838 IR RECEIVER, 38KHZ
R1: Datasheet recommends 100R
C1: Datasheet recommends 0.1 F

Eagle PCB files attached.
Attached Images
File Type: jpg IMG_20150603_223445-2.jpg (553.2 KB, 797 views)
File Type: jpg IMG_0026-2.jpg (494.9 KB, 450 views)
File Type: jpg IMG_0028-2.jpg (515.1 KB, 513 views)
Attached Files
File Type: zip IR board.zip (33.4 KB, 46 views)
  Reply With Quote
Old 7th June 2015, 03:01 PM   #5
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
More to come soon
  Reply With Quote
Old 7th June 2015, 03:36 PM   #6
yilingcheng is offline yilingcheng  Canada
diyAudio Member
 
Join Date: Feb 2015
very very nice...

do you intend of selling it with smc soldered already?

2 of them (attenuator) would make a nice balanced pot

Martin Gagnon
  Reply With Quote
Old 8th June 2015, 09:53 AM   #7
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
Quote:
Originally Posted by yilingcheng View Post
very very nice...

do you intend of selling it with smc soldered already?

2 of them (attenuator) would make a nice balanced pot

Martin Gagnon
Thanks. I have two spare attenuator PCBs because the minimum order at OSHPark is 3. Beyond that I have no intention of selling anything, that's why uploaded the PCB files. Anyone can just download the files, upload them and then order as they wish!
  Reply With Quote
Old 13th June 2015, 06:52 PM   #8
linuxworks is offline linuxworks  United States
diyAudio Member
 
linuxworks's Avatar
 
Join Date: Jul 2008
Location: Santa Clara, CA
if you want boards already stocked and buyable, I would suggest a look at amb.org and search for delta1 (as max had pointed out in his 'other projects' intro). ob disc: I work with amb and I designed that delta1 and wrote the firmware for it

fwiw, amb does stock decent quality boards, they are US made and are not done offshore. they do cost a bit more but they are trustable quality, which is why we sourced from the more expensive place.

btw, I really do not suggest going passive. each time I've done that I've regretted it. for relays, you end up with a pretty high-z at the output once all the stages are passed thru and unless your next stage is about an inch away, cable's length, you are degrading the signal and will likely have ground issues and hum. I find its good to have some buffer right after the relay atten, as close as possible. after that, you are now low-z and can run your cables like any other preamp's output.

the solid state vol controls don't have this issue as they are all buffered internally. but relays do not have buffers unless you add them and I do strongly suggest you either locate the relays IN your next stage (box) or just buffer them with any buffer of your choice.

and yes, you can run a set of boards for balanced mode. you have to decide if you want to access the port expanders at the same addr (which is technically wrong but does often work) or if you want to access them as separate addresses; but realize that each relay atten needs 2 i2c addr's (a high to latch one way and a low to latch the other, for each of the 8 bits). each flip takes 2 i2c writes and if you have 2 boards, that's 4 i2c writes each time you change volume. also, at least in my code (and I think max's is based on mine) there are needed delays to let the latching 'take'; and so if you run 2 boards, the delays add up in series and make changes seem more clunky.

if you write to the same i2c addr for each of the boards (still there is a need for 2 addr's per board) then you can get a more parallel 'clunk' at change time but each chip is going to answer back and if you are lucky, they will overlay their replies and the collision will not be a problem. it may work but its not supposed to

finally, its very important that the digital ground and analog grounds are connected. even though they are logically quite separate, I have seen hum happen when they are not connected. it actually does not make sense that they would have to be connected but it just is a fact, for some strange reason.

anyway, have fun.
__________________
My Photostream:http://www.flickr.com/photos/linux-works/
  Reply With Quote
Old 14th June 2015, 09:30 PM   #9
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
For the case I used this model from Modushop.

It looks like this:

Click the image to open in full size.
  Reply With Quote
Old 14th June 2015, 09:41 PM   #10
maxw is offline maxw  United Kingdom
diyAudio Member
 
maxw's Avatar
 
Join Date: Jun 2004
Location: Berlin
Modushop have a customisation service where you can submit CAD drawings. I was keen to try it so I created Autocad files with the holes I wanted for the rear and the machining of the front panel. First time I've done something like this and it worked out pretty well I think. I've attached the CAD files in case someone wants them.
Attached Images
File Type: jpg preamp-cad-front.jpg (104.3 KB, 163 views)
File Type: jpg preamp-cad-rear.jpg (91.8 KB, 165 views)
File Type: jpg IMG_20150606_195447-2.jpg (718.8 KB, 180 views)
File Type: jpg IMG_20150606_195507-2.jpg (760.8 KB, 195 views)
File Type: jpg IMG_20150606_195535-2.jpg (656.5 KB, 202 views)
File Type: jpg IMG_20150607_142319-2.jpg (605.2 KB, 235 views)
File Type: jpg preamp-cad-front2.jpg (68.8 KB, 243 views)
Attached Files
File Type: zip small-preamp-front.zip (71.9 KB, 34 views)
File Type: zip small-preamp-rear.zip (54.6 KB, 23 views)
  Reply With Quote

Reply


Passive Preamp: Arduino based, remote control, Relay R2R, input selectionHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Another Modified PGA2311 kit with Arduino for volume control and input selection cjkpkg Analog Line Level 29 17th September 2019 12:04 PM
Building a complete Preamp with an Arduino, remote, volume and input control maxw Analog Line Level 166 25th May 2019 08:20 PM
LCDuino (arduino) R2R relay preamp linuxworks Analog Line Level 0 9th May 2015 04:35 PM
ES9023 DAC(subbu) + Tube Preamp with Remote and R2R volume control(Danzup) rvrazvan Tubes / Valves 5 20th December 2012 09:56 AM
Arduino based Input Selector for preamp _atari_ Analog Line Level 5 30th June 2010 03:42 PM


New To Site? Need Help?

All times are GMT. The time now is 02:09 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki