Digital potentiometer. Distortion and line level - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Headphone Systems Everything to do with Headphones

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
Thread Tools Search this Thread
Old 24th May 2015, 04:20 PM   #1
diyAudio Member
Join Date: Oct 2012
Default Digital potentiometer. Distortion and line level

Hi. I just added a MCP4231 8-bit digital pot to my headphone amplifier design. With some voltage dividers and blocking caps add a 2.5V offset, everything works just excellent and I enjoy using a rotary encoder instead of a regular potentiometer I have a couple of questions though, I've payed no attention to distortion when choosing a digital pot, I just used one I had laying around. Is it possible for the MCP4231 to add audible distortion or should I have nothing to worry about? I'm also a little dissatisfied with the lowest audible level I can choose. I have a gain of 2.5 and an input signal of about 1V peak and the lowest pot setting is still quite loud actually. 1V/256*2.5*0.707=1.1mVrms which is really quite audible into sensitive headphones. Is there a way to get way more attenuation some how? There aren't that many higher bit digital pots to be found, but perhaps cascading two pots could work? An attenuation of 256^2 would be plenty I think :P Any ideas?
  Reply With Quote
Old 24th May 2015, 04:27 PM   #2
diyAudio Member
Keruskerfuerst's Avatar
Join Date: May 2007
Location: Germany
You can use the volume control from TI/BB:
Volume Control | Products for Volume Control
  Reply With Quote
Old 24th May 2015, 05:10 PM   #3
jcx is offline jcx  United States
diyAudio Member
Join Date: Feb 2003
Location: ..
finer step volume controls aren't really the answer to bad gain structure

if you are using sensitive iem you could have as little as 200 mVrms drive some to 120 dB SPL

since many sources today are as much as 2 Vrms you really need low noise attenuation - not Voltage gain

someone should make audio output step down transformers optimized for these iem

cheaper is the "hiss buster" output resistor divider "power" attenuator
  Reply With Quote
Old 24th May 2015, 05:26 PM   #4
sreten is offline sreten  United Kingdom
diyAudio Member RIP
Join Date: Nov 2003
Location: Brighton UK

Just add a (switcheable) passive attenuator at the input.

Or as jcx alludes to at the output, reducing the noise.

rgds, sreten.
  Reply With Quote
Old 24th May 2015, 06:57 PM   #5
diyAudio Member
Join Date: Oct 2012
I see now that there are several dedicated volume control chips that does exactly what I want. Thank you
  Reply With Quote
Old 24th May 2015, 07:06 PM   #6
jcx is offline jcx  United States
diyAudio Member
Join Date: Feb 2003
Location: ..
you really should look into, try to understand "gain structure" for a better audio system

headphones bring this to the front because of their large range of sensitivities - you really have to design the amp for a restricted range of headphones or build in some method to switch system gains or attenuation in as much as 20 dB steps to accommodate even just dynamic headphones
  Reply With Quote
Old 24th May 2015, 07:09 PM   #7
diyAudio Member
Join Date: Oct 2012
My sources can only output 1Vp maximum, my cellphone is only outputting like 3-400mVp so I need a gain of minimum 2.5 for my current headset. My amplifier has an adjustable gain switch of 2.5, 6 and 40 in addition to the digital pot.
  Reply With Quote


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Headphone amp level = line level? (Maybe obvious question) Blue Jinn Headphone Systems 7 25th August 2014 05:49 PM
Digital line level for output to amplifier baytime123 Digital Line Level 1 2nd August 2012 12:21 PM
(minimal) speaker level vs. line level high pass filter noviygera Analog Line Level 1 15th October 2011 09:43 AM
trouble matching line level to guitar amp input level...any help? mondogenerator Instruments and Amps 5 19th December 2009 10:00 AM
lesser of two evils, high level -> line level, digital volume control mazurek Solid State 3 19th November 2006 12:25 AM

New To Site? Need Help?

All times are GMT. The time now is 03:13 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2