Buffer pre-amp - Page 3 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

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

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 12th February 2013, 03:23 PM   #21
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
CM distortion is likely to be mainly second-order (like most distortions) so percentage distortion will probably be proportional to CM voltage, and so proportional to signal level.
  Reply With Quote
Old 13th February 2013, 08:35 AM   #22
diyAudio Member
 
Join Date: Dec 2001
Location: South Sweden
So with 0.015% @ 10k source impedance, no compensation resistor in the feedback and 3V signallevel this buffer distortion would drop at least a magnitude with an input of 0,3V or less where I would reach about 96-98 dB SPL in my listening seat anf THD of the speakers reach 1% or even more.
__________________
listen! Can you hear that ...
  Reply With Quote
Old 13th February 2013, 03:44 PM   #23
diyAudio Member
 
Join Date: Dec 2001
Location: South Sweden
I did some testing with OPA2134 at lower levels, but I am limited both in lowest distortion level and.frequency range by my M-Audio Transit , but there is a clear reduction of distortion at lower signal levels.

And it is mostly second order that is visible. I will try to add some spectrum later and perhaps see if I can resolve any difference with added cancelation resistors.
To be continued...
__________________
listen! Can you hear that ...
  Reply With Quote
Old 13th February 2013, 07:31 PM   #24
diyAudio Member
 
Join Date: Dec 2001
Location: South Sweden
Here I attach some measurements from Arta.
My setup lack somewhat of resolution, limited by Arta and the alligatorclips all over the breadboard...

But 0dB signal level is 1,35V output, thus -20 dB is 0,135V, a more commonly encountered voltage in Hifi than 10Vrms.
Setup is a simple OPA2134 driven by +-12V, and a 12k resistor between Transit Line Out and + in of one of the op. The other has both inputs tied to ground.
Output of OP is going to the Line in of the Transit, and is loaded with 10k to ground. Fs = 48000 kHz, resolution is 24 bit.

First picture is the distortion vs level at 1, 5 and 10 kHz.
Second pirture is the spectra for an input of 0,135V , -20dB
Third is for -1dB.

Interesting is how CM voltage makes THD take of at higher frequencies. At the lower input, noise and resolution limitations increase the total THD regardless of frequency but there is far less of CM distortion wich rises at higher frequencies. That is how I interpret the curves. Tomorrow I will try to repeat with a 5,6k cancellation resistor in the feedback path.

Inputs?
Attached Images
File Type: png dist vs level.png (53.6 KB, 86 views)
File Type: jpg 12k -20dB.jpg (272.9 KB, 84 views)
File Type: jpg 12k -1dB.jpg (255.3 KB, 77 views)
__________________
listen! Can you hear that ...
  Reply With Quote

Reply


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
Arjen's tube buffer for pre-amp Josephjcole Class D 22 8th February 2010 01:18 PM
My pre-amp / buffer SimontY Solid State 12 15th November 2008 05:48 PM
Pre-Amp / Buffer on Ebay poynton Solid State 1 22nd June 2008 12:40 PM
Pre amp or Buffer for Inverted GC? 5150ed Chip Amps 9 11th July 2006 06:27 PM
Building a pre-amp output isolation buffer? rruss Solid State 4 18th October 2004 03:52 PM


New To Site? Need Help?

All times are GMT. The time now is 11:21 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2