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

Pass Labs This forum is dedicated to Pass Labs discussion.

Boz input distortion
Boz input distortion
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 24th June 2019, 01:50 PM   #1
Giovanni malluzzo is offline Giovanni malluzzo
diyAudio Member
 
Join Date: Nov 2017
Default Boz input distortion

Hello everyone. I made a BOZ preamplifier. I am very satisfied with the performance, but it has a small problem, at least I hope it is small, ie that the input signal goes into distortion when it is high level.
Looking here and there on the net I found a forum where even another owner of Boz had the same problem. He solved it by setting a bias current to around 0.3A, in this way symmetrical clipping occurs, measuring with the oscilloscope, and the input signal was no longer distorted.
I don't have an oscilloscope, so "by eye" I set a voltage on the Irf610 of 3V, instead of 4V as the project foresees (with 3V the current should approach about 0.3A, instead of the original 0.4A). The distortion has decreased a lot, but unfortunately there are still some impulsive peaks that go into distortion.
The Dac has a fairly strong output, while with old sources with low output there is no distortion.
If I put an input potentiometer (obviously eliminating the resistance R107) we create a mass noise (like 50hz of the network) that I can't eliminate with various mass tests, moreover we could create an audio band limitation since there is a 1uf capacitor in input.
I kindly ask you for a suggestion on how to eliminate the bias in input to Boz.
Tank, Giovanni!
  Reply With Quote
Old 24th June 2019, 01:57 PM   #2
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Boz input distortion
post exact schmtc and explanation what you have in front (source) and what are your needs , regarding output swing
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 24th June 2019, 06:22 PM   #3
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
I have made the BOZ, and found that the amplifier due to its high gain could easily clip on output. This is when the potmeter on the output is used af volume control.

Moving volume control to input solves this problem...
  Reply With Quote
Old 24th June 2019, 07:19 PM   #4
darrr is offline darrr  Poland
diyAudio Member
 
Join Date: Jan 2018
Location: Poland
I decrease gain (r104/r108) to ~x5,5 (850R/150R)
  Reply With Quote
Old 24th June 2019, 07:59 PM   #5
woody is offline woody
diyAudio Member
 
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
What about simply changing r100 from 100 ohms to 200 ohms and adjust for 8v across it instead of 4 v so to maintain the 40ma bias. That cut the gain thus lowered the miller capacitence while introduced a little more local feedback.
  Reply With Quote
Old 24th June 2019, 08:14 PM   #6
darrr is offline darrr  Poland
diyAudio Member
 
Join Date: Jan 2018
Location: Poland
Now I have ~ 3.5V . It give me the best sinusoide on oscilloscope. Second image when I had 4.1v
Attached Images
File Type: jpg IMG_20180420_213133447_2.jpg (61.8 KB, 106 views)
File Type: jpg IMG_20180420_211512185.jpg (48.3 KB, 107 views)
  Reply With Quote
Old 25th June 2019, 10:11 AM   #7
Giovanni malluzzo is offline Giovanni malluzzo
diyAudio Member
 
Join Date: Nov 2017
Quote:
Originally Posted by darrr View Post
Now I have ~ 3.5V . It give me the best sinusoide on oscilloscope. Second image when I had 4.1v
after having set the voltage to 3.5v you did not have more distortion in input?
And were you distorted before this setting?
  Reply With Quote
Old 25th June 2019, 02:40 PM   #8
darrr is offline darrr  Poland
diyAudio Member
 
Join Date: Jan 2018
Location: Poland
I didn't hear the distortion at all, but the sound was "incoherent" and too loud. I could not mute the signal to 0 (10k potentiometer is on the output) that's why I decrease gain.
  Reply With Quote

Reply


Boz input distortionHide 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
Low distortion opamp IC which can drive PWM input asenapati Class D 18 28th May 2016 04:53 PM
Low distortion current input VAS assembled Solid State 3 11th October 2011 10:25 PM
distortion measurement when input is distorted meconlen Everything Else 7 29th May 2010 07:23 PM
Input transformer: floating input = distortion ErikdeBest Tubes / Valves 13 20th January 2009 09:36 AM
Input pin distortion? jackinnj Solid State 7 31st January 2007 04:09 PM


New To Site? Need Help?

All times are GMT. The time now is 02:43 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki