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.

unbalanced/balanced to balanced converter
unbalanced/balanced to balanced converter
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 25th February 2013, 09:51 AM   #1
kevin gilmore is offline kevin gilmore  United States
diyAudio Member
Join Date: May 2002
Location: wheeling illinois
Default unbalanced/balanced to balanced converter

i've been working on this for a while, i wanted an input
stage that performs well both for unbalanced and balanced inputs
without feedback, fully dc coupled etc. I came up with this which
sounds really good and has a thd of <.01%
buildable with standardly available parts from mouser.
performs even better with jfets as the inputs.
  Reply With Quote
Old 25th February 2013, 09:49 PM   #2
tvrgeek is offline tvrgeek  United States
diyAudio Member
Join Date: Dec 2009
Location: Md
So, how is the CMRR? That's the bugger. Thermal stability?
  Reply With Quote
Old 25th February 2013, 10:12 PM   #3
googlyone is offline googlyone  Australia
diyAudio Member
Join Date: Nov 2006
Location: Adelaide, South Australia
unbalanced/balanced to balanced converter
without spending time analysing the detailed circuit I can't see how you are controlling the overall gain.

The input diff pairs are driving current mirrors - good. The current mirror drives into the common base cascade, which between the two pairs you develop the outputs in push pull.

The diff pair gain should be quite high given its load. How is this set? Similarly I note the output would normally have very high gain, those 430 odd ohm resistors on the output would "pull this down" but I suspect that in the absence of overall feedback the gain and more general performance would be quite load dependant.

Have you tried the heresy of upping the gain and adding overall feedback?
  Reply With Quote
Old 26th February 2013, 09:57 AM   #4
kevin gilmore is offline kevin gilmore  United States
diyAudio Member
Join Date: May 2002
Location: wheeling illinois
thermal stability seems rock solid with the output stage servo's.

the gain is set by the 475 ohm output resistors. current mirror into
a resistor is fixed gain.

Handles about 5 volts of common mode. That is what the 1k tail
resistors are for.

adding feedback would just lower the input resistance a bunch
so not sure that is a good idea.

Last edited by kevin gilmore; 26th February 2013 at 10:00 AM.
  Reply With Quote
Old 26th February 2013, 08:31 PM   #5
Ken Newton is offline Ken Newton  United States
diyAudio Member
Ken Newton's Avatar
Join Date: Apr 2003
Location: Eastern Pennsylvania

Reminds me a bit of the enhanced cascode gain circuit in fig.9 of the below linked Malcolm Hawksford paper. You've added a nice little local feedback-loop via the current-mirror implementation. I like it.


For me, the most interesting and, perhaps, challenging area of solid-state gain stage design involves low-ish distortion global open-loop circuits. Especially, those which do not greatly depend mostly on very precise device matching to achieve low distortion.

Last edited by Ken Newton; 26th February 2013 at 08:34 PM.
  Reply With Quote


unbalanced/balanced to balanced converterHide 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
line level unbalanced to balanced converter steevo Analog Line Level 17 16th February 2014 03:09 PM
unbalanced to balanced converter lumanauw Pass Labs 53 2nd June 2011 05:08 AM
Balanced To Unbalanced Audio Converter SprockeT1597 Parts 3 7th February 2009 04:03 AM
unbalanced to balanced converter Salsero Solid State 27 21st September 2003 09:12 AM
Wanted->Discrete balanced to unbalanced CMR converter Brian Guralnick Solid State 20 21st September 2003 03:32 AM

New To Site? Need Help?

All times are GMT. The time now is 02:13 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio