My Blameless - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

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 20th March 2014, 09:02 AM   #1
diyAudio Member
Join Date: Apr 2013
Default My Blameless

Hi all

I've been interested in the Linn/Blameless topology for a while and wanted to try my hand "designing" one of these.

I've got some spare DX Blame MkIII amplifier board from the last group buy and thought I'd have a go at selecting my own component values that will result in a "reference design" that is entirely conventional in every respect. The schematic is based on what I've learnt from reading Cordell and Self, and what I've seen from the DIY projects here - notably the DX designs from Carlos and Kevin's recent LTT4 project.

The MkIII boards support:
- LTP input stage with currrent mirror and cascoded CCS
- EF2 output stage

I know this will bore seasoned members here; however, I would really appreciate your advice in fine tuning the C and R values.

Attached Images
File Type: png CSH1.png (37.0 KB, 887 views)

Last edited by Ranchu32; 20th March 2014 at 09:22 AM.
  Reply With Quote
Old 20th March 2014, 09:07 AM   #2
mcd99 is offline mcd99  United Kingdom
diyAudio Member
Join Date: Mar 2008
Location: UK
Am I being blind? but I can't see any compensation around the VAS.
  Reply With Quote
Old 20th March 2014, 09:11 AM   #3
diyAudio Member
Join Date: Apr 2013
Fixed :-)
  Reply With Quote
Old 20th March 2014, 09:15 AM   #4
diyAudio Member
Join Date: Jan 2013
Looks like a good thread waiting to happen, there's a lot to be said for a reference, conventional design
  Reply With Quote
Old 20th March 2014, 09:54 AM   #5
diyAudio Member
still4given's Avatar
Join Date: Oct 2004
Location: Victorville, CA
Hi Christian,

Watching with great interest. Be sure to check out the end of the of the MKIII thread to see how to fix the lifted ground error on those boards. Wishing you great success with this.

Blessings, Terry
  Reply With Quote
Old 20th March 2014, 10:29 AM   #6
diyAudio Member
Join Date: Apr 2013
Thanks Terry - will do. I remember following your progress in the Builders Thead several months ago - I've got in my bookmarks to follow up on.
  Reply With Quote
Old 20th March 2014, 11:44 AM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
The Input 1uF DC blocker is in the wrong place.
It must go before the 47k.

Or move the 47k to after the 1uF.

R16 is tapped into the wrong end of R14.
The collector of Q10 drives the base stopper.

Reduce R13 to <=1k5
You have too much Vbias available with 2k2. Depending on actual Vbe of the transistors, you might find you can bias the output using just 1k0 or 1k1 for R13

R17 is far too high.
Try 1k0 to 2k0.

Add an output Zobel.

R10 is fed from the -ve rail, try increasing it's value substantially, or move it to Power Ground.
regards Andrew T.
Sent from my desktop computer using a keyboard

Last edited by AndrewT; 20th March 2014 at 12:02 PM.
  Reply With Quote
Old 20th March 2014, 12:06 PM   #8
mcd99 is offline mcd99  United Kingdom
diyAudio Member
Join Date: Mar 2008
Location: UK
Would like to add, I would use BC5x0c transistors where there is very low Vce.
  Reply With Quote
Old 20th March 2014, 12:09 PM   #9
diyAudio Moderator
TonyTecson's Avatar
Join Date: May 2003
Location: Palatiw, Pasig City
yes, the base of the left hand side of the ltp needs to be properly dc biased,
otherwise huge offset voltage at the output....
planet10 needs your help: Let's help Ruth and Dave...[B
  Reply With Quote
Old 20th March 2014, 09:36 PM   #10
diyAudio Member
Join Date: Apr 2013
Thanks everyone - I will make the changes to the schematic tonight.

The boards I'm using can accomodate one or two diodes strings (or resistors) on the rails between the driver and front end. However most designs I've seen here and in books have nothing. Would there be benefit in using them?

Also there are a couple of extra locations for power supply decoupling (HF). Again in most of the Linn/Blameless designs they aren't used.
Attached Files
File Type: pdf Dx Blame MKIII-Hx updated July, 28th - 2011.pdf (109.6 KB, 164 views)
  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
Beefing up the Blameless. 5th element Solid State 66 6th December 2010 11:08 PM
A tubular 'Blameless' GK Solid State 46 25th January 2010 11:53 PM
Blameless THD nicholas1113 Solid State 12 18th January 2010 11:22 AM
Please, help me with Self Blameless Ric_rock Solid State 45 13th January 2010 04:03 PM
Transistors for Blameless tommytube Solid State 2 3rd May 2007 08:10 AM

New To Site? Need Help?

All times are GMT. The time now is 07:29 PM.

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