My new mini Class A amp. - Page 6 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

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
Reply
 
Thread Tools Search this Thread
Old 11th January 2009, 10:15 PM   #51
atiq19 is offline atiq19  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Glen,

Do you have any spare pcbs left. I would be interested in building this state-of-the-art design. I wonder why there are few serious designs in low power level.

Thanks for sharing.

Atiq
  Reply With Quote
Old 16th January 2009, 09:51 AM   #52
GK is offline GK  Australia
Account disabled at member's request
 
Join Date: Jan 2006
Quote:
Originally posted by atiq19
I wonder why there are few serious designs in low power level.

Same here

Hi Atiq.

I never sold or had a batch of boards made for this amp. I've only ever done that for the K10A amp.
I etched my own boards for this one. I'm part way through writing up a webpage for this amp to add to my website which will have all the details. I am very busy with work and other things at the moment, so it's taking me a while.

Cheers,
Glen
  Reply With Quote
Old 18th January 2009, 12:16 AM   #53
GK is offline GK  Australia
Account disabled at member's request
 
Join Date: Jan 2006
OK, I've put up what I've written so far:

http://users.picknowl.com.au/~glenk/K12A.HTM

Full schematic diagram for the amp module included.

Cheers,
Glen
  Reply With Quote
Old 18th January 2009, 12:36 AM   #54
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Smoky Mountains , Tennessee
Well written article and schema.. one question, what is the
purpose of D2 - D3 in schema??
OS
  Reply With Quote
Old 18th January 2009, 01:37 AM   #55
GK is offline GK  Australia
Account disabled at member's request
 
Join Date: Jan 2006
Quote:
Originally posted by ostripper
Well written article and schema.. one question, what is the
purpose of D2 - D3 in schema??
OS

They are voltage clamps at the VAS bases which limit the maximum VAS current to ~20mA.

This keeps things under control when the amplifier clips.

Cheers,
Glen
  Reply With Quote
Old 18th January 2009, 02:38 AM   #56
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Smoky Mountains , Tennessee
Thank you, I thought they might be ...more simple
than cordells solution as well.
As we use the same cascoded VAS , looks like a cool upgrade.
just 2 more zeners/diodes.

Would you have to change D4/5 - D6/7 for a non-EF'ed
VAS as well?? How does it work? does it clamp input of VAS before
Q24/27 go into saturation??

When it works, does it eliminate "sticking"??
OS
  Reply With Quote
Old 18th January 2009, 03:04 AM   #57
GK is offline GK  Australia
Account disabled at member's request
 
Join Date: Jan 2006
Quote:
Originally posted by ostripper
Thank you, I thought they might be ...more simple
than cordells solution as well.
As we use the same cascoded VAS , looks like a cool upgrade.
just 2 more zeners/diodes.

Would you have to change D4/5 - D6/7 for a non-EF'ed
VAS as well?? How does it work? does it clamp input of VAS before
Q24/27 go into saturation??

When it works, does it eliminate "sticking"??
OS

It eliminates one cause of sticking which is addressed in the rather different Cordell amp by the reverse-parallel diodes connected across the differential output of the LTP.

Q24 and Q27 are prevented from saturating. The cascode transistors cannot saturate either as their collector voltage is limited by the lower voltage rails provided for the triple EF output stage.

There is only one unaddressed source of sticking in this amp the pre-drivers of the triple EF are allowed to saturate. The pre-drivers are fast small signal devices and recover quickly, however. Sticking time is about 1uS and can be seen here (post 2550):

http://www.diyaudio.com/forums/showt...55#post1707755

This sticking could be eliminated with the addition of a voltage clamp at the VAS output, but I decided against this, as I wanted the greatest output swing possible from the low power output stage. 1uS sticking is a pretty minor issue.

Cheers,
Glen
  Reply With Quote
Old 18th January 2009, 08:52 AM   #58
atiq19 is offline atiq19  United Kingdom
diyAudio Member
 
Join Date: Jun 2007
Glen,

Have you thought about further refinement (despite complexity) regarding potential LTP current mismatch which could be well managed by servo etc? Or it does not matter?

Thanks for your documentation on your site.

Atiq
  Reply With Quote
Old 18th January 2009, 05:04 PM   #59
FaTTy is offline FaTTy  Russian Federation
diyAudio Member
 
Join Date: Mar 2007
Hi ,Glen

Can you show us a PCB layout for your amp? I mean gerber or similar.

Thks.
  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
mini aleph VS gainclone VS Class D amp ecl86 Pass Labs 3 23rd June 2007 06:20 PM
M61571AFP,50W 5.1ch CLASS D mini amp projects digi01 Class D 8 8th September 2004 10:37 PM


New To Site? Need Help?

All times are GMT. The time now is 12:34 AM.


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