RMI-FC100 MKII, single ended folded cascode VAS - 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 30th September 2008, 07:20 AM   #1
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Default RMI-FC100 MKII, single ended folded cascode VAS

Enjoy
Attached Images
File Type: jpg rmi-fc100-mk2.jpg (98.5 KB, 2413 views)
  Reply With Quote
Old 30th September 2008, 07:22 AM   #2
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
SR > 120V/uS

OLG gain
Attached Images
File Type: jpg olg_rmi-fc100-mk2.jpg (75.8 KB, 2062 views)
  Reply With Quote
Old 30th September 2008, 08:40 AM   #3
AKSA is offline AKSA  Australia
diyAudio Member
 
Join Date: Sep 2001
Location: Melbourne, Australia
Exceptional performance.....

Congratulations, Mihai!

Hugh
__________________
Aspen Amplifiers P/L (Australia)
www.aksaonline.com
  Reply With Quote
Old 30th September 2008, 12:19 PM   #4
mlloyd1 is offline mlloyd1  United States
diyAudio Member
 
mlloyd1's Avatar
 
Join Date: Feb 2001
Location: illinois
i don't think i've seen a current mirror used that way with a VAS like that before. it seems strange that it would work so well.
very clever!
when's the first model ready?
( i had to ask )

mlloyd1
  Reply With Quote
Old 30th September 2008, 12:19 PM   #5
tvicol is offline tvicol  Romania
vicol-audio.ro
diyAudio Member
 
tvicol's Avatar
 
Join Date: Jan 2005
Location: Bucharest
Send a message via Yahoo to tvicol Send a message via Skype™ to tvicol
I'm really impressed !

Keep up good work and I'm waiting you for a listening session.

Regards,
Tibi
  Reply With Quote
Old 30th September 2008, 12:32 PM   #6
diyAudio Member
 
Join Date: Aug 2001
Location: USA,NorthCarolina
Well done! Mihai.

Cambe

  Reply With Quote
Old 30th September 2008, 09:13 PM   #7
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Thank you all for your kind words.
I have a question for all of you. Did you see this type of folded cascode VAS used before in a commercial or DIY amplifier?
With the help of Q14 I was able to obtain an almost constant current over R14 which means a very high and linear OLG.
The current mirror is inherited from MKI version but isn't necessary and can be replaced with a bootstrap CCS. In this configuration, colector of Q14 can be conected to ground.
R13 can be used to null the offset

Cheers,
Mihai
  Reply With Quote
Old 30th September 2008, 09:49 PM   #8
AKSA is offline AKSA  Australia
diyAudio Member
 
Join Date: Sep 2001
Location: Melbourne, Australia
Mihai,

Your (unique) circuit appears to be a combination of a topology attributed to a German named Lender, and a folded cascode. I'm pretty sure Borbely has used it.

Lender arranged the two resistor loaded collector outputs from the LTP so that one was connected to the VAS base, and the other to the VAS emitter, enhancing OLG with diff drive. You've interposed an additional transistor cleverly.... I have not seen this before but that's not to say it hasn't been done. The truth is, almost nothing is new...... but I do not criticise, it is very clever.

Cheers,

Hugh
__________________
Aspen Amplifiers P/L (Australia)
www.aksaonline.com
  Reply With Quote
Old 30th September 2008, 10:10 PM   #9
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
I make big efforts to decrease components count but without loose sonic quality.
I will compare two version of this type of VAS. The one as in posted schematics and the other without mirror and with a simple bootstrapped 3ma CCS form the (-) rail to folded cascode transistor.
  Reply With Quote
Old 30th September 2008, 10:51 PM   #10
Account disabled at member's request
 
Join Date: May 2006
I dont think anyone has used that vas single ended before, but with dual differencial Ltps. Nearly all of Pavel dudeks amps use the scheme. For reference you could look at his DPA range of amps, Im pretty sure Bobberly would also have gone dual differencial.

Congrats on a nice design, very good performance.
  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
RMI-FC100, a single stage audio power amplifier roender Solid State 1273 10th July 2014 08:56 AM
folded cascode the_tool Chip Amps 1 27th June 2006 09:53 PM


New To Site? Need Help?

All times are GMT. The time now is 05:08 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