Simple cirklotron with Lateral MOSFETs - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 4th January 2010, 05:25 PM   #1
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Default Simple cirklotron with Lateral MOSFETs

Being a good buddy as he is, Jacco shared some of his 2sk135s with me, and not having the counter-part (2sj50) I decided to use them for a nice circlotron amp.
Different topologies were tried and here is what gave the best sonic result - Source Follower ie. power buffer driven with opa1632. I really love this chip (it's not an OpAmp but a full differential amp) - it sounds most natural and most appealing and I didn't found better sounding circuit as long as you don't ask for more than 12-13Vpeak per phase (per output) which is all I needed to drive this circlotron to full power.
I used two pairs of MOSFETs per channel 'cause I want them to drive 4 Ohm loads easily without worries about Pd.
The amp is very stable (thermally too) - DC offset drifts 2mV from 20 to 60 degrees Celsius on heatsink. Offset to GND is +/- 3mV in the same temp. range and the total bias drift is 20mA for 1.2A bias (600mA per MOSFET). BTW, Jacco sent me pretty well matched MOSFETs (8 pieces are in 50mV range Vgs difference).
With not so good matching Rsource should be 0R47. Off course, 2sk1058 can be used instead of 2sk135.
R29 and R30 - 100k multi-turn pots are used to set the MOSFET's Vgs => Id => DC offset in pretty much the same way as in F5.
The sound is very rewarding, and since this is my first circlotron now I understand why Broskie, EUVL, Circlomanen and some other guys often use this topology.
Attached Images
File Type: gif scl v2-sch.gif (13.5 KB, 2172 views)
File Type: gif scl-psu.gif (6.8 KB, 2074 views)
File Type: gif scl v.2 pcb.GIF (30.5 KB, 2022 views)
File Type: jpg DSC00956.JPG (323.5 KB, 1977 views)
File Type: jpg DSC00961.JPG (323.7 KB, 1857 views)
File Type: jpg DSC00962.JPG (436.2 KB, 1058 views)
  Reply With Quote
Old 4th January 2010, 06:07 PM   #2
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Quote:
Originally Posted by juma View Post
Being a good buddy as he is, Jacco shared some of his 2sk135s with me, ...The sound is very rewarding, and since this is my first circlotron now I understand why Broskie, EUVL, Circlomanen and some other guys often use this topology.
touché Jacco & Juma. It's one of my old favorites too! Now we just need to convince N.P. to work his magic on one of those variants too!
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  Reply With Quote
Old 5th January 2010, 01:15 PM   #3
diyAudio Member
 
Join Date: May 2007
Quote:
(it's not an OpAmp but a full differential amp)
Hey Juma,

Even TI says OP-amp about the 78dB open loop gain, "Black Widow" in the middle of your PCB. The topology of the OP is like a typical poweramp with folded-cascode, except for its separate output-buffers with some kind of error amp(?). But it might sound OK anyway.

Still the 2SK135(I have bunch too) output stage looks simple and straightforward.
  Reply With Quote
Old 5th January 2010, 02:02 PM   #4
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by revintage View Post
.... But it might sound OK anyway.
...
Hi revintage,
that's the thing in audio, quite often you won't know unless you build it
How is the progress with your gain stage (JFET/Gyrator) ?
  Reply With Quote
Old 5th January 2010, 02:08 PM   #5
RLa is offline RLa
diyAudio Member
 
Join Date: Jan 2010
Hello!

Getting a circlotron running (and correctly biasing the output stage) is not a very easy task. I like the use of capacitors and the special opamp that also has an inverted output. However, isn't it a problem when the output swings to positive (opamp output 4 is positive), the bias of the negative (lower) side is turned off since the output 5 is negative and the sources of both output halves are referenced to the ground through R5, R4 and R17, R8? Won't this cause some distortion that does not happen in a conventional push-pull output stage? This might not be a problem because circlotrons usually sound very good I have built about 4-5 such amps but with a bit different schematics.
  Reply With Quote
Old 5th January 2010, 03:57 PM   #6
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by juma View Post
How is the progress with your gain stage (JFET/Gyrator) ?
Going slow as always. Spent more time with my woman, wine and whiskey than expected during the holidays .

But got the sand(2SK223, 2SK170 and IRF610) I ordered anyway. So if I could stay away from the above mentioned it could soon be done.
  Reply With Quote
Old 5th January 2010, 06:41 PM   #7
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by RLa View Post
... the special opamp....
Come on, i put in the post #1 - it's not an opamp, it's a full differential amplifier, a great SuSy chip


Quote:
Originally Posted by RLa View Post
... isn't it a problem ...
No, it's not - read the OPA1632/THS4131 datasheet
  Reply With Quote
Old 5th January 2010, 06:44 PM   #8
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by revintage View Post
...woman, wine and whiskey ...
A DIYer's bane
  Reply With Quote
Old 5th January 2010, 07:33 PM   #9
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Fugly !

and overcomplicated .....



__________________
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 5th January 2010, 11:12 PM   #10
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
Quote:
Originally Posted by Zen Mod View Post
...overcomplicated .....
Sure, we'll wait for Nelson to find a perfect active device, then it won't be hard to make it less overcomplicated

  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
New Lateral MOSFETs Just Released! The Saint Aussie Amplifiers 41 14th November 2009 10:52 PM
Lateral Mosfets for sale Fanuc Swap Meet 20 28th March 2009 11:17 AM
Substitute Lateral Mosfets joensd Parts 33 21st December 2008 02:57 PM
Lateral mosfets - why ? Stormo Solid State 5 2nd July 2003 08:14 AM
Lateral Type Mosfets Diogo Solid State 4 30th September 2002 09:11 AM


New To Site? Need Help?

All times are GMT. The time now is 04:27 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