F5 meets Buzquito - Page 2 - 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 25th February 2010, 03:17 AM   #11
fab is offline fab  Canada
diyAudio Member
 
fab's Avatar
 
Join Date: Mar 2004
Location: Canada
Quote:
Originally Posted by juma View Post
I tried using Hitachi/Renesas lateral MOSFETs in F5 but they lack transconductance and can not provide sufficient gain as drain followers without harming the sound.
Since they perform great as source followers it's obvious that another gain stage is needed between input JFETs and output laterals. ....

Schematic resembles Buzquito but feedback network is F5-like.....Here are the schematic and PCB layout (both open for discussion ) :
I had a "similar" idea almost 2 years ago...
F4 Type amp but with gain
  Reply With Quote
Old 25th February 2010, 08:52 AM   #12
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
yeah - world turns around in circles

DIY is jazz !!
__________________
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 25th February 2010, 09:04 AM   #13
osscar is offline osscar  Latvia
diyAudio Member
 
osscar's Avatar
 
Join Date: May 2009
Location: Riga, LV
You should give the name for this amp -Fuzquito
__________________
If time is money then I'm out of time
  Reply With Quote
Old 25th February 2010, 11:25 AM   #14
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Quote:
Originally Posted by njepitt View Post
...
So, did I get it?...
Yes you did - "same current" for the amp as a whole

Quote:
Originally Posted by VladimirK View Post
Do you really need source resistors for output laterals ? With idle currents above 150mA the laterals balance themselves very good.
Without source resistord you'll have current hogging regardless of Id - that's how many good lateral MOSFET died...
Only insanely tight matching might get you rid of source resistors.

Quote:
Originally Posted by fab View Post
I had a "similar" idea almost 2 years ago...
F4 Type amp but with gain
Yes, I remember that. I don't like the sound of JFETs with such a low Id. Second stage (with BJTs) is also not at all to my liking.
How did that project ended?
  Reply With Quote
Old 26th February 2010, 03:47 AM   #15
fab is offline fab  Canada
diyAudio Member
 
fab's Avatar
 
Join Date: Mar 2004
Location: Canada
Default Fab-Four Amp

Quote:
Originally Posted by juma View Post
...Yes, I remember that. I don't like the sound of JFETs with such a low Id. Second stage (with BJTs) is also not at all to my liking.
How did that project ended?
Hi

I have increased the jfet Id to 5 times more than original (5 to 6 ma from what I remember). For the second stage I have used a BJT enhanced cascode.

It ended like this:
fab-fourpoweramp (fabaudio)

  Reply With Quote
Old 26th February 2010, 04:02 AM   #16
diyAudio Member
 
Join Date: Feb 2007
Location: Tashkent
Quote:
Originally Posted by juma View Post
Without source resistord you'll have current hogging regardless of Id - that's how many good lateral MOSFET died...
Only insanely tight matching might get you rid of source resistors.
Matching costs a lot, but I believe it is needed for sound quality, irrespective to current equalization. If laterals are so much different that die without source resistors, than sound will be so-so.
  Reply With Quote
Old 26th February 2010, 12:07 PM   #17
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Quote:
Originally Posted by fab View Post
..
It ended like this:
fab-fourpoweramp (fabaudio)
Nice

Quote:
Originally Posted by VladimirK View Post
Matching costs a lot, but I believe it is needed for sound quality, irrespective to current equalization. If laterals are so much different that die without source resistors, than sound will be so-so.
Matching is always nice, but it's not the thing that will per se make your amp sound great or bad.
Lateral MOSFETs have their distinctive properties but diyng from too much current is not what makes them exclusive - BJTs and HEXFETs have Pd max limit too.
Actually, you are saying that output devices which use source resistors can never sound good, right ?
  Reply With Quote
Old 26th February 2010, 12:22 PM   #18
diyAudio Member
 
Join Date: Feb 2007
Location: Tashkent
Quote:
Originally Posted by juma View Post
Actually, you are saying that output devices which use source resistors can never sound good, right ?
No, I only say that paralleled laterals tend to diminish an effect of dismatch between them, opposed to HEXFETs and BJTs, that tend to rise even a minor dismatch. Therefore HEXFETs and BJTs ALWAYs need source/emitter resistors, while laterals usually don't need them, except for probably a case of terribly dismatched pair. But in the last case sound will also suffer.
  Reply With Quote
Old 26th February 2010, 12:53 PM   #19
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Quote:
Originally Posted by VladimirK View Post
No, I only say that paralleled laterals tend to diminish an effect of dismatch between them....

....laterals usually don't need them (source resistors)...
Not in my experience (2sk135/2sj50).

What laterals did you use to obtain such results?
  Reply With Quote
Old 26th February 2010, 01:12 PM   #20
diyAudio Member
 
Join Date: Feb 2007
Location: Tashkent
Quote:
Originally Posted by juma View Post
Not in my experience (2sk135/2sj50).
What laterals did you use to obtain such results?
In my 50W Zen9 I use matched triplets of 2SK1058, total current 3,9A (1,3A and 40W per transistor), do not feel any problem.
  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
LM4702 meets up with 6550's jackinnj Tubes / Valves 4 16th December 2007 11:04 PM
Old meets new but can this be solved? barchetta Pass Labs 4 11th March 2007 07:29 PM
The SACD Meets Tubes alexmoose Tubes / Valves 9 25th August 2006 06:33 PM
Old Meets New philipbarrett Tubes / Valves 3 22nd August 2005 12:03 AM


New To Site? Need Help?

All times are GMT. The time now is 04:35 PM.


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