input mosfet matching (aleph) - 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 26th July 2001, 09:28 AM   #1
hifi is offline hifi  Sweden
diyAudio Member
 
Join Date: Mar 2001
Location: sweden
if i have understand correctly the input current sorce delivers 20ma ? and that is split up by the input mosfets to 10ma each?...cuz i have just read mark finnis "cloning manual" where he matches his input mosfet att 20ma each..that must be wrong??


/micke
  Reply With Quote
Old 26th July 2001, 11:09 AM   #2
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
Hi...

mark finnis "cloning manual" ... ????

can you post a link to that so I can have a look ?


greets,
thijs
  Reply With Quote
Old 26th July 2001, 06:01 PM   #3
hifi is offline hifi  Sweden
diyAudio Member
 
Join Date: Mar 2001
Location: sweden
maybe i excagerated he has a description of how he made his diy aleph 4 it is found on http://www.passlabs.com under galleries
  Reply With Quote
Old 27th July 2001, 02:11 AM   #4
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
Micke,
Match devices at the current that you intend to use in the circuit. I'm relying on memory, but I believe that you're correct--the front end of an Aleph runs at 20mA for the pair, hence 10mA each device. So you should test them at 10mA.

Grey
  Reply With Quote
Old 27th July 2001, 05:40 AM   #5
diyAudio Member
 
mefinnis's Avatar
 
Join Date: Feb 2001
Location: Adelaide, Australia
Unhappy Err ... YES

This is quite correct. Test them at 10mA .... the original description I used was wrong.

Fortunately, when I looked at the remainder at 10mA cf the 20mA it didn't actually make any appreciable difference to the ranking ......

Yes, I should get around to altering the construction notes :-(

Sorry ...... Mark

  Reply With Quote
Old 27th July 2001, 04:58 PM   #6
hifi is offline hifi  Sweden
diyAudio Member
 
Join Date: Mar 2001
Location: sweden
no sweat....i tried both and i didnt find much of a difference anyway....

/micke
  Reply With Quote
Old 27th July 2001, 05:47 PM   #7
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Blog Entries: 1
Send a message via Yahoo to vdi_nenna
What do you guys think about using low-level dual mosfets for an input stage. It looks like a TO-39 can w/ six leads. I think I read in an old Audio Electronics mag that Erno Borbley uses these in the input stage of his amps. It negated the need for matching since it's on the same chip. Any ideas on this??
  Reply With Quote
Old 27th July 2001, 10:02 PM   #8
diyAudio Member
 
Join Date: Jan 2001
Location: Scandinavia
Thumbs down What are they?

Are these MOSFET's from Linear Systems? In which case, last time I checked they did not have the power rating to suit my taste. For low power stuff, consider using JFET's which probably perform better (unless your circuit is sensitive to input leakage current or you need more quiescent current before device saturation).

What are the names of the units you mention?

You can find a list of devices used by Borbely at his website http://www.borbely.com. Check out schematics and note heavy use of cascoding -- sometimes with J-FET's other times with FETs (when he needs more power dissipation?)

In my humble opinion, I think his designs have not changed much from what he published in Audio Electronics around 1990, but I am perhaps being a little cynical.

Petter
  Reply With Quote
Old 27th July 2001, 11:39 PM   #9
diyAudio Member
 
vdi_nenna's Avatar
 
Join Date: Oct 2000
Location: PA, USA
Blog Entries: 1
Send a message via Yahoo to vdi_nenna
Don't know what they are. Iwas on his site today, but I was reading about JFETs, I didn't take not of make or model.

JFET come in the dual monolithic state also.

Just thought I'd ask.
  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
Matching MOSFET's for Aleph 2 Thago Pass Labs 4 5th June 2007 08:05 PM
Matching Aleph 30 mosfet same Pass Labs 15 5th May 2007 02:03 PM
Aleph 5 (Mosfet Matching) billy Pass Labs 3 17th January 2003 03:18 PM
Aleph : Output Mosfet Matching vinay Pass Labs 8 10th October 2002 09:27 PM
Matching MOSFET for Zen V4/Aleph 5 ??? PsykoK Pass Labs 5 26th September 2002 10:04 PM


New To Site? Need Help?

All times are GMT. The time now is 06:46 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