The Aleph Jango - Page 11 - 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 30th December 2012, 04:23 PM   #101
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
IF you are using Aleoh J in SE mode, the negative input has to be shorted, correct. Nelson did this with pin in xlr.

As for transistor screw up. I had transistors in second position. This meant that the mosfet source was not attached to the bjt gate through 1K resistor. THe bjt gate was effectively connected to nothing.
__________________
...Shape the sound , Man!
  Reply With Quote
Old 30th December 2012, 04:27 PM   #102
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
for start-up testing/setting and measurements - both inputs need to be shorted to gnd

always , with all amps

for screw up - I got it

keep us informed
__________________
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 30th December 2012, 05:26 PM   #103
diyAudio Member
 
Join Date: Feb 2004
Location: Davis,CA
[QUOTE=Zen Mod;3304454]for start-up testing/setting and measurements - both inputs need to be shorted to gnd

always , with all amps

My brain is really going in circles Can't remember if I shorted things when I set up "the 6"

looking forward to the Jango - found some 109s from a Borbely DAC - hopefully I didn't save non working Fets

Picking up a lot of tips from you guys - will double check everything and post the pix when back in Davis

Best

Bob

Last edited by flocchini; 30th December 2012 at 05:26 PM. Reason: grammar
  Reply With Quote
Old 30th December 2012, 07:52 PM   #104
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Got it working. One caveat. The max bias I can get and still have zero offset is 560mv across Rs, about 1.2A. This is using 10k pot in parallel woth 470R resistor in tail of FE. If you want more and are using FQA Mosfet, you need 1k pot. 500 may do, but doesn't hurt to have extra. I may just pull pot and use whatever 470R resistor gives me. Thanks ZM. Will share impressions later.
__________________
...Shape the sound , Man!
  Reply With Quote
Old 30th December 2012, 07:59 PM   #105
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
lazy buzz

use 680 or 820 , in parallel with whatever pot you have

same for A CCS Iq - combine

resistors are invented in so many values , exactly for that



__________________
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 30th December 2012, 08:17 PM   #106
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
True, but I don't have all those values. Other channel is little off, but all is ok now I know little.
__________________
...Shape the sound , Man!
  Reply With Quote
Old 30th December 2012, 10:36 PM   #107
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
So, I dont think that the Jango will work with FQA as ACS. I can get the channels at zero offset when they are good and warm, but cold start up shows a nasty DC across the output of about 750mV. Perhaps I am doing something wrong, but I have pretty much eliminated all that i know to do including increasing LTP pot value and putting a pot as R27 for adjustablilty of the ACS. I can get zero offset when cold at lower bias, but not at 1A+. Apparently there different temperature coefficients make the case difficult. Probably wrong. I will tryagain later with IRF in top. Unless of course, there are other ideas.
__________________
...Shape the sound , Man!

Last edited by buzzforb; 30th December 2012 at 10:39 PM.
  Reply With Quote
Old 30th December 2012, 10:44 PM   #108
6L6 is offline 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Install the IRF and see what happens. Occam's razor might apply here.

The simple solution is often the best.
  Reply With Quote
Old 30th December 2012, 11:08 PM   #109
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Got them sitting at 1A bias and all is ok, but one SS is biased at about 1.7V and the other is about 1.9V for same current. One of the channels can be biased higher and still zeroed out at the offset, but the other channel is definitely limited to 1A. Odd thing is, I think it is do to the SS and not the FQA, as the offset is positive. IN other words, I have to drop the bias of the FQA in order for things to line up, as if the SS cant keep up or match it in terms of output. Kinda Bizarre! I might curve trace all the fets and make sure they are matched well. Perhaps that is the problem
__________________
...Shape the sound , Man!
  Reply With Quote
Old 30th December 2012, 11:14 PM   #110
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
as I said - laid as that - output offset is lower half thing
__________________
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

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
Aleph (Single Ended) + Larvadin (no Memory Distortion) = Ultimate Aleph? tiefbassuebertr Pass Labs 19 25th January 2014 02:15 AM
First version Aleph 0 (Null, ZERO, O, Os, 0s) versus later Aleph versions tiefbassuebertr Pass Labs 13 27th April 2012 02:13 AM
First version Aleph 0 (Null, ZERO, O, Os, 0s) versus later Aleph versions tiefbassuebertr Pass Labs 0 6th August 2009 11:11 AM
WTB: Aleph-mini PCBs and transistor set for Aleph 30 needtubes Swap Meet 4 6th November 2005 06:29 PM
PCBs for Aleph 2, Aleph 3, Aleph 4 and Aleph 5 amplifiers kristijan-k Swap Meet 64 12th September 2002 07:55 AM


New To Site? Need Help?

All times are GMT. The time now is 10:33 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